ZSM-22分子筛的合成、表征及烷基化性能研究

Synthesis and characterization of ZSM-22 zeolites and their catalytic performance in alkylation reaction

通过不同合成方法制备聚束状、粗棒状和细棒状ZSM-22分子筛,采用XRD、SEM、BET、MAS NMR、NH_3-TPD及PyFTIR等表征手段对分子筛的形貌、织构、硅铝配位环境及酸性进行研究。以甲苯-甲醇烷基化制备对二甲苯为探针反应,考察不同形貌ZSM-22分子筛催化剂的催化性能。结果表明,不同形貌ZSM-22分子筛的晶胞参数、织构、硅铝配位环境及酸性等存在明显差异。聚束状ZSM-22分子筛由于各束之间的相互作用导致Si(4Si)配位结构发生变化,Al原子的嵌入导致T3和T4比例较高、T2较少,并表现出更多的L酸中心。在380℃反应温度下,聚束状ZSM-22分子筛催化剂在甲苯-甲醇烷基化反应转化率为16.7%时,对二甲苯选择性达到76.1%。

The ZSM-22 molecular sieves with various morphologies were synthesized by different methods. XRD, SEM, BET, MAS NMR, NH3-TPD and Py-FTIR were used to study the structure, morphology, surface area, Si-Al coordination and acidity of the samples. Furthermore, the toluene-methanol alkylation as probe reaction was used to investigate the effect of ZSM-22 zeolites morphology on catalytic performance. The lattice parameters, surface areas, Si-Al coordination and acidity of all samples are obviously different. As a result, the interaction of each bundle of the bundle-like ZSM-22 zeolites leads to the structure change of Si （ 4 Si ） coordination, the increase of T3 and T4 with decrease of T2 location, and thus displays more L acid sites. At 380 ℃ reaction temperature, the bundle-like ZSM-22 zeolite catalyst shows high selectivity to p-xylene （76. 1%） at about 16. 7% conversion in the toluene-methanol alkylation.