Catalytic pyrolysis behavior of heavy crude oil over acid-base composite catalysts

Direct pyrolysis of crude oil to petrochemical feedstocks (light olefins and aromatics) is a trend for the transformation of refineries. In order to combine the advantages of solid base and acid catalysts to boost the yields of light olefins and BTX (benzene, toluene and xylene), catalytic pyrolysis behavior of heavy crude oil over acid, base and composite catalysts were studied using Py-GC/MS. The results showed that maximum content of alkenes was obtained over the calcium aluminate (CaAl) catalyst due to the inhibited hydrogen transfer reactions, but its catalytic activity was lower than ZSM-5 with Si/Al ratio of 40 (Z-40). For different composite catalyst ratios, maximum light olefins and BTX content of 65 % was obtained with 40Z catalyst (60 %CaAl + 40 %Z-40), which was higher than that obtained with pure Z-40 and CaAl catalysts. Compared to commercial ZSM-5 based and USY based catalysts, the 40Z catalyst demonstrated superior catalytic cracking performance, with the highest content of light olefins and BTX, while significantly higher content of C9+ aromatics were obtained over FCC catalyst. This revealed that catalyst type and appropriate composite catalyst blend ratio all play important role in enhancing the generation of light olefins and aromatics.