CATALYTIC CRACKING OF A HYDROCARBON MIXTURE ON COMBINATIONS OF HY AND HZSM-5 ZEOLITES

Catalytic cracking of a hydrocarbon mixture has been examined on HY and HZSM-5, using both individual catalysts and a combination of these zeolites. Product distributions obtained from cracking on the faujasite alone have been compared with those on the zeolite combination. Product distributions have been calculated for reactions on the catalyst combinations by assuming relativecontributions based on the individual product distributions as well as the conversions on the individual components. A comparison of product distributions for cracking on the faujasite with that on the faujasite-pentasil combination shows that the ZSM-5 additive inhibits secondary reaction processes, particularly hydrogen transfer occurring on the faujasite. The olefins produced on the faujasite are further cracked on the pentasil additive, leading toincreased yields of C3 and C4 olefins.Shifts in branched-to-linear ratios for both paraffins and olefins maybe attributed to isomerisation processes occurring on the ZSM-5. Calculated distributions provide a reasonable approximation to those observed, with variances in the product yields providing further evidence for reduced hydrogen transfer on zeolite combinations. © 1993 Academic Press, Inc.