Chemical structural variations of asphaltene during solvent swelling characterized by 13C nuclear magnetic resonance and X-ray diffraction

Chemical structural variations of asphaltene during solvent swelling characterized by 13C nuclear magnetic resonance and X-ray diffraction | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Chemical structural variations of asphaltene during solvent swelling characterized by 13 C nuclear magnetic resonance and X-ray diffraction Shuyong Shi, Tian Liang, Xiaohui Lin, Yunpeng Wang, Yanrong Zou, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7683338/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 17 Dec, 2025 Read the published version in Scientific Reports → Version 1 posted 14 You are reading this latest preprint version Abstract In this study, the 13 C nuclear magnetic resonance (NMR) and X-ray diffraction (XRD) were employed to investigate adsorption capacity and chemical structural variations of the asphaltene during the solvent swelling. The results show that the saturates and aromatics mainly accumulate between the aliphatic carbon chains both for the asphaltenes with long and short aliphatic chains. However, it is difficult for the aromatics to accumulate between aromatic carbon chains in short aliphatic chain asphaltene. The aliphaticity-f(al) of kerogen, asphaltene, and solid bitumen shows an increasing trend with the saturation swelling ratio of saturates (R 2 = 0.80). By comparison, the saturation swelling ratio of aromatics for them with the aromaticity-f(ar) shows three different evolution trends, which can be attributed to their differences of chemical structures. Three types of organic macromolecules evolve more stable structures at higher thermal maturity, so that the saturation swelling ratio of aromatics for them gradually become smaller and tend to be the same. Furthermore, two new methods are established to calculate the amounts of saturates and aromatics adsorbed by asphaltene and kerogen. The asphaltene is the main fraction of kerogen cracking during oil generation and has strong adsorption capacity on liquid hydrocarbons, so its adsorption capacity for liquid hydrocarbons should be also considered in the future studies about hydrocarbon expulsion of the shale. Physical sciences/Chemistry Physical sciences/Energy science and technology Physical sciences/Materials science adsorption ability chemical structure organic macromolecule molecular model Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 1. Introduction Asphaltene, an organic compound in crude oil and source rock and reservoir extracts, generally precipitates in n -hexane, but dissolves in dichloromethane 1 – 3 . The asphaltene is generally composed of aliphatic side and naphthenic chains, multiple aromatic rings, and various functional groups 4 , 5 . It has been demonstrated that the degradation of kerogen results in the generation of significant quantities of asphaltenes, especially in the relatively low-mature stage with thermal maturity (Ro%) lower than 1.0% 6 . Many studies have shown that the generated hydrocarbons undergo component fractionation during the hydrocarbon expulsion processes 7 – 9 . The kerogen preferentially adsorbs high-molecule polar compounds due to their high retention capacity, whereas low-molecule hydrocarbons can easily expel from source rocks 10 , 11 . As one of organic macromolecules, the asphaltene exhibits relatively high-molecule weight (500–2000 g/mol), complex chemical structure, and strong polarity, which is analogous to the kerogen 1 , 5 , 12 , 13 . The asphaltene also has the capacity to absorb certain saturates and aromatics in a manner similar to the kerogen, which is attributed to its special chemical structures. Therefore, interactions between the asphaltene and liquid hydrocarbons are vital in the study of the hydrocarbon generation and expulsion processes of source rocks. The swelling is an important phenomenon of the interaction between solid and liquid organic matters and is classical method for studying hydrocarbon expulsion capacity of solid organic matter 14 – 16 . The swelling experiments have been widely used to investigate the interactions between solid and liquid organic matters. Previous studies mainly focused on the solid organic matter changes in volume and the ability to dissolve hydrocarbons during solvent swelling 17 – 20 . With further research, Several studies related to the chemical structure variations of organic macromolecules, such as kerogen 14 , 21 – 23 , solid bitumen 24 and coal 23 , 25 during this process have been also conducted. Furthermore, the interactions between the asphaltene and liquid hydrocarbons also occur during the solvent swelling, representing a key process relevant to the hydrocarbon retention and expulsion. The asphaltene is not only the product of kerogen cracking, but also plays a critical role in the adsorption of liquid hydrocarbons during solvent swelling. However, this aspect was generally overlooked in previous swelling experiments. Consequently, chemical structural variations of asphaltene and its adsorption capacity on the liquid hydrocarbons during this process is still unclear. Numerous analysis techniques have been developed to characterize chemical structures of organic macromolecules, such as the solid-state 13 C nuclear magnetic resonance (NMR), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Liang et al. (2021, 2022, 2024) 7 , 20 , 26 have developed the method of combining NMR and XRD analysis technologies, which are successful to characterize the changs in chemical structures of solid bitumen, kerogen and coal during solvent swelling. This method is also used to investigate chemical structural variations of asphaltene during the swelling process in this paper. The chemical structure of asphaltene is of pivotal importance in terms of its capacity to adsorb liquid hydrocarbons, and its variations during solvent swelling need to be well studied. To address this question, The solvent swelling experiments serve as a classical methodology for investigating the interactions between the asphaltene and liquid organic matter 7 , 20 , 26 , 27 . In this study, three asphaltene samples were prepared to conduct solvent swelling experiments. Prior to the swelling experiments, the structural properties of three samples were also investigated using the solid-state 13 C NMR technology, providing basic structural information of three asphaltene samples. The n -hexadecane (C 16 H 34 ) and n -heptylbenzene (C 13 H 20 ) were selected as the swelling solvents to represent the swelling behaviors of saturated and aromatic hydrocarbons, respectively. Following the swelling experiments, the XRD analysis was employed to acquire the structural parameters of swollen asphaltene, such as the interlayer spacing of amorphous carbon in aliphatic carbon (d γ ) and the microcrystals in the chemical structures (d 002 ). The purposes of this study are: (1) to reveal the adsorption capacity of asphaltene on liquid hydrocarbons; (2) to investigate chemical structural variations of asphaltene during solvent swelling process; and (3) to establish methods to calculate the amounts of saturates and aromatics adsorbed by asphaltene and kerogen under different thermal maturities. 2. Samples and methods 2.1 Preparation of asphaltene samples The crude oils are composed of saturates, aromatics, resin and asphaltene. Three crude oils were selected to precipitate the asphaltenes in this study. Sample KL was from the Kelamayi City, Tarim Basin, sample LG was from the Tarim Basin (Lunnan County, Aksu Autonomous Prefecture, Xinjiang province), and sample SC was from northwestern Sichuan Basin (Qingchuan, Guangyuan city), from the Cambrian Changjianggou Formation. The crude oils were dissolved in excess n -hexane and mixed thoroughly by the ultrasound machine. The mixed solutions were then centrifuged at a speed of 3, 500 rpm. Subsequently, the asphaltene fractions were precipitated at the bottom of the solutions, and the supernatant solutions were removed by a dropper. This process was repeated approximately 5 times until the supernatant liquor was colorless. The asphaltene powder samples were finally obtained after dying at 60 ℃ for 12 hours. 2.2 Rock-Eval analysis The basic pyrolysis of three asphaltene samples were analyzed on the Rock-Eval VI instrument. The powder samples (ca. 5–10 mg) were heated to 300 ℃ to obtain S 1 (free hydrocarbons), then pyrolyzed from 300 to 600 ℃ at the heating rate of 25 ℃/min to obtain S 2 (pyrolysis hydrocarbons), S 3 (organic carbon dioxide) and T max (temperature of peak S 2 maximum). Subsequently, the total organic carbon (TOC) and hydrogen index (HI) can be calculated according to these parameters 28 . 2.3 Solid-state 13 C nuclear magnetic resonance analysis The solid-state 13 C NMR technology was used to characterize the structural properties of three asphaltene samples. The 13 C NMR experiments were performed using a Bruker AVANCE III 400 MHz NMR instrument equipped with a 4 mm dual-resonance probe, with an analysis speed of 14, 000 Hz. 2.4 Swelling experiments The n -hexadecane (C 16 H 34 ) and n -heptylbenzene (C 13 H 20 ) were selected as the swelling solvents to represent the swelling behaviors of saturated and aromatic hydrocarbons, respectively22. The swelling experiments were performed at 20 ℃ in the laboratory to reduce the volatilization of organic solvents. Two groups of swelling experiments were designed using the two organic solvents. The asphaltene samples were weighed and added to a clean 4 mL glass bottle with each point having two such bottles. The quantities of two solvents were subsequently added to the two bottles of each point, respectively, with the percentage of the solvents increasing regularly. The percentage and the weight of the two solvents, as well as the corresponding swelling ratio of each point are presented in Table 1 . Table 1 The swelling ratio, proportion of solvent and adsorption amount of three asphaltene samples. Swelling ratio Proportion of solvent (%) KL-C 16 H 34 (mg) LG-C 16 H 34 (mg) SC-C 16 H 34 (mg) KL -C 13 H 20 (mg) LG-C 13 H 20 (mg) SC-C 13 H 20 (mg) Solid Liquid Solid Liquid Solid Liquid Solid Liquid Solid Liquid Solid Liquid 1.11 10 53.0 5.88 53.4 5.93 - - 61.2 6.80 55.9 6.21 60.6 6.73 1.25 20 70.0 17.5 44.0 11.0 52.3 13.1 64.3 16.1 60.6 15.2 53.0 13.3 1.43 30 46.8 20.1 36.6 15.7 59.9 25.7 73.4 31.5 75.6 32.4 49.9 21.4 1.54 35 - - - - 43.1 23.2 - - - - 43.1 23.2 1.67 40 51.5 34.4 44.8 29.8 - - 82.3 54.9 67.2 44.8 42.2 34.5 2.00 50 70.3 70.3 47.3 47.3 - - 69.9 69.9 81.2 81.2 54.2 54.2 2.22 55 103 126 59.0 72.1 - - - - 79.7 97.4 60.6 6.73 2.50 60 - - - - - - 65.6 98.4 - - 53.0 13.3 2.86 65 - - - - - - 81.8 151.8 - - - - 3.33 70 - - - - - - 80.8 188 - - - - All samples of each point were left to stand for 72 hours in order to ensure that the asphaltene and solvent were fully mixed. The point was considered as the effective point when there was an absence of free-flowing solvents in the mixed samples. It was thought that the solvent was completely adsorbed by the asphaltene 23 , 24 . In contrast, the presence of free-flowing solvents indicated that the amount of the solvents exceeded the adsorption ability of the asphaltene, and these points were considered as ineffective data points. After that, these mixed samples of each effective point were prepared for the XRD analysis. 2.5 X-ray diffraction analysis The XRD experiments were conducted with an XRD-6100 instrument equipped with a copper (Cu) tube target operating 40 kv voltage and 30 mA current. The scanning range and speed were 10–80°and 2.0 deg/min, respectively. The chemical structures of asphaltenes after solvent swelling can be characterized by the γ and 002 peaks in the XRD spectra. The parameters of d γ and d 002 are calculated using the Bragg and Scherrer equations, which can be expressed as follows: d γ = \(\:\frac{\lambda\:}{{2sin\theta\:}_{\gamma\:}}\) (1) d 002 = \(\:\frac{\lambda\:}{{2sin\theta\:}_{002}}\) (2) where λ is the x-ray wavelength (0.15405 nm), θ γ and θ 002 are the diffraction angles of γ and 002. d γ and d 002 are the interlayer spacing of amorphous carbon in aliphatic carbon and the microcrystals in the chemical structures of swollen asphaltenes, respectively. 3. Results 3.1 Basic geochemical characteristics of three asphaltene samples The pyrolysis characteristics of three asphaltene samples are shown in Fig. 1 and listed in Table 2 . The HI and T max values of samples KL, LG and SC range from 489–703 mg/gTOC and from 434–444 ℃, which represents that they are type I organic matters. Based on the relationship between R eq (equivalent vitrinite reflectance) and T max by Jarvie et al. 29 , the R eq values of samples KL, SC, and LG are 0.65%, 0.72%, and 0.83%, respectively. Table 2 The Rock-Eval data of three asphaltene samples. Sample S 1 S 2 T max HI OI TOC R eq (%) Type (mg/g) (℃) (mg/gTOC) (%) KL 10.82 526 434 703 4 74.8 0.65 I LG 2.76 236 444 489 1 48.3 0.83 I SC 18.42 421 438 536 2 78.6 0.72 I Equivalent vitrinite reflectance (Req) = 0.018 × T max − 7.16 29 . The chemical structural characteristics of three asphaltene samples are obtained by the solid-state 13 C NMR. The aliphatic and aromatic carbon functional groups are identified with their chemical shifts of 5–95 ppm and 95–150 ppm, respectively ( Fig. 2 ) . The aliphatic carbon functional groups are further divided into six sub-groups ( Table 3 ) : aliphatic methyl (f CH3al ), aromatic methyl (f CH3ar ), methylene (f CH2 ), methine (f CH ), quaternary (f C ), and O-alkyl (f O ), with their chemical shifts of 10–19 ppm, 19–22 ppm, 22–35 ppm, 35–40 ppm, 40–55 ppm, and 55–95 ppm, respectively. Additionally, the protonated aromatic carbon (f Ha , 95 − 118 ppm), bridgehead aromatic carbon (f Ba , 118 − 135 ppm), branched aromatic carbons (f a , 135 − 145 ppm), and oxy-aromatic (f Oa , 145 − 155 ppm) belong to the aromatic carbon functional groups. Despite their classification as type I organic matters, there are differences in the relative percentages of aliphatic and aromatic carbons ( Table 3 ) . Sample KL exhibits the highest percentage of aliphatic carbon (73.82%), followed by samples LG and SC with the percentages of 61.52% and 54.59%, respectively. The results of chemical structures show that samples KL and SC have high ratio of long aliphatic carbon chains ( Fig. 2 a, c ) , and sample LG has high ratio of aromatic carbons ( Fig. 2 b ) . Table 3 Structural parameters of three asphaltene samples according the solid-state 13 C NMR. Sample Aliphatic (%, 5–95 nm) Aromatic (%, 95–150 nm) f(al) (%) f(ar) (%) f(CH 3 al) f (CH 3 ar) f(CH 2 ) f (CH) f (C) f (O) f (Ha) f (Ba) f(Ca) f(Oa) KL 5.29 17.89 24.81 15.85 6.67 3.32 7.06 10.86 6.66 1.59 73.82 26.18 LG 11.02 24.73 14.55 8.61 1.59 1.02 7.73 16.07 10.93 3.76 61.52 38.48 SC 4.03 13.36 16.24 11.58 6.82 2.55 10.34 14.00 15.76 5.32 54.59 45.41 Notes: f(al) = f(CH 3 al) + f (CH 3 ar) + f(CH 2 ) + f(CH) + f (C) + f (O); f(ar) = f (Ha) + f (Ba) + f (Ca) + f (Oa) 3.2 Comparison of the saturation adsorption amount of three asphaltene samples The swelling ratio generally reflects the adsorption capacity of three asphaltene samples on the n -hexadecane and n -heptylbenzene swollen solvents ( Table 1 ) . The amount of each swollen solvent that is adsorbed by the asphaltenes gradually approach saturation as the weight of two solvents increases. The adsorption amounts of n -hexadecane of samples KL and LG reach saturation at the swelling ratio of 2.22 ( Fig. 3 and Table 1 ) . In contrast to the above two samples, sample SC reaches saturation at the swelling ratio of 1.54, which indicates that its adsorption capacity on saturates is lower than the other two samples. In terms of n -heptylbenzene adsorption amount, samples KL, SC and LG reach saturation at swelling ratios of 3.33, 2.50 and 2.22, respectively. In comparison with the adsorption ability of three asphaltene samples on n -hexadecane, it is found that samples KL and SC are able to adsorb more n -heptylbenzene, indicating the two samples exhibit stronger adsorption capacity on aromatics than saturates. 3.3 Variations of asphaltenes’ chemical structures during solvent swelling The XRD spectra of three swollen asphaltene samples in n -hexadecane and n -heptylbenzene solvents are shown in Figs. 4 and 5 . A broad γ-peak (2θ = 19°) and 002 (2θ = 26°) reflect the characteristics of aliphatic carbon functional groups and the stacking of aromatic rings. According to equations (1) and (2), the d γ and d 002 variations of three asphaltene samples at different swelling ratios can be calculated. As illustrated in Fig. 6 , the original d γ values of samples of KL, LG and SC are 4.74, 4.61 and 4.60, respectively, and decreases as the swelling ratio increases ( Fig. 6 a-c and Table 4 ) . Furthermore, the d γ value under the n -hexadecane is lower than that under the n -heptylbenzene at the same swelling ratio ( Fig. 6 ) . However, there is a sharp decrease of from the beginning to the swelling ratio of 1.11. The decline of d 002 with the swelling ratio can be also discerned in samples KL and SC ( Fig. 6 d, f ) , whereas the d 002 of sample LG does not appear to follow this evolution ( Fig. 6 e ) . Unlike the evolution of d γ ( Fig. 6 b ) , the d 002 of sample LG increases sharply during the primary swelling stage and then decrease with the swelling ratio ( Fig. 6 e ) . The d 002 values of this sample under n -hexadecane (3.50) and n -heptylbenzene (3.52) at the swelling ratio of 2.00 are very close the original value (3.51). Table 4 Changs of d γ and d 002 of three asphaltene sample during n -hexadecane (C 16 H 34 ) and n -heptylbenzene (C 13 H 20 ) swelling processes. Swelling ratio Proportion of solvent (%) KL-C 16 H 34 LG-C 16 H 34 SC-C 16 H 34 KL -C 13 H 20 LG-C 13 H 20 SC-C 13 H 20 d γ d 002 d γ d 002 d γ d 002 d γ d 002 d γ d 002 d γ d 002 1.00* 0 4.74 3.55 4.61 3.51 4.60 3.59 4.74 3.55 4.61 3.51 4.60 3.59 1.11 10 4.70 3.56 4.39 3.59 4.50 3.56 4.59 3.55 4.45 3.48 1.25 20 4.62 3.55 4.33 3.50 4.44 3.52 4.73 3.53 4.44 3.58 4.56 3.51 1.43 30 4.57 3.54 4.41 3.50 4.41 3.50 4.62 3.52 4.48 3.54 4.54 3.50 1.54 35 4.41 3.46 1.67 40 4.46 3.48 4.39 3.46 4.57 3.45 4.44 3.54 4.43 3.52 2.00 50 4.47 3.49 4.41 3.50 4.53 3.46 4.34 3.52 4.48 3.47 2.22 55 2.50 60 4.56 3.58 2.86 65 3.33 70 4.52 3.45 Note: the d γ and d 002 values at the swelling ratio of 1.00 represent the original values with no solvent swelling. 4. Discussion 4.1 Factors influencing the saturation adsorption amount of saturates and aromatics on the asphaltene The factors influencing the saturation adsorption amount on the asphaltene mainly depend on the characteristics of swollen solvents and chemical structures of the asphaltene. The saturates mainly consist of C-C and C-H bonds with symmetrical electron cloud distributions and weak polarity. Their interaction with organic macromolecules is mainly Van der Walas force. Compared to the saturates, the aromatics consist of a series of benzene rings that can adsorb on organic macromolecules with π-π interaction 30 . Therefore, the saturation adsorption amounts of aromatics is higher than that of saturates in samples KL and SC. Liang et al. (2021) 24 proposed that high aliphatic carbon content of solid bitumen was the cause of the significant differences in the swelling ratios between n -hexadecane and n -heptylbenzene solvents. It is found that sample KL exhibits the largest differences in the saturation swelling ratios between the two swollen solvents ( Fig. 3 ) , which is also related to its highest f(al) and HI in three samples ( Fig. 1 and Table 3 ) . The f(ar) is a measure of the aromatic carbon content of organic macromolecules and is commonly employed to describe the adsorption ability of aromatics. Despite the f(ar) of this sample being the highest among the three samples, the saturation swelling ratio in n -heptylbenzene solvent is the greatest, which is attributed to its low thermal maturity, high HI, and molecular weight. In comparison with sample LG, the higher HI, lower thermal maturity, and higher f(ar) resulted in the higher saturation adsorption amounts of aromatics for sample SC ( Fig. 3 , Tables 1 , 3 ) . With regard to the sample LG, the saturation amounts of aromatics and saturates for sample LG are same ( Fig. 3 ) . This phenomenon has been also observed in a previous study 23 , while the main factors remain unclear. It is speculated that the higher thermal maturity and lower HI together with appropriate f(ar) caused the decline of saturation adsorption amount of aromatics, approaching the amount of saturates, nonetheless, the factors need to be further studied. 4.2 Molecular model of asphaltene during the solvent swelling According to the results of solid-state 13 C NMR analysis, swelling experiments, and XRD analysis, molecular models of chemical structure variations in asphaltenes with long and short aliphatic chains during solvent swelling have been established ( Fig. 7 ) . Prior to the solvent swelling, the amorphous carbons in the asphaltene are densely packed. For the asphaltene with long aliphatic chains, most of the saturates and aromatics accumulate between the aliphatic carbon chains, resulting an obvious decline in d γ as the swelling ration increases ( Fig. 6 a, c ) . Additionally, the d 002 value also decrease as the swelling ratio increases, indicating some aromatics accumulate between the aromatic carbon chains ( Fig. 7 ) . The asphaltene with short aliphatic carbon chains shows different characteristic of structural changes during the solvent swelling. The saturates and aromatics mainly accumulate between the aliphatic carbon chains ( Fig. 7 ) . By comparison, the aromatics accumulate between aromatic carbon chains in short aliphatic chain asphaltene more difficultly than in long aliphatic chain asphaltene ( Fig. 7 ) , which causes a lower saturation adsorption amount of aromatics ( Fig. 3 ) . Our results show that the asphaltene has strong adsorption capacity on liquid hydrocarbons, and the interactions between the asphaltene and liquid hydrocarbon should be studied in the future. 4.3 The differences of swelling characteristics of asphaltene, kerogen and solid bitumen The asphaltene, kerogen, and solid bitumen are common organic macromolecules in the crude oil, reservoir, and source rocks. Our study integrates the swelling data of kerogen 22 , 23 , solid bitumen 24 , and our asphaltene samples to reveal the evolution pattern of the saturation swelling ratio of saturates with f(al) and the saturation swelling ratio of aromatics with f(ar) ( Fig. 8 ) . The long aliphatic chains can easily escape from high-molecule organic matters as thermal maturity increases, which results in the decline of HI f(al) of organic macromolecules. The saturation swelling ratio of saturates for kerogen, solid bitumen and asphaltene decreases with the decreasing of the f(al) with R 2 of 0.80 ( Fig. 8 a ) . According to the principle of “compatibility with similar components”, it can be speculated that the higher f(al) value of organic macromolecules in an indicative of their ability to adsorb more saturates. Consequently, a better fitting relationship shows that the saturation swelling ratio of saturates is principally determined by the f(al). With the increasing of thermal maturity, the aliphatic chains escape from the organic matters, causing the increase in f(al). The adsorption amount of aromatics is higher than that of saturates under the same conditions ( Fig. 8 ) . Compared to the saturation swelling ratio of saturates, it is worth noting that the saturation swelling ratio of aromatics with the f(ar) shows different evolution trends ( Fig. 8 b ) . Under the similar f(ar), the saturation swelling ratio of aromatics for solid bitumen is obviously higher than that for asphaltene and kerogen. Although factors influencing adsorption ability of aromatics are more complex than that of saturates, the differences are also influenced by different chemical structures of different organic matters. The solid bitumen and asphaltene are the products of kerogen or crude oil cracking. During the early thermal maturation stage, the C-C bonds in long aliphatic chains connected with benzene can be easily cracked with the increasing of thermal maturity due to its low activation energies 31 , 32 . By comparison, the length of aliphatic chains of kerogen is higher than its cracking products. The solid bitumen and asphaltene mainly consist of lower aliphatic chains than kerogen under the similar f(ar), which cause that they can adsorb more aromatics. With further increasing of thermal maturity and f(ar), the three types of organic macromolecules evolve more stable structures, so that the saturation swelling ratio of aromatics for them gradually become smaller at higher thermal maturity and f(ar) ( Fig. 8 b ) . 5. Implications for the hydrocarbon expulsion process of the shale The expulsion of generated oil from the shale is governed by the retention capacity 19 , 33 . When the generated oil reaches the shale’s retention amount, it can expel from the shale 10 . The resource potential of shale oil primarily depends on the content of the retained oil in the shale, so the expulsion process serves as a critical link connecting hydrocarbon generation, migration, and accumulation 9 . Previous swelling experiments mainly focused on the influences of adsorption ability of kerogen 17 , 19 , 20 , 26 , 33 , and neglected the influences of asphaltene. The adsorption ability of saturates for asphaltene is related to its f(al) ( Fig. 8 a ) , so the amount of saturates adsorbed by kerogen and asphaltene at the same thermal maturity can be expressed by: f = M a /M k (3) M sa = S k (sa) × M k × (1 + f) (4) Where M sa is the amounts of saturates adsorbed by asphaltene and kerogen. M a and M k are the amounts of asphaltene and kerogen. f is the ratio of the amounts of asphaltene and kerogen. S k (sa) is the amount of saturates adsorbed by kerogen. The adsorption ability of aromatics for asphaltene is greater than that for kerogen at the same f(ar) ( Fig. 8 b ) , so the amount of aromatics adsorbed by kerogen and asphaltene at the same thermal maturity can be expressed by: S = S a (ar)/ S k (ar) (5) M ar = S k (ar) × M k × (1 + S × f) (6) Where M ar is the amounts of aromatics adsorbed by asphaltene and kerogen. S a (ar) and S k (ar) are the amounts of aromatics adsorbed by asphaltene and kerogen. S is the ratio of the amounts of aromatics adsorbed by asphaltene and kerogen. Liang et al. (2023) 34 calculated values of f(al) and f(ar) of the Lucaogou kerogen under different EasyRo%. On this basis, f is calculated by evolution lines of asphaltene and kerogen in Fig. 8 b. Thereby, the determination of f under different thermal maturities can be referenced by Table 5 and Fig. 9 . Table 5 The aromaticity, aliphaticity and the ratio of the amounts of aromatics adsorbed by asphaltene and kerogen from the Lucaogou shale under different thermal maturities. EasyRo (%) f(ar) f(al) S a /S k (%) 0.56 39 61 1.27 0.7 41 59 1.26 0.75 49 51 1.23 0.84 57 43 1.20 1.0 80 2 1.10 1.05 87 13 1.06 1.16 92 8 1.03 1.27 95 5 1.01 1.54 96 4 1.01 Notes: f(ar) and f(al) represent the aromaticity and aliphaticity, S a /S k is the ratio of the amounts of aromatics adsorbed by asphaltene and kerogen. The data of f(ar) and f(al) under different thermal maturities are from ref 34 , and the corresponding is calculated based on Fig. 8 b According to the results of gold tube pyrolysis experiments of the Lucaogou kerogen 33 , 35 , the ratio of amounts of asphaltene versus kerogen (M a /M k ) firstly increases and then decreases with EasyRo (%), and shows obvious variation in the EasyRo (%) range of 0.7 − 1.3%, and the amount of asphaltene is even equal to the kerogen at EasyRo (%) = 0.87% ( Fig. 10 ) . The asphaltene is the main fraction of kerogen cracking during the oil generation stage, consequently, its adsorption capacity for saturates and aromatics should be considered in the future studies about hydrocarbon expulsion of the shale. 6. Conclusions In this research, we took three asphaltene samples as the research target, designed swelling experiments, and conducted the 13 C nuclear magnetic resonance (NMR) and X-ray diffraction (XRD) analysis. The following conclusions can be drawn: (1) The saturates mainly consist of C-C and C-H bonds with symmetrical electron cloud distributions and weak polarity. Their interaction with organic macromolecules is mainly Van der Walas force. The asphaltene have abundant benzene rings that can adsorb on organic macromolecules with π-π interaction. Most of the saturates and aromatics accumulate between the aliphatic carbon chains in the asphaltenes with long and short aliphatic chains. whereas it is difficult for the aromatics to accumulate between aromatic carbon chains in short aliphatic chain asphaltene. (2) The saturation swelling ratio of saturates for kerogen, solid bitumen and asphaltene decreases with the decreasing of the f(al) with R 2 of 0.80. The high f(al) value of organic macromolecules is an indicative of their ability to adsorb more saturates. Consequently, a better fitting relationship shows that the saturation swelling ratio of saturates is principally determined by the f(al). By comparison, the saturation swelling ratio of aromatics for them with the aromaticity-f(ar) shows three different evolution trends, which can be attributed to their differences of chemical structures. Three types of organic macromolecules evolve more stable structures at higher thermal maturity, so that the saturation swelling ratio of aromatics for them gradually become smaller and tend to be the same. (3) The adsorption ability of saturates for asphaltene, solid bitumen, kerogen is related to their f(al), and the adsorption ability of aromatics for asphaltene is greater than that for kerogen at the same f(ar). Three types of organic macromolecules evolve more stable structures at higher thermal maturity, so that the saturation swelling ratio of aromatics for them gradually become smaller and tend to be the same. (4) Two new methods are established to calculated the amounts of saturates and aromatics adsorbed by asphaltene and kerogen under different thermal maturities. The asphaltene is the main fraction of kerogen cracking during the early thermal maturation stage, so its capacity for liquid hydrocarbons adsorption should be also considered in the future studies about hydrocarbon expulsion of the shale. Declarations Funding This work was financially supported by the National Natural Science Foundation of China (No. 42273053, 42402136), Basic and Applied Basic Research Foundation of Guangdong Province (2023A1515011646), Director’s Fund of Guangzhou Institute of Geochemistry, CAS (2022SZJ5T-06). Author Contribution Shi Shuyong and Liang Tian wrote the mainuscript, Lin Xianhui and Shi Shuyong prepared the figures and tables, all authors reviewed the manuscript. Data Availability Data is provided within the manuscript or supplementary information files. References Nikooyeh, K., Bagheri, S. 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14:47:20","extension":"html","order_by":39,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":153578,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-7683338/v1/54f337e08b014cbd05c14ad8.html"},{"id":93507524,"identity":"58d446f2-b8eb-4d26-86ba-2118324910ed","added_by":"auto","created_at":"2025-10-14 14:55:19","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":548783,"visible":true,"origin":"","legend":"\u003cp\u003eThe HI (mg/gTOC) versus T\u003csub\u003emax\u003c/sub\u003e (℃) of three asphaltene samples.\u003c/p\u003e","description":"","filename":"Figure1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7683338/v1/1526d3d042f6f053923232be.jpg"},{"id":93506320,"identity":"917c7ade-fab0-4cfe-81b9-0445659ba02c","added_by":"auto","created_at":"2025-10-14 14:47:19","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":608253,"visible":true,"origin":"","legend":"\u003cp\u003eThe solid-state \u003csup\u003e13\u003c/sup\u003eC nuclear magnetic resonance spectra of KL (a), LG (b), and SC (c) asphaltene samples.\u003c/p\u003e","description":"","filename":"Figure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7683338/v1/a47e54d8bc2cdf6830e642cf.jpg"},{"id":93507854,"identity":"069bf664-a70b-4799-bca4-e26918d7292e","added_by":"auto","created_at":"2025-10-14 15:03:19","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":987798,"visible":true,"origin":"","legend":"\u003cp\u003eThe swelling ratios of three asphaltene samples at saturation state. C\u003csub\u003e16\u003c/sub\u003eH\u003csub\u003e34\u003c/sub\u003e and C\u003csub\u003e13\u003c/sub\u003eH\u003csub\u003e20\u003c/sub\u003e represent \u003cem\u003en\u003c/em\u003e-hexadecane and \u003cem\u003en\u003c/em\u003e-heptylbenzene, respectively.\u003c/p\u003e","description":"","filename":"Figure3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7683338/v1/96325bd8ab0c6e3044abcbca.jpg"},{"id":93506322,"identity":"5b25577e-e774-49f0-b46d-498689ecafeb","added_by":"auto","created_at":"2025-10-14 14:47:19","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":661835,"visible":true,"origin":"","legend":"\u003cp\u003eThe X-ray diffraction spectra of solvent-swollen asphaltene with\u003cem\u003e n\u003c/em\u003e-heptylbenzene (C\u003csub\u003e13\u003c/sub\u003eH\u003csub\u003e20\u003c/sub\u003e) of three samples.\u003c/p\u003e","description":"","filename":"Figure4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7683338/v1/1de861d0283f2ddef0b91f14.jpg"},{"id":93507526,"identity":"59f5ec3d-8e5e-46b0-a065-67fba29f8364","added_by":"auto","created_at":"2025-10-14 14:55:19","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":639522,"visible":true,"origin":"","legend":"\u003cp\u003eThe X-ray diffraction spectra of solvent-swollen asphaltene with \u003cem\u003en\u003c/em\u003e-hexadecane (C\u003csub\u003e16\u003c/sub\u003eH\u003csub\u003e34\u003c/sub\u003e) of three asphaltene samples. (a) KL, (b) LG, and (c) SC.\u003c/p\u003e","description":"","filename":"Figure5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7683338/v1/92039bd2b34fe9bec6236615.jpg"},{"id":93507536,"identity":"5a12d525-2664-4ad6-bf44-d4236df74425","added_by":"auto","created_at":"2025-10-14 14:55:19","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":456058,"visible":true,"origin":"","legend":"\u003cp\u003eThe d\u003csub\u003ey\u003c/sub\u003e and d\u003csub\u003e002\u003c/sub\u003e versus swelling ratio of KL (a, d), LG (b, e) and SC (c, f) asphaltene samples in the\u003cem\u003e n\u003c/em\u003e-hexadecane (C\u003csub\u003e16\u003c/sub\u003eH\u003csub\u003e34\u003c/sub\u003e) and \u003cem\u003en\u003c/em\u003e-heptylbenzene (C\u003csub\u003e13\u003c/sub\u003eH\u003csub\u003e20\u003c/sub\u003e) solvents.\u003c/p\u003e","description":"","filename":"Figure6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7683338/v1/3fc7eb557f0d8ba3325072da.jpg"},{"id":93509122,"identity":"3a85a504-385c-4f0d-a567-c3b8757cc777","added_by":"auto","created_at":"2025-10-14 15:19:19","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":169736,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagrams of the swelling model of asphaltenes with long or short aliphatic chains.\u003c/p\u003e","description":"","filename":"Figure7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7683338/v1/2ce18456593a5d4695afcaf1.jpg"},{"id":93507856,"identity":"5dbaa1e1-1a6a-429a-865d-1a7df8826656","added_by":"auto","created_at":"2025-10-14 15:03:19","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":362073,"visible":true,"origin":"","legend":"\u003cp\u003eThe aliphaticity-f(al) versus saturation swelling ratio under \u003cem\u003en\u003c/em\u003e-hexadecane solvent (a) and the aromaticity-f(ar) versus saturation swelling ratio under \u003cem\u003en\u003c/em\u003e-heptylbenzene solvent (b) for different organic matters. Notes: the direction of arrows represents the increasing trend of thermal maturity.\u003c/p\u003e","description":"","filename":"Figure8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7683338/v1/67c05c5b93768ee96a198930.jpg"},{"id":93507528,"identity":"66f60d4a-5213-45b7-9c02-052efcecb221","added_by":"auto","created_at":"2025-10-14 14:55:19","extension":"jpg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":178451,"visible":true,"origin":"","legend":"\u003cp\u003eThe ratio of the amounts of aromatics adsorbed by asphaltene and kerogen (S\u003csub\u003ea\u003c/sub\u003e(ar)/ S\u003csub\u003ek\u003c/sub\u003e(ar)) of the Lucaogou shale under different thermal maturities (EasyRo%).\u003c/p\u003e","description":"","filename":"Figure9.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7683338/v1/496c725ba3f71c7289d920d4.jpg"},{"id":93507531,"identity":"ef7a8953-9d7d-410f-a892-295afee5762e","added_by":"auto","created_at":"2025-10-14 14:55:19","extension":"jpg","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":189702,"visible":true,"origin":"","legend":"\u003cp\u003eThe ratio of the amounts of asphaltene and kerogen (M\u003csub\u003ea\u003c/sub\u003e/M\u003csub\u003ek\u003c/sub\u003e) of the Lucaogou shale under different thermal maturities (EasyRo%). The data are from refs 33 and 35.\u003c/p\u003e","description":"","filename":"Figure10.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7683338/v1/8be2ea773a1b2dd84ab881c4.jpg"},{"id":98813869,"identity":"dc4f5334-bc55-479a-8cd5-470434bef5cb","added_by":"auto","created_at":"2025-12-22 16:06:22","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":6353645,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7683338/v1/465497a8-67e1-4c44-aa78-aca63d1bff4c.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eChemical structural variations of asphaltene during solvent swelling characterized by \u003csup\u003e13\u003c/sup\u003eC nuclear magnetic resonance and X-ray diffraction\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eAsphaltene, an organic compound in crude oil and source rock and reservoir extracts, generally precipitates in \u003cem\u003en\u003c/em\u003e-hexane, but dissolves in dichloromethane\u003csup\u003e\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. The asphaltene is generally composed of aliphatic side and naphthenic chains, multiple aromatic rings, and various functional groups\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. It has been demonstrated that the degradation of kerogen results in the generation of significant quantities of asphaltenes, especially in the relatively low-mature stage with thermal maturity (Ro%) lower than 1.0%\u003csup\u003e6\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eMany studies have shown that the generated hydrocarbons undergo component fractionation during the hydrocarbon expulsion processes\u003csup\u003e\u003cspan additionalcitationids=\"CR8\" citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. The kerogen preferentially adsorbs high-molecule polar compounds due to their high retention capacity, whereas low-molecule hydrocarbons can easily expel from source rocks\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e,\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. As one of organic macromolecules, the asphaltene exhibits relatively high-molecule weight (500\u0026ndash;2000 g/mol), complex chemical structure, and strong polarity, which is analogous to the kerogen\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e,\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. The asphaltene also has the capacity to absorb certain saturates and aromatics in a manner similar to the kerogen, which is attributed to its special chemical structures. Therefore, interactions between the asphaltene and liquid hydrocarbons are vital in the study of the hydrocarbon generation and expulsion processes of source rocks.\u003c/p\u003e\u003cp\u003eThe swelling is an important phenomenon of the interaction between solid and liquid organic matters and is classical method for studying hydrocarbon expulsion capacity of solid organic matter\u003csup\u003e\u003cspan additionalcitationids=\"CR15\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. The swelling experiments have been widely used to investigate the interactions between solid and liquid organic matters. Previous studies mainly focused on the solid organic matter changes in volume and the ability to dissolve hydrocarbons during solvent swelling\u003csup\u003e\u003cspan additionalcitationids=\"CR18 CR19\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e. With further research, Several studies related to the chemical structure variations of organic macromolecules, such as kerogen\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e,\u003cspan additionalcitationids=\"CR22\" citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e, solid bitumen\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e and coal\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e,\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e during this process have been also conducted. Furthermore, the interactions between the asphaltene and liquid hydrocarbons also occur during the solvent swelling, representing a key process relevant to the hydrocarbon retention and expulsion. The asphaltene is not only the product of kerogen cracking, but also plays a critical role in the adsorption of liquid hydrocarbons during solvent swelling. However, this aspect was generally overlooked in previous swelling experiments. Consequently, chemical structural variations of asphaltene and its adsorption capacity on the liquid hydrocarbons during this process is still unclear.\u003c/p\u003e\u003cp\u003eNumerous analysis techniques have been developed to characterize chemical structures of organic macromolecules, such as the solid-state \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003eC nuclear magnetic resonance (NMR), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Liang et al. (2021, 2022, 2024)\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e,\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e have developed the method of combining NMR and XRD analysis technologies, which are successful to characterize the changs in chemical structures of solid bitumen, kerogen and coal during solvent swelling. This method is also used to investigate chemical structural variations of asphaltene during the swelling process in this paper.\u003c/p\u003e\u003cp\u003eThe chemical structure of asphaltene is of pivotal importance in terms of its capacity to adsorb liquid hydrocarbons, and its variations during solvent swelling need to be well studied. To address this question, The solvent swelling experiments serve as a classical methodology for investigating the interactions between the asphaltene and liquid organic matter\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e,\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e,\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. In this study, three asphaltene samples were prepared to conduct solvent swelling experiments. Prior to the swelling experiments, the structural properties of three samples were also investigated using the solid-state \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003eC NMR technology, providing basic structural information of three asphaltene samples. The \u003cem\u003en\u003c/em\u003e-hexadecane (C\u003csub\u003e16\u003c/sub\u003eH\u003csub\u003e34\u003c/sub\u003e) and \u003cem\u003en\u003c/em\u003e-heptylbenzene (C\u003csub\u003e13\u003c/sub\u003eH\u003csub\u003e20\u003c/sub\u003e) were selected as the swelling solvents to represent the swelling behaviors of saturated and aromatic hydrocarbons, respectively. Following the swelling experiments, the XRD analysis was employed to acquire the structural parameters of swollen asphaltene, such as the interlayer spacing of amorphous carbon in aliphatic carbon (d\u003csub\u003eγ\u003c/sub\u003e) and the microcrystals in the chemical structures (d\u003csub\u003e002\u003c/sub\u003e). The purposes of this study are: (1) to reveal the adsorption capacity of asphaltene on liquid hydrocarbons; (2) to investigate chemical structural variations of asphaltene during solvent swelling process; and (3) to establish methods to calculate the amounts of saturates and aromatics adsorbed by asphaltene and kerogen under different thermal maturities.\u003c/p\u003e"},{"header":"2. Samples and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Preparation of asphaltene samples\u003c/h2\u003e\u003cp\u003eThe crude oils are composed of saturates, aromatics, resin and asphaltene. Three crude oils were selected to precipitate the asphaltenes in this study. Sample KL was from the Kelamayi City, Tarim Basin, sample LG was from the Tarim Basin (Lunnan County, Aksu Autonomous Prefecture, Xinjiang province), and sample SC was from northwestern Sichuan Basin (Qingchuan, Guangyuan city), from the Cambrian Changjianggou Formation. The crude oils were dissolved in excess \u003cem\u003en\u003c/em\u003e-hexane and mixed thoroughly by the ultrasound machine. The mixed solutions were then centrifuged at a speed of 3, 500 rpm. Subsequently, the asphaltene fractions were precipitated at the bottom of the solutions, and the supernatant solutions were removed by a dropper. This process was repeated approximately 5 times until the supernatant liquor was colorless. The asphaltene powder samples were finally obtained after dying at 60 ℃ for 12 hours.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Rock-Eval analysis\u003c/h2\u003e\u003cp\u003eThe basic pyrolysis of three asphaltene samples were analyzed on the Rock-Eval VI instrument. The powder samples (ca. 5\u0026ndash;10 mg) were heated to 300 ℃ to obtain S\u003csub\u003e1\u003c/sub\u003e (free hydrocarbons), then pyrolyzed from 300 to 600 ℃ at the heating rate of 25 ℃/min to obtain S\u003csub\u003e2\u003c/sub\u003e (pyrolysis hydrocarbons), S\u003csub\u003e3\u003c/sub\u003e (organic carbon dioxide) and T\u003csub\u003emax\u003c/sub\u003e (temperature of peak S\u003csub\u003e2\u003c/sub\u003e maximum). Subsequently, the total organic carbon (TOC) and hydrogen index (HI) can be calculated according to these parameters\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3 Solid-state \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003eC nuclear magnetic resonance analysis\u003c/h2\u003e\u003cp\u003eThe solid-state \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003eC NMR technology was used to characterize the structural properties of three asphaltene samples. The \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003eC NMR experiments were performed using a Bruker AVANCE III 400 MHz NMR instrument equipped with a 4 mm dual-resonance probe, with an analysis speed of 14, 000 Hz.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4 Swelling experiments\u003c/h2\u003e\u003cp\u003eThe \u003cem\u003en\u003c/em\u003e-hexadecane (C\u003csub\u003e16\u003c/sub\u003eH\u003csub\u003e34\u003c/sub\u003e) and \u003cem\u003en\u003c/em\u003e-heptylbenzene (C\u003csub\u003e13\u003c/sub\u003eH\u003csub\u003e20\u003c/sub\u003e) were selected as the swelling solvents to represent the swelling behaviors of saturated and aromatic hydrocarbons, respectively22. The swelling experiments were performed at 20 ℃ in the laboratory to reduce the volatilization of organic solvents. Two groups of swelling experiments were designed using the two organic solvents. The asphaltene samples were weighed and added to a clean 4 mL glass bottle with each point having two such bottles. The quantities of two solvents were subsequently added to the two bottles of each point, respectively, with the percentage of the solvents increasing regularly. The percentage and the weight of the two solvents, as well as the corresponding swelling ratio of each point are presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eThe swelling ratio, proportion of solvent and adsorption amount of three asphaltene samples.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"19\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c14\" colnum=\"14\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c15\" colnum=\"15\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c16\" colnum=\"16\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c17\" colnum=\"17\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c18\" colnum=\"18\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c19\" colnum=\"19\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eSwelling\u003c/p\u003e\u003cp\u003eratio\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eProportion\u003c/p\u003e\u003cp\u003eof solvent\u003c/p\u003e\u003cp\u003e(%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003eKL-C\u003csub\u003e16\u003c/sub\u003eH\u003csub\u003e34\u003c/sub\u003e\u003c/p\u003e\u003cp\u003e(mg)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003eLG-C\u003csub\u003e16\u003c/sub\u003eH\u003csub\u003e34\u003c/sub\u003e\u003c/p\u003e\u003cp\u003e(mg)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c10\" namest=\"c9\"\u003e\u003cp\u003eSC-C\u003csub\u003e16\u003c/sub\u003eH\u003csub\u003e34\u003c/sub\u003e\u003c/p\u003e\u003cp\u003e(mg)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c13\" namest=\"c12\"\u003e\u003cp\u003eKL -C\u003csub\u003e13\u003c/sub\u003eH\u003csub\u003e20\u003c/sub\u003e\u003c/p\u003e\u003cp\u003e(mg)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c16\" namest=\"c15\"\u003e\u003cp\u003eLG-C\u003csub\u003e13\u003c/sub\u003eH\u003csub\u003e20\u003c/sub\u003e\u003c/p\u003e\u003cp\u003e(mg)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c19\" namest=\"c18\"\u003e\u003cp\u003eSC-C\u003csub\u003e13\u003c/sub\u003eH\u003csub\u003e20\u003c/sub\u003e\u003c/p\u003e\u003cp\u003e(mg)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eSolid\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eLiquid\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eSolid\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eLiquid\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c9\"\u003e\u003cp\u003eSolid\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c10\"\u003e\u003cp\u003eLiquid\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c12\"\u003e\u003cp\u003eSolid\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c13\"\u003e\u003cp\u003eLiquid\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c15\"\u003e\u003cp\u003eSolid\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c16\"\u003e\u003cp\u003eLiquid\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c18\"\u003e\u003cp\u003eSolid\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c19\"\u003e\u003cp\u003eLiquid\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e53.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e5.88\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e53.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e5.93\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e61.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e6.80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c15\"\u003e\u003cp\u003e55.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c16\"\u003e\u003cp\u003e6.21\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c18\"\u003e\u003cp\u003e60.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c19\"\u003e\u003cp\u003e6.73\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e70.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e17.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e44.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e11.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e52.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e13.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e64.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e16.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c15\"\u003e\u003cp\u003e60.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c16\"\u003e\u003cp\u003e15.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c18\"\u003e\u003cp\u003e53.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c19\"\u003e\u003cp\u003e13.3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e46.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e20.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e36.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e15.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e59.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e25.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e73.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e31.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c15\"\u003e\u003cp\u003e75.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c16\"\u003e\u003cp\u003e32.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c18\"\u003e\u003cp\u003e49.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c19\"\u003e\u003cp\u003e21.4\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1.54\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e43.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e23.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c15\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c16\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c18\"\u003e\u003cp\u003e43.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c19\"\u003e\u003cp\u003e23.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e51.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e34.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e44.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e29.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e82.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e54.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c15\"\u003e\u003cp\u003e67.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c16\"\u003e\u003cp\u003e44.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c18\"\u003e\u003cp\u003e42.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c19\"\u003e\u003cp\u003e34.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e70.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e70.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e47.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e47.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e69.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e69.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c15\"\u003e\u003cp\u003e81.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c16\"\u003e\u003cp\u003e81.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c18\"\u003e\u003cp\u003e54.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c19\"\u003e\u003cp\u003e54.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2.22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e103\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e126\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e59.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e72.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c15\"\u003e\u003cp\u003e79.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c16\"\u003e\u003cp\u003e97.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c18\"\u003e\u003cp\u003e60.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c19\"\u003e\u003cp\u003e6.73\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e60\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e65.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e98.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c15\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c16\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c18\"\u003e\u003cp\u003e53.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c19\"\u003e\u003cp\u003e13.3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2.86\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e81.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e151.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c15\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c16\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c18\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c19\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e70\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u003cp\u003e80.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u003cp\u003e188\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c15\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c16\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c18\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c19\"\u003e\u003cp\u003e-\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eAll samples of each point were left to stand for 72 hours in order to ensure that the asphaltene and solvent were fully mixed. The point was considered as the effective point when there was an absence of free-flowing solvents in the mixed samples. It was thought that the solvent was completely adsorbed by the asphaltene\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e,\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. In contrast, the presence of free-flowing solvents indicated that the amount of the solvents exceeded the adsorption ability of the asphaltene, and these points were considered as ineffective data points. After that, these mixed samples of each effective point were prepared for the XRD analysis.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.5 X-ray diffraction analysis\u003c/h2\u003e\u003cp\u003eThe XRD experiments were conducted with an XRD-6100 instrument equipped with a copper (Cu) tube target operating 40 kv voltage and 30 mA current. The scanning range and speed were 10\u0026ndash;80\u0026deg;and 2.0 deg/min, respectively. The chemical structures of asphaltenes after solvent swelling can be characterized by the γ and 002 peaks in the XRD spectra. The parameters of d\u003csub\u003eγ\u003c/sub\u003e and d\u003csub\u003e002\u003c/sub\u003e are calculated using the Bragg and Scherrer equations, which can be expressed as follows:\u003c/p\u003e\u003cp\u003ed\u003csub\u003eγ\u003c/sub\u003e = \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\frac{\\lambda\\:}{{2sin\\theta\\:}_{\\gamma\\:}}\\)\u003c/span\u003e\u003c/span\u003e (1)\u003c/p\u003e\u003cp\u003ed\u003csub\u003e002\u003c/sub\u003e = \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\frac{\\lambda\\:}{{2sin\\theta\\:}_{002}}\\)\u003c/span\u003e\u003c/span\u003e (2)\u003c/p\u003e\u003cp\u003ewhere λ is the x-ray wavelength (0.15405 nm), θ\u003csub\u003eγ\u003c/sub\u003e and θ\u003csub\u003e002\u003c/sub\u003e are the diffraction angles of γ and 002. d\u003csub\u003eγ\u003c/sub\u003e and d\u003csub\u003e002\u003c/sub\u003e are the interlayer spacing of amorphous carbon in aliphatic carbon and the microcrystals in the chemical structures of swollen asphaltenes, respectively.\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Basic geochemical characteristics of three asphaltene samples\u003c/h2\u003e\u003cp\u003eThe pyrolysis characteristics of three asphaltene samples are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e \u003cb\u003eand listed in\u003c/b\u003e Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The HI and T\u003csub\u003emax\u003c/sub\u003e values of samples KL, LG and SC range from 489\u0026ndash;703 mg/gTOC and from 434\u0026ndash;444 ℃, which represents that they are type I organic matters. Based on the relationship between R\u003csub\u003eeq\u003c/sub\u003e (equivalent vitrinite reflectance) and T\u003csub\u003emax\u003c/sub\u003e by Jarvie et al.\u003csup\u003e29\u003c/sup\u003e, the R\u003csub\u003eeq\u003c/sub\u003e values of samples KL, SC, and LG are 0.65%, 0.72%, and 0.83%, respectively.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eThe Rock-Eval data of three asphaltene samples.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"9\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eSample\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eS\u003csub\u003e1\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eS\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eT\u003csub\u003emax\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eHI\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eOI\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eTOC\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eR\u003csub\u003eeq\u003c/sub\u003e\u003c/p\u003e\u003cp\u003e(%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c9\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eType\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003e(mg/g)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e(℃)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e\u003cp\u003e(mg/gTOC)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003e(%)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eKL\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e10.82\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e526\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e434\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e703\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e74.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e0.65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003eI\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLG\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e2.76\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e236\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e444\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e489\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e48.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e0.83\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003eI\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e18.42\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e421\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e438\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e536\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e78.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e0.72\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u003cp\u003eI\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"9\"\u003eEquivalent vitrinite reflectance (Req)\u0026thinsp;=\u0026thinsp;0.018 \u0026times; T\u003csub\u003emax\u003c/sub\u003e \u0026minus;\u0026thinsp;7.16\u003csup\u003e29\u003c/sup\u003e.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe chemical structural characteristics of three asphaltene samples are obtained by the solid-state \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003eC NMR. The aliphatic and aromatic carbon functional groups are identified with their chemical shifts of 5\u0026ndash;95 ppm and 95\u0026ndash;150 ppm, respectively \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. The aliphatic carbon functional groups are further divided into six sub-groups \u003cb\u003e(\u003c/b\u003eTable\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e: aliphatic methyl (f\u003csub\u003eCH3al\u003c/sub\u003e), aromatic methyl (f\u003csub\u003eCH3ar\u003c/sub\u003e), methylene (f\u003csub\u003eCH2\u003c/sub\u003e), methine (f\u003csub\u003eCH\u003c/sub\u003e), quaternary (f\u003csub\u003eC\u003c/sub\u003e), and O-alkyl (f\u003csub\u003eO\u003c/sub\u003e), with their chemical shifts of 10\u0026ndash;19 ppm, 19\u0026ndash;22 ppm, 22\u0026ndash;35 ppm, 35\u0026ndash;40 ppm, 40\u0026ndash;55 ppm, and 55\u0026ndash;95 ppm, respectively. Additionally, the protonated aromatic carbon (f\u003csub\u003eHa\u003c/sub\u003e, 95\u0026thinsp;\u0026minus;\u0026thinsp;118 ppm), bridgehead aromatic carbon (f\u003csub\u003eBa\u003c/sub\u003e, 118\u0026thinsp;\u0026minus;\u0026thinsp;135 ppm), branched aromatic carbons (f\u003csub\u003ea\u003c/sub\u003e, 135\u0026thinsp;\u0026minus;\u0026thinsp;145 ppm), and oxy-aromatic (f\u003csub\u003eOa\u003c/sub\u003e, 145\u0026thinsp;\u0026minus;\u0026thinsp;155 ppm) belong to the aromatic carbon functional groups. Despite their classification as type I organic matters, there are differences in the relative percentages of aliphatic and aromatic carbons \u003cb\u003e(\u003c/b\u003eTable\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. Sample KL exhibits the highest percentage of aliphatic carbon (73.82%), followed by samples LG and SC with the percentages of 61.52% and 54.59%, respectively. The results of chemical structures show that samples KL and SC have high ratio of long aliphatic carbon chains \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea, c\u003cb\u003e)\u003c/b\u003e, and sample LG has high ratio of aromatic carbons \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb\u003cb\u003e)\u003c/b\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eStructural parameters of three asphaltene samples according the solid-state \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003eC NMR.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"15\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c14\" colnum=\"14\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c15\" colnum=\"15\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eSample\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"6\" nameend=\"c7\" namest=\"c2\"\u003e\u003cp\u003eAliphatic (%, 5\u0026ndash;95 nm)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"4\" nameend=\"c12\" namest=\"c9\"\u003e\u003cp\u003eAromatic (%, 95\u0026ndash;150 nm)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c13\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c14\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003ef(al)\u003c/p\u003e\u003cp\u003e(%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c15\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003ef(ar)\u003c/p\u003e\u003cp\u003e(%)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ef(CH\u003csub\u003e3\u003c/sub\u003eal)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003ef (CH\u003csub\u003e3\u003c/sub\u003ear)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003ef(CH\u003csub\u003e2\u003c/sub\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003ef (CH)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003ef (C)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003ef (O)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c9\"\u003e\u003cp\u003ef (Ha)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c10\"\u003e\u003cp\u003ef (Ba)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c11\"\u003e\u003cp\u003ef(Ca)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c12\"\u003e\u003cp\u003ef(Oa)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c13\"\u003e\u0026nbsp;\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eKL\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e5.29\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e17.89\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e24.81\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e15.85\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e6.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e3.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e7.06\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e10.86\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e6.66\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e\u003cp\u003e1.59\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c14\"\u003e\u003cp\u003e73.82\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c15\"\u003e\u003cp\u003e26.18\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLG\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e11.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e24.73\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e14.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e8.61\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e1.59\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e1.02\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e7.73\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e16.07\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e10.93\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e\u003cp\u003e3.76\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c14\"\u003e\u003cp\u003e61.52\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c15\"\u003e\u003cp\u003e38.48\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e4.03\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e13.36\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e16.24\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e11.58\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e6.82\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e2.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e10.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e14.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c11\"\u003e\u003cp\u003e15.76\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e\u003cp\u003e5.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c14\"\u003e\u003cp\u003e54.59\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c15\"\u003e\u003cp\u003e45.41\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"15\"\u003eNotes: f(al)\u0026thinsp;=\u0026thinsp;f(CH\u003csub\u003e3\u003c/sub\u003eal)\u0026thinsp;+\u0026thinsp;f (CH\u003csub\u003e3\u003c/sub\u003ear)\u0026thinsp;+\u0026thinsp;f(CH\u003csub\u003e2\u003c/sub\u003e)\u0026thinsp;+\u0026thinsp;f(CH)\u0026thinsp;+\u0026thinsp;f (C)\u0026thinsp;+\u0026thinsp;f (O); f(ar)\u0026thinsp;=\u0026thinsp;f (Ha)\u0026thinsp;+\u0026thinsp;f (Ba)\u0026thinsp;+\u0026thinsp;f (Ca)\u0026thinsp;+\u0026thinsp;f (Oa)\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e3.2 Comparison of the saturation adsorption amount of three asphaltene samples\u003c/h2\u003e\u003cp\u003eThe swelling ratio generally reflects the adsorption capacity of three asphaltene samples on the \u003cem\u003en\u003c/em\u003e-hexadecane and \u003cem\u003en\u003c/em\u003e-heptylbenzene swollen solvents \u003cb\u003e(\u003c/b\u003eTable\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. The amount of each swollen solvent that is adsorbed by the asphaltenes gradually approach saturation as the weight of two solvents increases. The adsorption amounts of \u003cem\u003en\u003c/em\u003e-hexadecane of samples KL and LG reach saturation at the swelling ratio of 2.22 \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e \u003cb\u003eand\u003c/b\u003e Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. In contrast to the above two samples, sample SC reaches saturation at the swelling ratio of 1.54, which indicates that its adsorption capacity on saturates is lower than the other two samples. In terms of \u003cem\u003en\u003c/em\u003e-heptylbenzene adsorption amount, samples KL, SC and LG reach saturation at swelling ratios of 3.33, 2.50 and 2.22, respectively. In comparison with the adsorption ability of three asphaltene samples on \u003cem\u003en\u003c/em\u003e-hexadecane, it is found that samples KL and SC are able to adsorb more \u003cem\u003en\u003c/em\u003e-heptylbenzene, indicating the two samples exhibit stronger adsorption capacity on aromatics than saturates.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e3.3 Variations of asphaltenes\u0026rsquo; chemical structures during solvent swelling\u003c/h2\u003e\u003cp\u003eThe XRD spectra of three swollen asphaltene samples in \u003cem\u003en\u003c/em\u003e-hexadecane and \u003cem\u003en\u003c/em\u003e-heptylbenzene solvents are shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e and \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. A broad γ-peak (2θ\u0026thinsp;=\u0026thinsp;19\u0026deg;) and 002 (2θ\u0026thinsp;=\u0026thinsp;26\u0026deg;) reflect the characteristics of aliphatic carbon functional groups and the stacking of aromatic rings. According to equations (1) and (2), the d\u003csub\u003eγ\u003c/sub\u003e and d\u003csub\u003e002\u003c/sub\u003e variations of three asphaltene samples at different swelling ratios can be calculated. As illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, the original d\u003csub\u003eγ\u003c/sub\u003e values of samples of KL, LG and SC are 4.74, 4.61 and 4.60, respectively, and decreases as the swelling ratio increases \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea-c \u003cb\u003eand\u003c/b\u003e Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. Furthermore, the d\u003csub\u003eγ\u003c/sub\u003e value under the \u003cem\u003en\u003c/em\u003e-hexadecane is lower than that under the \u003cem\u003en\u003c/em\u003e-heptylbenzene at the same swelling ratio \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. However, there is a sharp decrease of from the beginning to the swelling ratio of 1.11. The decline of d\u003csub\u003e002\u003c/sub\u003e with the swelling ratio can be also discerned in samples KL and SC \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ed, f\u003cb\u003e)\u003c/b\u003e, whereas the d\u003csub\u003e002\u003c/sub\u003e of sample LG does not appear to follow this evolution \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ee\u003cb\u003e)\u003c/b\u003e. Unlike the evolution of d\u003csub\u003eγ\u003c/sub\u003e \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb\u003cb\u003e)\u003c/b\u003e, the d\u003csub\u003e002\u003c/sub\u003e of sample LG increases sharply during the primary swelling stage and then decrease with the swelling ratio \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ee\u003cb\u003e)\u003c/b\u003e. The d\u003csub\u003e002\u003c/sub\u003e values of this sample under \u003cem\u003en\u003c/em\u003e-hexadecane (3.50) and \u003cem\u003en\u003c/em\u003e-heptylbenzene (3.52) at the swelling ratio of 2.00 are very close the original value (3.51).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eChangs of d\u003csub\u003eγ\u003c/sub\u003e and d\u003csub\u003e002\u003c/sub\u003e of three asphaltene sample during \u003cem\u003en\u003c/em\u003e-hexadecane (C\u003csub\u003e16\u003c/sub\u003eH\u003csub\u003e34\u003c/sub\u003e) and \u003cem\u003en\u003c/em\u003e-heptylbenzene (C\u003csub\u003e13\u003c/sub\u003eH\u003csub\u003e20\u003c/sub\u003e) swelling processes.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"19\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c14\" colnum=\"14\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c15\" colnum=\"15\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c16\" colnum=\"16\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c17\" colnum=\"17\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c18\" colnum=\"18\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c19\" colnum=\"19\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eSwelling\u003c/p\u003e\u003cp\u003eratio\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eProportion\u003c/p\u003e\u003cp\u003eof solvent\u003c/p\u003e\u003cp\u003e(%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e\u003cp\u003eKL-C\u003csub\u003e16\u003c/sub\u003eH\u003csub\u003e34\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c7\" namest=\"c6\"\u003e\u003cp\u003eLG-C\u003csub\u003e16\u003c/sub\u003eH\u003csub\u003e34\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c10\" namest=\"c9\"\u003e\u003cp\u003eSC-C\u003csub\u003e16\u003c/sub\u003eH\u003csub\u003e34\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c13\" namest=\"c12\"\u003e\u003cp\u003eKL -C\u003csub\u003e13\u003c/sub\u003eH\u003csub\u003e20\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c16\" namest=\"c15\"\u003e\u003cp\u003eLG-C\u003csub\u003e13\u003c/sub\u003eH\u003csub\u003e20\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c19\" namest=\"c18\"\u003e\u003cp\u003eSC-C\u003csub\u003e13\u003c/sub\u003eH\u003csub\u003e20\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003ed\u003csub\u003eγ\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003ed\u003csub\u003e002\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003ed\u003csub\u003eγ\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003ed\u003csub\u003e002\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c9\"\u003e\u003cp\u003ed\u003csub\u003eγ\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c10\"\u003e\u003cp\u003ed\u003csub\u003e002\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c12\"\u003e\u003cp\u003ed\u003csub\u003eγ\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c13\"\u003e\u003cp\u003ed\u003csub\u003e002\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c15\"\u003e\u003cp\u003ed\u003csub\u003eγ\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c16\"\u003e\u003cp\u003ed\u003csub\u003e002\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c18\"\u003e\u003cp\u003ed\u003csub\u003eγ\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c19\"\u003e\u003cp\u003ed\u003csub\u003e002\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1.00*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.74\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e3.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.61\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e3.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e4.60\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e3.59\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e\u003cp\u003e4.74\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e\u003cp\u003e3.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c15\"\u003e\u003cp\u003e4.61\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c16\"\u003e\u003cp\u003e3.51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c18\"\u003e\u003cp\u003e4.60\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c19\"\u003e\u003cp\u003e3.59\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1.11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e10\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.70\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e3.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e3.59\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e4.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e3.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e\u003cp\u003e4.59\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e\u003cp\u003e3.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c15\"\u003e\u003cp\u003e4.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c16\"\u003e\u003cp\u003e3.48\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c18\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c19\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e20\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.62\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e3.55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e3.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e4.44\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e3.52\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e\u003cp\u003e4.73\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e\u003cp\u003e3.53\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c15\"\u003e\u003cp\u003e4.44\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c16\"\u003e\u003cp\u003e3.58\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c18\"\u003e\u003cp\u003e4.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c19\"\u003e\u003cp\u003e3.51\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e30\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.57\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e3.54\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e3.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e4.41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e3.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e\u003cp\u003e4.62\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e\u003cp\u003e3.52\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c15\"\u003e\u003cp\u003e4.48\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c16\"\u003e\u003cp\u003e3.54\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c18\"\u003e\u003cp\u003e4.54\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c19\"\u003e\u003cp\u003e3.50\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1.54\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e35\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e\u003cp\u003e4.41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e\u003cp\u003e3.46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c15\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c16\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c18\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c19\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1.67\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e40\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e3.48\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e3.46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e\u003cp\u003e4.57\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e\u003cp\u003e3.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c15\"\u003e\u003cp\u003e4.44\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c16\"\u003e\u003cp\u003e3.54\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c18\"\u003e\u003cp\u003e4.43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c19\"\u003e\u003cp\u003e3.52\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2.00\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4.47\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e3.49\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e\u003cp\u003e4.41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e3.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e\u003cp\u003e4.53\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e\u003cp\u003e3.46\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c15\"\u003e\u003cp\u003e4.34\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c16\"\u003e\u003cp\u003e3.52\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c18\"\u003e\u003cp\u003e4.48\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c19\"\u003e\u003cp\u003e3.47\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2.22\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e55\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c15\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c16\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c18\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c19\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2.50\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e60\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e\u003cp\u003e4.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e\u003cp\u003e3.58\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c15\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c16\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c18\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c19\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e2.86\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c15\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c16\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c18\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c19\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e3.33\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e70\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c12\"\u003e\u003cp\u003e4.52\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e\u003cp\u003e3.45\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c14\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c15\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c16\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c17\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c18\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c19\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"19\"\u003eNote: the d\u003csub\u003eγ\u003c/sub\u003e and d\u003csub\u003e002\u003c/sub\u003e values at the swelling ratio of 1.00 represent the original values with no solvent swelling.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e4.1 Factors influencing the saturation adsorption amount of saturates and aromatics on the asphaltene\u003c/h2\u003e\u003cp\u003eThe factors influencing the saturation adsorption amount on the asphaltene mainly depend on the characteristics of swollen solvents and chemical structures of the asphaltene. The saturates mainly consist of C-C and C-H bonds with symmetrical electron cloud distributions and weak polarity. Their interaction with organic macromolecules is mainly Van der Walas force. Compared to the saturates, the aromatics consist of a series of benzene rings that can adsorb on organic macromolecules with π-π interaction\u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e. Therefore, the saturation adsorption amounts of aromatics is higher than that of saturates in samples KL and SC.\u003c/p\u003e\u003cp\u003eLiang et al. (2021)\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e proposed that high aliphatic carbon content of solid bitumen was the cause of the significant differences in the swelling ratios between \u003cem\u003en\u003c/em\u003e-hexadecane and \u003cem\u003en\u003c/em\u003e-heptylbenzene solvents. It is found that sample KL exhibits the largest differences in the saturation swelling ratios between the two swollen solvents \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e, which is also related to its highest f(al) and HI in three samples \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e \u003cb\u003eand\u003c/b\u003e Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. The f(ar) is a measure of the aromatic carbon content of organic macromolecules and is commonly employed to describe the adsorption ability of aromatics. Despite the f(ar) of this sample being the highest among the three samples, the saturation swelling ratio in \u003cem\u003en\u003c/em\u003e-heptylbenzene solvent is the greatest, which is attributed to its low thermal maturity, high HI, and molecular weight. In comparison with sample LG, the higher HI, lower thermal maturity, and higher f(ar) resulted in the higher saturation adsorption amounts of aromatics for sample SC \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, Tables\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, \u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e.\u003c/p\u003e\u003cp\u003eWith regard to the sample LG, the saturation amounts of aromatics and saturates for sample LG are same \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. This phenomenon has been also observed in a previous study\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e, while the main factors remain unclear. It is speculated that the higher thermal maturity and lower HI together with appropriate f(ar) caused the decline of saturation adsorption amount of aromatics, approaching the amount of saturates, nonetheless, the factors need to be further studied.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e4.2 Molecular model of asphaltene during the solvent swelling\u003c/h2\u003e\u003cp\u003eAccording to the results of solid-state \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003eC NMR analysis, swelling experiments, and XRD analysis, molecular models of chemical structure variations in asphaltenes with long and short aliphatic chains during solvent swelling have been established \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. Prior to the solvent swelling, the amorphous carbons in the asphaltene are densely packed. For the asphaltene with long aliphatic chains, most of the saturates and aromatics accumulate between the aliphatic carbon chains, resulting an obvious decline in d\u003csub\u003eγ\u003c/sub\u003e as the swelling ration increases \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea, c\u003cb\u003e)\u003c/b\u003e. Additionally, the d\u003csub\u003e002\u003c/sub\u003e value also decrease as the swelling ratio increases, indicating some aromatics accumulate between the aromatic carbon chains \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. The asphaltene with short aliphatic carbon chains shows different characteristic of structural changes during the solvent swelling. The saturates and aromatics mainly accumulate between the aliphatic carbon chains \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. By comparison, the aromatics accumulate between aromatic carbon chains in short aliphatic chain asphaltene more difficultly than in long aliphatic chain asphaltene \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e, which causes a lower saturation adsorption amount of aromatics \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. Our results show that the asphaltene has strong adsorption capacity on liquid hydrocarbons, and the interactions between the asphaltene and liquid hydrocarbon should be studied in the future.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003e4.3 The differences of swelling characteristics of asphaltene, kerogen and solid bitumen\u003c/h2\u003e\u003cp\u003eThe asphaltene, kerogen, and solid bitumen are common organic macromolecules in the crude oil, reservoir, and source rocks. Our study integrates the swelling data of kerogen\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e,\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e, solid bitumen\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e, and our asphaltene samples to reveal the evolution pattern of the saturation swelling ratio of saturates with f(al) and the saturation swelling ratio of aromatics with f(ar) \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe long aliphatic chains can easily escape from high-molecule organic matters as thermal maturity increases, which results in the decline of HI f(al) of organic macromolecules. The saturation swelling ratio of saturates for kerogen, solid bitumen and asphaltene decreases with the decreasing of the f(al) with R\u003csup\u003e2\u003c/sup\u003e of 0.80 \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ea\u003cb\u003e)\u003c/b\u003e. According to the principle of \u0026ldquo;compatibility with similar components\u0026rdquo;, it can be speculated that the higher f(al) value of organic macromolecules in an indicative of their ability to adsorb more saturates. Consequently, a better fitting relationship shows that the saturation swelling ratio of saturates is principally determined by the f(al).\u003c/p\u003e\u003cp\u003eWith the increasing of thermal maturity, the aliphatic chains escape from the organic matters, causing the increase in f(al). The adsorption amount of aromatics is higher than that of saturates under the same conditions \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. Compared to the saturation swelling ratio of saturates, it is worth noting that the saturation swelling ratio of aromatics with the f(ar) shows different evolution trends \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eb\u003cb\u003e)\u003c/b\u003e. Under the similar f(ar), the saturation swelling ratio of aromatics for solid bitumen is obviously higher than that for asphaltene and kerogen. Although factors influencing adsorption ability of aromatics are more complex than that of saturates, the differences are also influenced by different chemical structures of different organic matters. The solid bitumen and asphaltene are the products of kerogen or crude oil cracking. During the early thermal maturation stage, the C-C bonds in long aliphatic chains connected with benzene can be easily cracked with the increasing of thermal maturity due to its low activation energies \u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e,\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e. By comparison, the length of aliphatic chains of kerogen is higher than its cracking products. The solid bitumen and asphaltene mainly consist of lower aliphatic chains than kerogen under the similar f(ar), which cause that they can adsorb more aromatics. With further increasing of thermal maturity and f(ar), the three types of organic macromolecules evolve more stable structures, so that the saturation swelling ratio of aromatics for them gradually become smaller at higher thermal maturity and f(ar) \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eb\u003cb\u003e)\u003c/b\u003e.\u003c/p\u003e\u003c/div\u003e"},{"header":"5. Implications for the hydrocarbon expulsion process of the shale","content":"\u003cp\u003eThe expulsion of generated oil from the shale is governed by the retention capacity\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e,\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e. When the generated oil reaches the shale\u0026rsquo;s retention amount, it can expel from the shale\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. The resource potential of shale oil primarily depends on the content of the retained oil in the shale, so the expulsion process serves as a critical link connecting hydrocarbon generation, migration, and accumulation\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. Previous swelling experiments mainly focused on the influences of adsorption ability of kerogen\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e,\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e,\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e,\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e,\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e, and neglected the influences of asphaltene.\u003c/p\u003e\u003cp\u003eThe adsorption ability of saturates for asphaltene is related to its f(al) \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ea\u003cb\u003e)\u003c/b\u003e, so the amount of saturates adsorbed by kerogen and asphaltene at the same thermal maturity can be expressed by:\u003c/p\u003e\u003cp\u003ef\u0026thinsp;=\u0026thinsp;M\u003csub\u003ea\u003c/sub\u003e/M\u003csub\u003ek\u003c/sub\u003e (3)\u003c/p\u003e\u003cp\u003eM\u003csub\u003esa\u003c/sub\u003e = S\u003csub\u003ek\u003c/sub\u003e(sa) \u0026times; M\u003csub\u003ek\u003c/sub\u003e \u0026times; (1\u0026thinsp;+\u0026thinsp;f) (4)\u003c/p\u003e\u003cp\u003eWhere M\u003csub\u003esa\u003c/sub\u003e is the amounts of saturates adsorbed by asphaltene and kerogen. M\u003csub\u003ea\u003c/sub\u003e and M\u003csub\u003ek\u003c/sub\u003e are the amounts of asphaltene and kerogen. f is the ratio of the amounts of asphaltene and kerogen. S\u003csub\u003ek\u003c/sub\u003e(sa) is the amount of saturates adsorbed by kerogen.\u003c/p\u003e\u003cp\u003eThe adsorption ability of aromatics for asphaltene is greater than that for kerogen at the same f(ar) \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eb\u003cb\u003e)\u003c/b\u003e, so the amount of aromatics adsorbed by kerogen and asphaltene at the same thermal maturity can be expressed by:\u003c/p\u003e\u003cp\u003eS\u0026thinsp;=\u0026thinsp;S\u003csub\u003ea\u003c/sub\u003e(ar)/ S\u003csub\u003ek\u003c/sub\u003e(ar) (5)\u003c/p\u003e\u003cp\u003eM\u003csub\u003ear\u003c/sub\u003e = S\u003csub\u003ek\u003c/sub\u003e(ar) \u0026times; M\u003csub\u003ek\u003c/sub\u003e \u0026times; (1\u0026thinsp;+\u0026thinsp;S \u0026times; f) (6)\u003c/p\u003e\u003cp\u003eWhere M\u003csub\u003ear\u003c/sub\u003e is the amounts of aromatics adsorbed by asphaltene and kerogen. S\u003csub\u003ea\u003c/sub\u003e(ar) and S\u003csub\u003ek\u003c/sub\u003e(ar) are the amounts of aromatics adsorbed by asphaltene and kerogen. S is the ratio of the amounts of aromatics adsorbed by asphaltene and kerogen. Liang et al. (2023)\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e calculated values of f(al) and f(ar) of the Lucaogou kerogen under different EasyRo%. On this basis, f is calculated by evolution lines of asphaltene and kerogen in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eb. Thereby, the determination of f under different thermal maturities can be referenced by Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e \u003cb\u003eand\u003c/b\u003e Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eThe aromaticity, aliphaticity and the ratio of the amounts of aromatics adsorbed by asphaltene and kerogen from the Lucaogou shale under different thermal maturities.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eEasyRo\u003c/p\u003e\u003cp\u003e(%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003ef(ar) f(al)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e\u003cp\u003eS\u003csub\u003ea\u003c/sub\u003e/S\u003csub\u003ek\u003c/sub\u003e\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colspan=\"2\" nameend=\"c3\" namest=\"c2\"\u003e\u003cp\u003e(%)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e0.56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e61\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.27\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e0.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e41\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e59\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.26\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e0.75\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e49\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e51\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.23\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e0.84\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e57\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e43\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.20\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e80\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.10\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1.05\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e87\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.06\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1.16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e92\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.03\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1.27\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e95\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.01\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1.54\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e96\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.01\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eNotes: f(ar) and f(al) represent the aromaticity and aliphaticity, S\u003csub\u003ea\u003c/sub\u003e/S\u003csub\u003ek\u003c/sub\u003e is the ratio of the amounts of aromatics adsorbed by asphaltene and kerogen. The data of f(ar) and f(al) under different thermal maturities are from \u003cb\u003eref 34\u003c/b\u003e, and the corresponding is calculated based on Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eb\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAccording to the results of gold tube pyrolysis experiments of the Lucaogou kerogen\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e,\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e, the ratio of amounts of asphaltene versus kerogen (M\u003csub\u003ea\u003c/sub\u003e/M\u003csub\u003ek\u003c/sub\u003e) firstly increases and then decreases with EasyRo (%), and shows obvious variation in the EasyRo (%) range of 0.7\u0026thinsp;\u0026minus;\u0026thinsp;1.3%, and the amount of asphaltene is even equal to the kerogen at EasyRo (%)\u0026thinsp;=\u0026thinsp;0.87% \u003cb\u003e(\u003c/b\u003eFig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e\u003cb\u003e)\u003c/b\u003e. The asphaltene is the main fraction of kerogen cracking during the oil generation stage, consequently, its adsorption capacity for saturates and aromatics should be considered in the future studies about hydrocarbon expulsion of the shale.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"6. Conclusions","content":"\u003cp\u003eIn this research, we took three asphaltene samples as the research target, designed swelling experiments, and conducted the \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003eC nuclear magnetic resonance (NMR) and X-ray diffraction (XRD) analysis. The following conclusions can be drawn:\u003c/p\u003e\u003cp\u003e(1) The saturates mainly consist of C-C and C-H bonds with symmetrical electron cloud distributions and weak polarity. Their interaction with organic macromolecules is mainly Van der Walas force. The asphaltene have abundant benzene rings that can adsorb on organic macromolecules with π-π interaction. Most of the saturates and aromatics accumulate between the aliphatic carbon chains in the asphaltenes with long and short aliphatic chains. whereas it is difficult for the aromatics to accumulate between aromatic carbon chains in short aliphatic chain asphaltene.\u003c/p\u003e\u003cp\u003e(2) The saturation swelling ratio of saturates for kerogen, solid bitumen and asphaltene decreases with the decreasing of the f(al) with R\u003csup\u003e2\u003c/sup\u003e of 0.80. The high f(al) value of organic macromolecules is an indicative of their ability to adsorb more saturates. Consequently, a better fitting relationship shows that the saturation swelling ratio of saturates is principally determined by the f(al). By comparison, the saturation swelling ratio of aromatics for them with the aromaticity-f(ar) shows three different evolution trends, which can be attributed to their differences of chemical structures. Three types of organic macromolecules evolve more stable structures at higher thermal maturity, so that the saturation swelling ratio of aromatics for them gradually become smaller and tend to be the same.\u003c/p\u003e\u003cp\u003e(3) The adsorption ability of saturates for asphaltene, solid bitumen, kerogen is related to their f(al), and the adsorption ability of aromatics for asphaltene is greater than that for kerogen at the same f(ar). Three types of organic macromolecules evolve more stable structures at higher thermal maturity, so that the saturation swelling ratio of aromatics for them gradually become smaller and tend to be the same.\u003c/p\u003e\u003cp\u003e(4) Two new methods are established to calculated the amounts of saturates and aromatics adsorbed by asphaltene and kerogen under different thermal maturities. The asphaltene is the main fraction of kerogen cracking during the early thermal maturation stage, so its capacity for liquid hydrocarbons adsorption should be also considered in the future studies about hydrocarbon expulsion of the shale.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eFunding\u003c/h2\u003e\u003cp\u003eThis work was financially supported by the National Natural Science Foundation of China (No. 42273053, 42402136), Basic and Applied Basic Research Foundation of Guangdong Province (2023A1515011646), Director\u0026rsquo;s Fund of Guangzhou Institute of Geochemistry, CAS (2022SZJ5T-06).\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eShi Shuyong and Liang Tian wrote the mainuscript, Lin Xianhui and Shi Shuyong prepared the figures and tables, all authors reviewed the manuscript.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eData is provided within the manuscript or supplementary information files.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eNikooyeh, K., Bagheri, S. 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Hydrocarbon evolution pattern and spectrum characteristics of products of kerogen of Lucaogou Formation. (2018).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"adsorption ability, chemical structure, organic macromolecule, molecular model","lastPublishedDoi":"10.21203/rs.3.rs-7683338/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7683338/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn this study, the \u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003eC nuclear magnetic resonance (NMR) and X-ray diffraction (XRD) were employed to investigate adsorption capacity and chemical structural variations of the asphaltene during the solvent swelling. The results show that the saturates and aromatics mainly accumulate between the aliphatic carbon chains both for the asphaltenes with long and short aliphatic chains. However, it is difficult for the aromatics to accumulate between aromatic carbon chains in short aliphatic chain asphaltene. The aliphaticity-f(al) of kerogen, asphaltene, and solid bitumen shows an increasing trend with the saturation swelling ratio of saturates (R\u003csup\u003e2\u003c/sup\u003e\u0026thinsp;=\u0026thinsp;0.80). By comparison, the saturation swelling ratio of aromatics for them with the aromaticity-f(ar) shows three different evolution trends, which can be attributed to their differences of chemical structures. Three types of organic macromolecules evolve more stable structures at higher thermal maturity, so that the saturation swelling ratio of aromatics for them gradually become smaller and tend to be the same. Furthermore, two new methods are established to calculate the amounts of saturates and aromatics adsorbed by asphaltene and kerogen. The asphaltene is the main fraction of kerogen cracking during oil generation and has strong adsorption capacity on liquid hydrocarbons, so its adsorption capacity for liquid hydrocarbons should be also considered in the future studies about hydrocarbon expulsion of the shale.\u003c/p\u003e","manuscriptTitle":"Chemical structural variations of asphaltene during solvent swelling characterized by 13C nuclear magnetic resonance and X-ray diffraction","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-14 14:47:14","doi":"10.21203/rs.3.rs-7683338/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-10-07T03:59:19+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-05T07:32:52+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-05T06:52:41+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"173116016243835168437052506689036068101","date":"2025-10-03T14:16:51+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"78885332826977159301495632932753092301","date":"2025-10-03T07:00:20+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"32005306668077291223837994078322196135","date":"2025-10-01T16:10:01+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"296169491952284094627978638425881018230","date":"2025-10-01T06:20:09+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"50305343878788145347716046344654757452","date":"2025-10-01T05:52:07+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"167779492828495665835772557905956057686","date":"2025-10-01T05:30:25+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-10-01T05:24:24+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-09-29T11:12:14+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-09-29T05:44:33+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-09-28T08:33:53+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2025-09-28T08:26:00+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"dfbe3aba-8c34-4ad4-95bf-069fe8ff9256","owner":[],"postedDate":"October 14th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":56284740,"name":"Physical sciences/Chemistry"},{"id":56284741,"name":"Physical sciences/Energy science and technology"},{"id":56284742,"name":"Physical sciences/Materials science"}],"tags":[],"updatedAt":"2025-12-22T16:00:04+00:00","versionOfRecord":{"articleIdentity":"rs-7683338","link":"https://doi.org/10.1038/s41598-025-27672-9","journal":{"identity":"scientific-reports","isVorOnly":false,"title":"Scientific Reports"},"publishedOn":"2025-12-17 15:57:02","publishedOnDateReadable":"December 17th, 2025"},"versionCreatedAt":"2025-10-14 14:47:14","video":"","vorDoi":"10.1038/s41598-025-27672-9","vorDoiUrl":"https://doi.org/10.1038/s41598-025-27672-9","workflowStages":[]},"version":"v1","identity":"rs-7683338","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7683338","identity":"rs-7683338","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}