Study On Precursor Preparation Technology And Performance Of CuZnAl Catalyst For CO Hydrogenation

At present,China is in the period of transition of green energy.On the one hand,the clean and efficient use of coal resources is the crucial.On the other hand,there is a huge absence in the promotion of ethanol gasoline at the moment time.Therefore,the study of ethanol production by coal-derived syngas is not only one of the hot spots of contemporary chemical processing of coal,but one of the important ways of energy transformation.Our research team has achieved certain results with an array of experimental and theoretical studies on the preparation of CuZnAl catalysts for the synthesis of ethanol from syngas in complete liquid phase technology.Nevertheless,the balance between catalyst activity and ethanol selectivity has not been well resolved yet.Based on this situation,in this paper,the CuZnAl catalysts prepared by the complete liquid-phase technology,and their CO hydrogenation performances were tested in the high-pressure reactor.Copper and zinc salt solvents,citric acid dosage and heat treatment temperature were investigated for the impact of CuZnAl catalysts'structure and catalytic performance.Then,the influence of the mixing temperature of the copper and zinc salt components and the aluminum components on the structure and catalytic performance of the precursor was inspected.Finally,on basis of study mentioned above,the effects of nonionic surfactant polyvinyl pyrrolidone?PVP?,cationic surfactant tetrapropylammonium hydroxide?TPAOH?,anionic surfactant sodium oleate?NaOA?and the amount of NaOA on the catalyst were examined.The catalysts were characterized by XRD,H₂-TPR,XPS,NH₃-TPD-MS,FT-IR,N₂-adsorption and TEM.Associating characterization results with activity data,we reach the main conclusions as follows:1.For the precursors prepared by sol-gel method,the catalysts prepared with deionized water and anhydrous ethanol as copper and zinc salt solvent have higher activity,but their main product is methanol;The catalytic activity and the selectivity of the total alcohol with ethylene glycol as solvent are low.However,the selectivity of DME and hydrocarbons in the product is relatively high.The proportion of C₂₊OH in the total alcohol reaches 27.11%,indicating that the catalyst posspesses a certain ability to form higher alcohol.2.The addition of CA can significantly reduce the size of copper grain over CuZnAl catalysts,inhibit the agglomeration of copper components but increase the amount of surface acid.As the amount of CA increases,the catalytic activity first increase but then decrease,especially at CA:AIP=1,the sudden drop in activity.The change amount of CA did not significantly improve the ability of ethanol formation.3.The structure of the catalyst obtained by the heat treatment of the same catalyst precursor at 300°C is more stable than at 280°C,and the interaction between the active component and the support is stronger.4.When the precursor is prepared by the modified sol-gel method,the mixing temperature of the copper and zinc salt component and the aluminum component directly affects the interaction between the components.An appropriately high mixing temperature is conductive to enhance the interaction.The ethanol selectivity of the catalyst prepared at 70°C can reach 29%,and the ratio of C₂₊OH in total alcohol is 67.48%,but the CO conversion is lower.5.The addition of surfactant can improve the CO hydrogenation activity of the catalyst to a certain extent.When the amount of NaOA surfactant added is0.1%,the effect on the formation of ethanol is small,but when the amount added is more than 0.1%,the ethanol selectivity drops suddenly.6.The activity of CuZnAl catalyst of this paper does not have a direct relationship with its specific surface area.