CRACKING OF AN INDUSTRIAL FEEDSTOCK OVER COMBINATIONS OF H-ZSM-5 AND HY - THE INFLUENCE OF H-ZSM-5 PRETREATMENT

The influence of H-ZSM-5 addition to a HY catalyst in the cracking of a Gippsland reduced crude was investigated. The mode of pretreatment ( particularly steaming) of the H-ZSM-5 additive appears to effect the r eaction mechanism associated with octane enhancement. Cracking the fee dstock over combinations of HY and unsteamed H-ZSM-5, suggest that the pentasil is active in the selective removal of linear alkanes from th e heavier product fractions formed on HY, producing gasoline range lin ear alkanes. This results in a decreased branched to linear ratio for gasoline range alkanes. The corresponding ratio for alkenes is increas ed upon pentasil addition due to the isomerisation of linear alkenes. For combinations of HY with steamed H-ZSM-5, selective removal of alka nes is negligible. The major influence of the additive is to isomerise and crack linear alkenes, leading to increased branched to linear rat ios for both alkanes and alkenes.