Silylation enhances the performance of Au/Ti–SiO2 catalysts in direct epoxidation of propene using H2 and O2

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

“…The same authors also reported that the addition of CO to the feed can suppress propene hydrogenation 18 . Later it was found that the formation of propane can be controlled to some extent by optimizing the Ti grafting procedure 19,20 . Other groups have also reported propane formation on different catalysts [21][22][23][24] along with other side-products (acetone, propanal, acrolein, acetaldehyde and CO2) but the origin of propane formation remains under debate.…”

“…Silylation involves exposing the catalyst to a silylating agent which leads to the replacement of surface hydroxyls with R3Si groups. Typical agents include hexamethyldisilazane(HMDS) 27,33,37 , trimethylchlorosilane(TMCS) 29,38 , triethoxyfluorosilane(TEFS) 39 , (trimethylsilyl)trifluoroacetamide(MSTFA) 35 , methoxytrimethylsilane(TMMS) 11,20,35 and tetramethyldisilazane(TMDS) 33 . Silylation is generally accompanied by an increase in surface hydrophobicity which is proposed to be the underlying cause of the observed change in catalytic activity.…”

Advances in Designing Au Nanoparticles for Catalytic Epoxidation of Propylene with H2 and O2

“…Some studies focused on designing isolated and highly dispersed tetrahedral-coordinated Ti-oxide centers in the ligand-to-metal charge-transferred state ((Ti 4+ −O 2− )*), which is associated with the adsorption of propylene [5,48] and the nucleation sites for Au nanoparticles [49]. In previous studies, Au nanoparticles were deposited on Ti-modified mesoporous silica supports, such as SiO 2 [27,28], TUD [29], SBA-15 [30,31], MCM-41 [19,32,33], MCM-48 [15], MCM-36 [34], YNU-1 [34], MWW [34,35], TS-1 [20][21][22][23][37][38][39][40][41][42][43][44][45][46]50], and TS-2 [47], to enhance the epoxidation of propylene. In the last, support materials play a key role in slowing the deactivation.…”

Epoxidation of propene using Au/TiO2: on the difference between H2 and CO as a co-reactant

“…The detailed support preparation can be found in the literature. 8,9 Catalyst characterization Transmission Electron Microscopy (TEM) was used to determine the size distribution of the Au particles in both catalysts. The TEM images were recorded using a FEI Tecnai G2 Sphera transmission electron microscope at an accelerating voltage of 200 kV.…”

“…Some examples of active catalysts are gold dispersed on TS-1, Ti-SiO 2 , Ti-MCM-41 and Ti-SBA-15. [5][6][7][8][9][10] An inherent drawback of this approach is the formation of an excessive amount of water by oxidation of hydrogen. Overall, the low H 2 efficiency constitutes a major economic hurdle.…”