The Study Of Cu-Zn Based Catalyst For Higher Alcohols Synthesis From Syngas

The key of technology of higher alcohols synthesis is the preparation of the catalyst.Cu-Zn based catalyst has the advantages of simple preparation process,low cost,mild reaction conditions,high reaction activity and higher total alcohol selectivity,which has attracted wide interest of many scholars.Additives play an important role in improving the structure of the catalyst,reaction performance,product distribution and so on.The addition of K,Cr,Fe and Ni can improve the anti-sintering performance of Cu-Zn based catalysts,and promote the dispersion of CuO particles,but the effect on the performance of the catalyst is different.The addition of K promoter increased the conversion rate of CO and the total alcohol selectivity of K-CuFeCrNi/ZnO,and inhibited the formation of hydrocarbon.The addition of Cr promoter reduced the activity of K-CuFeCrNi/ZnO catalyst,inhibited the WGS activity of the catalyst,improved the time and space yield of the total alcohol and the selectivity of the alcohol.The addition of Fe promoter increased the activity of K-CuFeCrNi/ZnO catalyst and the selectivity of C₂+OH.Ni promoter has the obvious ability to promote the growth of carbon chain,the appropriate amount of Ni additives can effectively promote the production of C₂+OH products.Support can improve the dispersion of the active components of CuO,its pore structure,acidity and alkalinity,and the interaction between the carrier and the active center will affect the catalytic performance of the catalyst.The specific surface area,pore volume and pore size of the K-CuFeNiZn/MOx catalyst?MOx=Cr₂O₃,Al₂O₃,ZrO₂,CeO₂?are different from each other as the result of differences between the source and nature of the support.Compared with other oxide supported K-CuFeNiZn/MOx catalysts,the total alcohol selectivity?42.86%?and the ethanol space time(1.02g·mL^-1·h^-1)of K-CuFeNiZn/Cr₂O₃ catalyst is highest.The liquid phase products were mainly MeOH and PrOH,and C₂+OH accounted for 46.73%of the total content of alcohols.The calcination temperature is the key condition to form a catalyst with a certain grain size and distribution,which affects the performance of the catalyst.With the increase of calcination temperature,the specific surface area and pore size decreased,and the CO conversion in the synthesis of alcohols increased and then decreased.The CO conversion rate?45.39%?,alcohol selectivity?43.05%?and alcohol space time yield(0.19g·mL^-1·h^-1)of K-CuFe NiZn/Cr₂O₃ catalyst prepared by calcination temperature of 400?were the maximum.Process conditions not only affect the adsorption and activation of reactive species,but also can change the activity and selectivity of the reaction.For K-CuFe NiZn/Cr₂O₃catalyst,the conversion rate of CO increases with the increase of reaction temperature,and the yield of total alcohol increases at first and then decreases.With the increase of the reaction pressure,the time and space yield of total alcohol and the conversion of CO were increased.With the increase of H₂/CO ratio,the conversion of CO increased,the total yield of alcohols increased at first and then decreased.Comprehensive analysis of optimal conditions of K-CuFeNiZn/Cr₂O₃ catalyst for preparing low carbon alcohols obtained:reaction temperature is 420?,reaction pressure is 6 MPa,H₂/CO is 2,space velocity is5000h^-1.