介孔材料为硅源合成多级孔Mo/H-IM-5催化剂及其在甲烷无氧芳构化反应中的应用

摘要

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。%A novel hierarchical porous IM-5 ( IM-5-K) was synthesized by using mesoporous silica KIT-6 as the silica sources. The physical properties and acidities of the samples were characterized by XRD, SEM, TEM, BET and NH3-TPD. Moreover, Mo-modified catalyst, Mo-IM-5-K was prepared for non-oxidative aromatization of methane. Compared with Mo-IM-5-C, the Mo-IM-5-K catalyst showed higher conversion of methane and yields of aromatics. In addition, Mo-IM-5-K exhibited better stability than Mo-IM-5-C. Different activities and stabilities of the catalysts may be due to their different structure properties and acidities. The existence of secondary mesoporous systems may influence the location and state of the active Mo species, simultaneously lead to easier access to the active sites for reactants and better diffusion of aromatic products, thus improvs the activities of the catalysts.