HYDROCARBON PRODUCT SELECTIVITY: A TOOL FOR CHARACTERIZING THE ACTIVE STATE OF PLATINUM CATALYSTS

Methylcyclopentane was caused to react over Pt-black, Pt-SiO2 (EUROPT-1) 0.2% and 10% Pt-Al2O3 and the mechanical mixtures of the first two catalysts with Al (to give Al2O3 upon oxidation) and TiO2. Product distributions and activation energies for hydrogenolysis, ring opening products and methylcyclopent-1-ene as well as the ratios of the ring opening products were determined. Three mechanisms of ring opening have been proposed, two of them occurring on metal sites, the third on the metal-support phase boundary (adlineation mechanism). All these have different ring opening selectivity. The adlineation mechanism is supported by changing this selectivity upon creating new phase boundaries in mechanical mixtures.