Novel preparation method for supported metal catalysts using water-in-oil microemulsion and catalytic activity in various reaction systems

A novel preparation method (ME method) using water-in-oil microemulsion was developed for supported metal catalysts. Colloids presynthesized in the mi croemulsion were immobilized by hydrolysis of metal alkoxide on supports wi thout aggregation of the colloid, resulting in catalysts with narrow distri butions of metal particle size. The Rh particle size of Rh/SiO2 catalysts c ould be controlled independently of Rh loadings by changing the synthesis c onditions of the colloid such as the type of microemulsion system and synth esis temperature. Using the particle size-controlled catalysts, the depende nce of the catalytic activity on Rh particle size in CO hydrogenation was i nvestigated, and the catalyst with the optimum Rh size for CO and CO2 hydro genation exhibited extremely high activity. Tbc ME method can also control the surface area of the supports. In addition, the ME method resulted in st ronger metal-support interaction of the catalyst than conventional impregna tion catalysts. Due to this strong interaction, Ni/Al2O3 and Fe/SiO2 cataly sts prepared by the ME method showed anomalous behavior for catalytic CH4-s team reforming and the CO hydrogenation, respectively. The Ni catalysts exh ibited high activity and high resistance to coke deposition, and the Fe cat alysts showed high activity and high selectivity for oxygenates with carbon number greater than one. The Rh/SiO2 and Pt/Al2O3 catalysts prepared by th e ME method also had high resistance to sintering of metal particles.