Study on acid-base coupled catalytic pyrolysis of heavy crude oil to light olefins and aromatics by Py-GC/MS and fixed bed reactor

Abstract

Direct catalytic cracking of heavy crude oil has gained attention as an alternative and cheapest method of producing raw materials for the petrochemical industry. The Py-GC/MS technique was used to study the effects of calcium aluminate base catalysts and ZSM-5 acid zeolites on heavy crude oil conversion. The results showed that ZSM-5 with a Si/Al ratio of 40 (40Z) outperformed zeolites with Si/Al ratios of 80 and 200, with a maximum selectivity of 65% for light olefins and BTX (benzene, toluene and xylene). Among all base catalysts studied, calcium aluminate (CaAl-3) had the highest selectivity of 23% of C2-C4 olefins and BTX. The “Mix” model outperformed the “Base + Acid” or “Acid + Base” models in terms of minimizing hydrogen transfer reactions and maximizing the yield and selectivity of light olefins. The 30 C catalyst (30%CaAl-3 +70%40Z) exhibited significant co-effect of basic and acidic catalysis, with maximum light olefin selectivity and total olefinicity of 72% and 81%, respectively. The results of the present work showed that acid-base coupled catalytic pyrolysis was a viable approach for improving the yield of light olefins and aromatics.