HYDROISOMERIZATION AND HYDROCRACKING OF N-HEPTANE ON PT SAPO-5 AND PT/SAPO-11 CATALYSTS/

The activity, stability, and selectivity of a series of bifunctional P t/SAPO-5 and Pt/SAPO-11 catalysts containing 0.5 wt% platinum were com pared for n-heptane transformation at 300-450 degrees C and atmospheri c and 3 and 5 bars hydrogen pressures. Hydrogen pressure had a strong influence on the activity, iso-heptane selectivity, and time-on-stream deactivation. Isomerization of n-heptane to iso-heptanes was the majo r reaction with Pt/SAPO-5 catalyst, especially at lower conversions, w hereas Pt/SAPO-11 shows high selectivity to isomers in all conversion range. The selectivity patterns found in these classes of molecular si eve catalysts are wed interpreted in terms of a series of reaction pat hways that incorporate both confinement effects and shape selectivity factors as being important in determining the observed product distrib ution. Based on experimental results, the protonated cyclopropane appe ars as an intermediate in the mechanism of this reaction. (C) 1995 Aca demic Press, Inc.