Molecular-size selective hydroconversion of FCC light cycle oil into petrochemical light aromatic hydrocarbons

Abstract

Abstract The catalytic hydroconversion of light cycle oil (LCO) from a fluid catalytic cracking (FCC) unit into petrochemical light aromatics was conducted in a fixed-bed down-flow reactor under 6 MPa. A hydrocracking (HDC) study was conducted using pre-hydrotreated LCO (HDT-LCO). Due to the wide molecular size distribution of the aromatic compounds in LCO, which range from mono- to tri+-ring aromatics, a combination of H-ZSM-5 (Z), H-Beta (B) and mesoporous H-Y(Y) zeolite was employed as zeolite supports for the HDC catalysts. The Mo-S/BYZ catalyst was found to achieve higher yield of light aromatics and higher conversion of large molecular-size C11+ heavy aromatics than those for Mo-S/BZ without mesoporous H-Y in the HDC of HDT-LCO. Although the Mo-S/ H-Y catalyst itself did not show selectivity toward light aromatics in the HDC of tetralin, the incorporation of a small fraction of mesoporous H-Y in the HDC catalyst promoted the cracking of large molecular-size C11+ heavy aromatics into light aromatics including benzene, toluene and xylene (BTX). The Mo-S/BYZ catalyst also exhibited an excellent stability over more than 100 h. Hence, the Mo-S/BYZ catalyst, which produced a high yield of BTX-rich light aromatics and demonstrated excellent catalyst stability, represents a promising HDC catalyst for LCO upgrading.