Size- and support-dependent silver cluster catalysis for chemoselective hydrogenation of nitroaromatics

• Published in: Journal of catalysis Vol. 270; no. 1; pp. 86 - 94
• Main Authors: Shimizu, Ken-ichi, Miyamoto, Yuji, Satsuma, Atsushi
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 22.03.2010; Elsevier
• Subjects: Catalysis; Chemistry; Chemoselective hydrogenations; Exact sciences and technology; General and physical chemistry; Hydrogenation of nitroaromatics; In situ FTIR; Silver catalysts; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Chemoselective hydrogenations; In situ FTIR; Hydrogenation of nitroaromatics; Silver catalysts; Binary compound; Particle size; Basic site; Support; Chemoselectivity; Adsorption site; In situ; Acidic site; Hydrogenation; Chemical reduction; Platinum; Reaction mechanism; Catalysis; Dissociation; Aluminium oxide; Catalytic reaction; Catalyst selectivity; Transition metal; Metal particle; Base; Silver; Heterogeneous catalysis; In situ FrIR; Acids; Kinetics; Alumina; Catalyst; Interface
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2009.12.009

Chemoselective reduction of nitro group for the reduction of substituted nitroaromatics by silver–alumina proceeds by cooperation of coordinatively unsaturated Ag sites and acid–base sites of the support. Silver clusters on θ-Al 2O 3 support catalyze highly chemoselective reduction of a nitro group for the reduction of substituted nitroaromatics such as nitrostyrene. These catalysts show higher selectivity than conventional platinum-group metal-based heterogeneous catalysts. Systematic studies on the influence of the metal particle size and support oxides show that the intrinsic activity increases with decrease in the silver particle size, and acid–base bifunctional supports such as Al 2O 3 give higher activity than acidic or basic supports. Kinetic and in situ infrared studies provide a reaction mechanism which explains fundamental reasons of these tendencies. Cooperation of the acid–base pair site on Al 2O 3 and the coordinatively unsaturated Ag sites on the silver cluster is responsible for the rate-limiting H 2 dissociation to yield a H +/H − pair at metal/support interface, while the basic site on oxides acts as an adsorption site of nitroaromatics. High chemoselectivity could be attributed to a preferential transfer of the H +/H − pair to the polar bonds in the nitro group.