Preparation of carbon-supported Pt catalysts covered with microporous silica layers using organosilanes: Sintering resistance and superior catalytic performance for cyclohexane dehydrogenation

Carbon black-supported Pt metal particles (Pt/CB) were covered with microporous silica layers using different organosilanes like methyltriethoxysilane (MTES)(SiO2(MTES)/Pt/CB) and phenyltriethoxysilane (PhTES) (SiO2(PhTES)/Pt/CB). Pt metal particles in Pt/CB covered with microporous silica layers were stable at high temperature up to 973 K in a hydrogen atmosphere, because the microporous silica layers that wrapped around the Pt metal particles essentially prevent particle sintering. Methyl or phenyl groups were introduced into the silica layers that covered the Pt metal particles using MTES or PhTES hydrolysis. Micropores were formed in the silica layers effectively after thermal treatment at 973 K. The microporous silica-coated Pt catalysts were used as model catalysts for the dehydrogenation of cyclohexane. The microporous silica-coated Pt catalysts with thermal treatment at 973 K exhibited a higher conversion of cyclohexane compared with Pt/CB. Especially, the SiO2(PhTES)/Pt/CB catalysts showed relatively higher conversion of cyclohexane compared with the other silica-coated Pt catalysts even when the SiO2 loading was high. Microporous silica layers with a larger micropore volume promoted the diffusion of cyclohexane during the catalytic reaction. (C) 2011 Elsevier B.V. All rights reserved.