Preparation Of Mo/Zeolite Catalyst And Its Application In Methane Dehydrogenation Aromatization

Methane is a major component of natural gas,shale gas,and combustible ice.It is widely used as a fuel supply,but also as source material for many industrial chemicals.In catalytic reaction,the conversion of methane is mainly divided into direct conversion and indirect conversion.Among them,the anaerobic methane aromatization reaction is an important reaction,in the process of natural gas directly into the reaction to avoid the depth of the methane oxidation caused a disadvantage of low aromatics selectivity,and the main product of the reaction of benzene,toluene and xylene is the important basic chemical raw materials,a liquid at room temperature,easily separated from the gas phase material,so as to simplify the production process,improve the use value of natural gas and other petrochemical energy.Zeolite supported Mo catalysts have been widely studied in this reaction due to their highly activated methane capacity.However,the pure molybdenum catalyst faces the problems of poor activity and serious carbon deposition.Therefore,it is of profound theoretical value to design and develop catalysts with high activity and high stability.This paper focuses on the methane dehydrogenation aromatization and draws the following conclusions:(1)By modifying HZSM-5 zeolite(Z5)with Ga and Zn,Mo-M/Z5 bifunctional catalyst for MDA reaction was prepared.Among them,the distribution of acid sites of the catalyst is adjusted,and the distribution of active metal Mo on the support is improved by doping Ga which the activation rate of CH4 increased by 71%and benzene production increased by 64%.The doping of Zn inhibits MDA reaction.(2)Using ZSM-5 zeolite as a carrier,the Mo-xGa/ZSM-5 difunctional catalyst was prepared,the distribution of acid sites of the catalyst is adjusted by adding different contents of Ga modified carriers.through the regulation of the second metal,and the conversion rate of methane and the yield of benzene were improved.When the Ga content is 0.7%,the B/L ratio of the catalyst is 1.2,with the best catalytic activity,the methane conversion rate is 20.2%,and the benzene yield is 12.8%.(3)MCM-22 zeolite(M22)has a better mass transfer effect due to its special pore structure,thus reducing the over-reaction carbon deposition and improving the stability of the catalyst.Based on the work of(1),the MCM-22 zeolite was studied as a carrier,and the second metal Ga was used to regulate the carrier to improve the stability of the reaction.Among them,when Ga content is 0.7%,the catalytic activity is the best,methane conversion is 15.7%,and benzene formation rate is 4.9%.Compared with Z5 zeolite as the carrier,the service life of the MCM-22 zeolite catalyst system is 80%longer.