n-Heptane hydroconversion on platinum-loaded mordenite and beta zeolites:: the effect of reaction pressure

Reaction mechanism and scheme of hydroconversion of n-heptane catalyzed by platinum-loaded H-form mordenite and beta zeolites has been studied. Product distributions are measured via conversion and reaction pressure in the range of 1-40.8 atm at a temperature range of 210-340 degrees C. Isomerization and cracking products are formed either simultaneously or consecutively as functions of reaction pressure and pore structure as well as the density of acid sites in zeolites. The intraframework void space of zeolite BEA is less hindered than that of zeolite MOR. In this case, Pt/BEA was found to be close to an ideal bifunctional catalyst for n-heptane transformation and isoheptane formation, and the effect of pressure is less pronounced. The isomerization selectivity on Pt/MOR was significantly improved by increasing reaction pressure, Pt concentration and Si/Al ratio of HMOR. This pressure effect on isomerization selectivity may be related to the activation of acid sites for the generation of C-7 carbenium ions and to the reduction of dehydrogenation of heptane to heptene. (C) 2000 Elsevier Science B.V. All rights reserved.