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

Sun, Kai, Tan, Minghui, Bai, Yunxing, Gao, Xiaofeng, Wang, Peng, Gong, Nana, Zhang, Tao, Yang, Guohui, Tan, Yisheng
Journal of catalysis 2019 v.378 pp. 1-16
X-ray diffraction, X-ray photoelectron spectroscopy, active sites, adsorption, carbon monoxide, catalysts, catalytic activity, cobalt, copper, coprecipitation, ethanol, geometry, hydrogenation, manganese, nanosheets, probability, synergism, synthesis gas
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.