Selective deep catalytic cracking process of hydrocarbon feedstocks for the production of light olefins:: II.: Cooperative effect of thermal cracking and catalytic reactions observed in a 1-zone reactor

Hybrid catalysts comprising a chromium-based cocatalyst and a silica-rich ZSM-5 zeolite, when doped with lithium, showed quite a high on-stream stability even at a relatively high reaction temperature (735 C). The cooperative effect of the thermal cracking and the catalytic reactions, and the interactions between the two catalyst components of the hybrid catalyst, resulted in maximum production of light olefins when the hybrid catalyst contained similar to40 wt% of zeolite. The main chemical links between the thermal cracking (TC) and the catalytic reactions were the conversions of diolefins and large olefins, the latter being produced by the TC and the active sites of the chromium-bearing cocatalyst, respectively.