Preparation Of Mo/ZSM-5 Hollow Catalyst And Its Reaction Performance Study For Methane Dehydroaromatization

There are abundant deposits of natural gas and shale gas in nature.As the main component of natural gas and shale gas,the transformation and utilization of methane presents great application value.Therefore,the rational transformation of methane into products with application value can not only make full use of natural resources,but also bring economic value to society and people’s life.Conversion of methane to benzene and other aromatic hydrocarbons in methane dehydroaromatization(MDA)is one of the important application paths of methane.Currently,Mo/HZSM-5 is the most widely used catalyst for this reaction path.However,the traditional molecular sieve pore channel has diffusion limit,which makes part of the active sites of the molecular sieve can not be fully used.Meanwhile,it also leads to benzene retention in molecular sieve pore secondary reaction to generate a large amount of carbon deposition,affecting catalyst activity and stability.Therefore,design and development of high stability and high catalyst has far-reaching theoretical and practical value.In this paper,the HZSM5 molecular sieve with hollow structure obtained from the treatment of zeolite with tetrapropyl ammonium hydroxide(TPAOH)solution was used as the carrier to prepare Mo/ZSM-5 hollow catalyst,and its catalytic performance in MDA was studied,mainly in the following aspects:(1)In 0.1 mol L-1 TPAOH solution,catalysts with different hollow structures were prepared by regulating the reaction time between molecular sieve and the solution,which used to study the reaction performance of MDA.It was confirmed that the HZSM-5 molecular sieve showed different degree of hollow structure after the above treatment,and the catalyst prepared after TPAOH treatment for 24 h had a perfect large cavity and a large amount of B acids in the catalyst,which had the best catalytic performance,with the highest methane conversion rate of 13.8%,and benzene yield of 6.69%.(2)On this basis,the influence of TPAOH concentration on the synthesis of cavity catalyst and its MDA reaction performance was investigated.The results showed that with the increase of TPAOH concentration,the amount of B acids and mesopore in the hollow catalyst increased.when the concentration of TPAOH solution was 0.3 mol L-1,the average selectivity of benzene stabilized at 75%,and the catalyst had the best stability(3)On the basis of the above studies,the effects of Mo loading and reaction conditions on the catalytic performance of the synthesized hollow structure catalyst were further investigated.The experimental results showed that the best performance of the hollow structure catalyst was obtained.when the Mo loading was 5wt.%,the reaction temperature was 700℃,and GHSV=4000 mL g-1 h-1.