Tuning CuO crystallite size by different solvents for higher alcohols synthesis from syngas over CuZnAl catalyst

Abstract

The crystallite size effect of metal oxides plays a vital role in the field of heterogeneous catalysis research. Herein, CuZnAl catalysts with varying CuO crystallite sizes are synthesized by coprecipitation method employing various solvents. The catalytic performance of CO hydrogenation is studied and the physical and chemical properties of catalysts are characterized by XRD, H2-TPR, N2 adsorption-desorption, and NH3/CO2-TPD-MS. The results indicate that the different types of solvents can effectively regulate CuO crystallite size, thereby affecting its reducibility and catalytic activity. Most importantly, we observe that CuO crystallite size is positive correlated with reduction temperature and negative correlated with C2+OH selectivity. The catalyst employing ethanol as a solvent exhibits the highest CO conversion (22.91 %) and the optimum proportion of C2+OH in total alcohols (18.96 %), which indicates that smaller CuO crystallite size facilitates reduction of Cu species and generation of larger pore size as well as suitable acid-basic sites, thereby promoting higher alcohols formation. Therefore, these findings greatly broaden understanding the size effect of CuO, providing a new strategy for rational design Cu-based catalysts for higher alcohols synthesis.