Reforming of C6 Hydrocarbons Over Model Pt Nanoparticle Catalysts

Size-controlled model Pt nanoparticle catalysts, synthesized by colloidal chemistry, were used to study the hydrogenative reforming of three C-6 hydrocarbons in mixtures with 5:1 excess of H-2: methylcyclopentane, n-hexane and 2-methylpentane. We found a strong particle size dependence on the distribution of different reaction products for the hydrogenolysis of methylcyclopentane. The reactions of 50 Torr methylcyclopentane in 250 Torr H-2 at 320 A degrees C, using 1.5 and 3.0 nm Pt nanoparticles produced predominantly C-6 isomers, especially 2-methylpentane, whereas 5.2 and 11.3 nm Pt nanoparticles were more selective for the formation of benzene. For the hydrogenolysis of n-hexane and 2-methylpentane, strong particle size effects on the turnover rates were observed. Hexane and 2-methylpentane reacted up to an order of magnitude slower over 3.0 nm Pt than over the other particle sizes. At 360 A degrees C the isomerization reactions were more selective than the other reaction pathways over 3.0 nm Pt, which also yielded relatively less benzene.