Effect Of HZSM-5 Molding Conditions And Raw Material Impurities On Alkylation Performance Of Benzene And Methanol

The survey found that the domestic benzene and methanol market is in a severe form of oversupply,and a large number of production facilities are shut down,and the products are unsalable;the p-xylene market is in short supply,and more than half of the demand still depends on foreign imports.In this paper,the process of alkylation of benzene and methanol to xylene is proposed to solve the problem of unreasonable product distribution in the domestic aromatics market.In this paper,the suitable reaction conditions for the alkylation of benzene and methanol on ZSM-5 zeolites catalyst were investigated.As the reaction temperature increases,the initial activity of the reaction increases,and the reaction stability increases first and then decreases.When the reaction temperature is 460 ℃,the reaction pressure is 0.4 MPa and the appropriate space velocity,the catalyst reaction activity and reaction stability are better.Considering the reduction of production costs in terms of raw material prices,this article examines the effects of common impurities in benzene and methanol on the alkylation reaction.When the impurity thiophene content in pure benzene is below 300 ppm,the presence of thiophene can appropriately improve the stability of the alkylation reaction between benzene and methanol.The impurities in methanol are headed by water and dimethyl ether.In the alkylation system of benzene and methanol,water acts as a buffer and forms a protective layer on the surface of the ZSM-5 zeolites to delay the coking rate;dimethyl ether acts as a poisoning agent in this reaction system,only 0.05% of dimethyl ether That will cause the catalyst reaction activity to decline rapidly.In order to speed up the application of ZSM-5 catalyst in the benzene and methanol alkylation industry,this article also investigated the effects of various molding conditions on the reaction during the extrusion molding process of ZSM-5 catalyst.In this paper,first of all,graphite is used as an extrusion aid,and the effects of the distribution ratio of graphite to Tianjing powder,graphite content and graphite particle size on the ZSM-5 molding catalyst and alkylation reaction are explored.It is found that the introduction of graphite improves the poor diffusion performance of the ZSM-5 catalyst after extrusion molding.When the graphite particle size is 100 nm and the mass fraction is 3.75%,the ZSM-5 molding catalyst has good diffusion performance and alkylation Reaction stability.At the same time,the effects of the amount of binder pseudoboehmite and peptizer nitric acid on the ZSM-5 forming catalyst were also investigated.It was found that the introduction of pseudoboehmite will increase the total acid amount and improve the hardness of the shaped catalyst;the amount of nitric acid affects the hardness,thickness uniformity and alkylation reaction performance of the shaped catalyst.S With the increase of nitric acid content,benzene and methanol The stability of the basification reaction showed a volcanic trend.Finally,this paper investigates the effects of different powder mixing methods and calcination temperature on the alkylation reaction of benzene and methanol during the molding process of ZSM-5 catalyst.The most reactive ZSM-5 molding catalyst is named as extruded bar-276.The shaped catalyst performed well in the long-cycle reaction at medium and low space velocity.When the space velocity was 15 h-1,the benzene conversion rate of Extrusion-276 decreased by 13% after 64 h of reaction and remained above 30%.