咪唑改性MCM-22分子筛的制备及甲烷无氧芳构化性能

摘要

以硅溶胶为硅源,环己亚胺为模板剂,在动态条件下利用水热合成法合成了MCM-22分子筛,并在该体系下以咪唑为添加剂合成了咪唑改性MCM-22-I分子筛,考察了咪唑对MCM-22-I分子筛合成的影响,利用FTIR、XRD、SEM、ICP、BET、NH3-TPD、H2-TPR和TG/DTG等手段分别对咪唑改性前后分子筛的物化性质进行了表征.结果表明,咪唑改性能够增大MCM-22的比表面积、孔容和酸性,同时可有效降低模板剂HMI的用量.采用等体积浸渍法制备了6Mo/MCM-22和6Mo/MCM-22-I双功能催化剂,在连续流动固定床反应器上,反应温度700℃、反应压力1.01×105Pa(1atm)、空速1500mL/(g-cat·h)的反应条件下,考察了催化剂催化甲烷无氧芳构化合成苯的催化剂性能.结果表明,与6Mo/MCM-22催化剂相比,咪唑改性的6Mo/MCM-22-I催化剂具有更高的择形性能和催化活性,甲烷的平均转化率提高了24.1％,苯的平均生成速率和选择性分别提高了24.3％和10.0％.%Imidazole modified MCM-22 molecular sieves (MCM-22-I) were synthesized by hydrothermal synthesis method under dynamic conditions using imidazole as additives. The effect of imidazole on the synthesis of MCM-22 zeolites was investigated. The physicochemical properties of the molecular sieve samples were characterized by FTIR, XRD, SEM, ICP, BET, NH3-TPD, H2-TPR, and TG/DTG. The results showed that MCM-22-I displayed large specific surface area, abundant pore structure and enhanced acidity and the modification by imidazole can reduce the amount of the template agent HMI used. The6 Mo/MCM-22-I and 6 Mo/MCM-22 catalysts were prepared by incipient-wetness impregnation method.The catalytic performance evaluation of the catalysts for methane dehydroaromatization were carried out in a fixed bed reactor under the reaction conditions of 700℃, P = 1 atm and space velocity of 1500 mL/ (g-cat·h). The results showed that methane conversion increased by 24.1％, the formation rate and the selectivity of benzene by using imidazole modified 6 Mo/MCM-22-I catalyst increased by 24.3％ and 10％, respectively, compared with conventional 6 Mo/MCM-22 catalyst.