添加β沸石的烃类裂化催化剂性能研究

采用固体硅源、铝源和四乙基氢氧化铵（TEAOH）在极浓体系中成功合成了硅铝摩尔比（SiO₂/Al₂O₃）分别为30和150的β沸石。同时用硅铝摩尔比为30的β沸石为原料，在70℃下采用草酸脱铝制备了硅铝摩尔比接近150的样品。直接合成或经脱铝改性的β沸石采用XRD、SEM、吡啶吸附红外光谱和N2吸附对其晶相、酸性、比表面积和孔体积进行了表征。将三种β沸石分别作为烃类裂化催化剂的活性组分添加剂，对其催化剂的性能进行了评价。结果表明,三种β沸石的引入都可以提高裂化催化剂的活性和改善产品分布，低硅β沸石催化剂能改善催化剂的异构化反应性能和提高乙烯、丙烯的选择性，高硅β沸石或脱铝β沸石催化剂有利于裂化汽油中烯烃的芳构化和C4烯烃产率的提高，并可减少结焦。

Effects of beta zeolites addition on the performances of a hydrocarbon cracking catalyst

Beta zeolites with the SiO_2/Al_2O_3 molar ratio of 30 and 150 were synthesized in an extremely dense aqueous system by using tetraethylammonium hydroxide (TEAOH) as template and solid silica gel as silica source. Meanwhile, another beta zeolite sample of high SiO_2/Al_2O_3 ratio (about 150) was obtained by dealuminization of the low SiO_2/Al_2O_3 ratio (30) zeolite in an oxalic acid solution at 70℃. All three zeolites samples were characterized by XRD, SEM, N_2-adsorption and pyridine adsorption IR spectrum. The effects of their addition on the performances of a hydrocarbon cracking catalyst were investigated in a microactivity test (MAT) unit at 460℃. The results indicated that the intrusion of zeolite beta into the cracking catalyst can enhance its catalytic activity and improve the product distributions. When the zeolite beta of low SiO_2/Al_2O_3 ratio was added in the cracking catalyst, the isomerization was promoted and the selectivity to ethene and propene was increased. On the other hand, the addition of high SiO_2/Al_2O_3 ratio beta zeolites or the dealuminized one was able to enhance the aromatization of olefins, to increase the C_4 olefin yield and to lower the carbon deposition during reaction.