Interaction of common cocatalysts in Ziegler–Natta‐catalyzed olefin polymerization

Fallah, Mehrdad; Bahri‐Laleh, Naeimeh; Didehban, Khadijeh; Poater, Albert

doi:10.1002/aoc.5333

Cited by 43 publications

(31 citation statements)

References 41 publications

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“…The residual Ti amount decreased progressively with increasing temperature, from ≈70% at 40 °C to ≈35% at 100 °C (Figure a and Table S1 (Supporting Information)); this observation is consistent with the DFT-D conclusion that TiCl 4 adsorption on MgCl 2 is weak . One can speculate that the (more) strongly bound Ti fraction features, at least in part, species in lower oxidation states (mainly Ti(III) , ) resulting from the alkylation/reduction of TiCl 4 by AlEt 3 , which is also known to be fast. ,,,,, It may be worthy to recall that previous experimental studies demonstrated that the fraction of TiCl 4 lost to the liquid phase is practically inactive in propene polymerization …”

Section: Resultssupporting

confidence: 82%

Monitoring the Kinetics of Internal Donor Clean-up from Ziegler–Natta Catalytic Surfaces: An Integrated Experimental and Computational Study

et al. 2020

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Surface modification of MgCl 2 -supported Ziegler−Natta catalysts (ZNCs) by means of organic Lewis bases, either used as precatalyst components ("internal donors", ID) or in combination with the AlEt 3 cocatalyst ("external donors", ED), is key for achieving a high stereoselectivity in propene polymerization. In fourth-generation systems, which are the working horses of this important catalyst class, the ID is an (ortho-)dialkyl phthalate; under polymerization conditions, this reacts with AlEt 3 and must be replaced by an ED (typically an alkoxysilane) in order to obtain the desired performance. In a previous study, we investigated the molecular kinetics of the reaction between dibutyl phthalate and AlEt 3 in solution by means of integrated experimental and computational protocols. A similar approach has now been applied to monitor the progress of the reaction for the complete catalyst system. Compared with solution (ΔH # ≈ 15 kcal mol −1 ; ΔS # ≈ −28 cal mol −1 K −1 ), the activation parameters in heterogeneous phase (ΔH # ≈ 10 kcal mol −1 ; ΔS # ≈ −49 cal mol −1 K −1 ) indicate that phthalate reduction is less activated, but suffers from an augmented entropic penalty. This suggests that the ID reacts with AlEt 3 while still on the MgCl 2 surface, rather than in the liquid phase after desorption, and that the surface is not innocent. Whether or not an alkoxysilane ED was present in the system turned out to be immaterial on reaction kinetics. High-level DFT calculations on a wellestablished MgCl 2 /dibutyphthalate model cluster reproduced the experimental data with a remarkably good agreement (ΔH # ≈ 10 kcal mol −1 ; ΔS # ≈ −46 cal mol −1 K −1 ). Experiments and calculations agree on the first ethyl transfer to the reacting ester group representing the rate-determining step, in solution as well in heterogeneous phase. In both cases, a four-membered transition state (TS) appears to be involved; in heterogeneous phase, though, the ester carbonyl is extra-activated by the interaction with a Lewisacidic surface Mg center, rather than a second AlEt 3 molecule. In our opinion, the interest of the proposed approach goes beyond the present study; indeed, further applications can be proposed for the design and engineering of novel ZNCs with tailored behaviors.

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Section: Resultssupporting

confidence: 82%

Monitoring the Kinetics of Internal Donor Clean-up from Ziegler–Natta Catalytic Surfaces: An Integrated Experimental and Computational Study

et al. 2020

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“…45 The same results were obtained by Fallah et al, when the AlMe 3 and AlMe 2 Cl species coordinated near the Ti active site on the (110) surface. 46 Since the external donor alkoxysilane is always used in combination with the cocatalyst AlR 3 during the polymerization, it is obvious that the AlR 2 Cl species can affect olefin insertion in the presence of the external donors.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Study on Effect of Electron Donors in Propylene Polymerization Using the Ziegler–Natta Catalyst

et al. 2021

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TiCl 4 /MgCl 2 catalysts are still the main industrial catalyst for isotactic polypropylene at present. However, the mechanism of isotactic polymerization of propylene has not been fully understood. DFT calculations revealed that the bare Ti active site was regioselective and nonstereoselective in the absence of an electron donor. The role of electron donor ethyl benzoate (EB), diethyl-2,3-diisobutylsuccinate (DiBS), cyclohexylmethyldimethoxysilane (CMDMS), and dicyclopentyldimethoxysilane (DCPDMS) on the active site was investigated. The presence of EB, DiBS, CMDMS, or DCPDMS around the Ti active site can promote the activity and retain the regioselectivity. It is worth noting that in the presence of EB and DCPDMS, the stereoselective behavior can be promoted with the advantage of 1 kcal/mol. The copresence of AlEt 2 Cl species and external donors can increase both the stereoselectivity and regioselectivity.

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“…[40,41] These bonds make PAO susceptible to cleavage at high temperature of application, which deteriorates PAOs unique characteristics and decreases its shelf life. [42,43] To overcome this drawback, PAO hydrofinishing, as an essential stage in its production, is usually accomplished. This stage needs harsh environment with high temperature and H 2 pressure (nearly above 200 C and 25 bar), which increases the risk and cost of PAO production.…”

Section: Introductionmentioning

confidence: 99%

Effect of support hydrophobicity of halloysite‐based catalysts on the polyalphaolefin hydrofinishing performance

Shams

Sadjadi

Duran

et al. 2022

Applied Organom Chemis

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Hydrogenation of polyalphaolefins (PAOs) is an industrial process catalyzed by supported precious metals. In this regard, halloysite (Hal) clay has been proven as an efficient support for the immobilization of Pd nanoparticles and development of high-performance catalysts under mild reaction condition. In this research, the effect of Hal hydrophobicity on the PAO hydrofinishing efficiency is studied. In this line, cetrimonium bromide (CTAB) was used for adjusting the hydrophobicity of halloysite surface. Three catalysts, Hal/Pd, Hal/Pd/CTAB, and Hal/CTAB/Pd, were fabricated by palladation of Hal, treating palladated Hal with CTAB and palladation of CTAB-treated Hal, respectively. The catalysts were characterized, and their activity for the hydrogenation of PAO was appraised. Moreover, a molecular simulation approach was employed to survey the effect of surface hydrophobicity of Hal on the alkene hydrogenation energy diagram and the steric maps of the main catalytic stages. Both experimental and computational studies approved that the presence of CTAB detracts the activity of the catalyst. Moreover, the order of introduction of Pd and CTAB affects the content of incorporated CTAB and Pd and Pd particle size, and the order of catalysts activity was as follows:

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Interaction of common cocatalysts in Ziegler–Natta‐catalyzed olefin polymerization

Cited by 43 publications

References 41 publications

Monitoring the Kinetics of Internal Donor Clean-up from Ziegler–Natta Catalytic Surfaces: An Integrated Experimental and Computational Study

Monitoring the Kinetics of Internal Donor Clean-up from Ziegler–Natta Catalytic Surfaces: An Integrated Experimental and Computational Study

Mechanistic Study on Effect of Electron Donors in Propylene Polymerization Using the Ziegler–Natta Catalyst

Effect of support hydrophobicity of halloysite‐based catalysts on the polyalphaolefin hydrofinishing performance

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