Dominant role of zeolite in coordination between metal and acid sites on an industrial catalyst for tetralin hydrocracking

Abstract

An effective approach for upgrading light cycle oil (LCO) is the targeted conversion of poly-aromatic hydrocarbons to valuable monoaromatic hydrocarbons. However, this development has been limited because of the lack of a deep understanding of the hydrocracking pathway and mechanism. Herein, industrial NiMo/Al₂O₃ + USY catalysts were used to investigate the matching actions of acid sites and metals in hydrocracking. The results showed that NiMo/Al₂O₃ + USY (30 : 70) exhibits high activity and BTX yield because the acid sites of USY zeolite are enough to consume the activated hydrogen, leading to a shift of tetralin towards ring-opening and -contraction and a decrease in the dehydrogenation of tetralin. Furthermore, by changing the Si/Al ratio of zeolite in the catalysts with the same NiMo/Al₂O₃ ratio, we found that tetralin conversion is unchanged when the Si/Al ratio of zeolite reaches 26 (i.e., 7.0 framework aluminum ions per unit cell) and above, following Haag–Dessau cracking. These findings provide a deep insight into the matching of metal and acid sites in LCO hydrocracking.