载钼分子筛催化剂上C_9^+重芳烃的轻质化

CONVERSION OF C_9^+ HEAVY AROMATICS TO LIGHT AROMATICS OVER MOLYBDENUM-BASED ZEOLITE CATALYSTS

采用等体积浸渍法制备了不同分子筛负载的MoO3催化剂,考察了它们在工业C9+重芳烃轻质化制苯、甲苯和二甲苯(BTX)反应中的催化活性,并采用X射线衍射、程序升温还原、N2吸附、吡啶吸附红外光谱和氨程序升温脱附等技术研究了分子筛载体对其所负载的MoO3催化剂催化C9+重芳烃轻质化反应性能的影响。结果表明,分子筛载体对MoO3催化剂催化C9+重芳烃轻质化反应性能的影响较大。分子筛孔道内与B酸位相互作用的Mo物种的存在极大地降低了反应的BTX选择性;催化剂上B酸的存在、酸量增加以及比表面积增大都可以提高反应的C9+芳烃转化率;一定范围内B酸的存在和酸量的增加均有利于苯、甲苯和二甲苯的生成,但酸量过多将促使二甲苯向苯和甲苯转化。MoO3/HMCM-56催化剂催化C9+重芳烃轻质化反应性能优异,在温度550℃、压力3.0MPa、重芳烃质量空速(MHSV)3.62h-1和氢/烃体积比1600的反应条件下,其BTX收率高达67.3%。

A series of molybdenum oxide catalysts supported on different zeolites were prepared by incipient impregnation method. And their catalytic activity in conversion of commercial C9^＋ 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 Bronsted acid site decreased the selectivity of BTX in conversion of commercial C9^＋ heavy aromatics to benzene significantly. The existence of Bronsted acid site, the increase of acid amount and specific surface area could all improve the conversion of C9^＋ heavy aromatics, and the existence of Bronsted 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 C9^＋ 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.