Preparation Of ZSM-5 Zeolite Oil-water Separation Network Based On Stainless Steel Mesh And Its Catalytic Performance For Acetic Acid Esterification

Ethyl acetate is a kind of commonly used organic solvents in chemical industry which is mainly produced by esterification reaction catalyzed by concentrated H₂SO₄as the main homogeneous catalyst.Meanwhile,with good miscibility in the reaction system,the separation of the concentrated H₂SO₄ from the reaction system and the acid neutralization process after reaction would call for much energy comsumption accompanying with the corrosion problem.Therefore,heterogeneous catalysts such as ion exchange resins and molecular sieves have received much more attention duiring these years.ZSM-5 zeolite has a relatively good catalytic performance on the esterification reaction due to its acidity and unique pore structure and pore size.Meanwhile,oil-water separation net could be used in the separation of the mixed liquids with great differences in polarities which could improve the conversion of esterification reaction at the same time.Combining together with catalytic reaction and separation,the separation of the products during the reaction could have a promoting effect on the reversible reaction.With mentioned above,this thesis is devoted to the research on the preparation of ZSM-5/stainless-steel mesh material with catalytic and separation functions and its catalytic performance in the esterification of acetic acid and ethanol.In the first part,a series of hydrophobic oil-water separation networks were prepared with polymer and ZSM-5 zeolite by electrospinning method.The microstructure of the prepared film was characterized by SEM,and the performance of the ethyl acetate and water mixture separation was also characterized.In order to improve the stability of the oil-water separation network,the stainless-steel mesh based network with ZSM-5 molecular sieve coating was prepared by seeding and secondary growth method.The prepared catalysts were characterized by XRD,NH₃-TPD,SEM and BET,and introduced into the esterification reaction.Meanwhile,the influence of the secondary crystallization temperature,Si/Al ratio of ZSM-5,esterification temperature,stainless-steel mesh layers and combination of polymer film on the catalytic esterification performance were also investigated.The results confirmed that the prepared films have large surface area with small particles of ZSM-5 successfully loaded on the surface of the linear spinning fibers.At the same time,the oil-water separation performance of the spinning film was tested and the results showed that with its good hydrophobicity,the film could block the water on the surface for a long time while the ethyl acetate was completely passed through it.It also found that during the process,the polymer in the film would be dissolved by ethyl acetate leading to the damage of the film.By increasing the molecular weight of the polymer and the thickness of the film,the solubility of the polymer in ethyl acetate could be reduced a lot leading to the lower degree of the destruction.The ZSM-5/stainless-steel mesh catalyst was prepared in order to increase the stability of the film in the reaction system,and the crystal structure of ZSM-5 could be maintained with XRD characterization.SEM images show that the stainless-steel mesh were successfully coated with ZSM-5 particles.With increasing the crystallization temperature,the coating degree could be effectively improved resulting in the promotion of the separation efficiency of ethyl acetate in the reaction.By combination of esterification reaction results over ZSM-5/stainless-steel mesh with different Si/Al ratios and characterization results of NH₃-TPD,it clearly showed that ZSM-5 with lower Si/Al ratio which had stronger acidity had better catalytic activity,while its stronger hydrophilic property would lead to the lower accessibility between active sites and reactants.From above,the appropriate Si/Al ratio（Si/Al=50）could effectively modulate the acid properties and the hydrophilicity,and promote the esterification reaction.Meanwhile,the investigation of the influence of reaction temperature on the reaction showed that the conversion of acetate acid over ZSM-5/stainless-steel mesh could be increased by increasing the reaction temperature,while the higher reaction temperature would lead to the excessive volatilization of reactants and products in the reaction system.Under the optimized reaction conditions,the catalyst with multipled mesh layers was tested and the results showed that with the layers amount of network increased from 1 to 6,the conversion of acetic acid increased a lot,at 6 layers,the conversion（78.1%）was closed to the equilibrium conversion（80.2%）at the same reaction conditions.All in all,the research results indicated that the ZSM-5/stainless-steel mesh could efficiently catalyze the esterification reaction and successfully achieve the ethyl acetate separation process which provides a novel reaction method for the design of high-efficiency catalysts by coupling catalysis and separation processes together.