Hydroisomerization of a hydrocarbon feed containing n-hexane, n-heptane and cyclohexane on zeolite-supported platinum catalysts

Bifunctional catalysts consisting of platinum supported on various types of zeolites (viz. beta, mordenite, USY, ZSM-5 and ferrierite) were prepared by using an incipient wetness impregnation method to obtain a 0.5 wt.% metal load. A beta zeolite sample was dealuminated with nitric or oxalic acid to obtain solids that were used as catalytic supports. The catalysts thus obtained were characterized by using various techniques. Analyses included specific surface area and acid properties; the latter were determined either by adsorption of pyridine or by temperature-programmed desorption of the same chemical. The metal phase was characterized by temperature-programmed desorption of hydrogen and by hydrogen chemisorption, which allowed the dispersion of the metal on the support surface to be determined. The catalysts obtained were assessed for activity and selectivity in the isomerization of a mixture consisting of n-hexane (65 wt.%), n-heptane (15 wt.%) and cyclohexane (20 wt.%). Both parameters were correlated with the acid and metal properties of the catalysts, as well as with the topology and pore geometry of the zeolites. The effect of each feed component on catalytic activity was also studied, using binary mixtures of the three hydrocarbons. (C) 2003 Elsevier Science B.V. All rights reserved.