Size-Dependent Catalytic Activity of Oxo-Hydroxo Titanium Sub-Nanoislets Grafted on Organically Modified Mesoporous Silica

Lin, Fang; Albela, Belén; Yang, Boting; Zheng, Yuting; Wu, Peng; He, Min; Bonneviot, Laurent

doi:10.1021/acs.langmuir.8b01932

Cited by 5 publications

(4 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These “TS‐1‐(OOH) 2 ” sites enable the epoxidation of propylene with H 2 O 2 via an oxygen‐transfer transition state (Scheme 3d, 9 ) similar to the electrophilic epoxidation by peracids. In fact, anterior studies also suggested that high epoxidation activity does not imply that Ti oligomers should be absent from the catalyst [81–83] . Nevertheless, it is usually admitted that highly coordinated Ti species are less active and selective in epoxidation, [56] whereas pure TiO 2 typically shows no activity as it lacks free coordination sites.…”

Section: Strategies To Improve Ti‐based Heterogeneous Epoxidation Catalystsmentioning

confidence: 99%

Titanosilicate Epoxidation Catalysts: A Review of Challenges and Opportunities

2021

View full text Add to dashboard Cite

Epoxidation reactions are tremendously important for modern chemistry, as they lead to series of highly useful bulk and fine chemicals, monomers, and intermediates for organic synthesis. Progress in epoxidation processes goes hand in hand with the advancement made in catalysis science. In this context, heterogeneous catalysts, and particularly Ti‐based formulations, are playing a central role and have seen tremendous developments over the past two decades, leveraging on advanced materials science. The aim of this review is to illustrate the various strategies of titanosilicate catalysts preparation that can lead to more versatile, more performant, and greener epoxidation processes. We successively cover (i) supported catalysts, obtained by the grafting of Ti species onto preformed silica supports, (ii) microporous crystalline titanosilicates (zeolites), and (iii) amorphous titanosilicates obtained by sol‐gel chemistry. For each category, with an emphasis on catalyst preparation, the challenges that have to be tackled to boost catalyst performance are highlighted. From that point, we present a critical review of the different approaches that have been proposed in the primary literature to tailor the properties that govern catalysts performance (activity, selectivity, stability, ease of handling). This is done by better controlling the nature of the active surface species, adapting particles size and shape, optimizing texture, modifying surface chemistry, etc. These lines of attack encompass molecular approaches for the grafting of well‐defined species, top‐down and bottom‐up synthesis of hierarchically porous zeolites, advanced sol‐gel routes potentially performed in non‐conventional media or coupled with original processing, preparation of self‐standing monoliths, etc. Future research directions are discussed with emphasis on the application scope of new catalytic materials and possible approaches to increase catalyst performance.

show abstract

Section: Strategies To Improve Ti‐based Heterogeneous Epoxidation Catalystsmentioning

confidence: 99%

Titanosilicate Epoxidation Catalysts: A Review of Challenges and Opportunities

2021

View full text Add to dashboard Cite

show abstract

“…Fang et al reported the epoxidation of cyclohexene by oxo-hydroxo Ti IV species grafted on organically modified mesoporous silica of 3 nm pore diameter. [25] While very elegant, the elaboration of the heterogenous catalyst required a multi-step surface molecular engineering to install the Ti IV active species in the confined space of the templated porous silica. Additionally, this catalytic system was poorly active with hydrogen peroxide as oxidant and required the use of the less benign tert-butyl hydroperoxide instead.…”

Section: Resultsmentioning

confidence: 99%

Iron ions embedded in hexagonal mesoporous silica via a simple method: implementation in mild oxidation catalysis

Guemati,

Rebilly,

Fornasieri

et al. 2023

ChemistrySelect

View full text Add to dashboard Cite

Mesoporous silica monoliths containing dispersed FeIII sites have been prepared following a direct and simple synthetic method. The iron‐containing materials are able to catalyze the epoxidation of cyclooctene by H2O2 under mild conditions. Textural and spectrophotometric analyses reveal that, when the thermal treatment temperature of the materials increases (from 500 °C to 1000 °C), the pore diameter of the silica matrix decreases while the formation of small oxo‐iron(III) clusters is promoted. Among the five materials obtained after treatment at 500, 700, 800, 900 or 1000 °C, the one prepared at 700 °C exhibits the best catalytic performances. This indicates that a compromise must be found between several parameters, such as the pore size (which decreases with calcination temperature) and the hydrophobicity of the channel surface (which is favored at higher temperature), for an optimal reactivity.

show abstract

“…This means that the travel of the reactants across the surface to the active site cannot be ignored. 12 Our goal is to isolate this travel step by sterically conning a reaction that follows the Langmuir-Hinshelwood pathway. By placing barriers at different distances, we hope to understand how much space a heterogeneous reaction needs in relation to the reactant's size.…”

Section: K ¼ a Ementioning

confidence: 99%