Design and synthesis of spherical-platelike ternary copper-cobalt-manganese catalysts for direct conversion of syngas to ethanol and higher alcohols

Abstract

Novel CuCoMn ternary catalyst with a “spherical-platelike” (CuMn-Co) nanosized particles structure was designed and successfully performed in ethanol and higher alcohols (HA) production via heterogeneous CO hydrogenation. The “spherical-platelike” CuCoMn catalyst, achieved through a simple co-precipitation (CP) route followed by a calcination-reduction process, contained a CuMn-rich sphere structure and a Co-dominated nanosheet. The catalyst demonstrated a total alcohols selectivity of 46.2%, and the fraction of ethanol reached up to 45.4% among the total alcohols products, which is superior to the classical modified CuCo-based catalysts. The outstanding catalytic performance was attributed to the unique “spherical-platelike” structure, which altered the surface Cu+/Cu0 distribution and the dispersion of Co species. As revealed by in situ XRD, H2-TPR, in situ XPS, HAADF-STEM and in situ DRIFT spectra techniques, a strong electronic and geometric interaction between Cu and Mn species in optimized CuCoMn catalyst modified the chemical states of Cu species to present a higher proportion of surface Cu+/(Cu0 + Cu+) and, especially, enhanced the linear CO adsorption on Cu+ active sites, which provided a higher probability of CO insertion, and eventually contributed to promotion of catalytic performance. In addition, a higher probability of bridge CO adsorption on metallic Co was also observed over the CuCoMn catalyst, which was beneficial for the formation of CHx intermediates. It is concluded that a synergistic effect between Cu+ and Co species, promoted by the presence of manganese species, was responsible for CO hydrogenation to produce ethanol.