Preparation Of CuZn-based Catalysts By Complete Liquid Phase-Solvothermal Method And Synthesis Of Ethanol From Syngas

It is a challenging project in the field of C1 chemistry for CO hydrogenation to ethanol.Because of the low yield of ethanol,it has not been industrialized till now.All of us pay attention to prepare an economical and excellent catalyst.The Cu-based catalysts prepared by the complete liquid-phase method developed by our research team independently has good performance on CO hydrogenation to C₂₊OH.It has been showed that the catalysts prepared by high-pressure heat treatment in flowing atmosphere and solvent heat treatment in a closed environment exhibited better performance on the selectivity to higher alcohols which reached 38.7%.Based on this,furtherer research has been made.In this paper,the CuZnAl catalyst was prepared by the complete liquid-solvent method.The influence of the change of crystallinity on the catalyst during the aging process of the precursor was investigated.Then,the doping method was proposed for the disadvantage that the activity of the catalyst with higher selectivity of ethanol was lower.The catalyst was modified by introducing SBA-15 molecular sieve and carbon nanotubes as structural assistants in the precursor preparation process.The addition position and addition amount of SBA-15 in the preparation stage of the precursor,the influence of the amount of short carbon nanotubes containing carboxyl groups and the longer carbon nanotubes treated by nitric acid on the catalyst were investigated.The catalyst was characterized by various methods and the CO hydrogenation performance of the catalyst was evaluated in a slurry bed.The results showed:1.The crystallinity of the precursor had a significant effect on the catalyst structure and catalytic performance when the Cu-Zn-Al catalyst was prepared by the complete liquid phase-solvent method.The results indicate that if a precursor showed higher crystallinity,that is,the Cu and Zn components mainly existed in the form of basic nitrate,which was beneficial to the dispersion of Cu species and the CO hydrogenation activity of the catalyst.On the contrary,The higher self-generated pressure due to a lower crystallinity of the precursor was conducive to the formation of spinels and relatively larger particles of Cu.Moreover,the coexistence of Cu⁺and Cu⁰ was easily formed,which was favorable for the formation of C₂₊OH.2.The addition of SBA-15 results in the formation of a certain amount of basic salt in the catalyst.The interaction between CuZn and SBA-15 surface was facilitated and larger particles of Cu were formed by adding SBA-15 to CuZn ethanol solution.3.The crystallite size of Cu⁰ and the amount of Cu⁺increased,as well as a certain weak acid and medium acid center are formed with the increase of SBA-15 addition,which promote the formation of ethanol.The average ethanol selectivity of the catalysts Cat0.2 and Cat0.6 during the activity test period were42.7%and 66.4%,respectively.4.Adding carboxylated short carbon nanotubes to CuZn ethanol solution facilitates the formation of difficult-reduced Cu⁺and amount of weak acid and medium-strong acid.Suitable addition of carboxylated short carbon nanotubes is beneficial for ethanol production.5.Adding longer carbon nanotubes to the solution of AIP and ethanol facilitates the growth of Cu particle,the increasing of amount of difficult-reduced Cu⁺,the complication environment of Cu species and amount of weak acid and medium-strong acid,a large amount of weak acid and a part of medium strong acid,which are beneficial for ethanol production.The average ethanol selectivity of CatL15%was 36.0%.6.There is no obvious correlation between the properties of the catalysts'texture parameters and it's activity and selectivity.