Structure control of silica-supported mono and bimetallic Au–Pt catalysts via mercapto capping synthesis

SiO2-supported monometallic and bimetallic platinum–gold catalysts are prepared by deposition of metal nanoparticles stabilized by mercaptopropyltriethoxysilane (MPTES) after different aging time of the solution containing metal ions and MPTES. The materials are tested in the hydrodesulfurization (HDS) reaction of thiophene and compared with corresponding catalysts prepared by the conventional deposition–precipitation (DP) method. The monometallic Pt and the bimetallic Au–Pt prepared by DP have comparable activity. With respect to the platinum catalyst prepared by DP, the corresponding platinum catalyst prepared by MPTES particle stabilization exhibits a substantial enhancement of the activity regardless the solution aging time. On the contrary, the MPTES-assisted Au–Pt catalysts have different activities, depending on the solution aging time, with the most active being the one obtained with the 5-day-aged solution. In accord with XRD, XPS, and FTIR, the aging time of the solution, through the different interaction of Pt or Au precursors with the mercapto groups, has a crucial effect on the structure and on the surface of the catalysts. The observed differences in the catalytic activity are related to the structural and compositional changes of the bimetallic particles.

The mercapto-assisted synthesis of supported Au–Pt catalysts allowed to obtain different bimetallic structures depending on the different aging time of the metal ions–MPTES solution. The particles obtained after long aging time had an Aucore–Ptshell like structure related to the higher HDS activity.Figure optionsDownload high-quality image (84 K)Download as PowerPoint slideHighlights
► MPTES – assisted synthesis produces dispersed Pt and AuPt catalysts on SiO2.
► Aging of MPTES–AuPt ion solution affects the core–shell structure of the system.
► XRD, XPS, and FTIR allow to discriminate different core–shell distribution.
► Thiophene HDS activity of MPTES-assisted catalysts is superior to the DP catalysts.