Fine tuning H-transfer and Β-scission reactions in VGO FCC using metal promoted dual functional ZSM-5

Recently the importance of Petroleum Refining Industries has gradually shifted from a supplier of nonrenewable fuels to a supplier of petrochemical feed stocks such as olefins and aromatics (BTX). Zeolite ZSM-5 still remains a zeolite of tremendous importance due to its application as a FCC additive among other applications. New cracking technologies such as deep catalytic cracking, which also use ZSM-5 catalyst to increase gas yields, are also being developed and commercialized. ZSM-5 increases the yields of gaseous fractions at the expense of gasoline and is a good source of Ethylene, Propylene, Butenes and Pentenes because of high alkene/alkane ratios in the gas fraction. Conventionally catalyst manufacturers have independently marketed propylene maximization and olefin reduction additives for the benefit of petroleum refiners. In this article, the use of metal promoted ZSM-5 based FCC additives for the increase of propylene yields along with simultaneous reduction of olefins in gasoline fraction is elaborated. A Dual Functional Index was proposed to compare the effectiveness of additives towards this objective. The effect of metal modification in same proportions on cracking ratios and product distribution over additives was analyzed and it was demonstrated that the extent of H-transfer, β-scission, protolytic cracking and dehydrogenation reactions could be fine-tuned by metal modifications. It was observed that an excess of H-transfer reactions led to high aromatics and high coke deposit on the additive whereas a balance between β-scission reactions and H-transfer reactions lead to high propylene yields along with a great reduction in cracked naphtha olefin content and minimum carbon loss as dry gas.