Applied Catalysis A: General, Vol.504, 361-372, 2015
Surface properties and catalytic performance of Pt-Ag supported on silica - The effect of preparation methods
Commercial silica (Ultrasil - BET surface area 158 m(2)/g) was modified with platinum and/or silver. Before metal loading, the silica was functionalized with one of the following organosilanes, 3-aminopropyltrimethoxysilane (APTMS) and 2-mercaptopropyltrimethoxysilane (MPTMS) or both of them. It was proved that the nature of organosilane (MPTMS or APTMS) used for functionalization of silica before silver and platinum loading, played an important role in the anchoring of Pt and Ag species and affected the kinds of bimetallic particles formed. The creation of alloy-like bimetallic structure depends oil a combination of two parameters, the nature of organosilane and the method of modification by platinum and silver. If the one-pot method of modification was used, the functionalization of silica by MPTMS favoured alloy formation (PtAg/Si-M and PtAg/Si-AM samples). APTMS functionalization promoted alloy formation if the step-by-step modification was applied, independently of the sequence of metals loading. Core-shell structure was formed only if MPTMS functionalization of silica was used and silver species were loaded first (1Ag2Pt/Si-M sample). Bimetallic particles were not formed in two samples, PtAg/Si-A and 1Pt2Ag/Si-M. The presented results have proved that selectivity of bimetallic catalysts in methanol oxidation depends on metals loading and dispersion, whereas their activity is influenced by the interaction between platinum and silver in bimetallic particles. The highest selectivity to methyl formate (84%) for 100% conversion of methanol was reached over PtAg/Si-M at 373 K. (C) 2015 Elsevier B.V. All rights reserved.