Ethanol and Higher Alcohols Synthesis from Syngas over CuCoM (M=Fe, Cr, Ga and Al) Nanoplates Derived From Hydrotalcite-Like Precursors

A series of CuCoM (M=Fe, Cr, Ga and Al) nanoplates derived from hydrotalcite-like precursors were synthesized by co-precipitation method and evaluated for ethanol and higher alcohols (HA) from syngas. The CuCoAl nanoplates demonstrated prominently improved HA selectivity of 54.9 %, and the fraction of ethanol/HA reached up to 55.9 % level. As revealed by XRD and HAADF-STEM results, the presence of Al species in the CuCoAl nanoplates obviously enhanced the dispersion ability of Cu and Co species. Moreover, the abundance of basic sites (surface hydroxyl groups) on CuCoAl nanoplates resulted in the formation of formate species, which was a significant C₁ species for the generation of CH_x intermediates. More importantly, a high probability of CO bridge adsorption on metallic Co atoms was found over optimized CuCoAl catalyst, which provided a favorable effect for CO dissociation, leading to the formation of CH_x intermediates. Therefore, more CH_x intermediates were generated from the formate species and CO bridge adsorption on metallic Co atoms, which provided a beneficial role for C−C chain growth in the higher alcohols production in CO hydrogenation reaction. Furthermore, a moderate ratio of surface Cu/Co was observed over optimized CuCoAl nanoplates, which can exert a synergetic effect between Cu and Co species. Ultimately, the enhanced catalytic performance was attributed to the combination of the Cu and Co species and the basic property of the CuCoAl nanoplates.