Study On The Reaction Performance Of Bimetal Modified H-MOR And Cu-based Catalysts For Indirect Production Of Ethanol From Syngas

Ethanol is a basic organic chemical raw material with a wide range of uses.It can be used in the synthesis of plastics,disinfectants and rubber.In addition,ethanol can also be used as a high-quality power fuel and fuel additive to replace gasoline additives that can adversely affect the environment and human health.At present,starting from coal-based synthesis gas,the process of preparing ethanol through direct or indirect methods has received extensive attention from researchers.Among them,syngas is carbonylated with dimethyl ether to produce methyl acetate,and methyl acetate hydrogenation to produce ethanol has high atomic utilization rate,simple product distribution,high ethanol selectivity and no need for precious metals or catalysts that are corrosive to production equipment.However,there are few research reports on this process,immature technical process,and unclear carbonylation mechanism.The author of this thesis realized the process of directional conversion from syngas to ethanol by constructing a three-stage tandem system.Almost only methanol and ethanol are the liquid phase products.By preparing different catalysts and combining different characterization methods,the authors focused on exploring the bimetallic Cu and Zn species in the carbonylation component and the effect of active metal Sn on the hydrogenation component.The specific research content of this paper is as follows:1.The contribution to carbonylation promoted by CuZn-HMOR in tandem catalysis on one-pass conversion of syngas to ethanolIn this paper,the metal oxide CuZnAl was prepared by the co-precipitation method,and CuZn-HMOR with different Cu/Zn ratios was prepared by the ion exchange method.A triple tandem catalytic system consisting of a CuZnAl and HZSM-5 composite catalyst（labeled CZA/HZSM-5）,bimetallic CuZn-modified mordenite（labeled CZ-HMOR）and CuZnAl（labeled CZA）,realized the conversion from syngas to ethanol in one reactor.Through XRD,N₂ adsorption,SEM,TEM,NH₃-TPD,XPS,UV-vis and other characterization methods,the role of Cu species and Zn species in the carbonylation component was investigated.Under mild temperature conditions（200℃）,the CZA/HZSM-5|CuZn-HMOR|CZA three-stage cascade system will produce dimethyl ether（STD）from syngas,carbonylation of dimethyl ether,and hydrogenation of methyl acetate.Efficiently couple and eventually produce ethanol.Among them,the carbonylation reaction on the zeolite-based catalyst plays a key role in the overall catalytic performance.Studies have shown that the appropriate concentration of copper and zinc species will promote the carbonylation process.When Cu/Zn=0.2,the best catalytic performance and stability are obtained.At a CO conversion rate of 7.91%,the total selectivity of ethanol is 17.71%.The selectivity in the liquid phase product can reach 51%.Characterization results based on XPS,UV-Vis and TEM show that during ion exchange,Zn is more likely to enter the 8-membered ring（8MR）than copper to form [Zn OH]⁺ to promote the carbonylation process,while copper tends to enter the 12-membered ring（12MR）and inhibit the formation of hydrocarbons.In addition,Cu⁺ is also an active site for the polymerization of dimethyl ether（DME）to form methanol.Compared with single metal modification,bimetal modification can improve the stability of the catalyst.Zn species helps to disperse Cuions to prevent CuO nanoparticles from blocking the pore structure,which extends the life of the catalyst to a certain extent.2.Study on the reaction performance of Sn modified copper-based catalyst for indirect production of ethanol from syngasCo-precipitation method and equal volume impregnation method were used to prepare Sn-modified copper-zinc-aluminum oxides with mass fractions of 0.1wt%,0.6wt% and 1.2wt%,and were characterized by XRD,H₂-TPR,N₂ adsorption,and TEM.Means to characterize the physical and chemical properties of the catalyst used.Mainly by constructing a three-stage series catalytic system,the effect of Sn on the hydrogenation components of copper,zinc and aluminum and the catalytic performance of the coupling were studied.Experimental results show that the introduction of tin can form an alloy with copper,which strengthens the interaction with copper species,making it more difficult for copper species to be reduced.Appropriate Sn loading is very important to the entire coupling reaction.The copper-zinc-aluminum oxide with 0.1wt% Sn loading not only inhibits the water gas reaction,improves the selectivity of ethanol,but also increases the stability of the catalytic system.However,as the loading of tin increases,the dispersibility of copper species will be weakened.When the loading of tin is 1.2wt%,it will promote the water gas reaction and increase the selectivity of hydrocarbons,which will adversely affect the catalytic reaction.