STUDY ON CONVERSION OF C9+ HEAVY AROMATICS TO LIGHT AROMATICS OVER MOLYBDENUM-BASED ZEOLITE CATALYSTS

A series of molybdenum oxide catalysts supported on different zeolites were prepared by incipient impregnation method.And their catalytic activity in conversion of commercial C+9 heavy aromatics to benzene,toluene and xylene(BTX)was investigated.Effects of different zeolites on catalytic performance of zeolite-supported molybdenum oxide catalysts were further studied by means of X-ray diffraction,temperature-programmed reduction,N2 adsorption,FT-IR spectroscopy of adsorbed pyridine and temperature-programmed desorption of NH3.It was found that zeolites influenced greatly the activity of zeolite-supported molybdenum oxide catalysts.Existence of the molybdenum species located in the channels of zeolite and associated with Brnsted acid site decreased the selectivity of BTX in conversion of commercial C+9 heavy aromatics to benzene significantly.The existence of Brnsted acid site,the increase of acid amount and specific surface area could all improve the conversion of C+9 heavy aromatics,and the existence of Brnsted acid site and the increase of acid amount were favourable to the formation of benzene,toluene and xylene,but excess acid amount could promote conversion of xylene to benzene and toluene.The MoO3/HMCM-56 catalyst exhibited a high activity to convert C+9 heavy aromatics to benzene,and the total yield of BTX could reach 67.3% under the reaction conditions of temperature 550℃,pressure 3.0 MPa,MHSV 3.62 h-1 and hydrogen to aromatics volume ratio of 1600.