Preparation Of Mo-Based MCM Series Zeolite Catalysts And Their Catalysis For Methane Non-Oxidative Aromatization

Methane is the main component of natural gas and shale gas.Direct conversion of methane includes methane pyrolysis to hydrogen and methane aromatization.Methane aromatization can be divided into oxidative aromatization and anaerobic aromatization.methane dehydro-aromatization（MDA）is an atomic economic reaction,which can effectively avoid the deep oxidation of methane under non-oxidative conditions and improve the selectivity of aromatization products（benzene,toluene and naphthalene）.The suitable metal components and zeolite should be selected as catalysts for MDA reaction.The existing catalysts are easy to deactivate due to the deposition of carbon.Therefore,the development of highly selective and highly active catalysts for large-scale industrial applications has attracted much attention.In this paper,different Mo based MCM series zeolite catalysts were designed,mainly including the following contents:MoO₃ nanoribbons were prepared by hydrothermal synthesis method,and corresponding Mo-based zeolite catalysts were fabricated by modification of MCM zeolite with MoO₃ nanoribbons.XRD,FT-IR,NH₃-TPD and N₂-adsorption and desorption result show that Mo species are successfully loaded onto the zeolite support,and part of Mo species migrate into the pores of the support to reduce the acidity of the zeolite.MDA reaction exhibits that MoO₃ nanoribbon modified HMCM-22 shows higher methane conversion（14.2%）and benzene yield（8.2%）.The methane conversion rate and benzene yield of MoO₃ nanoribbon modified HMCM-49 can reach13.4%and 8.0%respectively.The MCM-22 zeolite was modified by ammoniated ammonium molybdate solution,and the materials were analyzed by XRD,FT-IR,NH₃-TPD and N₂-adsorption and desorption.With the increase of Mo loading,the acid strength of the catalyst decreases gradually.The ammoniated AHM readily sublime and migrate to the pores of MCM-22 and bind to the Br（?）nsted acid center to form Mo-O-Al species,thereby reducing the acidity of the catalyst.The catalyst has high methane conversion（13.5%）and benzene yield（8.1%）in MDA reaction.α-MoO₃ was prepared by a simple method and MCM-22 zeolite was modified to prepare MDA catalyst.The catalysts were characterized by XRD,SEM,N₂-adsorption and desorption,NH₃-TPD and TG.The results show that MoO₃ decreases the crystallinity and acidity of HMCM-22 carrier,indicating that MoO₃ can effectively disperse in the pore of zeolite and bind to the strong acid center,thus reducing the acidity of zeolite.The catalyst shows high methane conversion（13.8%）and benzene yield（8.2%）in MDA reaction.