Study On Cu/Zn Ratio And Hundreds Of Kilogram Scale Up Preparation Of Ethanol From Syngas Over CuZnAl Catalyst

The coal consumption in China has been continue to growing year by year from 2014to 2020,and the consumption of traditional fossil energy mainly based on coal keep a relatively high level.The extensive utilization of coal has a serious impact on the environment and climate.The preparation of ethanol from syngas originated from coal can significantly alleviate the emission of various pollutants in the process of coal utilization.As an alternative fuel and an excellent fuel additive,ethanol has attracted extensive attention.It is also an ideal hydrogen carrier and one of the important raw materials for many fine chemicals.Direct synthesis of ethanol from syngas is considered to be one of the most efficient methods,so it has become one of the most attractive and valuable research topics in the field of C1 chemistry at present.Based on the the previous proposal that synergistic effect of Cu⁰-Cu⁺is the key to ethanol generation,CuZnAl catalyst was prepared with the unique complete liquid-phase technology of our group in this thesis,which was applied for direct synthesis of ethanol from CO hydrogenation in slurry bed reactor.The synergistic effect between Cu⁰ and Cu⁺and the effect of Cu⁰-Cu⁺on the performance of ethanol and higher alcohols is further investigated by adjusting the partition ratio of Cu and Zn and directly adding Cu⁰/Cu⁺species.At the same time,XRD,H₂-TPR,NH₃-TPD,N₂ adsorption,XPS,FT-IR,ICP,Raman,Al-MAS-NMR and SEM were carried out to characterize the catalyst.The optimal component distribution ratio was obtained and its stability was investigated.which provided laboratory basis for the hundreds of kilogram scale up preparation of the catalyst.In this work,the main conclusions were as follows:1.The appropriate proportion of Cu contributes to the increase the size of Cu particles,and greatly increases the fraction of Cu₂O hard to reduce in Cu⁺species.In addition,it improves the ratio of Cu⁺/Cu⁰+Cu⁺on the surface of the catalyst,and obviously increases the amount of weak acid on the surface of the catalyst and the stability of the catalyst structure in the reaction process.The results indicated that lower proportion of Cu⁺on the surface and the higher content of weak acid of the catalyst can promote the formation of ethanol and higher alcohols.2.The appropriate ratio of Zn can improves the grain size of Cu species and the structural stability of the catalyst during the reaction.In addition,it enhances the interaction between Zn,Al species and Cu₂O hard reduced,and adjusts the proportion of Cu⁺on the surface of the catalyst.The form existence of Zn and Al species is changed in the catalyst.The optimum ratio of Cu and Zn component was 35%at 250℃and the fraction of ethanol and C₂₊OH in total alcohol is up to 50%and 75%,respectively.3.The catalyst performance changed after adding Cu⁰/Cu⁺species,among which the addition of nano Cu powder can effectively improves the CO conversion;the addition of nano Cu powder and Cu Al O₂ effectively reduce the selectivity of hydrocarbons in the product,but it will aggravate the conversion reaction of water gas,leading to the improved CO₂ selectivity.The results show that the decrease of the selectivity of higher alcohols is not only related to the change of Cu⁺/Cu⁰+Cu⁺ratio on the catalyst surface,but also the stability of texture properties.4.The stability evaluation of CuZnAl catalyst prepared in the laboratory was carried out up to 500 h.After 96 h of reaction,the selectivity of total alcohol can be maintained at about 27%,and the proportion of ethanol and C₂₊OH in total alcohol can be maintained at around 25%and 50%respectively.5.The hundreds of kilogram scale up slurry catalyst preparation for ethanol synthesis have been completed.The phase structure of the catalyst was well maintained during the amplification process,and the results are similar to that of in the laboratory.The equipment,process and conditions of scale preparation have been finalized,which lays the foundation for one-step ethanol synthesis by large-scale slurry bed form syngas.