Novel preparation method for supported emtalcatalysts using water-in-oil microemulaion and catalytic activity in various reaction systems

摘要

A novel preparation method (ME method using wate-rin-oil microemulaion was developed for supported metalcatalysts.Colloids presyn the sized in the microemulsion were immobilized by hydrolyss of metal alkoxide on supports without aggregation of the colloid,resulting in catalysts with narrow distributions of metal particlesize.The Rh particle size of Rh/SiO_2 catalysts could be controleld independently of Rhloadings by changing thesynthesis conditios of the colloid such as the type of microemulsion system ad synthesis temperature.Using the particle size-controlled catalysts,te dependence of the catalytic activity on Rh particle size in CO hydrogenation was investigated,and thecatalyst with the optimum Rh size for CO and CO_2 hydrogenaton exhibited extremely high activity.The ME method can also control the surface area of the supports.Inaddition,the ME method resulted in stronger metal-support interaction of the catalyst than convention alimpregnation catalysts.Due to this strong interactoin,Ni/Al_2O_3 and Fe/SiO_2 catalysts prepared by the ME emthod showed anomalous behavior for catalytic CH_4-steam reforming and the CO hydrogeantion,respectively.The Ni catalysts exhibited high activity and high resistance to coked eposition,and the Fe catalysts showed high activity and high selectivity for oxygenates with carbon number greater than one.The Rh/SiO_2 and Pt/Al_2O_3 catalysts prepared by theME method also had high resistance to sintering of metalparticles.