Effect of solvents on propylene epoxidation over TS-1 catalyst

Wu, Yulong; Liu, Qingshan; Su, Xueli; Mi, Zhentao

doi:10.1007/s11458-008-0007-2

Cited by 11 publications

(10 citation statements)

References 12 publications

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“…The experimental studies by Wu et al showed that methanol exhibits more significant promotion on the epoxidation activity than other solvents examined, especially superior to the aprotic solvent such as acetonitrile and tetrahydrofuran. Based on the studies on various aspects of solvent effect, it was found that the steric effect, electronic influence, as well as polarity mainly contribute to solvent effect on epoxidation reactivity . Methanol is commonly used as the solvent for PL epoxidation with H 2 O 2 over TS-1 catalysts. ,,,,− In this section, we investigated the effect of the methanol solvent on PL epoxidation mechanisms and kinetics by including an explicit methanol molecule into the catalytic system.…”

Section: Results and Discussionmentioning

confidence: 99%

“…Based on the studies on various aspects of solvent effect, it was found that the steric effect, electronic influence, as well as polarity mainly contribute to solvent effect on epoxidation reactivity . Methanol is commonly used as the solvent for PL epoxidation with H 2 O 2 over TS-1 catalysts. ,,,,− In this section, we investigated the effect of the methanol solvent on PL epoxidation mechanisms and kinetics by including an explicit methanol molecule into the catalytic system. To uncover the effect of the nature of the solvent, the epoxidation property of PL with H 2 O 2 over TS-1 was also investigated in the presence of an aprotic acetonitrile solvent molecule and compared with the results from protic methanol solvent.…”

Section: Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

“…When a smaller crystal size (600 nm × 400 nm × 250 nm) of TS-1 catalyst was used, the conversion of H 2 O 2 and selectivity of PO can reach to 92 and 98 mol %, respectively . According to the experimental results reported in literature, the epoxidation performance can be tuned/improved by adjusting the coordination structure of the Ti center (coordination state, solvent coordination, defect formation, and hydrolysis process), − tuning the crystal size, , modifying pore structures, solvent addition, − and so forth. Although extensive experimental − ,,, and theoretical studies ,− have been conducted on this subject, the impact factors on the formation of active intermediate species, reaction pathways, kinetics, and selectivity for alkene epoxidation with H 2 O 2 over TS-1 catalysts have not been clearly elucidated to date.…”

Section: Introductionmentioning

confidence: 99%

“…The experimental studies have shown that the solvent has an important effect on the activity and selectivity of TS-1 catalysts in liquid-phase epoxidation; however, this influence is very complicated because of its dependence on both the catalyst properties and reaction conditions. , In Ti-containing catalytic systems, the epoxidation rates of alkenes are higher in protic solvents (e.g., methanol and ethanol) than that in aprotic solvents such as acetonitrile and acetone . Commonly, the direct participation of solvent molecules in reaction can tune the adsorption stability of guest molecules and impact the pathways and kinetics for alkene epoxidation with H 2 O 2 over TS-1 catalysts. ,,, Clerici and Ingallina, at the first time, proposed a five-membered ring (5MR) titanium hydroperoxy (Ti–OOH) active intermediate under solvent conditions, Ti–(η 1 -OOH)–ROH, in which the protic solvent ROH forms a hydrogen bond with the distal oxygen atom of Ti–OOH species while coordinating with the Ti center .…”

Section: Introductionmentioning

confidence: 99%

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Mechanistic Insight into Propylene Epoxidation with H₂O₂ over Titanium Silicalite-1: Effects of Zeolite Confinement and Solvent

Nie

Ren

et al. 2019

J. Phys. Chem. B

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Density functional theory (DFT) calculations were performed to investigate the effects of zeolite confinement and solvent on propylene epoxidation with H2O2 over the titanium silicalite-1 (TS-1) catalyst. The 144T and 143T cluster models containing typical 10MR channels of TS-1 were constructed to represent the tripodal(2I) and Ti/defect sites. It was found that the confinement of the zeolite pore channel not only impacts the adsorption stability of guest molecules but also alters reaction barriers, as compared to the results obtained based on small cluster models. When dispersion corrections were considered, an enhancement of the adsorption stability of guest molecules was observed because of the important contribution from van der Waals interactions, especially for propylene adsorption. An explicit protic methanol molecule was introduced into the catalytic system to probe the influence of the solvent on propylene epoxidation, based on which a significant enhancement of CH3OH–H2O2 co-adsorption was obtained owing to H-bond formation. More importantly, the energy barrier for H2O2 dissociation was largely reduced by ∼13 kcal/mol because of the participation of the methanol in the H-transfer process and the formation of H-bond network, resulting in an alteration of the rate-limiting step. By comparison, adding an aprotic acetonitrile solvent did not have substantial effect on reaction path and kinetics. The calculation results clearly demonstrate the important role of the protic methanol solvent, which not only strengthens the adsorption of guest molecules but also promotes the kinetics for propylene epoxidation with H2O2 over TS-1 catalyst.

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