Study On Hydrogenation Of Methyl Acetate To Ethanol Over Cu-Zn-Al Catalyst

Ethanol as fuel additive and green fuel has an important position in the energy structure.Hydrogenation of methyl acetate is one of key processes for ethanol production from syngas.Developing high activity,high selectivity,good stability catalyst is the key to the industrialization of the process.In this paper,hydrogenation of methyl acetate to ethanol was tested on a series of Cu-Zn-Al catalysts.The effects on catalytic performance were investigated,and the catalyst preparation parametes and reaction conditions were optimized.Finally,the stability of the catalyst was investigated.The catalyst preparation methods were investigated.The Cu-Al₂O₃ catalyst prepared by co-precipitating had the highest catalytic activity in hydrogenation of methyl acetate.The loading amounts of 20%Cu had best catalytic activity,which was attributed to the high dispersion of Cu active sites and the optimal Cu⁺/Cu⁰ molar ratio of 1.Cu-Zn-Al catalysts were prepared by co-precipitating method.The results indicated that Zn could increase the catalyst surface area and the dispertion of Cu.The catalyst with Cu/Zn molar ratio of 2/3 had the highest catalytic activity in hydrogenation of methyl acetate.The molar ratio of Cu⁺/Cu⁰ is 1.04 in this catalyst and the Cu has higher dispersion.Combined with evaluating the activities of catalysts and characterization results,the optimal operating conditions were determined as follows:parallel-flow-precipitation,8.0 of pH,1.5mol/L of solution concentration,500?of calcination temperature.The conversion of methyl acetate was 97.6%,and the selectivities of methanol and ethanol were98.6%and 96.2%.The reduction conditions were investigated,and the result shows that valences of copper are affected by reduction conditions.The catalyst regenerated at 300?in pure hydrogen atmosphere has the highest catalytic activity in hydrogenation of methyl acetate.The thermodynamics of this reaction system were determined,and the results showed that lower temperature,higher pressure and higher molar ratio H₂ and MA are thermodynamically beneficial,which can improve the reaction conversion and selectivity.The reaction process was studied with single factors test and the optimal operation conditions were as follows:240?of reaction temperature,3.0MPa of reaction pressure,1.2h^-1of LHSV and 20 of ratio of hydrogen and ester.The conversion of methyl acetate was98.8%.The selectivities of methanol and ethanol were 99.4%and 98.7%.Cu-Zn-Al catalyst has excellent catalytic activity and stability in hydrogenation of methyl acetate.The conversion of methyl acetate was always more than 98%and selectivity of methanol and ethanol were about 99%and 98%in the operation 300h time.