Synthesis And Catalytic Performance Of B-oriented ZSM-5 Zeolite/Coal Gangue Materials With Multiporous

As a non-petroleum route,the reaction of methanol to hydrocarbon has been widely concerned since its first discovery.ZSM-5 zeolite was widely used in the reaction of methanol to hydrocarbon because of its unique pore structure.Based on the advantages of the adsorption and diffusion in b-oriented ZSM-5 zeolite material,this paper proposes that b-oriented ZSM-5 zeolite is loaded on the substrate of multi-channel structure,in order to build b-oriented ZSM-5/porous substrate material,which applied to the reaction of methanol to hydrocarbon.In the experiment,coal gangue was selected to prepare porous substrate material.By using secondary growth of seed layer,b-oriented Silicalite-1 seed layer grown on the substrate surface,and then Zn/ZSM-5zeolite catalytic membrane was prepared by controlled seed layer secondary growth.First,inorganic modified agents?SiO2 and TiO2,nanoscale dispersion liquid?and organic modified agents?polyvinyl alcohol and chitosan?were used to modify the surface of the porous coal gangue,and then the Silicalite-1 seed layer was grown on the surface by hydrothermal crystallization.It was found that hydrophilicity of the surface modified by the inorganic modifier was slightly weak,but the surface of the substrate was relatively flat.The roughness of the substrate surface and the concentration or type of the hydroxyl group on the substrate surface have a direct influence on the orientation of synthesized zeolite membrane,but experiment showed that the smooth TiO2/substrate was more beneficial to the growth of b-oriented Silicalite-1 seed layer.Further modification of TiO2/substrate surface by temperature and ultraviolet radiation,and then followed by the same hydrothermal crystallization.It was found that temperature treatment changed the Ti-OH type on the surface of TiO2/substrate,and the Ti-OH type of anatase on the surface of TiO2/substrate was more conducive to the regulation of the orientation of the Silicalite-1 seed layer in b-axis.UV irradiation increased the concentration of Ti-OH on the surface of TiO2/substrate.When the TiO2/substrate was irradiated for 2 h,it had the strongest hydrophilicity,the concentration of Ti-OH was the largest.Under this condition,the seed layer was highly aligned with b-axis orientation and the coating was dense.Secondly,it was investigated that the effects of Al³⁺,Zn²⁺and solution pH on the synthetic crystals.It was found that Al³⁺and Zn²⁺reduced the growth rate of crystal,and the Zn²⁺significantly changed the morphology of the crystal,which made the typical coffin shape into microspheres.When the solution pH was changed to alkaline,it did not affect the crystal growth speed,but the addition of alkali into the synthetic solution containing Al³⁺made small crystal not completely fused together,resulting in the rough surface of the coffin type crystals.In the synthetic solution containing Zn²⁺,the addition of alkali made the microcrystalline crystal edges and corners passivated.The substrate loaded with the b-oriented Silicalite-1 seed layer was put into hydrothermal crystallization in the synthetic solution containing Al³⁺.It was found that a dense b-oriented HZSM-5 zeolite membrane with high crystallinity in?0h0?crystal face has been grown on its surface.Finally,it was compared that the methanol conversion,product selectivity and yield of b-oriented Zn/HZSM-5 zeolite catalytic membrane and two kinds of Zn/HZSM-5 powder catalysts?purchased commercial ZSM-5 and b-oriented ZSM-5 crystallized form secondary growth liquid?in the reaction of methanol to hydrocarbon.Experimental results showed that the rate of methanol conversion was always above 86%,the reaction product was basically olefins and its rate of olefin yield up to 90%,when the b-oriented Zn/HZSM-5 zeolite catalytic membrane material used in methanol to hydrocarbons reaction at 470 ^oC.In addition,the material has good carbon resistance and long service life,so the b-oriented Zn/HZSM-5 zeolite catalytic membrane was suitable for the reaction of methanol to olefin.