Exploring the role of ester electron donors in ethylene polymerization using bi-supported SiO2@MgCl2/TiCl4 type Ziegler-Natta catalysts

Exploring the role of ester electron donors in ethylene polymerization using bi-supported SiO2@MgCl2/TiCl4 type Ziegler-Natta catalysts | 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 Exploring the role of ester electron donors in ethylene polymerization using bi-supported SiO 2 @MgCl 2 /TiCl 4 type Ziegler-Natta catalysts Hamidreza Teimoury, Nazanin Moeini This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6828388/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 28 Nov, 2025 Read the published version in Journal of Polymer Research → Version 1 posted 5 You are reading this latest preprint version Abstract This study aimed to explore the effects of ester-based internal electron donors on the efficacy and characteristics of SiO 2 @MgCl 2 bi-supported Ziegler-Natta (ZN) catalysts. Four distinct ester-based electron donors were used during catalyst synthesis, including linear diesters with varying carbon chain lengths (diethyl succinate and diethyl malonate), aromatic diesters (di-n-butyl phthalate), and aromatic monoesters (ethyl benzoate). Synthesized catalysts were employed in ethylene polymerizations using H 2 as molar mass moderator. Various analytical techniques and measurements of bulk density were employed to analyze the prepared catalysts and polymers. SEM analysis revealed that most catalyst particles had a spherical morphology, except for the catalyst incorporating malonate as internal electron donor. The phthalate catalyst showed a larger diameter, mainly due to its role as a binding agent. The molecular weight, activity, and bulk density of polyethylene were found to be influenced by the type of electron donors. The catalyst with SiO 2 @MgCl 2 /THF/TiCl 4 /ethyl benzoate exhibited significantly higher catalytic activity and hydrogen response, which can be attributed to the reduced steric hindrance surrounding the ethyl benzoate compound. These findings have implications for the development of more efficient and sustainable polymerization processes, with potential applications in various industries using polyethylene. Bi-supported Ziegler-Natta catalysts Ester electron donors ethylene polymerization Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Introduction Polyolefins are considered as the most widely used synthetic polymers worldwide which have an annual commercial turnover of USD 300 billion and a yearly production of over 180 million tons. The most widely used polyolefins include polyethylene and polypropylene, which account for 31.2% and 22.7%, respectively, of the global polymer market. Indeed, in today’s human life, their applications surpass imagination [ 1 , 2 ]. Approximately 70 years ago, Ziegler and his colleagues discovered the synthesis of polyethylene under relatively mild conditions, lower temperatures, and lower pressures than those of the radical polymerization in the presence of transition metal (mainly Ti, V, and Zr) compound and organoaluminium compounds as co-catalyst. Also, Natta and his coworker (in Polytechnic University of Milan) succeeded in the polymerization of propylene using the TiCl 3 -AlEt 2 Cl system. Over the past decade, Ziegler-Natta catalysts have undergone significant developments and are utilized as efficient catalysts in the polymerization of olefins in the industrial sectors [ 3 , 4 ]. This type of catalyst typically consists of a combination of TiCl 4 supported on MgCl 2 , along with electron donors and cocatalyst such as triethylaluminium. However, there is potential to modify the catalyst system by using different electron donors (Lewis base) such as ethyl benzoate [ 5 ], phthalate [ 6 ], diether [ 7 ], succinate [ 8 ], glutarates [ 9 ], maleates [ 10 ], malonates [ 11 ], ketoesters [ 12 ], imine [ 13 ] and tetrahydrofuran (THF) [ 14 ]. Electron donors are typically classified in two categories: internal donors (IDs) and external donors (EDs). IDs are incorporated during the synthesis of pre-catalyst, while external donors are added along with the AlR 3 activator in the polymerization stage. The purpose of external donors is to compensate for the partial loss of internal donors resulting from their reaction with AlR 3 [ 15 – 19 ]. Electron donors profoundly impact the characteristics of both the catalyst ( such as its activity, stereoselectivity, and response to hydrogen), as well as the resulting polymer (including its molecular weight, molecular weight distribution, and tacticity) [ 20 ]. The internal donor plays a critical role in ensuring the stability of the MgCl 2 surface by preventing the coagulation of MgCl 2 particles during the milling process. This, in turn, increases the active surface area and supports the generation of isospecific sites on the MgCl 2 surface. Additionally, the internal donor acts as a poison to the active site when bound to the titanium center [ 21 ]. The potential coordination modes for donor molecules on the MgCl 2 surface include a) Mono coordination: where one oxygen atom of the donor molecule coordinates with a magnesium atom. b) Chelate coordination: involving two oxygen atoms of the donor molecule coordinated to a single magnesium atom. c) Bridge coordination: where two oxygen atoms of the donor molecule coordinate with two distinct magnesium atoms within the same layer. d) Zip coordination:with two oxygen atoms of the donor molecule coordinating with two magnesium atoms in adjacent layers [ 22 ] The studies conducted by Busico et al involved the utilization of various substituted ethylbenzene (EB) compounds in ZN catalysts for propylene polymerization. These studies discovered that as the length of the ester group increases, the stereo specificity of the polymerization process improves [ 23 ]. Compared to the catalyst system that includes ethylbenzene, utilizing the phthalate donor in the catalyst system provides an additional capability to enhance the stability of the MgCl 2 support through zip-coordination [ 24 ]. Numerous experimental and theoretical investigations have been conducted to examine the impact of electron donors in ZN olefin polymerization. However, as the best of our knowledge, there is no report on the role of the chemical structure of ester-type electron donors, specifically linear and aromatic esters with different carbon chain lengths, on the structure and performance of SiO 2 @MgCl 2 bi-supported ZN catalysts characteristic and performance in ethylene polymerizations. Thus, this current study aims to address this gap by employing four distinct categories of ester donors during catalyst synthesis process: diethyl succinate and diethyl malonate as linear diesters with varying chain lengths, di-n-butyl phthalate as an aromatic diester, and ethyl benzoate as an aromatic monoester. Experimental Raw materials Silica, triethylaluminum (TEA), titanium tetrachloride (TiCl 4 ), anhydrous MgCl 2 and tetrahydrofuran (THF) were purchased from Merck and used without further purification. Di-n-butyl phthalate, ethyl benzoate, diethyl succinate and diethyl malonate were supplied from Aldrich and stored over molecular sieves. All air-sensitive and moisture-sensitive compounds were stored in an inert nitrogen atmosphere glove box. Nitrogen gas (purity 99.99%), hydrogen gas (purity 99.99%) and polymerization grade ethylene (purity 99.9%) were purified by passage through a molecular sieve column. n-Hexane was distilled over calcium hydride and stored over activated molecular sieve. Polymer and catalyst characterizations FTIR spectra of the catalysts were recorded with a Bruker Tensor27 instrument in the range of 400–4000 cm − 1 using a KBr pellet. The morphology of the catalysts was examined under a nitrogen atmosphere using scanning electron microscopy (SEM). The SEM instrument of Zeiss model: DSM-960A was applied. The surface area of the catalysts was determined by the BET method using the Quantachrome Corp. TPR Win v 1.0 instrument. The X-ray diffraction measurement of the catalysts was carried out using the Bruker D8 Advanced diffractometer with a copper tube as the Cu k -radiation generating X-ray source. The range of wide-angle diffraction 2θ was 10° to 100°. Differential scanning calorimetry (DSC) was performed with PerkinElmer DSC8500 on samples of approximately 5 mg sealed in aluminum pans under nitrogen atmosphere in a temperature range between 20°C and 180°C with a heating rate of 10°C/min. The bulk density of the polymers was measured according to ISO R60. The molecular weights and molecular weight distributions of the polyethylenes were determined by gel permeation chromatography (Alliance GPC 2000). The polymer samples were dissolved in 1,2,4-trichlorobenzene at 160°C. Catalyst Preparation At first, SiO 2 was calcined at 600°C for 2 h, collected and stored in a nitrogen atmosphere. Then, 5 g of anhydrous MgCl 2 in 500 mL of THF were placed in a 1 L round bottom flask equipped with a magnetic stirring bar, a reflux condenser, and a nitrogen inlet. The mixture was refluxed for 1 hour. In this stage, a clear and homogenous solution was obtained. Calcined SiO 2 was added to the solution ([Si]/[Mg] = 2). The mixture was refluxed for 1 hour. Then, THF was evaporated by a stream of nitrogen gas, and the residual solid mixture was collected and dried in the nitrogen atmosphere. In a 0.5 L steel reactor equipped with a mechanical stirrer and N 2 purged thermometer, 150 mL of TiCl 4 at 5°C was introduced into the reactor. 10 g of the synthesized support SiO 2 @MgCl 2 /THF was added under stirring. When the temperature inside the reactor reached 45°C, an appropriate amount of diester electron donors such as diethyl succinate, diethyl malonate, di-n-butyl phthalate and ethyl benzoate was added dropwise into the reactor. The molar ratio of internal electron donors to the magnesium chloride was 0.2. The temperature was raised to 90°C and held for 2 hours. The solution was hot-filtered, and the solid was washed five times with anhydrous hexane at 65°C. The solid was dried under a vacuum to give a solid catalyst product. Polymerization Procedure A 1 L Buchi type stainless steel reactor was employed in ethylene polymerizations under slurry conditions. A stirrer rotating at 600 rpm kept the reaction medium well mixed during the polymerizations. The polymerization temperature was controlled by circulating water using a Huber circulator. The reactor was heated to 130°C and repeatedly pressurized and evacuated with nitrogen to remove oxygen and moisture. After purging, the reactor was cooled under nitrogen pressure. For the polymerizations, the reactor was charged with 600 mL of dried hexane, then triethylaluminum (TEA) was injected as co-catalyst ([Al]/[Ti] = 150 mol/mol) and stirred for 10 minutes. During this step, the reactor temperature raised to 80°C. The reactor was pressurized with 0.5 or 1 bar of hydrogen and then ethylene was fed to keep the reactor pressure at 8 bar. At this stage, 7.5 mg of the synthesized catalyst was charged into the reactor. The polymerization time was kept constant at 1 hour. At the end, the temperature decreased, the polymer was collected and dried under a vacuum. Results and Discussion To study the effect of internal electron donors in the performance of bi-supported catalyst (SiO 2 @MgCl 2 /THF/TiCl 4 /ID), various ester electron donors were used in the Ziegler- Natta catalyst synthesis stage. To this end, two linear diesters with different chain lengths (diethyl succinate and diethyl malonate), one aromatic diester (di-n-butyl phthalate) and one aromatic monoester (ethyl benzoate) were utilized. The chemical structures of esters are shown in Fig. 1 . The synthesis conditions of the corresponding catalysts are listed in Table 1 . Four catalysts were synthesized under the optimal conditions (calcination temperature of SiO 2 was 600°C and [Si]/[Mg] = 2 mol/mol) described in the previous work [ 25 ]. The catalysts were subjected to a BET analysis to clarify the effect of electron donors on the specific surface area, Table 1 . Cat1, containing di-n-butyl phthalate, offers the highest surface area (199.6 m 2 /g) among the series. It has been observed that the presence of a larger electron donor results in an increase in the specific surface area of the catalyst. Table 1 The effect of internal electron donors on the performance of bi-supported catalyst Sample code Electron Donor Activity (kg PE/g Catalyst.h) BD 2 (g/cm 3 ) Catalyst surface area (m 2 /g) T m 3 (°C) M w (g/mol) MWD Cat 1 Di-n-butyl phthalate 5 0.37 199.6 137 55,049 2.2 Cat 2 Ethyl benzoate 14.2 0.39 152.2 136.7 218,117 3.5 Cat 3 Diethyl succinate 4.25 0.36 160.3 138 99,395 2.9 Cat 4 Diethyl malonate 5.13 0.32 158.1 137.4 428,733 4.6 1 Polymerization conditions: P Total = 8 bar, P H2 = 0.5 bar, T = 80°C, [Al]/[Ti] = 150 mol/mol, time = 1 h, 2 Bulk density of polyethylenes, 3 Melting temperature of polyethylenes. Infrared spectroscopy was used to identify the interaction of each electron donor with other ingredients on the catalyst composition. The IR spectra of 4 catalysts with different electron donors are shown in Fig. 2 . According to the spectra, the C = O stretching vibrations of the carbonyl group of the esters can be observed in the 1600–1700 cm − 1 range. Ester electron donors can bound to MgCl 2 through their carbonyl group. The red-shift in the stretching frequency corresponding to the free ester (1700–1750 cm − 1 ) to about 1620–1660 cm − 1 in the catalyst indicates the coordination of the ester electron donor to MgCl 2 support. This confirms the interaction of ester electron donors with the catalyst [ 28 ]. Furthermore, the peak related to Mg-Cl bond at the range of 1620–1660 cm − 1 merged with the carbonyl peak. The bands at 450–460 cm − 1 and 615 cm − 1 are attributed to the metal-halide stretching corresponding to Ti-Cl. The broad bands around 3200–3500 cm − 1 are due to the –OH stretching vibration of SiO 2 support. The band at range 1010–1100 cm − 1 is associated with the stretching vibration of Si–O of the SiO 2 as support [ 29 , 30 ]. There is a huge desire to obtain polymers with controlled particle size and morphology. If the structure of the catalyst is very fragile, particle attrition will cause the production of undesirable polymer fine powder. At the same time, because of the high rate of polymerization, crushing of polymer particles can prevent the phenomenon of replication of the catalyst particle shape and produce finer powders [ 31 ]. Considering the importance of the morphology of the catalyst and subsequent polymer, the morphology of the catalyst with different electron donors was investigated using SEM. As shown in Fig. 3 , all catalyst particles were spherical, except for catalyst 4, which contain malonate as the ID. In fact, the presence of cracks on catalysts 1 and 4 can be seen. By examining the diameter calculated from the SEM images, it was elucidated that the catalyst particles containing ethyl benzoate as an electron donor have the smallest particle diameter among the synthesized catalysts (diameter of Cat 1, 2 and 3 was 14.28, 0.5, and 4.8 µm, respectively). The reason for this outcome can be corelated to the smaller structure of ethyl benzoate compared to other electron donors. The largest catalyst particle size diameter is related to the catalyst containing phthalates, since the phthalates played the role of a binding agent and coordinated to (110) plane of magnesium chloride in the form of a bridge. Indeed, these IDs hold the adjacent MgCl layers through interlayer bonding, thus prevent mechanical fragmentation of the support during polymerization [ 26 , 27 ]. The larger diameter of catalyst 1 compared to others can be attributed to this reason [ 32 ]. The powder X-ray diffraction of the catalyst samples is shown in Fig. 4 . In the XRD patterns, the diffraction peaks at 2θ = 35° and 2θ ~ 50° indicated the structure of (104) and (110) planes of MgCl and demonstrated that all of them contain δ-phase MgCl 2 crystals [ 33 , 34 ]. The use of ester electron donors with a different structure did not affect the crystal structure [ 35 ]. Subsequently, all 4 catalysts were subjected to ethylene polymerization under the same conditions in the Buchi reactor to evaluate their performance. To study the effect of the electron donor on the characteristic of polymers, bulk density, GPC and DSC analyses were performed and the results collected in Table 1 . From the T m results, obtained from DSC curves (Fig. 5 ), it was concluded that the T m of PEs was less affected by the IDs type. As reported by Song, electron donors have a major impact on the molecular weight and molecular weight distribution of polyolefins [ 36 ]. Therefore, to examine the effect of various kinds of electron donors on these parameters, GPC test was conducted on polyethylene samples, Fig. 6 . As can be seen from the GPC curves and Table 1 data, between samples 1 and 2 (containing aromatic ester IDs), the later shows higher molecular weight, activity and bulk density. The activity of catalysts with diesters is almost in the same range, but the activity of ethyl benzoate (monoester) catalysts is dramatically higher. In fact, it was observed that diester IDs are less active than the monoester type in ethylene polymerizations. It can be corelated to the more acidic sites of TiCl 4 on MgCl 2 in the ethyl benzoate-containing catalyst. Yang et al. [ 37 ] reported that the presence of TiCl 4 ·monoester complex is much weaker compared to the TiCl 4 ·diester complex. Therefore, in catalysts containing monoester, strong acid sites (titanium chloride) are more present on magnesium chloride support, because titanium chloride has less participated in the reaction of complex formation with ester and this leads to higher activity of the ethyl benzoate-containing catalyst. Furthermore, it is known that an ester electron donor as a Lewis base can easily react with Lewis’s acid species in the polymerization system, such as alkylaluminum and leach out during the addition of cocatalyst. In view of these facts, since the same concentration of electron donors is used in the preparation of the catalyst in all cases, it is possible that ethyl benzoate immobilized on magnesium chloride is still present in the polymerization stage after the undesired reaction of ethyl benzoate with alkylaluminum. This likely increases the molecular weight of the polymer made in the presence of the benzoate catalyst compared to the polymer made from the phthalate containing catalyst. The broad molecular weight distribution of the polymers obtained from the benzoate catalyst is corelated to the diversity of generated active sites. On the other hand, the free ester group in the diesters (phthalate) can share electrons with some titanium chloride on the support surface and coordinate with TiCl 4 and subsequently deactivate some active sites moreover act as a poison. This interaction results in an increase in spatial order in the case of propylene polymerization, but in ethylene polymerization, where spatial order is absent, it decreases activity [ 37 , 38 , 39 ]. In the case of the catalysts with diethyl succinate and diethyl malonate (Cat3 and Cat4), the catalyst containing diethyl malonate with shorter chain length produces a polymer with a higher molecular weight, thereby broader molecular weight distribution and further the bulk density decreases. Therefore, from the above results, it can be concluded that in ZN catalysts, when the aim is to synthesize a polymer with a high molecular weight, an electron donor having a small structure such as ethyl benzoate and ethyl malonate can be used. On the other hand, it has been observed that the larger structure of the electron donor in the catalyst decreases the molecular weight of the produced polymer in the polymerization step and leads to a narrower molecular weight distribution. It should be noted that catalysts containing smaller esters in the linear ester category, such as malonate, produce higher molecular weight and broader molecular weight distribution polymer than catalysts containing smaller esters in the aromatic ester category. To study the effect of the hydrogen amount on the catalyst performance and the properties of the produced polymers, two hydrogen pressures (0.5 and 1 bar) were used in the ethylene polymerizations in the same reaction conditions. According to the results given in Table 2 in all catalysts, the activity and performance of the catalyst decreased as the hydrogen pressure increased. Also,, based on Fig. 6 and Fig. 7 , polymers with lower molecular weight and narrower MWD were produced, which is caused by the formation of more dormant sites. Dormant sites are usually formed by β-agostic interactions between β-hydrogen of the ethyl group and the titanium atom in the Cl 2 Ti-CH 2 -CH 3 site, which decrease the rate of polymerization in the presence of hydrogen [ 40 ]. Among the catalysts, the catalyst containing diethyl malonate showed a much better hydrogen response (lower molecular weight), furthermore produced a polymer with a narrower molecular weight distribution. The response to hydrogen in various types of catalysts with different electron donors was determined in the following order: Cat4 (ethyl malonate) > Cat2 (ethyl benzoate) > Cat3 (diethyl succinate) > Cat1 (di-n-butyl phthalate). And of course, the molecular weight distribution of polyethylene was in the same order. In fact, the response to hydrogen is better for catalysts with smaller electron donors. In this class of catalysts, the less sterically hindered donors cause increased access of hydrogen to the active sites. Comparing the group of linear and aromatic ester donors, the catalyst containing the linear ester donor has a higher hydrogen response than the catalyst containing the aromatic donor. Table 2 The effect of hydrogen pressure on the catalyst performance and final polymer properties 1 Catalyst H 2 pressure (bar) Activity (kg PE/g Catalyst.h) M w (g/mol) MWD Cat1 0.5 5 55049 2.2 Cat1 1.0 3.9 35233 1.6 Cat2 0.5 14.2 218117 3.5 Cat2 1.0 13.1 91529 2.0 Cat3 0.5 4.25 99395 2.9 Cat3 1.0 3 50393 1.7 Cat4 0.5 5.13 428733 4.6 Cat4 1.0 4.5 142393 2.3 1 Polymerization conditions: P Total = 8 bar, T = 80°C, [Al]/[Ti] = 150 mol/mol, time = 1 h SEM of the polymer produced in the presence of catalyst with an aromatic ester (di-n-butyl phthalate) and a linear ester (Diethyl succinate) is shown in Fig. 8 . The morphology of the polymers is almost the same in both images and polymer fibers interconnect the microparticles to form macroparticles. The formation of fibril polymers reduces the formation of fines during polymerization. Reducing the fines generated in the final polymer is a critical parameter in the industry. Conclusions As a matter of fact, the choice of electron donors for the catalyst system depends on the characteristic and quantity of the polymer produced by these catalysts. Therefore, four types of catalysts with diethyl succinate and diethyl malonate (linear diesters), di-n-butyl phthalate (aromatic diester) and ethyl benzoate (aromatic monoester) were synthesized and compared in terms of catalyst structures and their catalytic performance. SEM images illustrated that the morphology of the catalyst particles was spherical, except for the malonate catalyst (Cat 4) at magnification below 10 µm. The diameter in various types of catalysts with different electron donors was determined from the SEM images in the following order: Cat1 (di-n-butyl phthalate) > Cat3 (diethyl succinate) > Cat2 (ethyl benzoate). The presence of phthalate as a large electron donor, leads to an increase in the specific surface area of the catalyst, however, similar XRD pattern was obtained. Moreover, diesters based catalysts had lower activity than mono ester types. According to the GPC results, when the aim is to synthesize a polymer having a high molecular weight, small electron donors of both linear and aromatic esters such as diethyl malonate and ethyl benzoate can be used more effectively. On the other hand, in both the aromatic ester and linear ester categories, the larger electron donor structure reduces the molecular weight of the polymer produced. In comparing two categories of catalysts containing linear and aromatic small esters (malonate and ethyl benzoate), the catalyst containing a small linear ester produces a polymer with a higher molecular weight than the catalyst containing a small aromatic ester contains. Finally, the effect of hydrogen pressure on catalyst performance and final polymer properties was evaluated. According to the GPC results, the hydrogen response for catalysts containing smaller IDs is better. Also, a comparison of the group of linear and aromatic ester donors shows that the catalyst containing the linear ester donor has a higher hydrogen response than the catalyst containing the aromatic donor. Declarations Acknowledgements We acknowledge Bandar Imam Petrochemical Complex (BIPC) for support of this work. Conflict of interests The author claims that there is no conflict of interest. Funding Declaration This research received no external funding. Data Availability Statement The data that support the findings of this study are available from the corresponding author upon reasonable request. Author Contributions [Hamidreza Teimoury]: Conceptualization, Methodology, Supervision, Project Administration [Nazanin Moeini]: Data Curation, Methodology, Formal Analysis, Writing – Review & Editing. References Mehdizadeh M, Karkhaneh F, Nekoomanesh M, Sadjadi S, Emami M, Teimoury H, Salimi M, Solà M, Poater A, Bahri-Laleh N, Posada-Pérez S (2023) Influence of the ethanol content of adduct on the comonomer incorporation of related Ziegler–Natta catalysts in propylene (co)polymerizations. J Polym Res 15:4476 Makaryan IA, Sedov IV (2020) Analysis of the state and development prospects of the industrial catalysts market for polyolefins production. Russ J Gen Chem 90:1141–1162 Ziegler K, Holzkamp E, Breil H, Martin HJAC (1955) Das mülheimer normaldruck-polyäthylen-verfahren. Angew Chem 67:541–547 Natta G, Pino P, Corradini P, Danusso F, Mantica E, Mazzanti G, Moraglio GJ (1955) Crystalline high polymers of α-olefins. J Am Chem Soc 77:1708–1710 Potapov A, Bukatov G, Zakharov VJ (2009) DRIFTS study of the interaction of the AlEt3 cocatalyst with the internal donor ethyl benzoate in supported Ziegler–Natta catalysts. J Mol Catal A: Chem 301:18–23 Credendino R, Liguori D, Morini G, Cavallo L (2014) Investigating phthalate and 1,3-diether coverage and dynamics on the (104) and (110) surfaces of MgCl2-supported Ziegler–Natta catalysts. J Phys Chem C 118:8050–8058 Potapov AG, Politanskaya LV (2013) The study of the adsorption of 1,3-diethers on the MgCl2 surface. J Mol Catal A: Chem 368:159–162 Wen X, Ji M, Yi Q, Niu H, Dong J-Y (2010) Magnesium chloride supported Ziegler-Natta catalysts containing succinate internal electron donors for the polymerization of propylene. J Appl Polym Sci 118:1853–1858 Paghadar BR, Sainani JB, Bhagavath P (2021) Internal donors on supported Ziegler Natta catalysts for isotactic polypropylene: A brief tutorial review. J Polym Res 28:1–19 Poorsank F, Arabi H, Ghasemi Hamedani N (2021) Silyl diol ester as a new selectivity control agent in MgCl2-supported Ziegler–Natta systems for propylene polymerization: Catalyst structure and polymer properties. J Polym Res 28:185 Tanase S, Katayama K, Yabunouchi N, Sadashima T, Tomotsu N, Ishihara NJ (2007) Design of novel malonates as internal donors for MgCl2-supported TiCl4 type polypropylene catalysts and their mechanistic aspects, Part 1. J Mol Catal A: Chem 273:211–217 Kumawat J, Gupta VK (2020) Fundamental aspects of heterogeneous Ziegler–Natta olefin polymerization catalysis: An experimental and computational overview. Phys Chem Chem Phys 11:6107–6128 Sinha ASK, Ojha U (2021) Evolution of Ziegler-Natta catalysts for polymerization of olefins. In: Pant, K. K., Gupta, S. K., & Ahmad, E. (Eds.), Catalysis for Clean Energy and Environmental Sustainability , 2, 675–705 Grau E, Lesage A, Norsic S, Copéret C, Monteil V, Sautet P (2013) Tetrahydrofuran in TiCl4/THF/MgCl2: A non-innocent ligand for supported Ziegler–Natta polymerization catalysts. Angew Chem 3:52–56 Milanesi M, Piovano A, Wada T, Zarupski J, Chammingkwan P, Taniike T, Groppo E (2023) Influence of the synthetic procedure on the properties of three Ziegler-Natta catalysts with the same 1,3-diether internal donor. Catal Today 418:114077 Khatri V, Sahoo U, Kaur S, Rani R, Singh G, Kapur GS, Kashyap HK (2020) Control of Ziegler–Natta catalyst activity by the structural design of alkoxysilane-based external donors. New J Chem 44:6845–6852 Moeini N, Teimoury H, Salimi M, Bahri-Laleh N, Joshaghani M, Duran J, Posada-Pérez S (2024) Influence of the reaction conditions on the Ziegler-Natta catalyzed ethylene polymerization: Kinetics and properties of the resulting polymers. Polymer 293:126640 Weng Y, Jiang B, Fu Z, Fan Z (2018) Mechanism of internal and external electron donor effects on propylene polymerization with MgCl2-supported Ziegler–Natta catalyst: New evidences based on active center counting. J Appl Polym Sci 135:46605 Li B, Li H, Hu H, Zhou Y, Mao G, Xin S (2024) The Effects of Internal Electron Donors on MgCl2-Supported Ziegler–Natta Catalysts for Isotactic PP. Polymers 16(19):2687 Zhong W, Cai X, Shen X, Liu H, Fu Z, Wang Q, Song S, Du B, Fan Z (2025) Effects of Internal Electron Donor on the Distribution of Active Centers and Their Intrinsic Reactivities in Propylene Polymerization with MgCl2-Supported Ziegler–Natta Catalysts. Industrial & Engineering Chemistry Research Bazhenov A, Linnolahti M, Pakkanen TA, Denifl P, Leinonen T (2014) Modeling the stabilization of surface defects by donors in Ziegler–Natta catalyst support. J Phys Chem C 118(9):4791–4796 Correa A, Piemontesi F, Morini G, Cavallo LJM (2007) Key elements in the structure and function relationship of the MgCl₂/TiCl₄/lewis base Ziegler – Natta catalytic system. Macromol Chem Phys 40(24):9181–9189 Busico V, Corradini P, De Martino L, Proto A, Albizzati EJ D. M. C. M. C. (1986). Polymerization of propene in the presence of MgCl₂-supported Ziegler‐Natta catalysts, 2. Effects of the co‐catalyst composition. Macromol Chem Phys, 187(5), 1115–1124 Stukalov DV, Zilberberg IL, Zakharov VA (2009) Surface species of titanium (IV) and titanium (III) in MgCl2-supported Ziegler – Natta catalysts. A periodic density functional theory study. Macromolecules 42(21):8165–8171 Teimoury H, Moeini N, Bahri-Laleh N, Shih F-Y, Varnoosfaderani MV (2023) The effect of SiO₂ calcination temperature and [Si]/[Mg] molar ratio on the performance of bi-supported Ziegler-Natta catalysts in ethylene polymerizations. J Polym Res 30:73 Singh G, Kaur S, Makwana U, Patankar RB, Gupta VK (2009) Influence of internal donors on the performance and structure of MgCl₂ supported titanium catalysts for propylene polymerization. Macromol Chem Phys 210(1):69–76 Thongdonjui A, Trakarnpruk W, Strauss RH (2009) Effect of electron donor on PE polymerization. J Met Mater Minerals, 19(2) Zohuri G, Ahmadjou S, Jamjah R, Nekou MM (2001) Structural study of mono-and bi-supported Ziegler-Natta catalysts MgCl₂/SiO₂/TiCl₄/donor systems. Iran Polym J, 145–155 Mohamadi Z, Moradi G, Teimoury HR (2021) Comparison of Mg-ethoxide based Ziegler Natta catalysts using different internal donors employed for ethylene polymerization. J Polym Res 28:185 Fu T, Cheng R, He X, Liu Z, Tian Z, Liu B (2016) Imido-modified SiO₂-supported Ti/Mg Ziegler-Natta catalysts for ethylene polymerization and ethylene/1-hexene copolymerization. Polyolefins J 3(2):103–117 Liu X, Guo W, Wang X, Guo Y, Zhang B, Fu Z, Wang Q, Fan Z (2021) TiCl₄/MgCl₂/MCM-41 Bi-Supported Ziegler–Natta Catalyst: Effects of catalyst composition on ethylene/1-hexene copolymerization. Catalysts 11(12):1535 Vanka K, Singh G, Iyer D, Gupta VK (2010) DFT study of Lewis base interactions with the MgCl₂ surface in the Ziegler – Natta catalytic system: Expanding the role of the donors. J Phys Chem C 114(35):15771–15781 Xue B, Hui L, Yang H, Zhao Y, Hou L, Li W (2017) Immobilization of Ziegler–Natta catalyst for ethylene polymerization on macroporous SiO₂ with an open-framework structure. Ind Eng Chem Res 56(1):135–142 Abazari M, Jamjah R, Bahri-Laleh N, Hanifpour A (2022) Synthesis and evaluation of a new three-metallic high-performance Ziegler–Natta catalyst for ethylene polymerization: Experimental and computational studies. Polym Bull 79:7265–7280 Bukatov G, Maslov D, Sergeev S, Matsko M (2019) Effect of internal donors on the performance of Ti-Mg catalysts in propylene polymerization: Donor introduction during or after MgCl₂ formation. Appl Catal A 577:69–75 Song BG, Ihm SK (2014) The role of two different internal donors (phthalate and 1,3-diether) on the formation of surface structure in MgCl₂‐supported Ziegler–Natta catalysts and their catalytic performance in propylene polymerization. J Appl Polym Sci, 131 Yang C, Hsu C, Park Y, Shurvell H (1994) Infrared characterization of MgCl₂ supported Ziegler-Natta catalysts with monoester and diester as a modifier. Eur Polymer J 30(2):205–214 Cavallo L, Del Piero S, Ducéré J-M, Fedele R, Melchior A, Morini G, Piemontesi F, Tolazzi M (2007) Key interactions in heterogeneous Ziegler – Natta catalytic systems: Structure and energetics of TiCl₄–Lewis base complexes. J Phys Chem C 111(11):4412–4419 Correa A, Bahri-Laleh N, Cavallo L (2013) How well can DFT reproduce key interactions in Ziegler–Natta systems? Macromol Chem Phys 214(18):1980–1989 Sukulova V, Barabanov A, Mikenas T, Matsko M, Zakharov V (2018) Effect of hydrogen on the number of active centers and the propagation rate constant at ethylene polymerization over titanium-magnesium Ziegler-Natta catalysts. Mol Catal 445:299–306 Cite Share Download PDF Status: Published Journal Publication published 28 Nov, 2025 Read the published version in Journal of Polymer Research → Version 1 posted Reviewers agreed at journal 20 Aug, 2025 Reviewers invited by journal 20 Aug, 2025 Editor invited by journal 10 Aug, 2025 Editor assigned by journal 16 Jul, 2025 First submitted to journal 16 Jul, 2025 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. 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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-6828388","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":503009594,"identity":"3bd00180-b8de-4417-810b-4e1334c69033","order_by":0,"name":"Hamidreza Teimoury","email":"","orcid":"https://orcid.org/0000-0002-9101-2060","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Hamidreza","middleName":"","lastName":"Teimoury","suffix":""},{"id":503009595,"identity":"b2a28563-0b65-48d0-82d6-0721034cc546","order_by":1,"name":"Nazanin Moeini","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA9ElEQVRIiWNgGAWjYJCCAwwGMAYQ8IOIhAJStEg2gLQYkGKnAVgjHi267c0HDxcU3JGXbz8LZDDciTY+vzrxwwMDBnl+sQNYtZidOZZweIbBM8PGnjwgg+FZ7rYbbzdLAB1mOHN2AnYtN3IMDvMYHGZsZgAxGA4DtZzdANKSYHAbl5b8DyAt9m38byBaNs84u/kHfi05DCAtiT0SUFs28Pduw2/LmWNghyXPkHgDZuTOuMG7zSLBQAK3X443P/7M8+ew7fz+HOPPPBWHc/v7z26++aPCRp5fGrsWNACKDgmwSglilMMA/wFSVI+CUTAKRsEIAAAE82dwu2Fu9gAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0001-7022-3734","institution":"Kermanshah polymer Co.","correspondingAuthor":true,"prefix":"","firstName":"Nazanin","middleName":"","lastName":"Moeini","suffix":""}],"badges":[],"createdAt":"2025-06-05 10:52:31","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6828388/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6828388/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s10965-025-04675-8","type":"published","date":"2025-11-28T15:57:53+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":90106559,"identity":"ef709481-5ea8-45e2-ab47-8884e2f8c2d1","added_by":"auto","created_at":"2025-08-28 14:22:03","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":94521,"visible":true,"origin":"","legend":"\u003cp\u003eChemical structure of ester electron donors used in this study.\u003c/p\u003e","description":"","filename":"image1.png","url":"https://assets-eu.researchsquare.com/files/rs-6828388/v1/8fd2488be1195ae91839895f.png"},{"id":90106294,"identity":"5add5ac8-2930-4cc1-b544-858cbf1b6904","added_by":"auto","created_at":"2025-08-28 14:14:03","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":108708,"visible":true,"origin":"","legend":"\u003cp\u003eFT-IR spectra of synthesized ZN catalysts\u003c/p\u003e","description":"","filename":"image2.png","url":"https://assets-eu.researchsquare.com/files/rs-6828388/v1/756a4969c1cc28f1953f374b.png"},{"id":90106298,"identity":"f2921668-efd2-4aa5-8388-d2a129910513","added_by":"auto","created_at":"2025-08-28 14:14:03","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":297413,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of the catalysts a) Cat1, b) Cat2, c) Cat3 and d) Cat4\u003c/p\u003e","description":"","filename":"image3.png","url":"https://assets-eu.researchsquare.com/files/rs-6828388/v1/e3e074290793a758705b2e21.png"},{"id":90106560,"identity":"de748fc3-fea9-4b77-8863-0759c2416141","added_by":"auto","created_at":"2025-08-28 14:22:03","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":86926,"visible":true,"origin":"","legend":"\u003cp\u003eXRD pattern of the catalysts a) Cat1 b) Cat2 c) Cat3 d) Cat4\u003c/p\u003e","description":"","filename":"image4.png","url":"https://assets-eu.researchsquare.com/files/rs-6828388/v1/0fc3e400c71a97f39370e18f.png"},{"id":90106562,"identity":"5e273567-6d31-44ad-b209-6a3042b68890","added_by":"auto","created_at":"2025-08-28 14:22:03","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":143654,"visible":true,"origin":"","legend":"\u003cp\u003eThe DSC curves of polyethylene obtained through Cat1, Cat2, Cat3 and Cat4.\u003c/p\u003e","description":"","filename":"image5.png","url":"https://assets-eu.researchsquare.com/files/rs-6828388/v1/74a3b6a609ae10bfe827442f.png"},{"id":90106310,"identity":"adc50f34-4c8e-45a8-b061-691dcdbd0b04","added_by":"auto","created_at":"2025-08-28 14:14:04","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":236913,"visible":true,"origin":"","legend":"\u003cp\u003eGPC curves of PE obtained by (a) Cat 1, (b) Cat 2, (c) Cat 3, and (d) Cat 4 at Polymerization conditions: P\u003csub\u003eTotal\u003c/sub\u003e= 8 bar, P \u003csub\u003eH2\u003c/sub\u003e=0.5 bar, T= 80 °C, [Al]/[Ti]=150 mol/mol, time= 1 h.\u003c/p\u003e","description":"","filename":"image6.png","url":"https://assets-eu.researchsquare.com/files/rs-6828388/v1/1c3429ba252fb679d20b6ed6.png"},{"id":90106300,"identity":"4b6f80e1-498b-4d8a-8b3f-fb19c4d86257","added_by":"auto","created_at":"2025-08-28 14:14:03","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":136840,"visible":true,"origin":"","legend":"\u003cp\u003eGPC curves of PE obtained by (a) Cat1, (b) Cat2, (c) Cat3, and (d) Cat4 at Polymerization conditions: P\u003csub\u003eTotal\u003c/sub\u003e= 8 bar, P \u003csub\u003eH2\u003c/sub\u003e= 1 bar, T= 80 °C, [Al]/[Ti]=150 mol/mol, time= 1 h.\u003c/p\u003e","description":"","filename":"image7.png","url":"https://assets-eu.researchsquare.com/files/rs-6828388/v1/1971722fe791febce0f0cc99.png"},{"id":90106561,"identity":"77d7051e-cc4a-41ca-923e-d1bfdcd0b105","added_by":"auto","created_at":"2025-08-28 14:22:03","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":200215,"visible":true,"origin":"","legend":"\u003cp\u003eSEM images of polyethylenes produced in the presence of a) Cat1 and b) Cat3\u003c/p\u003e","description":"","filename":"image8.png","url":"https://assets-eu.researchsquare.com/files/rs-6828388/v1/7f8e0b3cbb4a7a61024b9d54.png"},{"id":97178687,"identity":"805cc9ae-95e5-4b53-8dfd-4d427933a811","added_by":"auto","created_at":"2025-12-01 16:12:46","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1909449,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6828388/v1/ea5a7758-99fa-4292-977d-da0eed5f0f79.pdf"}],"financialInterests":"","formattedTitle":"\u003cp\u003eExploring the role of ester electron donors in ethylene polymerization using bi-supported SiO\u003csub\u003e2\u003c/sub\u003e@MgCl\u003csub\u003e2\u003c/sub\u003e/TiCl\u003csub\u003e4\u003c/sub\u003e type Ziegler-Natta catalysts\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003ePolyolefins are considered as the most widely used synthetic polymers worldwide which have an annual commercial turnover of USD 300\u0026nbsp;billion and a yearly production of over 180\u0026nbsp;million tons. The most widely used polyolefins include polyethylene and polypropylene, which account for 31.2% and 22.7%, respectively, of the global polymer market. Indeed, in today\u0026rsquo;s human life, their applications surpass imagination [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Approximately 70 years ago, Ziegler and his colleagues discovered the synthesis of polyethylene under relatively mild conditions, lower temperatures, and lower pressures than those of the radical polymerization in the presence of transition metal (mainly Ti, V, and Zr) compound and organoaluminium compounds as co-catalyst. Also, Natta and his coworker (in Polytechnic University of Milan) succeeded in the polymerization of propylene using the TiCl\u003csub\u003e3\u003c/sub\u003e-AlEt\u003csub\u003e2\u003c/sub\u003eCl system. Over the past decade, Ziegler-Natta catalysts have undergone significant developments and are utilized as efficient catalysts in the polymerization of olefins in the industrial sectors [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThis type of catalyst typically consists of a combination of TiCl\u003csub\u003e4\u003c/sub\u003e supported on MgCl\u003csub\u003e2\u003c/sub\u003e, along with electron donors and cocatalyst such as triethylaluminium. However, there is potential to modify the catalyst system by using different electron donors (Lewis base) such as ethyl benzoate [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], phthalate [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], diether [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e], succinate [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], glutarates [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e], maleates [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e], malonates [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e], ketoesters [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e], imine [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] and tetrahydrofuran (THF) [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Electron donors are typically classified in two categories: internal donors (IDs) and external donors (EDs). IDs are incorporated during the synthesis of pre-catalyst, while external donors are added along with the AlR\u003csub\u003e3\u003c/sub\u003e activator in the polymerization stage. The purpose of external donors is to compensate for the partial loss of internal donors resulting from their reaction with AlR\u003csub\u003e3\u003c/sub\u003e [\u003cspan additionalcitationids=\"CR16 CR17 CR18\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eElectron donors profoundly impact the characteristics of both the catalyst ( such as its activity, stereoselectivity, and response to hydrogen), as well as the resulting polymer (including its molecular weight, molecular weight distribution, and tacticity) [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. The internal donor plays a critical role in ensuring the stability of the MgCl\u003csub\u003e2\u003c/sub\u003e surface by preventing the coagulation of MgCl\u003csub\u003e2\u003c/sub\u003e particles during the milling process. This, in turn, increases the active surface area and supports the generation of isospecific sites on the MgCl\u003csub\u003e2\u003c/sub\u003e surface. Additionally, the internal donor acts as a poison to the active site when bound to the titanium center [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. The potential coordination modes for donor molecules on the MgCl\u003csub\u003e2\u003c/sub\u003e surface include a) Mono coordination: where one oxygen atom of the donor molecule coordinates with a magnesium atom. b) Chelate coordination: involving two oxygen atoms of the donor molecule coordinated to a single magnesium atom. c) Bridge coordination: where two oxygen atoms of the donor molecule coordinate with two distinct magnesium atoms within the same layer. d) Zip coordination:with two oxygen atoms of the donor molecule coordinating with two magnesium atoms in adjacent layers [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]\u003c/p\u003e\u003cp\u003eThe studies conducted by Busico et al involved the utilization of various substituted ethylbenzene (EB) compounds in ZN catalysts for propylene polymerization. These studies discovered that as the length of the ester group increases, the stereo specificity of the polymerization process improves [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Compared to the catalyst system that includes ethylbenzene, utilizing the phthalate donor in the catalyst system provides an additional capability to enhance the stability of the MgCl\u003csub\u003e2\u003c/sub\u003e support through zip-coordination [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eNumerous experimental and theoretical investigations have been conducted to examine the impact of electron donors in ZN olefin polymerization. However, as the best of our knowledge, there is no report on the role of the chemical structure of ester-type electron donors, specifically linear and aromatic esters with different carbon chain lengths, on the structure and performance of SiO\u003csub\u003e2\u003c/sub\u003e@MgCl\u003csub\u003e2\u003c/sub\u003e bi-supported ZN catalysts characteristic and performance in ethylene polymerizations. Thus, this current study aims to address this gap by employing four distinct categories of ester donors during catalyst synthesis process: diethyl succinate and diethyl malonate as linear diesters with varying chain lengths, di-n-butyl phthalate as an aromatic diester, and ethyl benzoate as an aromatic monoester.\u003c/p\u003e"},{"header":"Experimental","content":"\u003cp\u003e\u003cb\u003eRaw materials\u003c/b\u003e\u003c/p\u003e\u003cp\u003eSilica, triethylaluminum (TEA), titanium tetrachloride (TiCl\u003csub\u003e4\u003c/sub\u003e), anhydrous MgCl\u003csub\u003e2\u003c/sub\u003e and tetrahydrofuran (THF) were purchased from Merck and used without further purification. Di-n-butyl phthalate, ethyl benzoate, diethyl succinate and diethyl malonate were supplied from Aldrich and stored over molecular sieves. All air-sensitive and moisture-sensitive compounds were stored in an inert nitrogen atmosphere glove box. Nitrogen gas (purity 99.99%), hydrogen gas (purity 99.99%) and polymerization grade ethylene (purity 99.9%) were purified by passage through a molecular sieve column. n-Hexane was distilled over calcium hydride and stored over activated molecular sieve.\u003c/p\u003e\u003cp\u003e\u003cb\u003ePolymer and catalyst characterizations\u003c/b\u003e\u003c/p\u003e\u003cp\u003eFTIR spectra of the catalysts were recorded with a Bruker Tensor27 instrument in the range of 400\u0026ndash;4000 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e using a KBr pellet. The morphology of the catalysts was examined under a nitrogen atmosphere using scanning electron microscopy (SEM). The SEM instrument of Zeiss model: DSM-960A was applied. The surface area of the catalysts was determined by the BET method using the Quantachrome Corp. TPR Win v 1.0 instrument. The X-ray diffraction measurement of the catalysts was carried out using the Bruker D8 Advanced diffractometer with a copper tube as the Cu k -radiation generating X-ray source. The range of wide-angle diffraction 2θ was 10\u0026deg; to 100\u0026deg;. Differential scanning calorimetry (DSC) was performed with PerkinElmer DSC8500 on samples of approximately 5 mg sealed in aluminum pans under nitrogen atmosphere in a temperature range between 20\u0026deg;C and 180\u0026deg;C with a heating rate of 10\u0026deg;C/min. The bulk density of the polymers was measured according to ISO R60. The molecular weights and molecular weight distributions of the polyethylenes were determined by gel permeation chromatography (Alliance GPC 2000). The polymer samples were dissolved in 1,2,4-trichlorobenzene at 160\u0026deg;C.\u003c/p\u003e\u003cp\u003e\u003cb\u003eCatalyst Preparation\u003c/b\u003e\u003c/p\u003e\u003cp\u003eAt first, SiO\u003csub\u003e2\u003c/sub\u003e was calcined at 600\u0026deg;C for 2 h, collected and stored in a nitrogen atmosphere. Then, 5 g of anhydrous MgCl\u003csub\u003e2\u003c/sub\u003e in 500 mL of THF were placed in a 1 L round bottom flask equipped with a magnetic stirring bar, a reflux condenser, and a nitrogen inlet. The mixture was refluxed for 1 hour. In this stage, a clear and homogenous solution was obtained. Calcined SiO\u003csub\u003e2\u003c/sub\u003e was added to the solution ([Si]/[Mg]\u0026thinsp;=\u0026thinsp;2). The mixture was refluxed for 1 hour. Then, THF was evaporated by a stream of nitrogen gas, and the residual solid mixture was collected and dried in the nitrogen atmosphere. In a 0.5 L steel reactor equipped with a mechanical stirrer and N\u003csub\u003e2\u003c/sub\u003e purged thermometer, 150 mL of TiCl\u003csub\u003e4\u003c/sub\u003e at 5\u0026deg;C was introduced into the reactor. 10 g of the synthesized support SiO\u003csub\u003e2\u003c/sub\u003e@MgCl\u003csub\u003e2\u003c/sub\u003e/THF was added under stirring. When the temperature inside the reactor reached 45\u0026deg;C, an appropriate amount of diester electron donors such as diethyl succinate, diethyl malonate, di-n-butyl phthalate and ethyl benzoate was added dropwise into the reactor. The molar ratio of internal electron donors to the magnesium chloride was 0.2. The temperature was raised to 90\u0026deg;C and held for 2 hours. The solution was hot-filtered, and the solid was washed five times with anhydrous hexane at 65\u0026deg;C. The solid was dried under a vacuum to give a solid catalyst product.\u003c/p\u003e\u003cp\u003e\u003cb\u003ePolymerization Procedure\u003c/b\u003e\u003c/p\u003e\u003cp\u003eA 1 L Buchi type stainless steel reactor was employed in ethylene polymerizations under slurry conditions. A stirrer rotating at 600 rpm kept the reaction medium well mixed during the polymerizations. The polymerization temperature was controlled by circulating water using a Huber circulator. The reactor was heated to 130\u0026deg;C and repeatedly pressurized and evacuated with nitrogen to remove oxygen and moisture. After purging, the reactor was cooled under nitrogen pressure. For the polymerizations, the reactor was charged with 600 mL of dried hexane, then triethylaluminum (TEA) was injected as co-catalyst ([Al]/[Ti]\u0026thinsp;=\u0026thinsp;150 mol/mol) and stirred for 10 minutes. During this step, the reactor temperature raised to 80\u0026deg;C. The reactor was pressurized with 0.5 or 1 bar of hydrogen and then ethylene was fed to keep the reactor pressure at 8 bar. At this stage, 7.5 mg of the synthesized catalyst was charged into the reactor. The polymerization time was kept constant at 1 hour. At the end, the temperature decreased, the polymer was collected and dried under a vacuum.\u003c/p\u003e"},{"header":"Results and Discussion","content":"\u003cp\u003eTo study the effect of internal electron donors in the performance of bi-supported catalyst (SiO\u003csub\u003e2\u003c/sub\u003e@MgCl\u003csub\u003e2\u003c/sub\u003e/THF/TiCl\u003csub\u003e4\u003c/sub\u003e/ID), various ester electron donors were used in the Ziegler- Natta catalyst synthesis stage. To this end, two linear diesters with different chain lengths (diethyl succinate and diethyl malonate), one aromatic diester (di-n-butyl phthalate) and one aromatic monoester (ethyl benzoate) were utilized. The chemical structures of esters are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe synthesis conditions of the corresponding catalysts are listed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Four catalysts were synthesized under the optimal conditions (calcination temperature of SiO\u003csub\u003e2\u003c/sub\u003e was 600\u0026deg;C and [Si]/[Mg]\u0026thinsp;=\u0026thinsp;2 mol/mol) described in the previous work [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. The catalysts were subjected to a BET analysis to clarify the effect of electron donors on the specific surface area, Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Cat1, containing di-n-butyl phthalate, offers the highest surface area (199.6 m\u003csup\u003e2\u003c/sup\u003e/g) among the series. It has been observed that the presence of a larger electron donor results in an increase in the specific surface area of the catalyst.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eThe effect of internal electron donors on the performance of bi-supported catalyst\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"8\"\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\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample code\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eElectron Donor\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eActivity\u003c/p\u003e\u003cp\u003e(kg PE/g Catalyst.h)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eBD \u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e\u003cp\u003e(g/cm\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eCatalyst surface area (m\u003csup\u003e2\u003c/sup\u003e/g)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e\u003cp\u003eT\u003csub\u003em\u003c/sub\u003e\u003csup\u003e3\u003c/sup\u003e\u003c/p\u003e\u003cp\u003e(\u0026deg;C)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u003cp\u003eM\u003csub\u003ew\u003c/sub\u003e (g/mol)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e\u003cp\u003eMWD\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCat 1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDi-n-butyl phthalate\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.37\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e199.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e137\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e55,049\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e2.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCat 2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eEthyl benzoate\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e14.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.39\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e152.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e136.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e218,117\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e3.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCat 3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDiethyl succinate\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.36\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e160.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e138\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e99,395\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e2.9\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCat 4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eDiethyl malonate\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5.13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.32\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e158.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e\u003cp\u003e137.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e\u003cp\u003e428,733\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e\u003cp\u003e4.6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003csup\u003e1\u003c/sup\u003ePolymerization conditions: P\u003csub\u003eTotal\u003c/sub\u003e= 8 bar, P \u003csub\u003eH2\u003c/sub\u003e= 0.5 bar, T\u0026thinsp;=\u0026thinsp;80\u0026deg;C, [Al]/[Ti]\u0026thinsp;=\u0026thinsp;150 mol/mol, time\u0026thinsp;=\u0026thinsp;1 h, \u003csup\u003e2\u003c/sup\u003e Bulk density of polyethylenes, \u003csup\u003e3\u003c/sup\u003e Melting temperature of polyethylenes.\u003c/p\u003e\u003cp\u003eInfrared spectroscopy was used to identify the interaction of each electron donor with other ingredients on the catalyst composition. The IR spectra of 4 catalysts with different electron donors are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. According to the spectra, the C\u0026thinsp;=\u0026thinsp;O stretching vibrations of the carbonyl group of the esters can be observed in the 1600\u0026ndash;1700 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e range. Ester electron donors can bound to MgCl\u003csub\u003e2\u003c/sub\u003e through their carbonyl group. The red-shift in the stretching frequency corresponding to the free ester (1700\u0026ndash;1750 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) to about 1620\u0026ndash;1660 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in the catalyst indicates the coordination of the ester electron donor to MgCl\u003csub\u003e2\u003c/sub\u003e support. This confirms the interaction of ester electron donors with the catalyst [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Furthermore, the peak related to Mg-Cl bond at the range of 1620\u0026ndash;1660 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e merged with the carbonyl peak. The bands at 450\u0026ndash;460 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 615 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are attributed to the metal-halide stretching corresponding to Ti-Cl. The broad bands around 3200\u0026ndash;3500 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e are due to the \u0026ndash;OH stretching vibration of SiO\u003csub\u003e2\u003c/sub\u003e support. The band at range 1010\u0026ndash;1100 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e is associated with the stretching vibration of Si\u0026ndash;O of the SiO\u003csub\u003e2\u003c/sub\u003e as support [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThere is a huge desire to obtain polymers with controlled particle size and morphology. If the structure of the catalyst is very fragile, particle attrition will cause the production of undesirable polymer fine powder. At the same time, because of the high rate of polymerization, crushing of polymer particles can prevent the phenomenon of replication of the catalyst particle shape and produce finer powders [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Considering the importance of the morphology of the catalyst and subsequent polymer, the morphology of the catalyst with different electron donors was investigated using SEM. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, all catalyst particles were spherical, except for catalyst 4, which contain malonate as the ID. In fact, the presence of cracks on catalysts 1 and 4 can be seen.\u003c/p\u003e\u003cp\u003eBy examining the diameter calculated from the SEM images, it was elucidated that the catalyst particles containing ethyl benzoate as an electron donor have the smallest particle diameter among the synthesized catalysts (diameter of Cat 1, 2 and 3 was 14.28, 0.5, and 4.8 \u0026micro;m, respectively). The reason for this outcome can be corelated to the smaller structure of ethyl benzoate compared to other electron donors. The largest catalyst particle size diameter is related to the catalyst containing phthalates, since the phthalates played the role of a binding agent and coordinated to (110) plane of magnesium chloride in the form of a bridge. Indeed, these IDs hold the adjacent MgCl layers through interlayer bonding, thus prevent mechanical fragmentation of the support during polymerization [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. The larger diameter of catalyst 1 compared to others can be attributed to this reason [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe powder X-ray diffraction of the catalyst samples is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. In the XRD patterns, the diffraction peaks at 2θ\u0026thinsp;=\u0026thinsp;35\u0026deg; and 2θ\u0026thinsp;~\u0026thinsp;50\u0026deg; indicated the structure of (104) and (110) planes of MgCl and demonstrated that all of them contain δ-phase MgCl\u003csub\u003e2\u003c/sub\u003e crystals [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. The use of ester electron donors with a different structure did not affect the crystal structure [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eSubsequently, all 4 catalysts were subjected to ethylene polymerization under the same conditions in the Buchi reactor to evaluate their performance. To study the effect of the electron donor on the characteristic of polymers, bulk density, GPC and DSC analyses were performed and the results collected in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. From the T\u003csub\u003em\u003c/sub\u003e results, obtained from DSC curves (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e), it was concluded that the T\u003csub\u003em\u003c/sub\u003e of PEs was less affected by the IDs type.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAs reported by Song, electron donors have a major impact on the molecular weight and molecular weight distribution of polyolefins [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. Therefore, to examine the effect of various kinds of electron donors on these parameters, GPC test was conducted on polyethylene samples, Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. As can be seen from the GPC curves and Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e data, between samples 1 and 2 (containing aromatic ester IDs), the later shows higher molecular weight, activity and bulk density. The activity of catalysts with diesters is almost in the same range, but the activity of ethyl benzoate (monoester) catalysts is dramatically higher. In fact, it was observed that diester IDs are less active than the monoester type in ethylene polymerizations. It can be corelated to the more acidic sites of TiCl\u003csub\u003e4\u003c/sub\u003e on MgCl\u003csub\u003e2\u003c/sub\u003e in the ethyl benzoate-containing catalyst. Yang et al. [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e] reported that the presence of TiCl\u003csub\u003e4\u003c/sub\u003e\u0026middot;monoester complex is much weaker compared to the TiCl\u003csub\u003e4\u003c/sub\u003e\u0026middot;diester complex. Therefore, in catalysts containing monoester, strong acid sites (titanium chloride) are more present on magnesium chloride support, because titanium chloride has less participated in the reaction of complex formation with ester and this leads to higher activity of the ethyl benzoate-containing catalyst. Furthermore, it is known that an ester electron donor as a Lewis base can easily react with Lewis\u0026rsquo;s acid species in the polymerization system, such as alkylaluminum and leach out during the addition of cocatalyst. In view of these facts, since the same concentration of electron donors is used in the preparation of the catalyst in all cases, it is possible that ethyl benzoate immobilized on magnesium chloride is still present in the polymerization stage after the undesired reaction of ethyl benzoate with alkylaluminum. This likely increases the molecular weight of the polymer made in the presence of the benzoate catalyst compared to the polymer made from the phthalate containing catalyst. The broad molecular weight distribution of the polymers obtained from the benzoate catalyst is corelated to the diversity of generated active sites. On the other hand, the free ester group in the diesters (phthalate) can share electrons with some titanium chloride on the support surface and coordinate with TiCl\u003csub\u003e4\u003c/sub\u003e and subsequently deactivate some active sites moreover act as a poison. This interaction results in an increase in spatial order in the case of propylene polymerization, but in ethylene polymerization, where spatial order is absent, it decreases activity [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. In the case of the catalysts with diethyl succinate and diethyl malonate (Cat3 and Cat4), the catalyst containing diethyl malonate with shorter chain length produces a polymer with a higher molecular weight, thereby broader molecular weight distribution and further the bulk density decreases.\u003c/p\u003e\u003cp\u003eTherefore, from the above results, it can be concluded that in ZN catalysts, when the aim is to synthesize a polymer with a high molecular weight, an electron donor having a small structure such as ethyl benzoate and ethyl malonate can be used. On the other hand, it has been observed that the larger structure of the electron donor in the catalyst decreases the molecular weight of the produced polymer in the polymerization step and leads to a narrower molecular weight distribution. It should be noted that catalysts containing smaller esters in the linear ester category, such as malonate, produce higher molecular weight and broader molecular weight distribution polymer than catalysts containing smaller esters in the aromatic ester category.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eTo study the effect of the hydrogen amount on the catalyst performance and the properties of the produced polymers, two hydrogen pressures (0.5 and 1 bar) were used in the ethylene polymerizations in the same reaction conditions. According to the results given in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e in all catalysts, the activity and performance of the catalyst decreased as the hydrogen pressure increased. Also,, based on Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e, polymers with lower molecular weight and narrower MWD were produced, which is caused by the formation of more dormant sites. Dormant sites are usually formed by β-agostic interactions between β-hydrogen of the ethyl group and the titanium atom in the Cl\u003csub\u003e2\u003c/sub\u003eTi-CH\u003csub\u003e2\u003c/sub\u003e-CH\u003csub\u003e3\u003c/sub\u003e site, which decrease the rate of polymerization in the presence of hydrogen [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. Among the catalysts, the catalyst containing diethyl malonate showed a much better hydrogen response (lower molecular weight), furthermore produced a polymer with a narrower molecular weight distribution. The response to hydrogen in various types of catalysts with different electron donors was determined in the following order: Cat4 (ethyl malonate)\u0026thinsp;\u0026gt;\u0026thinsp;Cat2 (ethyl benzoate)\u0026thinsp;\u0026gt;\u0026thinsp;Cat3 (diethyl succinate)\u0026thinsp;\u0026gt;\u0026thinsp;Cat1 (di-n-butyl phthalate). And of course, the molecular weight distribution of polyethylene was in the same order. In fact, the response to hydrogen is better for catalysts with smaller electron donors. In this class of catalysts, the less sterically hindered donors cause increased access of hydrogen to the active sites. Comparing the group of linear and aromatic ester donors, the catalyst containing the linear ester donor has a higher hydrogen response than the catalyst containing the aromatic donor.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eThe effect of hydrogen pressure on the catalyst performance and final polymer properties\u003csup\u003e1\u003c/sup\u003e\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCatalyst\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eH\u003csub\u003e2\u003c/sub\u003e pressure\u003c/p\u003e\u003cp\u003e(bar)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eActivity\u003c/p\u003e\u003cp\u003e(kg PE/g Catalyst.h)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eM\u003csub\u003ew\u003c/sub\u003e\u003c/p\u003e\u003cp\u003e(g/mol)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eMWD\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCat1\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e55049\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e2.2\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCat1\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e35233\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCat2\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e14.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e218117\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e3.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCat2\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e13.1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e91529\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e2.0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCat3\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.25\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e99395\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e2.9\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCat3\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e50393\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e1.7\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCat4\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e0.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e5.13\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e428733\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e4.6\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eCat4\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e4.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e142393\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e2.3\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"5\"\u003e\u003csup\u003e1\u003c/sup\u003ePolymerization conditions: P\u003csub\u003eTotal\u003c/sub\u003e= 8 bar, T\u0026thinsp;=\u0026thinsp;80\u0026deg;C, [Al]/[Ti]\u0026thinsp;=\u0026thinsp;150 mol/mol, time\u0026thinsp;=\u0026thinsp;1 h\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eSEM of the polymer produced in the presence of catalyst with an aromatic ester (di-n-butyl phthalate) and a linear ester (Diethyl succinate) is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e. The morphology of the polymers is almost the same in both images and polymer fibers interconnect the microparticles to form macroparticles. The formation of fibril polymers reduces the formation of fines during polymerization. Reducing the fines generated in the final polymer is a critical parameter in the industry.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eAs a matter of fact, the choice of electron donors for the catalyst system depends on the characteristic and quantity of the polymer produced by these catalysts. Therefore, four types of catalysts with diethyl succinate and diethyl malonate (linear diesters), di-n-butyl phthalate (aromatic diester) and ethyl benzoate (aromatic monoester) were synthesized and compared in terms of catalyst structures and their catalytic performance. SEM images illustrated that the morphology of the catalyst particles was spherical, except for the malonate catalyst (Cat 4) at magnification below 10 \u0026micro;m. The diameter in various types of catalysts with different electron donors was determined from the SEM images in the following order: Cat1 (di-n-butyl phthalate)\u0026thinsp;\u0026gt;\u0026thinsp;Cat3 (diethyl succinate)\u0026thinsp;\u0026gt;\u0026thinsp;Cat2 (ethyl benzoate). The presence of phthalate as a large electron donor, leads to an increase in the specific surface area of the catalyst, however, similar XRD pattern was obtained. Moreover, diesters based catalysts had lower activity than mono ester types. According to the GPC results, when the aim is to synthesize a polymer having a high molecular weight, small electron donors of both linear and aromatic esters such as diethyl malonate and ethyl benzoate can be used more effectively. On the other hand, in both the aromatic ester and linear ester categories, the larger electron donor structure reduces the molecular weight of the polymer produced. In comparing two categories of catalysts containing linear and aromatic small esters (malonate and ethyl benzoate), the catalyst containing a small linear ester produces a polymer with a higher molecular weight than the catalyst containing a small aromatic ester contains.\u003c/p\u003e\u003cp\u003eFinally, the effect of hydrogen pressure on catalyst performance and final polymer properties was evaluated. According to the GPC results, the hydrogen response for catalysts containing smaller IDs is better. Also, a comparison of the group of linear and aromatic ester donors shows that the catalyst containing the linear ester donor has a higher hydrogen response than the catalyst containing the aromatic donor.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe acknowledge Bandar Imam Petrochemical Complex (BIPC) for support of this work.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe author claims that there is no conflict of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding Declaration\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research received no external funding.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability Statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data that support the findings of this study are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e[Hamidreza Teimoury]: Conceptualization, Methodology, Supervision, Project Administration\u003c/p\u003e\n\u003cp\u003e[Nazanin Moeini]: Data Curation, Methodology, Formal Analysis, Writing \u0026ndash; Review \u0026amp; Editing.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eMehdizadeh M, Karkhaneh F, Nekoomanesh M, Sadjadi S, Emami M, Teimoury H, Salimi M, Sol\u0026agrave; M, Poater A, Bahri-Laleh N, Posada-P\u0026eacute;rez S (2023) Influence of the ethanol content of adduct on the comonomer incorporation of related Ziegler\u0026ndash;Natta catalysts in propylene (co)polymerizations. J Polym Res 15:4476\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMakaryan IA, Sedov IV (2020) Analysis of the state and development prospects of the industrial catalysts market for polyolefins production. Russ J Gen Chem 90:1141\u0026ndash;1162\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZiegler K, Holzkamp E, Breil H, Martin HJAC (1955) Das m\u0026uuml;lheimer normaldruck-poly\u0026auml;thylen-verfahren. Angew Chem 67:541\u0026ndash;547\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eNatta G, Pino P, Corradini P, Danusso F, Mantica E, Mazzanti G, Moraglio GJ (1955) Crystalline high polymers of α-olefins. J Am Chem Soc 77:1708\u0026ndash;1710\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePotapov A, Bukatov G, Zakharov VJ (2009) DRIFTS study of the interaction of the AlEt3 cocatalyst with the internal donor ethyl benzoate in supported Ziegler\u0026ndash;Natta catalysts. J Mol Catal A: Chem 301:18\u0026ndash;23\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCredendino R, Liguori D, Morini G, Cavallo L (2014) Investigating phthalate and 1,3-diether coverage and dynamics on the (104) and (110) surfaces of MgCl2-supported Ziegler\u0026ndash;Natta catalysts. J Phys Chem C 118:8050\u0026ndash;8058\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePotapov AG, Politanskaya LV (2013) The study of the adsorption of 1,3-diethers on the MgCl2 surface. J Mol Catal A: Chem 368:159\u0026ndash;162\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWen X, Ji M, Yi Q, Niu H, Dong J-Y (2010) Magnesium chloride supported Ziegler-Natta catalysts containing succinate internal electron donors for the polymerization of propylene. J Appl Polym Sci 118:1853\u0026ndash;1858\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePaghadar BR, Sainani JB, Bhagavath P (2021) Internal donors on supported Ziegler Natta catalysts for isotactic polypropylene: A brief tutorial review. J Polym Res 28:1\u0026ndash;19\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePoorsank F, Arabi H, Ghasemi Hamedani N (2021) Silyl diol ester as a new selectivity control agent in MgCl2-supported Ziegler\u0026ndash;Natta systems for propylene polymerization: Catalyst structure and polymer properties. J Polym Res 28:185\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTanase S, Katayama K, Yabunouchi N, Sadashima T, Tomotsu N, Ishihara NJ (2007) Design of novel malonates as internal donors for MgCl2-supported TiCl4 type polypropylene catalysts and their mechanistic aspects, Part 1. J Mol Catal A: Chem 273:211\u0026ndash;217\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKumawat J, Gupta VK (2020) Fundamental aspects of heterogeneous Ziegler\u0026ndash;Natta olefin polymerization catalysis: An experimental and computational overview. Phys Chem Chem Phys 11:6107\u0026ndash;6128\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSinha ASK, Ojha U (2021) Evolution of Ziegler-Natta catalysts for polymerization of olefins. In: Pant, K. K., Gupta, S. K., \u0026amp; Ahmad, E. (Eds.), \u003cem\u003eCatalysis for Clean Energy and Environmental Sustainability\u003c/em\u003e, 2, 675\u0026ndash;705\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eGrau E, Lesage A, Norsic S, Cop\u0026eacute;ret C, Monteil V, Sautet P (2013) Tetrahydrofuran in TiCl4/THF/MgCl2: A non-innocent ligand for supported Ziegler\u0026ndash;Natta polymerization catalysts. Angew Chem 3:52\u0026ndash;56\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMilanesi M, Piovano A, Wada T, Zarupski J, Chammingkwan P, Taniike T, Groppo E (2023) Influence of the synthetic procedure on the properties of three Ziegler-Natta catalysts with the same 1,3-diether internal donor. Catal Today 418:114077\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKhatri V, Sahoo U, Kaur S, Rani R, Singh G, Kapur GS, Kashyap HK (2020) Control of Ziegler\u0026ndash;Natta catalyst activity by the structural design of alkoxysilane-based external donors. New J Chem 44:6845\u0026ndash;6852\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMoeini N, Teimoury H, Salimi M, Bahri-Laleh N, Joshaghani M, Duran J, Posada-P\u0026eacute;rez S (2024) Influence of the reaction conditions on the Ziegler-Natta catalyzed ethylene polymerization: Kinetics and properties of the resulting polymers. Polymer 293:126640\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWeng Y, Jiang B, Fu Z, Fan Z (2018) Mechanism of internal and external electron donor effects on propylene polymerization with MgCl2-supported Ziegler\u0026ndash;Natta catalyst: New evidences based on active center counting. J Appl Polym Sci 135:46605\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLi B, Li H, Hu H, Zhou Y, Mao G, Xin S (2024) The Effects of Internal Electron Donors on MgCl2-Supported Ziegler\u0026ndash;Natta Catalysts for Isotactic PP. Polymers 16(19):2687\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZhong W, Cai X, Shen X, Liu H, Fu Z, Wang Q, Song S, Du B, Fan Z (2025) Effects of Internal Electron Donor on the Distribution of Active Centers and Their Intrinsic Reactivities in Propylene Polymerization with MgCl2-Supported Ziegler\u0026ndash;Natta Catalysts. Industrial \u0026amp; Engineering Chemistry Research\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBazhenov A, Linnolahti M, Pakkanen TA, Denifl P, Leinonen T (2014) Modeling the stabilization of surface defects by donors in Ziegler\u0026ndash;Natta catalyst support. J Phys Chem C 118(9):4791\u0026ndash;4796\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCorrea A, Piemontesi F, Morini G, Cavallo LJM (2007) Key elements in the structure and function relationship of the MgCl₂/TiCl₄/lewis base Ziegler\u0026thinsp;\u0026ndash;\u0026thinsp;Natta catalytic system. Macromol Chem Phys 40(24):9181\u0026ndash;9189\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBusico V, Corradini P, De Martino L, Proto A, Albizzati EJ D. M. C. M. C. (1986). Polymerization of propene in the presence of MgCl₂-supported Ziegler‐Natta catalysts, 2. Effects of the co‐catalyst composition. Macromol Chem Phys, 187(5), 1115\u0026ndash;1124\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eStukalov DV, Zilberberg IL, Zakharov VA (2009) Surface species of titanium (IV) and titanium (III) in MgCl2-supported Ziegler\u0026thinsp;\u0026ndash;\u0026thinsp;Natta catalysts. A periodic density functional theory study. Macromolecules 42(21):8165\u0026ndash;8171\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTeimoury H, Moeini N, Bahri-Laleh N, Shih F-Y, Varnoosfaderani MV (2023) The effect of SiO₂ calcination temperature and [Si]/[Mg] molar ratio on the performance of bi-supported Ziegler-Natta catalysts in ethylene polymerizations. J Polym Res 30:73\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSingh G, Kaur S, Makwana U, Patankar RB, Gupta VK (2009) Influence of internal donors on the performance and structure of MgCl₂ supported titanium catalysts for propylene polymerization. Macromol Chem Phys 210(1):69\u0026ndash;76\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eThongdonjui A, Trakarnpruk W, Strauss RH (2009) Effect of electron donor on PE polymerization. J Met Mater Minerals, 19(2)\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZohuri G, Ahmadjou S, Jamjah R, Nekou MM (2001) Structural study of mono-and bi-supported Ziegler-Natta catalysts MgCl₂/SiO₂/TiCl₄/donor systems. Iran Polym J, 145\u0026ndash;155\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMohamadi Z, Moradi G, Teimoury HR (2021) Comparison of Mg-ethoxide based Ziegler Natta catalysts using different internal donors employed for ethylene polymerization. J Polym Res 28:185\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFu T, Cheng R, He X, Liu Z, Tian Z, Liu B (2016) Imido-modified SiO₂-supported Ti/Mg Ziegler-Natta catalysts for ethylene polymerization and ethylene/1-hexene copolymerization. Polyolefins J 3(2):103\u0026ndash;117\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eLiu X, Guo W, Wang X, Guo Y, Zhang B, Fu Z, Wang Q, Fan Z (2021) TiCl₄/MgCl₂/MCM-41 Bi-Supported Ziegler\u0026ndash;Natta Catalyst: Effects of catalyst composition on ethylene/1-hexene copolymerization. Catalysts 11(12):1535\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eVanka K, Singh G, Iyer D, Gupta VK (2010) DFT study of Lewis base interactions with the MgCl₂ surface in the Ziegler\u0026thinsp;\u0026ndash;\u0026thinsp;Natta catalytic system: Expanding the role of the donors. J Phys Chem C 114(35):15771\u0026ndash;15781\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eXue B, Hui L, Yang H, Zhao Y, Hou L, Li W (2017) Immobilization of Ziegler\u0026ndash;Natta catalyst for ethylene polymerization on macroporous SiO₂ with an open-framework structure. Ind Eng Chem Res 56(1):135\u0026ndash;142\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAbazari M, Jamjah R, Bahri-Laleh N, Hanifpour A (2022) Synthesis and evaluation of a new three-metallic high-performance Ziegler\u0026ndash;Natta catalyst for ethylene polymerization: Experimental and computational studies. Polym Bull 79:7265\u0026ndash;7280\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBukatov G, Maslov D, Sergeev S, Matsko M (2019) Effect of internal donors on the performance of Ti-Mg catalysts in propylene polymerization: Donor introduction during or after MgCl₂ formation. Appl Catal A 577:69\u0026ndash;75\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSong BG, Ihm SK (2014) The role of two different internal donors (phthalate and 1,3-diether) on the formation of surface structure in MgCl₂‐supported Ziegler\u0026ndash;Natta catalysts and their catalytic performance in propylene polymerization. J Appl Polym Sci, 131\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eYang C, Hsu C, Park Y, Shurvell H (1994) Infrared characterization of MgCl₂ supported Ziegler-Natta catalysts with monoester and diester as a modifier. Eur Polymer J 30(2):205\u0026ndash;214\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCavallo L, Del Piero S, Duc\u0026eacute;r\u0026eacute; J-M, Fedele R, Melchior A, Morini G, Piemontesi F, Tolazzi M (2007) Key interactions in heterogeneous Ziegler\u0026thinsp;\u0026ndash;\u0026thinsp;Natta catalytic systems: Structure and energetics of TiCl₄\u0026ndash;Lewis base complexes. J Phys Chem C 111(11):4412\u0026ndash;4419\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCorrea A, Bahri-Laleh N, Cavallo L (2013) How well can DFT reproduce key interactions in Ziegler\u0026ndash;Natta systems? Macromol Chem Phys 214(18):1980\u0026ndash;1989\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSukulova V, Barabanov A, Mikenas T, Matsko M, Zakharov V (2018) Effect of hydrogen on the number of active centers and the propagation rate constant at ethylene polymerization over titanium-magnesium Ziegler-Natta catalysts. Mol Catal 445:299\u0026ndash;306\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-polymer-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jpol","sideBox":"Learn more about [Journal of Polymer Research](https://www.springer.com/journal/10965)","snPcode":"10965","submissionUrl":"https://www.editorialmanager.com/jpol/","title":"Journal of Polymer Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Bi-supported, Ziegler-Natta catalysts, Ester electron donors, ethylene polymerization","lastPublishedDoi":"10.21203/rs.3.rs-6828388/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6828388/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study aimed to explore the effects of ester-based internal electron donors on the efficacy and characteristics of SiO\u003csub\u003e2\u003c/sub\u003e@MgCl\u003csub\u003e2\u003c/sub\u003e bi-supported Ziegler-Natta (ZN) catalysts. Four distinct ester-based electron donors were used during catalyst synthesis, including linear diesters with varying carbon chain lengths (diethyl succinate and diethyl malonate), aromatic diesters (di-n-butyl phthalate), and aromatic monoesters (ethyl benzoate). Synthesized catalysts were employed in ethylene polymerizations using H\u003csub\u003e2\u003c/sub\u003e as molar mass moderator. Various analytical techniques and measurements of bulk density were employed to analyze the prepared catalysts and polymers. SEM analysis revealed that most catalyst particles had a spherical morphology, except for the catalyst incorporating malonate as internal electron donor. The phthalate catalyst showed a larger diameter, mainly due to its role as a binding agent. The molecular weight, activity, and bulk density of polyethylene were found to be influenced by the type of electron donors. The catalyst with SiO\u003csub\u003e2\u003c/sub\u003e@MgCl\u003csub\u003e2\u003c/sub\u003e/THF/TiCl\u003csub\u003e4\u003c/sub\u003e/ethyl benzoate exhibited significantly higher catalytic activity and hydrogen response, which can be attributed to the reduced steric hindrance surrounding the ethyl benzoate compound. These findings have implications for the development of more efficient and sustainable polymerization processes, with potential applications in various industries using polyethylene.\u003c/p\u003e","manuscriptTitle":"Exploring the role of ester electron donors in ethylene polymerization using bi-supported SiO2@MgCl2/TiCl4 type Ziegler-Natta catalysts","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-28 14:13:58","doi":"10.21203/rs.3.rs-6828388/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2025-08-20T11:27:49+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-08-20T09:18:15+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Journal of Polymer Research","date":"2025-08-10T17:48:40+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-07-17T02:36:28+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Polymer Research","date":"2025-07-16T05:59:47+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-polymer-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jpol","sideBox":"Learn more about [Journal of Polymer Research](https://www.springer.com/journal/10965)","snPcode":"10965","submissionUrl":"https://www.editorialmanager.com/jpol/","title":"Journal of Polymer Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"9ea64efd-0371-47af-8a67-945d8bea4758","owner":[],"postedDate":"August 28th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-12-01T16:06:32+00:00","versionOfRecord":{"articleIdentity":"rs-6828388","link":"https://doi.org/10.1007/s10965-025-04675-8","journal":{"identity":"journal-of-polymer-research","isVorOnly":false,"title":"Journal of Polymer Research"},"publishedOn":"2025-11-28 15:57:53","publishedOnDateReadable":"November 28th, 2025"},"versionCreatedAt":"2025-08-28 14:13:58","video":"","vorDoi":"10.1007/s10965-025-04675-8","vorDoiUrl":"https://doi.org/10.1007/s10965-025-04675-8","workflowStages":[]},"version":"v1","identity":"rs-6828388","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6828388","identity":"rs-6828388","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}