Study On The Preparation And Modification Of Catalysts For Methane Dehydroaromatization

Benzene is an important organic intermediate in petrochemical industry.At present,benzene is mainly obtained from crude oil.With the depletion of petroleum resources,more and more attention has been paid to the conversion and utilization of conventional and unconventional oil and gas resources rich in methane.Methane can be directly and efficiently converted into benzene and other important aromatic products by methane anaerobic aromatization,and a lot of hydrogen can be produced.After the research on the technology of methane aromatization without oxygen,the researchers found that the main reason why the technology has not been able to achieve industrial application is that the catalyst deactivation is fast.In view of this problem,this paper mainly seeks a breakthrough from the synthesis and modification of catalysts.HZSM-5 zeolite was synthesized under hydrothermal condition with tetraethyl orthosilicate as silicon source and glycerin as auxiliary agent.The effects of glycerin content and crystallization time on the crystal size,relative crystallinity and acidity of HZSM-5 zeolite were investigated.HZSM-5 zeolite was modified by alkali treatment,secondary hydrothermal crystallization and shell addition.The catalytic performance of HZSM-5 zeolite catalyst before and after modification was investigated.The conclusion is as follows:1.HZSM-5 molecular sieve was synthesized by using glycerol as auxiliary agent under static hydrothermal condition.The experimental results show that,when the hydrothermal time is 24h and x=N?C₃H₈O₃?:N?Si O₂?=2,the acid content and crystallinity of the sample are the highest.2.Compared with HZSM-5 molecular sieve,HZSM-5 molecular sieve synthesized by glycerin assisted synthesis has better catalytic performance for methane anaerobic aromatization when loaded with 6%mo.The conversion of methane reached 22.5%,increased by 6%;The selectivity of benzene and aromatics was 71%and 85%,respectively,which increased by 28%and 35%,and it has strong stability and capacity of carbon,which fully reflects its excellent catalytic performance.3.Compared with alkali treatment and secondary hydrothermal crystallization,HZSM-5 zeolite with shell modification has better catalytic performance for methane oxidation-free aromatization.