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在IM-5分子筛的合成体系中以介孔材料KIT-6作为硅源,制备出了多级孔IM-5复合分子筛(IM-5-K)。利用X射线衍射、扫描电镜、透射电镜、比表面积分析、NH3-TPD等手段对样品的物理性质和酸性进行表征。将经过钼修饰的Mo-IM-5-K催化剂应用于甲烷无氧芳构化反应中,考察其活性。催化测试结果显示,多级孔Mo-IM-5-K催化剂的最高甲烷转化率和芳烃产率为12.4%和6.9%,高于常规Mo-IM-5-C催化剂。同时,Mo-IM-5-K催化剂有更好的稳定性。催化剂反应活性和稳定性的差异是由于其具有不同的孔道结构和酸性所致。介孔的存在会影响活性Mo物种的落位及分布状态,有利于反应物与活性位的接触和芳烃产物的扩散,进而提高催化剂的活性和稳定性。
In the synthetic system of IM-5 molecular sieve, mesoporous material KIT-6 was used as the silicon source to prepare IM-5 composite molecular sieves (IM-5-K) with multi-porosity. The physical properties and acidity of the samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, specific surface area analysis and NH3-TPD. The molybdenum-modified Mo-IM-5-K catalyst was applied to methane anaerobic aromatization to investigate its activity. The results of the catalytic tests showed that the highest methane conversion and aromatics yields of the multi-staged Mo-IM-5-K catalyst were 12.4% and 6.9% higher than those of the conventional Mo-IM-5-C catalyst. At the same time, Mo-IM-5-K catalyst has better stability. The difference in catalyst reactivity and stability is due to its different pore structure and acidity. The existence of mesopores affects the dislocation and distribution of active Mo species, which is conducive to the contact of reactants with active sites and the diffusion of aromatic products, thereby enhancing the activity and stability of the catalyst.