Efficient preparation of no-glycerol biodiesel by tri-component coupling transesterification catalyzed over pollen-derived CaO

Efficient preparation of no-glycerol biodiesel by tri-component coupling transesterification catalyzed over pollen-derived CaO | 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 Research Article Efficient preparation of no-glycerol biodiesel by tri-component coupling transesterification catalyzed over pollen-derived CaO ying tang, Meng Li, Guangtao Li, Yi Yang, Ying Yang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4159944/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 5 You are reading this latest preprint version Abstract Rape pollen with fishnet-like network structure has been used as support in the construction of high dispersion CaO materials assigned to CaO(P) ("P" was symbol of the precipitation method) via precipitation and it has been employed in the enhanced no-glycerol biodiesel preparation. The relatively excellent activity was observed by yielding to no-glycerol biodiesel of 92.69% in the rapeseed 1/1/8 mixture of oil-methyl acetate-methanol at 65 ℃ for 3 h over 10 wt% of 1/1-CaO(P)-700 (calcinated at 700 ℃ and immernated in 1/1 of calcium nitrate to sodium carbonate). Characterizations over the templated CaO(P) samples have been conducted by means of Brunauer-Emmett-Teller (BET),X-ray diffraction (XRD), Fourier transform- infrared (FT-IR) and scanning electron microscope (SEM), respectively. Based on the results, it can be found that the catalytic effect of templated CaO(P) was depend on both stronger basicity and enlarged micro-pore distribution which provide more sites for better catalysis. Biodiesel Rape pollen Precipitation method Tri-component coupling transesterification CaO Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 1. Introduction Demand for the dieselization of vehicles has grown steadily due to the innovation of fuel market, which makes the promotion and development of diesel industry a focus attention [ 1 ] . As a model of biomass energy in the new era, biodiesel enjoys dual merits, not only socially but also economically, ranging from avoiding price fluctuations caused by traditional non-renewable fuels to achieving structural energy-saving and emission-reduction benefits [ 2 ] . However, the commercial petrochemical-diesel fuels are mainly derived from crude oil through a series of process methods such as distillation, catalytic cracking, thermal cracking, hydrocracking, and petroleum coking. Most of them are divided into hydrocarbons with carbon chain length concentrated between 12 and 25, which has the two major ailments of high sulfur and high nitrogen, severely shaking the construction of ecological civilization, especially its impact on the atmospheric environment [ 3 ][ 4 ] . At present, the most common theory about biodiesel synthesis is based on the transesterification reaction developed by the two chemicals of triglyceride (TG) and methanol (MeOH) [ 5 ] . The as-synthetized biodiesel is of a low-carbon higher fatty acid composed of C, H and O, also known as the fatty acid methyl esters (FAME) with carbon chain lengths ranging from 16 to 20 [ 6 ] . However, the generation of substantial low value-added glycerol could be found in the traditional synthesis technology. Therefore, the secondary utilization of glycerin resources has attracted extensive attention of the majority of researchers [ 7 ] by addition of the novel ester reagents to removal of by-product of glycerol [ 8 ] . In the common crafts, the assistance of homogeneous alkali (such as NaOH, KOH) or acid reagents (H 3 PO 4 , H 2 SO 4 ) have been generally required, but the addition of such substances cause a consequence for the corrosion of equipment [ 9 ][ 12 ] . The commodity oils could be obtained after neutralization, leading to the generation of the countless industrial wastewater, which does not accord well with the requirements of environmental catalysis. Calcium oxide with stronger alkalinity, low cost and low solubility in methanol, is one type of the potential alkaline earth metal oxides (H − value: 10.1–11.1), which is a solid base with commercial value and industrial prospects [ 14 ] . Therefore, the development of a green and efficient synthetic route for highly dispersed calcium oxide is of profound significance to solve the problem of energy shortage. In recent years, templates have attracted great attention for the prepare porous materials with uniform particle and well dispersion by controlling the growth of crystalline by preventing active species aggregation even under high calcination temperature during the removal process of template [ 15 ] . In addition to physical and chemical templates, a great deal of biologically functional tissues from nature could also provide new inspiration for modern material science and chemical reactions, ranging from insect wings, pollen grains, plant fiber, paper and eggshell membranes to bacteria, DNA, viruses, etc [ 16 ] . Pollen has a rich porous structure and large specific surface area, and its outer wall has reticulated cavities with a large amount of proteins and phospholipids, which are easy to attach precursors and provide a medium for the doping of heteroelements [ 18 ] . It has been reported in the literature that many plants such as sunflower, pine, lotus flower and camellia were used as templates to prepare porous materials [ 19 ] . The precipitation method is one of the most common ways in preparing solid catalysts, which refers to the employment of the precipitation agent (NaOH, Na 2 CO 3 ) in the aqueous solution containing the metal salt under the control of a certain temperature and pH, to the formation of metal salt precipitation, such as hydrous oxide, carbonate crystals or gels. Subsequently, the as-obtained powder could be obtained by a series of processes, such as wash, dry, calcination [ 23 ] . Since the critical factor in the synthesis of solid base materials is to tailor and control dispersion, the aim of the present paper is to develop the precipitation approach based on pollen to prepare high dispered CaO for enhanced no-glycerol biodiesel preparation by tri-component coupling transesterification. Meanwhile, the templated CaO(P) was also characterised to reveal its structure and properties. 2. MATERIALS AND METHODS 2.1 Chemicals and materials All analytical chemicals reagent related to catalyst synthesis and biodiesel preparation such as CH 3 COOCH 3 (Kelon Co., Chengdu, China), CH 3 OH (Fuyu Co., Tianjin, China), NaOH (Tianli Co., Tianjin, China), C 6 H 12 (Tianli Co., Tianjin, China), C 18 H 38 O 2 (TCI Co., Shanghai, China), C 2 H 5 OH (Fuyu Co., Tianjin, China), Ca(NO 3 ) 2 ·4H 2 O (Damao Co., Tianjin, China), Na 2 CO 3 ( Beilian Co., Tianjin, China) had no further treatment. Rapeseed oil as raw material was obtained from Jianxing Co., Shanxi, China. The chemical and physical properties of rapeseed oil are shown in Table 1 . The broken rape pollen (diameter of 30–40 µm, density of 0.6 ~ 1.0 g/cm 3 ) was obtained from Changge Yanyuan Bee Products Co., Ltd. Commercial CaO was purchased from Kermel Co., Ltd. Table 1 Properties of rapeseed oil Properties wt % Saturated C16 fatty acid 3.7 Saturated C18 fatty acid 1.4 Unsaturated C16:1 fatty acid 61.6 Unsaturated C18:2 fatty acid 21.8 Unsaturated C18:3 fatty acid 0 Density (kg/m 3 ) 878 Kinematic viscosity (mm 2 /s) 4.13 2.2 Catalyst preparation The rape pollen (60 g) was cleaned by anhydrous alcohol (90 g) for 1 h under ultrasound for further experiments (step 1) . The CaO(P) preparation was carried out by precipitation approach as suggested as follow: 20 g processed pollen was added into calcium nitrate solution (1 mol/L 100 mL) under stirring. After 3 h the suspension was obtained and heated to 70 ℃, and then sodium carbonate solution with the different molar mass as calcium nitrate was added into suspension under continuous stirring and controlled temperature (70 ℃) for the formation of calcium carbonate (step 2) , following by centrifugation, washing, drying, calcination to obtain solid base CaO(P) (step 3) as shown in Fig. 1 . The templated CaO(P) were assigned to X-CaO(P)-Y, where "X" was the mole ratio of calcium nitrate to sodium carbonate, "Y" was symbol of the calcination temperature, as well as the expression of "P" was referred to the precipitation method. 2.3 Experimental process The solid base CaO(P) were well distributed in flask equipped with a mixture of refined rapeseed oil, methyl acetate, and methanol at moderate temperature (65 ℃) under a magnetic stirrer and reflux for 3.5 h, following by centrifugation and rotary evaporation to complete the preparation of no-glycerol biodiesel. The yield of FAME in different periods (20, 40, 60, 90, 120, 150, 180 and 210 min) was measured using a GC-7860 gas chromatograph with KB-Wax capillary column (30 m×0.32 mm×0.25 µm) and a flame ionization detector (FID). The temperature program is as follows: the temperature gradient in the range of 100–200 ℃ with heating rate of 20 ℃ min − 1 for 3 min and then increased in the range of 200–220 ℃ with heating rate of 10 ℃ min − 1 for 3 min. At last, the temperature gradient was in the range of 220–240 ℃ with the heating rate of 10 ℃ min − 1 for 3 min. In the investigation of catalytic performance,calcination temperature, mole ratio of nitrate and sodium carbonate,CaO(P) dosage, reaction temperature and ratio of oil, ester, alcohol were presented in detail because of their significant effects on the catalytic capacity. The calculation results of FAME yield was measured in accordance with algorithm (1) to determine the optimum conditions for obtaining CaO(P), where \(\sum {{A_i}}\) , \({A_{MH}}\) , \({C_{MH}}\) (1mg mL − 1 ) and \({V_{MH}}\) (1 µL) are a symbol of the peak area of the all FAME, the peak area of methyl heptadecanoate, the concentration of the methyl heptadecanoate, the injection volume, respectively. (mg) is of the quality of product oil. $$yield\left( \% \right)=\left[ {\frac{{\left( {\sum {{A_i} - {A_{MH}}} } \right)}}{{{A_{MH}}}}} \right]\frac{{{C_{MH}}{V_{MH}} \times 100}}{W}$$ 1 2.4. Reusability The reusability of 10 wt.% CaO(P) was investigated at same react condition by repeating the transesterification reaction several times with used catalysts. After each reaction, Catalysts were separated from the previous reaction mixture by centrifugation, washed with hexane, and then introduced into the fresh substrates after drying at 60 ℃. 2.5 Catalyst characterization The more structure details about templated CaO(P) were characterized by various characterization techniques. By employment of Micromeritics ASAP 2020 HD88, the BET surface areas and pore size distribution (PSD) of the CaO(P) were measured based on BET equation and BJH model [ 25 ] . It was noted that the thermal properties in range of 25 ℃-800 ℃ of the CaO(P) were collected by TGA-SDTA851 analyzer [ 26 ] . As shown by FT-IR spectras of the CaO(P) in the wavenumber range of 4000 − 500 cm − 1 were recorded on Nicolet 5700 by means of KBr pellet technique [ 27 ] . Finally, the SEM pictures and XRD patterns (2 θ :10°⁓80°) of the CaO(P) were presented, where they were performed by using JSM-6390A [ 28 ] and D8 ADVAHCL with Cu-K α radiation of 40 kV and 30 mA [ 26 ] . 3. RESULTS AND DISCUSSION 3.1 Characterization of catalysts 3.1.1 BET analysis For the Table 2 – 3 and Fig. 2 (a-b), it was depicted the textural details of pores from as-obtained templated CaO(P) calcined in various temperatures range from 600 to 800 ℃ and the mole ratios of nitrate to sodium carbonate(n(Ca 2+ ):n(Na 2 CO 3 )) between 1/0.5-1/1.5. It was seen that the calcination temperature had been an important factor for the textural performance of CaO(P) by showing that the BET surface area, pore volume, pore size keep an increase tendency from 10.5682 to 14.9162 m 2 /g, 0.0273 to 0.0446 cm 3 /g, 10.3537 to 11.9584 nm, respectively, as the calcination temperature changed from 600 to 700 ℃. However, with the increased calcination temperature to 800 ℃, the textural parameters declined as presented by BET surface area of 13.033 m 2 /g and pore volume of 0.0411 cm 3 /g, which attributed the sintering of CaO(P) surface and the reduction in mesopores numbers as shown in Fig. 2 . CaO(P) obtained under different calcination conditions were of a typical IV isotherm with a H3-type hysteresis loop (P/P 0 >0.4) for interpretation of mesopore materials [ 6 ] . It could be further confirmed by PSD results centered at 3.5 nm and 7 nm, indicating the generation of hierarchical structure. Besides, it was also found that 1/1-CaO(P)-700 had best BET surface area (14.916 m 2 /g) and pore volume (0.0446 cm 3 /g) which providing an extensive potential for efficient catalysis of no-glycerol biodiesel and suggested that the more sodium carbonate was to the disadvantage of the improvement to the textural properties due to the blockage of pore. Table 2 Pore structure properties of derived CaO(P) from different calcination temperature and commercial CaO Type of catalyst BET surface area (m 2 /g) Pore volume (cm 3 /g) Average pore diamete (nm) 1/1-CaO(P)-600 10.5682 0.027355 10.35372 1/1-CaO(P)-700 14.9162 0.044594 11.95842 1/1-CaO(P)-800 13.0337 0.041159 12.63141 Commercial CaO-700 11.4456 0.032367 11.31162 Table 3 Pore structure properties of derived CaO(P) from different proportion of nitrate to sodium carbonate and commercial CaO Type of catalyst BET surface area (m 2 /g) Pore volume (cm 3 /g) Average pore diamete (nm) 1/0.5-CaO(P)-700 14.1560 0.042359 11.96927 1/1-CaO(P)-700 14.9162 0.044594 11.95842 1/1.5-CaO(P)-700 10.3449 0.024471 9.46190 Commercial CaO-700 11.4456 0.032367 11.31162 3.1.2 XRD analysis To further explore the effect of prepare conditions of as-obtained CaO(P) powder on its phase composition, the evaluations in this section were the position of diffraction peak of CaO (JCPDS 48-1467), Ca(OH) 2 (JCPDS 44-1481) and CaCO 3 (JCPDS 33–0268) [ 29 ] . The details of diffraction peaks of CaO(P) were presented in Fig. 3 (a). It can be seen clearly that the calcinating temperature had positive impact on composition of CaO and Ca(OH) 2 for reasons of the carbonate decomposition. The crystal planes (111), (200), (202), (311) and (222), meanwhile, were observed at 2 θ = 32.21˚, 37.36˚, 53.86˚, 64.19˚ and 67.38˚ from 1/1-CaO(P)-700 [ 30 ] presented to CaO phase. Moreover, it can been found that the relatively sharp and intense diffraction peaks of CaO over 1/1-CaO(P)-700 indicated its better crystallite, while the broad peaks of the commercial CaO-700 indicated its smaller grain size and poor meso-macropore distribution according to the Scherrer formula (D = Kλ/Bcosθ). However, the relatively sharp diffraction peaks of CaO over 1/1-CaO(P)-800 was an indication of poor dispersion according to the Scherrer formula (D = Kλ/Bcosθ), which was due to the sintering surface and a decrease in specific surface area, suggesting that a proper calcination temperature was conducive to promote the dispersion of CaO particles so as to its catalytic performance to transesterification reaction. Furthermore, it can be found that the phase of CaCO 3 with poor catalytic activity can be discomposed completely when calcination temperature above 600 o C which is well consistent with the thermal analysis result as shown in Fig. 5 . Meanwhile, it was found that the molar ratio of nitrate and sodium carbonate is also one of the important factors affecting the morphology, structure and composition of CaO(P) samples. As shown in Fig. 3 b, with an incremental sodium carbonate (1/1.5-CaO(P)-700), the presence of CaCO 3 during the pyrolysis process under 700 ℃ to the worse catalytic performance on account of the weak conjugated base of CaCO 3 . 3.1.3 FT-IR analysis FT-IR spectras measurements on the pyrolysed CaO(P) had offered the more detailed evidences to explain its thermal behavior. Typical FT-IR spectras, for 1/1-CaO(P)-600, 1/1-CaO(P)-700 and 1/1-CaO(P)-800 samples, were presented at Fig. 4 (a). It was encountered that the stretching vibrations of -OH at 3648 cm − 1 , 3448 cm − 1 and 1647 cm − 1 , respectively [ 30 ] , due to the hydroxyls groups from the physisorbed water molecules in materials. Meanwhile, the sharp-pointed bands of carbonate were seen from the wave number of 1459 cm − 1 , 871 cm − 1 and 713cm − 1[ 31 ] . Further an advancement in calcinations temperature from 600 to 800 ℃, the intensity of two types of bands started getting a little smaller and weaker, which was due to the full thermal decomposition of generated precipitation CaCO 3 . Furthermore, the increasingly sharp vibration band of CO 3 2− was observed in as-obtained 1/1-CaO(P)-600 sample, suggesting that the calcination temperature of 600 o C was supposed to imcompletely remove carbonate. While it was significant to comprehend that the increased temperature (700 ℃) promoted to the ameliorated diffusivity leading to faster crystallization of CaO and then the shrinkage was prevented. Figure 4 (b) shows that the CaO(P) samples calcined at 700 ℃with different sodium carbonate contents consist of CaO, Ca(OH) 2 and CaCO 3 , and it can be seen from the figure that sharp carbonate bands can be seen from the wave numbers of 1459 cm − 1 , 871 cm − 1 and 713 cm − 1 , which become larger and stronger as the amount of sodium carbonate increases due to the generated more precipitate CaCO 3 . 3.1.4 TG analysis TG and DTG curves of the as-synthesized CaO(P) samples after various calcination treatment were presented in Fig. 5 (a-b). It was observed that there were one major weightloss interval assigned to the pyrolyzation of CaCO 3 , which was visible in 510 ~ 790 ℃ with the weightloss value of 26%, 6% and 2%, expressed by 1/1-CaO(P)-600, 1/1-CaO(P)-700 and 1/1-CaO(P)-800, respectively. Conversely, commercial CaO-700 had two decomposition intervals corresponding to decomposed Ca(OH) 2 and CaCO 3 at 330 ~ 400 ℃ and 510 ~ 790 ℃, as well as the more weightlessness was observed (13%). For a series of CaO(P) materials derived from nitrate and sodium carbonate with mole ratio of 1/1 under different calcination temperatures, a shift to higher temperature could be seen with calcination temperature from 600 to 800 ℃, which maybe indicated the stronger stability as well as avoidance from the impact of the air. Certainly, the more obvious weight loss of CaCO 3 was observed (Fig. 5 (c-d)) due to sodium carbonate consumption. It should be mentioned, however, that the weightlessness of 1/0.5-CaO(P)-700, 1/1-CaO(P)-700 and 1/1.5-CaO(P)-700 were reflected in 4%, 6% and 13%. From the result it can be observed that all of sample can be transformed to CaO after calcined above 510 ℃ and an increase in the weightloss of CaCO 3 with the higher concentration of CaO(P) (calcium nitrate/sodium carbonate), due to the generation of more precipitation or severe corrosion by air. Therefore, the CaO(P) samples over an appropriate pyrolysis temperature (700 ℃) and the addition amount of sodium carbonate (1/1) was comparatively favourable to obtain well dispersion and stability CaO particles. 3.1.5 CO 2 -TPD analysis The CO 2 -TPD curves of CaO(P) under different calcination conditions are shown in Fig. 6 (a). It can be seen that the CO 2 -TPD curves with a single peak were presented by CaO(P), and the CO 2 -desorption temperature appeared around 700 ℃, suggesting that CaO(P) had strong basic site. When n(Ca 2+ ):n(Na 2 CO 3 ) = 1/1, the CO 2 -TPD curve of CaO(P) shifted to right and the peak area gradually increased so as to the highest total basicity (4.4795 mmol/g) as the calcination temperature increases from 600 ℃ to 700 ℃. However, it was found that the surface of the 1/1-CaO(P)-800 had 13.034m 2 /g (BET specific surface area) after sintering, which caused its total basicity to drop to 3.3697 mmol/g. As seen in Fig. 6 (b), it can be observed that when n(Ca 2+ )/n(Na 2 CO 3 ) increased from 1/0.5 to 1/1, the total basicity of CaO(P) were calculated to 4.0005 mmol/g and 4.4795 mmol/g, respectively, which was attributed to the hydrolysis of Na 2 CO 3 in aqueous solution to generate CO 3 2− and OH − , followed by reaction with Ca 2+ to form CaCO 3 and Ca(OH) 2 , thus effectively avoiding the precipitation of Ca 2+ . Besides, the increase of BET specific surface area was beneficial to the change of total basicity as result of the increase of surface basic sites. A large amount of CaCO 3 and Ca(OH) 2 were produced on the pollen surface as n(Ca 2+ )/n(Na 2 CO 3 ) was 1/1.5, which reduced the BET specific surface area of 1/1.5-CaO(P)-700 to 10.345 m 2 /g so as to the decreased total basicity (1.3605 mmol/g). Therefore, 700 ℃ of calcination and 1/1 of n(Ca 2+ )/n(Na 2 CO 3 ) were selected as the optimal preparation conditions for CaO(P). Table 4 Total basicity of CaO(P) and Commercial CaO-700 Type of catalyst Total basicity (mmol/g) Desorption peaks (area%) 1/1-CaO(P)-600 - - 1/1-CaO(P)-700 4.4795 1.0418 1/1-CaO(P)-800 3.3697 0.7837 1/0.5-CaO(P)-700 4.0005 0.9304 1/1.5-CaO(P)-700 1.3605 0.3164 Commercial CaO-700 0.7903 0.1838 3.1.6 SEM analysis The SEM pictures of the original pollen, pretreated pollen (Fig. 7 . (a-b)), synthesized CaO(P) samples (Fig. 7 . (b-g)), as well as commercial CaO prepared under 700 ℃ (Fig. 7 . (h)) had been shown. It was conspicuous that the microstructure of the original pollen was similar to ultrasonic treated pretreated pollen with germination holes and germination grooves. However, it was clearly seen that the collapse of the 3D structure after the high temperature pyrolysis. Figure 7 (c-e) depicts images of CaO(P) calcined in the temperature range of 600 ℃ to 800 ℃, where the degree of calcination agglomeration becomes increasingly apparent as the temperature increases. It can be seen that the samples calcined at 800°C were agglomerated and sintered on the surface so as to its relatively low yields, while at 600 ℃ and 700 ℃, the particle size distribution was uniform with good dispersion. Meanwhile, it was important to find the significant differences of morphology in the three templated CaO(P) pyrolysed calcined at 700°C from several mole ratio,1/0.5, 1/1 and 1/1.5 of nitrate to sodium carbonate, as presented in Fig. 7 . (f), (d) and (g). It was found that when the molar ratio were 1:0.5 and 1:1.5, the CaO crystal particles aggregated into lumps with poor dispersion at insufficient or excessive amount of sodium carbonate. The experimental results showed that the dispersion of CaO(P) particles were not only temperature dependent, but also the amount of sodium carbonate was a key factor, and it was observed that the best dispersion performance was obtained at 700 ℃ and 1/1.5. 3.2 No-glycerol biodiesel preparation 3.2.1 Comparison of catalytic properties Interesting distinctions of FAME yield regularity had been drawn between as-synthesized 1/1-CaO(P)-700 and commercial CaO-700 as depicted in Fig. 8 . In a typical reaction, the mixture consisting of 1mol rapeseed oil (960 g mol − 1 ), 1mol methyl acetate and 8 mol anhydrous methanol were magnetically stirred in a 65 ℃ water bath with the participation of the commercial CaO-700 or 1/1-CaO(P)-700 (10 wt%). As shown, over 3 h, the FAME yield over templated 1/1-CaO(P)-700 material can be obtained more than 90% which is better than over commercial CaO with less than 80%. It indicates that the templated CaO(P) material provides more active sites which providing a great opportunity to increase the rate of transesterification reaction. 3.2.2 Effect of preparation parameters on FAME yield The yield of no-glycerol biodiesel generally refers to the content of fatty acid methyl ester (FAME) that determined over a gas chromatography by testing for the product. Accordingly, the FAME yield is an important parameter for the catalytic performance of solid base. Calcination, as the most critical step in preparation of templated CaO(P), is the most significant step affecting its catalytic performance reflected in the strength of alkalinity, phase composition and pore size distribution. The chemical and physical properties of FAME are shown in Table 5 . The effect of resulting CaO(P) samples calcinated in range from 600–800 ℃ on FAME yield had been seen in Fig. 9 (a), implying that the catalytic performance of 1/1-CaO(P)-700 was effective, which was due to the formation of dispersed CaO from lower calcination temperature, however, the reduction of the specific surface area (SSA) on catalyst surface for agglomeration and sintering over higher calcination temperature [ 32 ] . Simultaneously, the transesterification was carried out in 1/1/8 (oil/ester/alcohol) mixture under stirring for 3 h, which showed that the addition of 10 wt% 1/1-CaO(P)-700 resulted in a considerable increase in FAME yield (92.69%) at 65 ℃. Nevertheless, the catalytic behaviors of 1/1-CaO(P)-600 and1/1-CaO(P)-800 were obviously weakened, yielding to no-glycerol biodiesel of 2.23% and 85.65%, respectively. Table 5 Fuel properties of FAME Properties Test method EN14214 Relative density, 298 K 0.89 0.86–0.90 Viscosity, 313 K (mm 2 /s) 4.6 3.5–5.0 Flashpoint (K) 437 > 373 Ester content (%) 91.8–99.8 96.5 Free glycerol (%, m/m) 0.018 < 0.02 To determine the optimum mole ratio of nitrate and sodium carbonate of CaO(P), the effect of the amount of sodium carbonate on FAME yield was visualized as shown in Fig. 9 (b). As shown, the catalytic effect of CaO(P) (dosage: 10 wt%) in the mixed solvent (1/1/8 rapeseed oil-methyl acetate-methanol) increased from 74.69–92.69% after 3h at 65℃, which attributed that a growing number in sodium carbonate was conducive to the formation of more active ingredients such as CaO. Besides, it should be noted that the FAME yield over 1/1.5-CaO(P)-700 could only reach 73.80% (Fig. 9 (b)) due to the accumulation of a large amount of calcium salt deposits on the template, which further affecting the porous structure of the obtained solid base CaO(P). 3.2.3 Effects of reaction parameters on FAME yield The amount of templated CaO(P) had a significant effect on catalytic efficiency of transesterification, which was investigated in Fig. 10 (a). It was observed that the variation of FAME yield at different dosages of 1/1-CaO(P)-700 sample in presence of mixed solution composed of 1/1/8 oil/methyl acetate/methanol at 65 ℃ for 3 h. As expected, the FAME yield grew from 12.25–92.69% as the number of CaO(P) increased from 5 wt% to 10 wt%, which was in agreement with other reported studies that more provision of active sites resulted in the easier attraction of triglyceride molecules and methanol to recombination [ 33 ] . On the contrary, an excess of added CaO(P) will make the catalytic effect reduce greatly, which was related to the increase in the viscosity of the reaction and the generation of side reactions such as saponification, expressed in the yield of 54.31% at 15 wt% CaO(P) [ 34 ] . In conclusion, the following series of experimental research will be conducted at the addition of 10 wt% CaO(P). Within these selected parameters, the reaction temperature, as a representative, affecting FAME yield was especially prominent, and the positive correlation relationship between FAME yield and reaction temperature in certain range was available due to its classification of endothermic reaction [ 36 ] . In this section, the empirical results proposed in Fig. 10 (b) are cited to determine the optimal value of reaction temperature. Comparison of the measured curves of 10 wt% 1/1-CaO(P)-700 in three mixed reagents (1/1/8: oil/methyl acetate/methanol) under 60 ℃, 65 ℃, 70 ℃, respectively, it can be observed that the FAME yield can reach 92.69% after 3 h under 65 ℃, nevertheless, methanol could be vaporized to its lower content in the solution under higher reaction temperature (70 ℃), which was detrimental to the forward movement of the equilibrium reaction [ 37 ] , resulting in a decrease in the yield of biodiesel, expressed as 81.60%. Contrary to traditional injected quantity of methanol with 1/3 mol L − 1 ratio of oil/alcohol, methanol were customarily arranged by overdose, reflected 1/15 mol L − 1 ratio. The varied molar ratio of oil-methyl acetate-methanol were examined under optimized factors containing temperature of 65 ℃ and the dosage of 10 wt%, executed by 1/1-CaO(P)-700, which were shown in Fig. 10 (c). Since the increase in the amount of methanol for the reversible esterification reaction contributed to increase the reaction rate and accelerate the reaction process, it can be seen that the FAME yield shot up to 92.69% at 1/1/8. However, the ratio was increased to 1/1/10, the FAME yield decreased to 44.15% due to dilution caused by large amounts of methanol [ 38 ] . 3.2.4 Reutilization experiments The reusable property of commercial CaO and 10 wt.% CaO(P) was investigated under the optimum reaction condition (Fig. 11 ). The results showed that, the yield of FAME over the modified catalyst was enhanced to nearly 95%. The catalyst maintained sustaining activity even after being used for six cycles and the FAME yield slightly decreased due to the sensitivity of the catalyst to water and/or CO 2 in the reaction. 4. CONCLUSION In this paper, a kind of hierarchically porous solid base CaO(P) catalyst was prepared from pollen as template by using a mixed solution of calcium nitrate and sodium carbonate as a precursor through chemical precipitation. Its catalytic performance in tri-component coupling transesterification (rapeseed oil-methyl acetate-methanol), where the yield of no-glycerol biodiesel was investigated. It was found that the as-obtained CaO(P) catalyst calcined at 700 ℃ and impregnated in 1/1 molar ratio of calcium nitrate to sodium carbonate had favorable catalytic behavior, yielding to no-glycerol biodiesel of 92.69% when the reaction was carried out in mixed reagents of 1/1/8 oil/methyl acetate/methanol at 65 ℃ for 3 h and the CaO(P) dosage of 10 wt%, which suggested remarkable achievements in practice. Furthermore, a series of analysis, such as BET, XRD, FT-IR, TG, SEM, were employed to study the structure and morphology of templated CaO(P), which revealed that CaO(P) had better thermal stability, as well as the broad porous distribution with micro-mesoporous, which was promising alternatives in mass transportation in this heterogeneous reaction and then enhancing the no-glycerol biodiesel manufacture. Declarations Acknowlege The work was supported financially by the National Natural Science Foundation of China (51974252), Scientific Research Program Funded by Shaanxi Provincial (Program No. 2023-YBGY-052) and the Youth Innovation Team of Shaanxi University. And we thank the work of Modern Analysis and Testing Center of Xi'an Shiyou University. References Hong H, Wang M, Zhang X, et al. Projection of energy use and greenhouse gas emissions by motor vehicles in China: Policy options and impacts[J]. Energy Policy, 2012, 43: 37–48. Roy MM, Islam MS, Alam MN. 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Synthesis of hierarchical MgO based on a cotton template and its adsorption properties for efficient treatment of oilfield wastewater[J]. RSC Advances, 2020, 10(48): 28695–28704. Yuan CZ, Zhang XG, et al. Synthesis and electrochemical capacitance of mesoporous Co(OH) 2 [J]. Materials Chemistry & Physics, 2007, 101(1): 148–152. Knk A, Sns B, Csak C. Optimization and kinetic study of biodiesel production from Hydnocarpus wightiana oil and dairy waste scum using snail shell CaO nano catalyst[J]. Renewable Energy, 2020, 146: 280–296. Mar WW, Somsook E. Methanolysis of soybean oil over KCl/CaO solid base catalyst for biodiesel production[J]. Scienceasia, 2012, 38(1): 90–94. Wong YC, Tan YP, et al. Effect of calcination temperatures of CaO/Nb 2 O 5 mixed oxides catalysts on biodiesel production[J]. Sains Malaysiana, 2014, 43(5): 783–790. Sutrisno B, Nafiah AD, Fauziah IS. CaO/Natural dolomite as a heterogeneous catalyst for biodiesel production[C]. Materials Science Forum, 2020, 6079: 117–122. Tan KT, Lee KT, Nohamed AR. Optimization of supercritical dimethyl carbonate (SCDMC) technology for the production of biodiesel and value-added glycerol carbonate[J]. Fuel, 2010, 89: 3833–3839. Shi AP, Zhu JM, Ma Q. Biodiesel preparation with solid base catalyst under ultrasonic assistant[J]. Applied Mechanics & Materials, 2014, 548: 158–163. Kaur N, Ali A. One-pot transesterification and esterification of waste cooking oil via ethanolysis using Sr:Zr mixed oxide as solid catalyst[J]. RSC Advances, 2014, 4(82): 43671–43681. Dianursanti, Delaamira M, Bismo S. Effect of Reaction Temperature on Biodiesel Production from Chlorella vulgaris using CuO/Zeolite as Heterogeneous Catalyst[J]. IOP Conference Series: Earth and Environmental Science, 2017, 55(1): 012033. Kojima Y, Takai S. Transesterification of vegetable oil with methanol using solid base catalyst of calcium oxide under ultrasonication[J]. Chemical Engineering and Processing, 2018, 136. Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Major Revisions Needed 11 Apr, 2024 Reviewers agreed at journal 30 Mar, 2024 Reviewers invited by journal 29 Mar, 2024 Editor assigned by journal 28 Mar, 2024 First submitted to journal 24 Mar, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4159944","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":285522105,"identity":"398bea98-c74d-437c-8349-441d438d7162","order_by":0,"name":"ying tang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+UlEQVRIiWNgGAWjYNACAwYG++PNB6C8BPyKeWBaGM4cgyklSgsI3MgxIE6LPfvZw695Cu7YNfac+Sb5s+0wAz87UO/PHXhs4clLs+YxeJbczN672ZgXqEWy540BY+8ZfA7LMTPmMTiczMZzduNjRqAWA6ALmRnb8GjhfwPRwiOR8+AgyGH2BLVI5Bg/Bmqxk5DIYXwAcpiBBCEtN96YMc4xOJxgwHPM2JjnXDqPxJlnBQd78Whh788x/vDmz2F7A/bmZ5I/yqzl+NuTNz74iUcLELBJASMnsQHEZGSDRNQBvBoYGJg//gDGD4T9h4DaUTAKRsEoGJEAAIdpUXLpNrEKAAAAAElFTkSuQmCC","orcid":"","institution":"Xi'an Shiyou University","correspondingAuthor":true,"prefix":"","firstName":"ying","middleName":"","lastName":"tang","suffix":""},{"id":285522106,"identity":"5720bb5f-18aa-47a5-9acb-22eeb1ba6333","order_by":1,"name":"Meng Li","email":"","orcid":"","institution":"Xi'an Shiyou University","correspondingAuthor":false,"prefix":"","firstName":"Meng","middleName":"","lastName":"Li","suffix":""},{"id":285522107,"identity":"16064eda-6f27-43d9-a93e-a3a1ffe323e2","order_by":2,"name":"Guangtao Li","email":"","orcid":"","institution":"Xi'an Shiyou University","correspondingAuthor":false,"prefix":"","firstName":"Guangtao","middleName":"","lastName":"Li","suffix":""},{"id":285522108,"identity":"d5f47786-81de-4caf-af38-7652652922ea","order_by":3,"name":"Yi Yang","email":"","orcid":"","institution":"Xi'an Shiyou University","correspondingAuthor":false,"prefix":"","firstName":"Yi","middleName":"","lastName":"Yang","suffix":""},{"id":285522109,"identity":"f6cead33-fc1a-49a5-aacb-39e9f675bc98","order_by":4,"name":"Ying Yang","email":"","orcid":"","institution":"Xi'an Shiyou University","correspondingAuthor":false,"prefix":"","firstName":"Ying","middleName":"","lastName":"Yang","suffix":""}],"badges":[],"createdAt":"2024-03-25 01:36:23","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4159944/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4159944/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":54106592,"identity":"18bb551e-069a-4695-9582-7a6c4810976d","added_by":"auto","created_at":"2024-04-04 17:22:42","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":55469,"visible":true,"origin":"","legend":"\u003cp\u003eThe preparation pollen-derived CaO\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-4159944/v1/4e4244f8dd840f584447bde5.png"},{"id":54106599,"identity":"2d826835-7edf-41c1-9f15-cd382e7644cd","added_by":"auto","created_at":"2024-04-04 17:22:42","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":15147,"visible":true,"origin":"","legend":"\u003cp\u003e\u0026nbsp;a) the calcination temperature; b) the mole ratio of nitrate and sodium carbonate\u003c/p\u003e\n\u003cp\u003e. the N\u003csub\u003e2\u003c/sub\u003e-adsorption-desorption isotherms and pore-size distributions (PSD) of the synthesized CaO(P) samples\u003c/p\u003e","description":"","filename":"F2.png","url":"https://assets-eu.researchsquare.com/files/rs-4159944/v1/279ab7ffa0afef1ddf130c5e.png"},{"id":54106595,"identity":"32b9f1a4-ef5d-4f12-827d-1bba3e5ef4a7","added_by":"auto","created_at":"2024-04-04 17:22:42","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":9555,"visible":true,"origin":"","legend":"\u003cp\u003eXRD patterns of the synthesized CaO(P) samples\u003c/p\u003e\n\u003cp\u003ea) the calcination temperature; b) the mole ratio of nitrate and sodium carbonate\u003c/p\u003e","description":"","filename":"F3.png","url":"https://assets-eu.researchsquare.com/files/rs-4159944/v1/7e85d9ef4118a812aa7d0c21.png"},{"id":54107701,"identity":"71318b62-1b60-48d1-a9eb-8b0dd1b90830","added_by":"auto","created_at":"2024-04-04 17:30:42","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":12815,"visible":true,"origin":"","legend":"\u003cp\u003eFT-IR spectras of the synthesized CaO(P) samples\u003c/p\u003e\n\u003cp\u003ea) the calcination temperature; b) the mole ratio of nitrate and sodium carbonate\u003c/p\u003e","description":"","filename":"F4.png","url":"https://assets-eu.researchsquare.com/files/rs-4159944/v1/ec24b30eed7bca3361b53619.png"},{"id":54106602,"identity":"783e8c3b-bd70-4721-98ed-764792cb1ead","added_by":"auto","created_at":"2024-04-04 17:22:43","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":18128,"visible":true,"origin":"","legend":"\u003cp\u003eTG curves of the synthesized CaO(P) samples\u003c/p\u003e\n\u003cp\u003ea-b) the calcination temperature; c-d) the mole ratio of nitrate and sodium carbonate\u003c/p\u003e","description":"","filename":"F5.png","url":"https://assets-eu.researchsquare.com/files/rs-4159944/v1/5f582b07cc7efb34a35cf873.png"},{"id":54108783,"identity":"771f8966-62dd-4c4c-937d-495d170ca791","added_by":"auto","created_at":"2024-04-04 17:38:42","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":10269,"visible":true,"origin":"","legend":"\u003cp\u003eCO\u003csub\u003e2\u003c/sub\u003e-TPD curves of the synthesized CaO(P)\u003c/p\u003e\n\u003cp\u003ea) calcination conditions; b) the mole ratio of nitrate and sodium carbonate\u003c/p\u003e","description":"","filename":"F6.png","url":"https://assets-eu.researchsquare.com/files/rs-4159944/v1/b675933599b369ac3e4ee4cf.png"},{"id":54106600,"identity":"59e68e7e-2c8c-41d5-8197-8e017b65892d","added_by":"auto","created_at":"2024-04-04 17:22:42","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":546868,"visible":true,"origin":"","legend":"\u003cp\u003eSEM pictures of the synthesized CaO(P) samples\u003c/p\u003e\n\u003cp\u003ethe original pollen; b) pretreated pollen; c) 1/1-CaO(P)-600; d) 1/1-CaO(P)-700;\u003c/p\u003e\n\u003cp\u003ee) 1/1-CaO(P)-800; f) 1/0.5-CaO(P)-700; g) 1/1.5-CaO(P)-700 ; h) commercial CaO\u003c/p\u003e","description":"","filename":"F7.png","url":"https://assets-eu.researchsquare.com/files/rs-4159944/v1/7d1e3f7a3e89571cfa6401a7.png"},{"id":54106593,"identity":"9f9f3e4c-989b-4e9e-8325-092c0a3f79e9","added_by":"auto","created_at":"2024-04-04 17:22:42","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":7991,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of templated 1/1-CaO(P)-700 and commercial CaO-700\u003c/p\u003e","description":"","filename":"F8.png","url":"https://assets-eu.researchsquare.com/files/rs-4159944/v1/003e06d0992f002779d385f1.png"},{"id":54106597,"identity":"3630279b-6258-413c-975c-ba0268e3dc4a","added_by":"auto","created_at":"2024-04-04 17:22:42","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":7122,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of templated CaO(P) preparation parameters on yield\u003c/p\u003e\n\u003cp\u003ea) the calcination temperature; b) the mole ratio of nitrate and sodium carbonate\u003c/p\u003e","description":"","filename":"F9.png","url":"https://assets-eu.researchsquare.com/files/rs-4159944/v1/e7085d4ceaaa9100736c8b45.png"},{"id":54106601,"identity":"b52827b4-bcb0-4f4a-8cab-c1ff3df78230","added_by":"auto","created_at":"2024-04-04 17:22:43","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":11804,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of reaction parameters on FAME yield\u003c/p\u003e\n\u003cp\u003ea) the catalyst amount; b) the reaction temperature; c) the oil/ester/alcohol ratio\u003c/p\u003e","description":"","filename":"F10.png","url":"https://assets-eu.researchsquare.com/files/rs-4159944/v1/398da084208e6f86e3cf53b0.png"},{"id":54106598,"identity":"1b1ae0d4-7b28-4387-b61b-12d250bc4862","added_by":"auto","created_at":"2024-04-04 17:22:42","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":3704,"visible":true,"origin":"","legend":"\u003cp\u003eFAME yield upon transesterification of rapeseed oil for repeated use of commercial CaO and 10 wt.% CaO(P) at a reaction temperature of 65 ℃, a reaction time of 3 h, and a oil: methyl acetate: methanol ratio of 1:1:8\u003c/p\u003e","description":"","filename":"F11.png","url":"https://assets-eu.researchsquare.com/files/rs-4159944/v1/091b450987197217031c43cd.png"},{"id":54109614,"identity":"54a0ae68-0716-4299-96b7-a0eb1bcb7d70","added_by":"auto","created_at":"2024-04-04 17:46:43","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1035277,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4159944/v1/e2fa1ee2-2414-4b65-865a-3c53f5091d51.pdf"}],"financialInterests":"","formattedTitle":"Efficient preparation of no-glycerol biodiesel by tri-component coupling transesterification catalyzed over pollen-derived CaO","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eDemand for the dieselization of vehicles has grown steadily due to the innovation of fuel market, which makes the promotion and development of diesel industry a focus attention\u003csup\u003e[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]\u003c/sup\u003e. As a model of biomass energy in the new era, biodiesel enjoys dual merits, not only socially but also economically, ranging from avoiding price fluctuations caused by traditional non-renewable fuels to achieving structural energy-saving and emission-reduction benefits\u003csup\u003e[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]\u003c/sup\u003e. However, the commercial petrochemical-diesel fuels are mainly derived from crude oil through a series of process methods such as distillation, catalytic cracking, thermal cracking, hydrocracking, and petroleum coking. Most of them are divided into hydrocarbons with carbon chain length concentrated between 12 and 25, which has the two major ailments of high sulfur and high nitrogen, severely shaking the construction of ecological civilization, especially its impact on the atmospheric environment \u003csup\u003e[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e][\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eAt present, the most common theory about biodiesel synthesis is based on the transesterification reaction developed by the two chemicals of triglyceride (TG) and methanol (MeOH)\u003csup\u003e[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]\u003c/sup\u003e. The as-synthetized biodiesel is of a low-carbon higher fatty acid composed of C, H and O, also known as the fatty acid methyl esters (FAME) with carbon chain lengths ranging from 16 to 20\u003csup\u003e[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e. However, the generation of substantial low value-added glycerol could be found in the traditional synthesis technology. Therefore, the secondary utilization of glycerin resources has attracted extensive attention of the majority of researchers\u003csup\u003e[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]\u003c/sup\u003e by addition of the novel ester reagents to removal of by-product of glycerol\u003csup\u003e[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]\u003c/sup\u003e. In the common crafts, the assistance of homogeneous alkali (such as NaOH, KOH) or acid reagents (H\u003csub\u003e3\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e, H\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e) have been generally required, but the addition of such substances cause a consequence for the corrosion of equipment\u003csup\u003e[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e][\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/sup\u003e. The commodity oils could be obtained after neutralization, leading to the generation of the countless industrial wastewater, which does not accord well with the requirements of environmental catalysis. Calcium oxide with stronger alkalinity, low cost and low solubility in methanol, is one type of the potential alkaline earth metal oxides (H\u003csub\u003e\u0026minus;\u003c/sub\u003e value: 10.1\u0026ndash;11.1), which is a solid base with commercial value and industrial prospects\u003csup\u003e[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]\u003c/sup\u003e. Therefore, the development of a green and efficient synthetic route for highly dispersed calcium oxide is of profound significance to solve the problem of energy shortage.\u003c/p\u003e \u003cp\u003eIn recent years, templates have attracted great attention for the prepare porous materials with uniform particle and well dispersion by controlling the growth of crystalline by preventing active species aggregation even under high calcination temperature during the removal process of template\u003csup\u003e[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]\u003c/sup\u003e. In addition to physical and chemical templates, a great deal of biologically functional tissues from nature could also provide new inspiration for modern material science and chemical reactions, ranging from insect wings, pollen grains, plant fiber, paper and eggshell membranes to bacteria, DNA, viruses, etc\u003csup\u003e[\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]\u003c/sup\u003e. Pollen has a rich porous structure and large specific surface area, and its outer wall has reticulated cavities with a large amount of proteins and phospholipids, which are easy to attach precursors and provide a medium for the doping of heteroelements\u003csup\u003e[\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u003c/sup\u003e. It has been reported in the literature that many plants such as sunflower, pine, lotus flower and camellia were used as templates to prepare porous materials\u003csup\u003e[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]\u003c/sup\u003e. The precipitation method is one of the most common ways in preparing solid catalysts, which refers to the employment of the precipitation agent (NaOH, Na\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e) in the aqueous solution containing the metal salt under the control of a certain temperature and pH, to the formation of metal salt precipitation, such as hydrous oxide, carbonate crystals or gels. Subsequently, the as-obtained powder could be obtained by a series of processes, such as wash, dry, calcination\u003csup\u003e[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eSince the critical factor in the synthesis of solid base materials is to tailor and control dispersion, the aim of the present paper is to develop the precipitation approach based on pollen to prepare high dispered CaO for enhanced no-glycerol biodiesel preparation by tri-component coupling transesterification. Meanwhile, the templated CaO(P) was also characterised to reveal its structure and properties.\u003c/p\u003e"},{"header":"2. MATERIALS AND METHODS","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Chemicals and materials\u003c/h2\u003e \u003cp\u003eAll analytical chemicals reagent related to catalyst synthesis and biodiesel preparation such as CH\u003csub\u003e3\u003c/sub\u003eCOOCH\u003csub\u003e3\u003c/sub\u003e (Kelon Co., Chengdu, China), CH\u003csub\u003e3\u003c/sub\u003eOH (Fuyu Co., Tianjin, China), NaOH (Tianli Co., Tianjin, China), C\u003csub\u003e6\u003c/sub\u003eH\u003csub\u003e12\u003c/sub\u003e (Tianli Co., Tianjin, China), C\u003csub\u003e18\u003c/sub\u003eH\u003csub\u003e38\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e (TCI Co., Shanghai, China), C\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e5\u003c/sub\u003eOH (Fuyu Co., Tianjin, China), Ca(NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026middot;4H\u003csub\u003e2\u003c/sub\u003eO (Damao Co., Tianjin, China), Na\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e ( Beilian Co., Tianjin, China) had no further treatment. Rapeseed oil as raw material was obtained from Jianxing Co., Shanxi, China. The chemical and physical properties of rapeseed oil are shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The broken rape pollen (diameter of 30\u0026ndash;40 \u0026micro;m, density of 0.6\u0026thinsp;~\u0026thinsp;1.0 g/cm\u003csup\u003e3\u003c/sup\u003e) was obtained from Changge Yanyuan Bee Products Co., Ltd. Commercial CaO was purchased from Kermel Co., Ltd.\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\u003eProperties of rapeseed oil\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eProperties\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003ewt %\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSaturated C16 fatty acid\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.7\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSaturated C18 fatty acid\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUnsaturated C16:1 fatty acid\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e61.6\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUnsaturated C18:2 fatty acid\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e21.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eUnsaturated C18:3 fatty acid\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDensity (kg/m\u003csup\u003e3\u003c/sup\u003e )\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e878\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKinematic viscosity (mm\u003csup\u003e2\u003c/sup\u003e /s)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.13\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Catalyst preparation\u003c/h2\u003e \u003cp\u003eThe rape pollen (60 g) was cleaned by anhydrous alcohol (90 g) for 1 h under ultrasound for further experiments \u003cb\u003e(step 1)\u003c/b\u003e. The CaO(P) preparation was carried out by precipitation approach as suggested as follow: 20 g processed pollen was added into calcium nitrate solution (1 mol/L 100 mL) under stirring. After 3 h the suspension was obtained and heated to 70 ℃, and then sodium carbonate solution with the different molar mass as calcium nitrate was added into suspension under continuous stirring and controlled temperature (70 ℃) for the formation of calcium carbonate \u003cb\u003e(step 2)\u003c/b\u003e, following by centrifugation, washing, drying, calcination to obtain solid base CaO(P) \u003cb\u003e(step 3)\u003c/b\u003e as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The templated CaO(P) were assigned to X-CaO(P)-Y, where \"X\" was the mole ratio of calcium nitrate to sodium carbonate, \"Y\" was symbol of the calcination temperature, as well as the expression of \"P\" was referred to the precipitation method.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Experimental process\u003c/h2\u003e \u003cp\u003eThe solid base CaO(P) were well distributed in flask equipped with a mixture of refined rapeseed oil, methyl acetate, and methanol at moderate temperature (65 ℃) under a magnetic stirrer and reflux for 3.5 h, following by centrifugation and rotary evaporation to complete the preparation of no-glycerol biodiesel.\u003c/p\u003e \u003cp\u003eThe yield of FAME in different periods (20, 40, 60, 90, 120, 150, 180 and 210 min) was measured using a GC-7860 gas chromatograph with KB-Wax capillary column (30 m\u0026times;0.32 mm\u0026times;0.25 \u0026micro;m) and a flame ionization detector (FID). The temperature program is as follows: the temperature gradient in the range of 100\u0026ndash;200 ℃ with heating rate of 20 ℃ min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for 3 min and then increased in the range of 200\u0026ndash;220 ℃ with heating rate of 10 ℃ min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for 3 min. At last, the temperature gradient was in the range of 220\u0026ndash;240 ℃ with the heating rate of 10 ℃ min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for 3 min. In the investigation of catalytic performance,calcination temperature, mole ratio of nitrate and sodium carbonate,CaO(P) dosage, reaction temperature and ratio of oil, ester, alcohol were presented in detail because of their significant effects on the catalytic capacity. The calculation results of FAME yield was measured in accordance with algorithm (1) to determine the optimum conditions for obtaining CaO(P), where \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\sum {{A_i}}\\)\u003c/span\u003e\u003c/span\u003e, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({A_{MH}}\\)\u003c/span\u003e\u003c/span\u003e, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({C_{MH}}\\)\u003c/span\u003e\u003c/span\u003e (1mg mL\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({V_{MH}}\\)\u003c/span\u003e\u003c/span\u003e (1 \u0026micro;L) are a symbol of the peak area of the all FAME, the peak area of methyl heptadecanoate, the concentration of the methyl heptadecanoate, the injection volume, respectively. \u003cspan class=\"InlineEquation\"\u003e\u003c/span\u003e(mg) is of the quality of product oil.\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$yield\\left( \\% \\right)=\\left[ {\\frac{{\\left( {\\sum {{A_i} - {A_{MH}}} } \\right)}}{{{A_{MH}}}}} \\right]\\frac{{{C_{MH}}{V_{MH}} \\times 100}}{W}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Reusability\u003c/h2\u003e \u003cp\u003eThe reusability of 10 wt.% CaO(P) was investigated at same react condition by repeating the transesterification reaction several times with used catalysts. After each reaction, Catalysts were separated from the previous reaction mixture by centrifugation, washed with hexane, and then introduced into the fresh substrates after drying at 60 ℃.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Catalyst characterization\u003c/h2\u003e \u003cp\u003eThe more structure details about templated CaO(P) were characterized by various characterization techniques. By employment of Micromeritics ASAP 2020 HD88, the BET surface areas and pore size distribution (PSD) of the CaO(P) were measured based on BET equation and BJH model\u003csup\u003e[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]\u003c/sup\u003e. It was noted that the thermal properties in range of 25 ℃-800 ℃ of the CaO(P) were collected by TGA-SDTA851 analyzer\u003csup\u003e[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e. As shown by FT-IR spectras of the CaO(P) in the wavenumber range of 4000\u0026thinsp;\u0026minus;\u0026thinsp;500 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e were recorded on Nicolet 5700 by means of KBr pellet technique\u003csup\u003e[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]\u003c/sup\u003e. Finally, the SEM pictures and XRD patterns (2\u003cem\u003eθ\u003c/em\u003e:10\u0026deg;⁓80\u0026deg;) of the CaO(P) were presented, where they were performed by using JSM-6390A\u003csup\u003e[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]\u003c/sup\u003e and D8 ADVAHCL with Cu-K\u003csub\u003eα\u003c/sub\u003e radiation of 40 kV and 30 mA\u003csup\u003e[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. RESULTS AND DISCUSSION","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n \u003ch2\u003e3.1 Characterization of catalysts\u003c/h2\u003e\n \u003cdiv id=\"Sec10\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.1 BET analysis\u003c/h2\u003e\n \u003cp\u003eFor the Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e and Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e(a-b), it was depicted the textural details of pores from as-obtained templated CaO(P) calcined in various temperatures range from 600 to 800 ℃ and the mole ratios of nitrate to sodium carbonate(n(Ca\u003csup\u003e2+\u003c/sup\u003e):n(Na\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e)) between 1/0.5-1/1.5. It was seen that the calcination temperature had been an important factor for the textural performance of CaO(P) by showing that the BET surface area, pore volume, pore size keep an increase tendency from 10.5682 to 14.9162 m\u003csup\u003e2\u003c/sup\u003e/g, 0.0273 to 0.0446 cm\u003csup\u003e3\u003c/sup\u003e/g, 10.3537 to 11.9584 nm, respectively, as the calcination temperature changed from 600 to 700 ℃. However, with the increased calcination temperature to 800 ℃, the textural parameters declined as presented by BET surface area of 13.033 m\u003csup\u003e2\u003c/sup\u003e/g and pore volume of 0.0411 cm\u003csup\u003e3\u003c/sup\u003e/g, which attributed the sintering of CaO(P) surface and the reduction in mesopores numbers as shown in Fig. \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\n \u003cp\u003eCaO(P) obtained under different calcination conditions were of a typical IV isotherm with a H3-type hysteresis loop (P/P\u003csub\u003e0\u003c/sub\u003e\u0026gt;0.4) for interpretation of mesopore materials\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e6\u003c/span\u003e]\u003c/sup\u003e. It could be further confirmed by PSD results centered at 3.5 nm and 7 nm, indicating the generation of hierarchical structure. Besides, it was also found that 1/1-CaO(P)-700 had best BET surface area (14.916 m\u003csup\u003e2\u003c/sup\u003e/g) and pore volume (0.0446 cm\u003csup\u003e3\u003c/sup\u003e/g) which providing an extensive potential for efficient catalysis of no-glycerol biodiesel and suggested that the more sodium carbonate was to the disadvantage of the improvement to the textural properties due to the blockage of pore.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u0026nbsp;\u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003ePore structure properties of derived CaO(P) from different calcination temperature and commercial CaO\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eType of catalyst\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eBET surface area\u003c/p\u003e\n \u003cp\u003e(m\u003csup\u003e2\u003c/sup\u003e/g)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ePore volume\u003c/p\u003e\n \u003cp\u003e(cm\u003csup\u003e3\u003c/sup\u003e/g)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAverage pore diamete (nm)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1/1-CaO(P)-600\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e10.5682\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.027355\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e10.35372\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1/1-CaO(P)-700\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14.9162\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.044594\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e11.95842\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1/1-CaO(P)-800\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13.0337\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.041159\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e12.63141\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCommercial CaO-700\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e11.4456\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.032367\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e11.31162\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003cdiv align=\"char\" class=\"colspec\"\u003e\u003cbr\u003e\u003c/div\u003e\u0026nbsp;\u0026nbsp;\u003ctable id=\"Tab3\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003ePore structure properties of derived CaO(P) from different proportion of nitrate to sodium carbonate and commercial CaO\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eType of catalyst\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eBET surface area\u003c/p\u003e\n \u003cp\u003e(m\u003csup\u003e2\u003c/sup\u003e/g)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ePore volume\u003c/p\u003e\n \u003cp\u003e(cm\u003csup\u003e3\u003c/sup\u003e/g)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eAverage pore diamete (nm)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1/0.5-CaO(P)-700\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14.1560\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.042359\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e11.96927\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1/1-CaO(P)-700\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e14.9162\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.044594\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e11.95842\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1/1.5-CaO(P)-700\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e10.3449\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.024471\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e9.46190\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCommercial CaO-700\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e11.4456\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e0.032367\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e11.31162\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec11\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.2 XRD analysis\u003c/h2\u003e\n \u003cp\u003eTo further explore the effect of prepare conditions of as-obtained CaO(P) powder on its phase composition, the evaluations in this section were the position of diffraction peak of CaO (JCPDS 48-1467), Ca(OH)\u003csub\u003e2\u003c/sub\u003e (JCPDS 44-1481) and CaCO\u003csub\u003e3\u003c/sub\u003e (JCPDS 33\u0026ndash;0268)\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e29\u003c/span\u003e]\u003c/sup\u003e. The details of diffraction peaks of CaO(P) were presented in Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003e(a). It can be seen clearly that the calcinating temperature had positive impact on composition of CaO and Ca(OH)\u003csub\u003e2\u003c/sub\u003e for reasons of the carbonate decomposition. The crystal planes (111), (200), (202), (311) and (222), meanwhile, were observed at 2\u003cem\u003e\u0026theta;\u003c/em\u003e\u0026thinsp;=\u0026thinsp;32.21˚, 37.36˚, 53.86˚, 64.19˚ and 67.38˚ from 1/1-CaO(P)-700\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e30\u003c/span\u003e]\u003c/sup\u003e presented to CaO phase. Moreover, it can been found that the relatively sharp and intense diffraction peaks of CaO over 1/1-CaO(P)-700 indicated its better crystallite, while the broad peaks of the commercial CaO-700 indicated its smaller grain size and poor meso-macropore distribution according to the Scherrer formula (D\u0026thinsp;=\u0026thinsp;K\u0026lambda;/Bcos\u0026theta;). However, the relatively sharp diffraction peaks of CaO over 1/1-CaO(P)-800 was an indication of poor dispersion according to the Scherrer formula (D\u0026thinsp;=\u0026thinsp;K\u0026lambda;/Bcos\u0026theta;), which was due to the sintering surface and a decrease in specific surface area, suggesting that a proper calcination temperature was conducive to promote the dispersion of CaO particles so as to its catalytic performance to transesterification reaction. Furthermore, it can be found that the phase of CaCO\u003csub\u003e3\u003c/sub\u003e with poor catalytic activity can be discomposed completely when calcination temperature above 600\u003csup\u003eo\u003c/sup\u003eC which is well consistent with the thermal analysis result as shown in Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e. Meanwhile, it was found that the molar ratio of nitrate and sodium carbonate is also one of the important factors affecting the morphology, structure and composition of CaO(P) samples. As shown in Fig. \u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eb, with an incremental sodium carbonate (1/1.5-CaO(P)-700), the presence of CaCO\u003csub\u003e3\u003c/sub\u003e during the pyrolysis process under 700 ℃ to the worse catalytic performance on account of the weak conjugated base of CaCO\u003csub\u003e3\u003c/sub\u003e.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec12\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.3 FT-IR analysis\u003c/h2\u003e\n \u003cp\u003eFT-IR spectras measurements on the pyrolysed CaO(P) had offered the more detailed evidences to explain its thermal behavior. Typical FT-IR spectras, for 1/1-CaO(P)-600, 1/1-CaO(P)-700 and 1/1-CaO(P)-800 samples, were presented at Fig. \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e(a). It was encountered that the stretching vibrations of -OH at 3648 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003csub\u003e,\u003c/sub\u003e 3448 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1647 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e30\u003c/span\u003e]\u003c/sup\u003e, due to the hydroxyls groups from the physisorbed water molecules in materials. Meanwhile, the sharp-pointed bands of carbonate were seen from the wave number of 1459 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 871 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 713cm\u003csup\u003e\u0026minus;\u0026thinsp;1[\u003cspan class=\"CitationRef\"\u003e31\u003c/span\u003e]\u003c/sup\u003e. Further an advancement in calcinations temperature from 600 to 800 ℃, the intensity of two types of bands started getting a little smaller and weaker, which was due to the full thermal decomposition of generated precipitation CaCO\u003csub\u003e3\u003c/sub\u003e. Furthermore, the increasingly sharp vibration band of CO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e was observed in as-obtained 1/1-CaO(P)-600 sample, suggesting that the calcination temperature of 600\u003csup\u003eo\u003c/sup\u003eC was supposed to imcompletely remove carbonate. While it was significant to comprehend that the increased temperature (700 ℃) promoted to the ameliorated diffusivity leading to faster crystallization of CaO and then the shrinkage was prevented. Figure \u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e(b) shows that the CaO(P) samples calcined at 700 ℃with different sodium carbonate contents consist of CaO, Ca(OH)\u003csub\u003e2\u003c/sub\u003e and CaCO\u003csub\u003e3\u003c/sub\u003e, and it can be seen from the figure that sharp carbonate bands can be seen from the wave numbers of 1459 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 871 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 713 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, which become larger and stronger as the amount of sodium carbonate increases due to the generated more precipitate CaCO\u003csub\u003e3\u003c/sub\u003e.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec13\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.4 TG analysis\u003c/h2\u003e\n \u003cp\u003eTG and DTG curves of the as-synthesized CaO(P) samples after various calcination treatment were presented in Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e(a-b). It was observed that there were one major weightloss interval assigned to the pyrolyzation of CaCO\u003csub\u003e3\u003c/sub\u003e, which was visible in 510\u0026thinsp;~\u0026thinsp;790 ℃ with the weightloss value of 26%, 6% and 2%, expressed by 1/1-CaO(P)-600, 1/1-CaO(P)-700 and 1/1-CaO(P)-800, respectively. Conversely, commercial CaO-700 had two decomposition intervals corresponding to decomposed Ca(OH)\u003csub\u003e2\u003c/sub\u003e and CaCO\u003csub\u003e3\u003c/sub\u003e at 330\u0026thinsp;~\u0026thinsp;400 ℃ and 510\u0026thinsp;~\u0026thinsp;790 ℃, as well as the more weightlessness was observed (13%). For a series of CaO(P) materials derived from nitrate and sodium carbonate with mole ratio of 1/1 under different calcination temperatures, a shift to higher temperature could be seen with calcination temperature from 600 to 800 ℃, which maybe indicated the stronger stability as well as avoidance from the impact of the air. Certainly, the more obvious weight loss of CaCO\u003csub\u003e3\u003c/sub\u003e was observed (Fig. \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e(c-d)) due to sodium carbonate consumption. It should be mentioned, however, that the weightlessness of 1/0.5-CaO(P)-700, 1/1-CaO(P)-700 and 1/1.5-CaO(P)-700 were reflected in 4%, 6% and 13%. From the result it can be observed that all of sample can be transformed to CaO after calcined above 510 ℃ and an increase in the weightloss of CaCO\u003csub\u003e3\u003c/sub\u003e with the higher concentration of CaO(P) (calcium nitrate/sodium carbonate), due to the generation of more precipitation or severe corrosion by air. Therefore, the CaO(P) samples over an appropriate pyrolysis temperature (700 ℃) and the addition amount of sodium carbonate (1/1) was comparatively favourable to obtain well dispersion and stability CaO particles.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec14\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.5 CO\u003csub\u003e2\u003c/sub\u003e-TPD analysis\u003c/h2\u003e\n \u003cp\u003eThe CO\u003csub\u003e2\u003c/sub\u003e-TPD curves of CaO(P) under different calcination conditions are shown in Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e(a). It can be seen that the CO\u003csub\u003e2\u003c/sub\u003e-TPD curves with a single peak were presented by CaO(P), and the CO\u003csub\u003e2\u003c/sub\u003e-desorption temperature appeared around 700 ℃, suggesting that CaO(P) had strong basic site. When n(Ca\u003csup\u003e2+\u003c/sup\u003e):n(Na\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e)\u0026thinsp;=\u0026thinsp;1/1, the CO\u003csub\u003e2\u003c/sub\u003e-TPD curve of CaO(P) shifted to right and the peak area gradually increased so as to the highest total basicity (4.4795 mmol/g) as the calcination temperature increases from 600 ℃ to 700 ℃. However, it was found that the surface of the 1/1-CaO(P)-800 had 13.034m\u003csup\u003e2\u003c/sup\u003e/g (BET specific surface area) after sintering, which caused its total basicity to drop to 3.3697 mmol/g. As seen in Fig. \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e(b), it can be observed that when n(Ca\u003csup\u003e2+\u003c/sup\u003e)/n(Na\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e) increased from 1/0.5 to 1/1, the total basicity of CaO(P) were calculated to 4.0005 mmol/g and 4.4795 mmol/g, respectively, which was attributed to the hydrolysis of Na\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e in aqueous solution to generate CO\u003csub\u003e3\u003c/sub\u003e\u003csup\u003e2\u0026minus;\u003c/sup\u003e and OH\u003csup\u003e\u0026minus;\u003c/sup\u003e, followed by reaction with Ca\u003csup\u003e2+\u003c/sup\u003e to form CaCO\u003csub\u003e3\u003c/sub\u003e and Ca(OH)\u003csub\u003e2\u003c/sub\u003e, thus effectively avoiding the precipitation of Ca\u003csup\u003e2+\u003c/sup\u003e. Besides, the increase of BET specific surface area was beneficial to the change of total basicity as result of the increase of surface basic sites. A large amount of CaCO\u003csub\u003e3\u003c/sub\u003e and Ca(OH)\u003csub\u003e2\u003c/sub\u003e were produced on the pollen surface as n(Ca\u003csup\u003e2+\u003c/sup\u003e)/n(Na\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e) was 1/1.5, which reduced the BET specific surface area of 1/1.5-CaO(P)-700 to 10.345 m\u003csup\u003e2\u003c/sup\u003e/g so as to the decreased total basicity (1.3605 mmol/g). Therefore, 700 ℃ of calcination and 1/1 of n(Ca\u003csup\u003e2+\u003c/sup\u003e)/n(Na\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e) were selected as the optimal preparation conditions for CaO(P).\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u0026nbsp;\u003ctable id=\"Tab4\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eTotal basicity of CaO(P) and Commercial CaO-700\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eType of catalyst\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTotal basicity (mmol/g)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eDesorption peaks (area%)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1/1-CaO(P)-600\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e-\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1/1-CaO(P)-700\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.4795\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.0418\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1/1-CaO(P)-800\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.3697\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.7837\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1/0.5-CaO(P)-700\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.0005\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.9304\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1/1.5-CaO(P)-700\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.3605\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3164\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCommercial CaO-700\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.7903\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.1838\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec15\" class=\"Section3\"\u003e\n \u003ch2\u003e3.1.6 SEM analysis\u003c/h2\u003e\n \u003cp\u003eThe SEM pictures of the original pollen, pretreated pollen (Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e. (a-b)), synthesized CaO(P) samples (Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e. (b-g)), as well as commercial CaO prepared under 700 ℃ (Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e. (h)) had been shown. It was conspicuous that the microstructure of the original pollen was similar to ultrasonic treated pretreated pollen with germination holes and germination grooves. However, it was clearly seen that the collapse of the 3D structure after the high temperature pyrolysis. Figure \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e(c-e) depicts images of CaO(P) calcined in the temperature range of 600 ℃ to 800 ℃, where the degree of calcination agglomeration becomes increasingly apparent as the temperature increases. It can be seen that the samples calcined at 800\u0026deg;C were agglomerated and sintered on the surface so as to its relatively low yields, while at 600 ℃ and 700 ℃, the particle size distribution was uniform with good dispersion. Meanwhile, it was important to find the significant differences of morphology in the three templated CaO(P) pyrolysed calcined at 700\u0026deg;C from several mole ratio,1/0.5, 1/1 and 1/1.5 of nitrate to sodium carbonate, as presented in Fig. \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e. (f), (d) and (g). It was found that when the molar ratio were 1:0.5 and 1:1.5, the CaO crystal particles aggregated into lumps with poor dispersion at insufficient or excessive amount of sodium carbonate. The experimental results showed that the dispersion of CaO(P) particles were not only temperature dependent, but also the amount of sodium carbonate was a key factor, and it was observed that the best dispersion performance was obtained at 700 ℃ and 1/1.5.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\n \u003ch2\u003e3.2 No-glycerol biodiesel preparation\u003c/h2\u003e\n \u003cdiv id=\"Sec17\" class=\"Section3\"\u003e\n \u003ch2\u003e3.2.1 Comparison of catalytic properties\u003c/h2\u003e\n \u003cp\u003eInteresting distinctions of FAME yield regularity had been drawn between as-synthesized 1/1-CaO(P)-700 and commercial CaO-700 as depicted in Fig. \u003cspan class=\"InternalRef\"\u003e8\u003c/span\u003e. In a typical reaction, the mixture consisting of 1mol rapeseed oil (960 g mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), 1mol methyl acetate and 8 mol anhydrous methanol were magnetically stirred in a 65 ℃ water bath with the participation of the commercial CaO-700 or 1/1-CaO(P)-700 (10 wt%). As shown, over 3 h, the FAME yield over templated 1/1-CaO(P)-700 material can be obtained more than 90% which is better than over commercial CaO with less than 80%. It indicates that the templated CaO(P) material provides more active sites which providing a great opportunity to increase the rate of transesterification reaction.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec18\" class=\"Section3\"\u003e\n \u003ch2\u003e3.2.2 Effect of preparation parameters on FAME yield\u003c/h2\u003e\n \u003cp\u003eThe yield of no-glycerol biodiesel generally refers to the content of fatty acid methyl ester (FAME) that determined over a gas chromatography by testing for the product. Accordingly, the FAME yield is an important parameter for the catalytic performance of solid base. Calcination, as the most critical step in preparation of templated CaO(P), is the most significant step affecting its catalytic performance reflected in the strength of alkalinity, phase composition and pore size distribution. The chemical and physical properties of FAME are shown in Table \u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e. The effect of resulting CaO(P) samples calcinated in range from 600\u0026ndash;800 ℃ on FAME yield had been seen in Fig. \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e(a), implying that the catalytic performance of 1/1-CaO(P)-700 was effective, which was due to the formation of dispersed CaO from lower calcination temperature, however, the reduction of the specific surface area (SSA) on catalyst surface for agglomeration and sintering over higher calcination temperature\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e32\u003c/span\u003e]\u003c/sup\u003e. Simultaneously, the transesterification was carried out in 1/1/8 (oil/ester/alcohol) mixture under stirring for 3 h, which showed that the addition of 10 wt% 1/1-CaO(P)-700 resulted in a considerable increase in FAME yield (92.69%) at 65 ℃. Nevertheless, the catalytic behaviors of 1/1-CaO(P)-600 and1/1-CaO(P)-800 were obviously weakened, yielding to no-glycerol biodiesel of 2.23% and 85.65%, respectively.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\u0026nbsp;\u0026nbsp;\u003ctable id=\"Tab5\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eFuel properties of FAME\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eProperties\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eTest method\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eEN14214\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eRelative density, 298 K\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.89\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.86\u0026ndash;0.90\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eViscosity, 313 K (mm\u003csup\u003e2\u003c/sup\u003e /s)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.5\u0026ndash;5.0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFlashpoint (K)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e437\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026gt;\u0026thinsp;373\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eEster content (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e91.8\u0026ndash;99.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e96.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eFree glycerol (%, m/m)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.018\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u0026lt;\u0026thinsp;0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cp\u003eTo determine the optimum mole ratio of nitrate and sodium carbonate of CaO(P), the effect of the amount of sodium carbonate on FAME yield was visualized as shown in Fig. \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e(b). As shown, the catalytic effect of CaO(P) (dosage: 10 wt%) in the mixed solvent (1/1/8 rapeseed oil-methyl acetate-methanol) increased from 74.69\u0026ndash;92.69% after 3h at 65℃, which attributed that a growing number in sodium carbonate was conducive to the formation of more active ingredients such as CaO. Besides, it should be noted that the FAME yield over 1/1.5-CaO(P)-700 could only reach 73.80% (Fig. \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e(b)) due to the accumulation of a large amount of calcium salt deposits on the template, which further affecting the porous structure of the obtained solid base CaO(P).\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec19\" class=\"Section3\"\u003e\n \u003ch2\u003e3.2.3 Effects of reaction parameters on FAME yield\u003c/h2\u003e\n \u003cp\u003eThe amount of templated CaO(P) had a significant effect on catalytic efficiency of transesterification, which was investigated in Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e(a). It was observed that the variation of FAME yield at different dosages of 1/1-CaO(P)-700 sample in presence of mixed solution composed of 1/1/8 oil/methyl acetate/methanol at 65 ℃ for 3 h. As expected, the FAME yield grew from 12.25\u0026ndash;92.69% as the number of CaO(P) increased from 5 wt% to 10 wt%, which was in agreement with other reported studies that more provision of active sites resulted in the easier attraction of triglyceride molecules and methanol to recombination\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e33\u003c/span\u003e]\u003c/sup\u003e. On the contrary, an excess of added CaO(P) will make the catalytic effect reduce greatly, which was related to the increase in the viscosity of the reaction and the generation of side reactions such as saponification, expressed in the yield of 54.31% at 15 wt% CaO(P)\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e34\u003c/span\u003e]\u003c/sup\u003e. In conclusion, the following series of experimental research will be conducted at the addition of 10 wt% CaO(P).\u003c/p\u003e\n \u003cp\u003eWithin these selected parameters, the reaction temperature, as a representative, affecting FAME yield was especially prominent, and the positive correlation relationship between FAME yield and reaction temperature in certain range was available due to its classification of endothermic reaction\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e36\u003c/span\u003e]\u003c/sup\u003e. In this section, the empirical results proposed in Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e(b) are cited to determine the optimal value of reaction temperature. Comparison of the measured curves of 10 wt% 1/1-CaO(P)-700 in three mixed reagents (1/1/8: oil/methyl acetate/methanol) under 60 ℃, 65 ℃, 70 ℃, respectively, it can be observed that the FAME yield can reach 92.69% after 3 h under 65 ℃, nevertheless, methanol could be vaporized to its lower content in the solution under higher reaction temperature (70 ℃), which was detrimental to the forward movement of the equilibrium reaction\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e37\u003c/span\u003e]\u003c/sup\u003e, resulting in a decrease in the yield of biodiesel, expressed as 81.60%.\u003c/p\u003e\n \u003cp\u003eContrary to traditional injected quantity of methanol with 1/3 mol L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e ratio of oil/alcohol, methanol were customarily arranged by overdose, reflected 1/15 mol L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e ratio. The varied molar ratio of oil-methyl acetate-methanol were examined under optimized factors containing temperature of 65 ℃ and the dosage of 10 wt%, executed by 1/1-CaO(P)-700, which were shown in Fig. \u003cspan class=\"InternalRef\"\u003e10\u003c/span\u003e(c). Since the increase in the amount of methanol for the reversible esterification reaction contributed to increase the reaction rate and accelerate the reaction process, it can be seen that the FAME yield shot up to 92.69% at 1/1/8. However, the ratio was increased to 1/1/10, the FAME yield decreased to 44.15% due to dilution caused by large amounts of methanol\u003csup\u003e[\u003cspan class=\"CitationRef\"\u003e38\u003c/span\u003e]\u003c/sup\u003e.\u003c/p\u003e\n \u003c/div\u003e\n \u003cdiv id=\"Sec20\" class=\"Section3\"\u003e\n \u003ch2\u003e3.2.4 Reutilization experiments\u003c/h2\u003e\n \u003cp\u003eThe reusable property of commercial CaO and 10 wt.% CaO(P) was investigated under the optimum reaction condition (Fig. \u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003e). The results showed that, the yield of FAME over the modified catalyst was enhanced to nearly 95%. The catalyst maintained sustaining activity even after being used for six cycles and the FAME yield slightly decreased due to the sensitivity of the catalyst to water and/or CO\u003csub\u003e2\u003c/sub\u003e in the reaction.\u003c/p\u003e\n \u003c/div\u003e\n\u003c/div\u003e"},{"header":"4. CONCLUSION","content":"\u003cp\u003eIn this paper, a kind of hierarchically porous solid base CaO(P) catalyst was prepared from pollen as template by using a mixed solution of calcium nitrate and sodium carbonate as a precursor through chemical precipitation. Its catalytic performance in tri-component coupling transesterification (rapeseed oil-methyl acetate-methanol), where the yield of no-glycerol biodiesel was investigated. It was found that the as-obtained CaO(P) catalyst calcined at 700 ℃ and impregnated in 1/1 molar ratio of calcium nitrate to sodium carbonate had favorable catalytic behavior, yielding to no-glycerol biodiesel of 92.69% when the reaction was carried out in mixed reagents of 1/1/8 oil/methyl acetate/methanol at 65 ℃ for 3 h and the CaO(P) dosage of 10 wt%, which suggested remarkable achievements in practice. Furthermore, a series of analysis, such as BET, XRD, FT-IR, TG, SEM, were employed to study the structure and morphology of templated CaO(P), which revealed that CaO(P) had better thermal stability, as well as the broad porous distribution with micro-mesoporous, which was promising alternatives in mass transportation in this heterogeneous reaction and then enhancing the no-glycerol biodiesel manufacture.\u003c/p\u003e"},{"header":"Declarations","content":" \u003cp\u003e \u003cstrong\u003eAcknowlege\u003c/strong\u003e \u003cp\u003eThe work was supported financially by the National Natural Science Foundation of China (51974252), Scientific Research Program Funded by Shaanxi Provincial (Program No. 2023-YBGY-052) and the Youth Innovation Team of Shaanxi University. And we thank the work of Modern Analysis and Testing Center of Xi'an Shiyou University.\u003c/p\u003e \u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eHong H, Wang M, Zhang X, et al. Projection of energy use and greenhouse gas emissions by motor vehicles in China: Policy options and impacts[J]. Energy Policy, 2012, 43: 37\u0026ndash;48.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRoy MM, Islam MS, Alam MN. Biodiesel from crude tall oil and its NO\u003csub\u003ex\u003c/sub\u003e and aldehydes emissions in a diesel engine fueled by biodiesel-diesel blends with water emulsions[J]. Processes, 2021, 9(1): 126.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMansir N, Teo SH, Mijan NA, et al. Efficient reaction for biodiesel manufacturing using bi-functional oxide catalyst[J]. 2021, 149.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTang Y, Liu H, et al. 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Chemical Engineering and Processing, 2018, 136.\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":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"korean-journal-of-chemical-engineering","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"kjce","sideBox":"Learn more about [Korean Journal of Chemical Engineering](http://link.springer.com/journal/11814)","snPcode":"11814","submissionUrl":"https://www.editorialmanager.com/kjce/default2.aspx","title":"Korean Journal of Chemical Engineering","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Subscription","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Biodiesel, Rape pollen, Precipitation method, Tri-component coupling transesterification, CaO","lastPublishedDoi":"10.21203/rs.3.rs-4159944/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4159944/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eRape pollen with fishnet-like network structure has been used as support in the construction of high dispersion CaO materials assigned to CaO(P) (\"P\" was symbol of the precipitation method) via precipitation and it has been employed in the enhanced no-glycerol biodiesel preparation. The relatively excellent activity was observed by yielding to no-glycerol biodiesel of 92.69% in the rapeseed 1/1/8 mixture of oil-methyl acetate-methanol at 65 ℃ for 3 h over 10 wt% of 1/1-CaO(P)-700 (calcinated at 700 ℃ and immernated in 1/1 of calcium nitrate to sodium carbonate). Characterizations over the templated CaO(P) samples have been conducted by means of Brunauer-Emmett-Teller (BET),X-ray diffraction (XRD), Fourier transform- infrared (FT-IR) and scanning electron microscope (SEM), respectively. Based on the results, it can be found that the catalytic effect of templated CaO(P) was depend on both stronger basicity and enlarged micro-pore distribution which provide more sites for better catalysis.\u003c/p\u003e","manuscriptTitle":"Efficient preparation of no-glycerol biodiesel by tri-component coupling transesterification catalyzed over pollen-derived CaO","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-04-04 17:22:34","doi":"10.21203/rs.3.rs-4159944/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major Revisions Needed","date":"2024-04-11T11:00:49+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2024-03-30T16:41:29+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-03-30T00:35:47+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-03-28T06:08:22+00:00","index":"","fulltext":""},{"type":"submitted","content":"Korean Journal of Chemical Engineering","date":"2024-03-24T21:36:09+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"korean-journal-of-chemical-engineering","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"kjce","sideBox":"Learn more about [Korean Journal of Chemical Engineering](http://link.springer.com/journal/11814)","snPcode":"11814","submissionUrl":"https://www.editorialmanager.com/kjce/default2.aspx","title":"Korean Journal of Chemical Engineering","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Subscription","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"d025b932-7531-4593-9c10-21fb1541132a","owner":[],"postedDate":"April 4th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2024-06-25T10:08:54+00:00","versionOfRecord":[],"versionCreatedAt":"2024-04-04 17:22:34","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4159944","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4159944","identity":"rs-4159944","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}