Direct epoxidation of propene on silylated Au–Ti catalysts: a study on silylation procedures and the effect on propane formation

Kanungo, S.; Keshri, Kumer Saurav; Hensen, Emiel J. M.; Chowdhury, Biswajit; Schouten, J.C.; d’Angelo, M.F. Neira

doi:10.1039/c8cy00439k

Cited by 17 publications

(11 citation statements)

References 43 publications

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“…Moreover, it has been proposed that the formation of byproducts is mainly caused by the ring-opening and isomerization of PO catalyzed by the acidic sites on the catalyst surface. ,, To weaken the PO adsorption and thus suppress its side reaction, surface modification would be a promising strategy to enhance the catalytic performance. Previous studies hasve demonstrated that increasing the hydrophobicity of the catalyst surface could improve the catalytic activity and selectivity. ,− However, these studies are not in the scope of this work, which would be investigated in our future study.…”

Section: Resultsmentioning

confidence: 97%

Surface Engineering and Kinetics Behaviors of Au/Uncalcined TS-1 Catalysts for Propylene Epoxidation with H₂ and O₂

Wang

Cao

Zhang

et al. 2019

Ind. Eng. Chem. Res.

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Uncalcined TS-1-immobilized Au bifunctional catalysts have been demonstrated to be highly active yet stable for the propylene epoxidation with H2 and O2. The objective of this study is to further engineer the surface properties of uncalcined TS-1 toward enhanced bifunctional catalysis. A strategy by increasing the reduction temperature is proposed to remove the residual TPA+ template on the external surfaces, and the resultant Au/TS-1-B-300 catalyst gives rise to simultaneously enhanced activity, propylene oxide (PO) selectivity, and H2 efficiency. These phenomena are explained by more exposed Ti-active sites and targeted catalysts’ electronic properties based on high-angle annular dark-field scanning transmission electron microscopy, thermal gravimetric analysis, UV–vis, Fourier transform infrared spectra, and X-ray photoelectron spectroscopy measurements. Furthermore, kinetics analysis demonstrates a much lower activation energy for the main reaction to form PO, suggesting the existence of an appropriate reaction temperature for the PO yield. The obtained insights could shed new light on rationally designing and optimizing the catalysts by engineering the surface properties.

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Section: Resultsmentioning

confidence: 97%

Surface Engineering and Kinetics Behaviors of Au/Uncalcined TS-1 Catalysts for Propylene Epoxidation with H₂ and O₂

Wang

Cao

Zhang

et al. 2019

Ind. Eng. Chem. Res.

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“…As is the case for mesoporous titanosilicates, hydrophobicity of the catalyst is important for enhancing the catalytic activity and silylation of acidic Ti–OH sites (together with Si–OH sites) by alkoxysilane improved catalytic activity, because acidic Ti–OH sites are responsible for propane formation and/or propionaldehyde formation. , Nijhuis et al performed kinetic studies − and reported that PO was formed at Au sites near the Ti 4+ site, while unfavorable H 2 oxidation occurred at both isolated Au sites and Au sites near the Ti 4+ . In both cases, the OOH species is an active intermediate.…”

Section: Catalysis By Gold In Gas-phase Reactionsmentioning

confidence: 99%

Importance of Size and Contact Structure of Gold Nanoparticles for the Genesis of Unique Catalytic Processes

et al. 2019

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Since the discovery of catalysis by Au nanoparticles (NPs), unique catalytic features of Au have appeared that are greatly different from those of Pd and Pt. In this Review, we aimed to disclose how the unique catalytic abilities of Au are generated with respect to (a) the contact structures between Au and its supports and (b) the size of the Au particles. For CO oxidation, the catalytic activity of Au on reducible metal oxides (MO x ) is strongly correlated with the amount of oxygen vacancies of the MO x surface, which play a key role in O2 activation. Single atoms, bilayers of Au, sub-nm clusters, clusters (1–2 nm), and NPs (2–5 nm) have been proposed as the active sizes of the Au species, which may depend on the type of support. For propylene epoxidation, the presence of isolated TiO4 units in SiO2 supports is important for the production of propylene oxide (PO). Au NPs facilitate the formation of Ti–OOH species, which leads to PO in the presence of H2 and O2, whereas Au clusters facilitate propylene hydrogenation. However, Au clusters can produce PO by using only O2 and water, whereas Au NPs cannot. For alcohol oxidation, the reducibility of the MO x supports greatly influences the catalytic activity of Au, and single Au atoms more effectively activate the lattice oxygen of CeO2. The basic and acidic sites of the MO x surface also play an important role in the deprotonation of alcohols and the activation of aldehydes, respectively. For selective hydrogenation, heterolytic dissociation of H2 takes place at the interface between Au and MO x , and the basic sites of MO x contribute to H2 activation. Recent research into the reaction mechanisms and the development of well-designed Au catalysts has provided new insights into the preparation of high-performance Au catalysts.

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“…Moreover, as described in the Introduction section, the strategy that silylation to consume hydroxyl groups with silane coupling agent could be effective over the Au catalyst to improve the catalytic performance by weakening PO adsorption on the catalysts surface. 11, 17–19 To further increase the PO activity, bubbling HMDSO through the catalysts bed for 40 min followed by flushing with reactants was carried out over the Au 20 Pt 1 /TS‐1‐B catalyst after its performance had been relatively stable. Surprisingly, simultaneously enhanced PO formation rate to 356 g PO /h/kg cat , PO selectivity to 88% and H 2 efficiency to 41%, corresponding to the propylene conversion of 11%, were observed in Figure 2D over the silylated catalyst.…”

Section: Resultsmentioning

confidence: 99%

“…In this regard, as a facile and effective method, surface silylation could consume partial hydroxyl groups and graft hydrophobic groups onto the catalyst surface. 11, 17–19 It is noted that in principle, the grafted electron‐rich alkyl groups have a possible impact on the electronic properties of active sites. Therefore, an attempt is made to probe the effects of surface silylation on the geometric and electronic properties and then to guide the rational design of silylated Au/TS‐1 catalyst for the reaction.…”

Section: Introductionmentioning

confidence: 99%

Combining trace Pt with surface silylation to boost Au/uncalcined TS‐1 catalyzed propylene epoxidation with H₂ and O₂

Wang

Zhang

et al. 2021

AIChE Journal

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Modification of bifunctional Au‐Ti catalysts for direct epoxidation of propylene with H2 and O2 is of burgeoning interest for potential commercialization requirements with desirable overall catalytic performance. Herein, we report a strategy by combining the addition of trace Pt into Au particles to enhance hydroperoxide species formation with the surface silylation to promote propylene oxide (PO) desorption. The resultant catalyst, that is, silylated Au20Pt1/uncalcined TS‐1, gives rise to significantly enhanced propylene conversion of 11%, PO selectivity of 88%, and H2 efficiency of 41%. The underlying nature of the above enhanced performance is elucidated by multiple techniques, such as high‐angle annular dark‐field scanning transmission electron microscopy, X‐ray photoelectron spectroscopy, Fourier transform infrared spectra, and theoretical calculations. The insights revealed here, the synergy of Au‐Pt‐Ti triple active sites together with the surface silylation, could guide the rational design of Au‐Ti catalysts for propylene epoxidation to boost PO production.

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Direct epoxidation of propene on silylated Au–Ti catalysts: a study on silylation procedures and the effect on propane formation

Abstract: Silylation was employed on an active Au/Ti–SiO2 catalyst, in order to enhance catalyst performance for the direct epoxidation of propene to propene oxide (PO) using H2 and O2.

Cited by 17 publications

References 43 publications

Surface Engineering and Kinetics Behaviors of Au/Uncalcined TS-1 Catalysts for Propylene Epoxidation with H₂ and O₂

Surface Engineering and Kinetics Behaviors of Au/Uncalcined TS-1 Catalysts for Propylene Epoxidation with H₂ and O₂

Importance of Size and Contact Structure of Gold Nanoparticles for the Genesis of Unique Catalytic Processes

Combining trace Pt with surface silylation to boost Au/uncalcined TS‐1 catalyzed propylene epoxidation with H₂ and O₂

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Direct epoxidation of propene on silylated Au–Ti catalysts: a study on silylation procedures and the effect on propane formation

Abstract: Silylation was employed on an active Au/Ti–SiO2 catalyst, in order to enhance catalyst performance for the direct epoxidation of propene to propene oxide (PO) using H2 and O2.

Cited by 17 publications

References 43 publications

Surface Engineering and Kinetics Behaviors of Au/Uncalcined TS-1 Catalysts for Propylene Epoxidation with H2 and O2

Surface Engineering and Kinetics Behaviors of Au/Uncalcined TS-1 Catalysts for Propylene Epoxidation with H2 and O2

Importance of Size and Contact Structure of Gold Nanoparticles for the Genesis of Unique Catalytic Processes

Combining trace Pt with surface silylation to boost Au/uncalcined TS‐1 catalyzed propylene epoxidation with H2 and O2

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Product

Resources

About

Surface Engineering and Kinetics Behaviors of Au/Uncalcined TS-1 Catalysts for Propylene Epoxidation with H₂ and O₂

Surface Engineering and Kinetics Behaviors of Au/Uncalcined TS-1 Catalysts for Propylene Epoxidation with H₂ and O₂

Combining trace Pt with surface silylation to boost Au/uncalcined TS‐1 catalyzed propylene epoxidation with H₂ and O₂