Vapor-phase epoxidation of propene using H2 and O2 over Au/Ti-MCM-41 and Au/Ti-MCM-48

Synthesis of Gold Catalysts Supported on Mesoporous Silica Materials: Recent Developments

“…In Figure 9 the distribution of AuNPs on different mesoporous SiO 2 -based supports is depicted, while some synthesis procedures and catalytic applications are briefly discussed below. In the late of 90s, the Haruta's group initiated the investigation of the catalytic activity of gold deposited on titanium-containing mesoporous MCM-41 and MCM-48 materials, for the partial oxidation of propylene to propylene oxide, in the presence of oxygen and hydrogen [188][189][190][191][192][193][194][218][219][220][221][222][223]. They prepared Ti-doped MCM-41 and MCM-48 by means of a sol-gel process using tetrabutylorthotitanate [Ti(OC 4 H 9 ) 4 ] as titanium source, and then gold (4-12%wt) was loaded on these supports by DP (T = 70 °C, pH = 6.5-7.0) or by liquid grafting methods using HAuCl 4 or (CH 3 ) 2 Au(O 2 C 5 H 7 ) as gold precursors, respectively.…”

Synergetic photo-epoxidation of propylene with molecular oxygen over bimetallic Au–Ag/TS-1 photocatalysts

“…Recently, substantial efforts have been devoted to the engineering and tailoring of silica-supported metal oxides such as V2O5/SiO2 [5], Nb2O5/SiO2 [6], TiO2/SiO2 [7], ZnO/SiO2 [8], MgO/SiO2 [9], and CuOx/SiO2 [10] to promote the photo-epoxidation of propylene in the presence of molecular oxygen. However, studies on Ti-based materials including titanium silicalite-1, TS-2, TS-β, Ti-MCM-41, and Ti-MCM-48 [11][12][13][14][15][16][17][18][19][20] for Au chemical immobilization have demonstrated that tetrahedrally coordinated Ti is favorable for the enhanced activity and stability of Au species compared with the aforementioned materials. Both enhanced selectivity toward epoxides and stability toward C3H6 conversion are accessible via Au incorporation.…”

The effect of mesoporous scale defects on the activity of Au/TS-1 for the epoxidation of propylene

“…The detrimental effect of titanium connectivity has since been well established through the examination of titania supported on silica, sub-monolayer titania on silica, and finally titanium inserted into zeolitic frameworks [4,7,8]. The emphasis on catalysts prepared by DP of gold onto isolated titanium containing supports, encouraged by the inherent epoxidation activity of tetrahedrally coordinated titanium for the liquid phase epoxidation reactions [9], has led to a number of state of the art catalysts prepared through the insertion of titanium into nanoporous silicalite frameworks [4,7,8,[10][11][12][13][14][15][16][17][18][19][20][21][22][23]. The marrying of nanoscale gold size effects, Au-Ti synergy and nanoporous support materials has resulted in catalysts over an order of magnitude more active [24,25] and in some cases several orders of magnitude more stable [4,5,25] than the pioneering catalysts of this system [1].…”