Effect of heat treatment time on the performance of CuZnAl catalysts in the synthesis of higher alcohols from syngas

A series of CuZnAl catalysts were prepared by the complete liquid-phase method with different heat treatment times and characterized by XPS, XRD, H₂-TPR, NH₃-TPD-MS and N₂ adsorption-desorption; their catalytic performances in the synthesis of higher alcohols from syngas were investigated in a slurry bed reactor. The results indicate that an increase in the heat treatment time can enhance the interaction between the Cu and Al species and alter the amount of Cu⁺ species over the CuZnAl catalysts, influencing the synergistic effect of Cu⁺-Cu⁰ sites. In addition, with the increase of heat treatment time, the surface acidity of CuZnAl catalyst decreases, accompanying with an increase in the pore volume and pore size; small amount of surface weak acid sites, large pore volume and large pore size are beneficial to the formation of higher alcohols. The CuZnAl catalyst obtained by heat-treating for 7 h exhibits excellent performance in the synthesis of higher alcohols, with a CO conversion of 38.1% and a higher alcohols mass fraction of 65.9% in the total alcohols.