REACTIONS OF LABELED HEXANES ON PT-WO3/AL2O3 CATALYSTS

Pt-WO3/Al2O3 (Pt:W = 1:1) catalysts were prepared by different methods and characterized by chemisorption, TPD, TPR, and TEM techniques. The various catalysts do not show important differences in the catalytic reactions studied. Pt-WO3/Al2O3 systems catalyse hexane isomerisation with low selectivity. Isotopic tracer measurements show that the reaction proceeds via classical cyclic and bond-shift mechanisms. Inside the general reactian pathways of the isoalkanes, methyl migration is favoured and involves the participation of the tertiary carbon atom both in the carboncarbon bond rupture and in the carboncarbon bond reformation. On these catalysts no correlation between the relative contribution of the cyclic mechanism and the nonselective hydrogenolysis of the methylcyclopentane was found. Moreover, 2-methyl-2-pentene follows an exactly similar reaction pathway to 2-methylpentane. The results are explained by the suggestion that the “Pt-WOx” interface is responsible for the catalytic behavior of these systems. A mechanism for hydrocracking and isomerisation is proposed. © 1993 Academic Press, Inc.