Catalytic mechanisms of methylcyclohexane cracking and light olefins production over zeolites

Abstract

In this work, the catalytic mechanisms of methylcyclohexane (MCH) cracking and light olefins production were systematically investigated over three zeolites catalysts of Si-ZSM-5, hydrated ZSM-5 and HZSM-5. HZSM-5 exhibited the highest activity in terms of MCH conversion and selectivity towards light olefins. The mechanisms of MCH activation over HZSM-5 show that protolytic ring-opening is more energetically favorable when compared to protolytic dehydrogenation and thermal cracking. Four distinct pathways can result in the production of light olefins. But the pathway for the productions of propylene and butane is energetically favorable. Both protolytic C–C bond cleavage and the regeneration of the Brønsted acid site significantly influence production of light olefins. The rate-limiting steps for protolytic ring-opening and the production of light olefins are the initial protonation of C–C bonds. We hope this work can provide potential significance in understanding the hydrocarbon fuels cracking and aiding in identifying target products.