多级孔ZSM-5分子筛催化剂对四氢萘加氢裂化多产轻质芳烃反应的影响

采用碱处理法制备了多级孔ZSM-5分子筛，并分别以多级孔ZSM-5分子筛和常规ZSM-5分子筛作为酸性组分制备了加氢裂化催化剂。采用氮气吸附-脱附、X射线衍射光谱、吡啶吸附红外光谱、氨气吸附-脱附、透射电镜等分析手段对分子筛样品进行表征。采用高压固定床微型反应装置对四氢萘在加氢裂化催化剂上的加氢裂化反应性能进行评价。结果表明：在反应温度350 ℃、氢分压4 MPa、氢/油体积比500/1、质量空速5.9 h^-1、反应时间2 h的反应条件下，与常规ZSM-5分子筛加氢裂化催化剂相比，多级孔ZSM-5分子筛加氢裂化催化剂对四氢萘的转化率提升了10百分点以上，BTX收率提升了2～8百分点，开环反应选择性提高了约20百分点。这是因为介孔的引入提高了四氢萘对分子筛内部酸性位点的可接近性，是提高其开环反应选择性和BTX收率的关键因素。

Effects of Hierarchical ZSM-5 Zeolite Catalyst on Tetralin Hydrocracking Reactions to Produce Aromatics

Hierarchical porous ZSM-5 zeolite was prepared through alkali treatment. Two different types of hydrocracking catalyst were prepared with using either the above hierarchical porous ZSM-5 zeolite or conventional ZSM-5 zeolite as acidic components, respectively. Different analytical methods, including nitrogen adsorption-desorption, X-ray diffraction, pyridine adsorption infrared, ammonia adsorption-desorption and transmission electron microscopy, were used to characterize the zeolite samples. A high-pressure fixed-bed micro-reactor was employed to evaluate hydrocracking reaction performance of tetralin over various catalysts. Under the reaction conditions of temperature 350 ℃， hydrogen partial pressure 4 MPa, hydrogen-oil volume ratio 500/1, reaction space velocity of 5.9 h^-1 and reaction time 2 h, compared with the catalyst containing conventional ZSM-5 zeolite, tetralin conversion ratio on the catalyst prepared with hierarchical porous ZSM-5 zeolite can increase ca. 10 percentage point. In addition, BTX yield can improve 2 to 8 percentage point, and selectivity of ring-opening (SRO) reaction can increase ca. 20 percentage point. Evaluation experimental results suggest that the introduced mesopores can improve tetralin accessibility to the acidic sites of ZSM-5 zeolite. This is why both tetralin ring-opening reaction selectivity and BTX yield are improved.