Co0 − Coδ+ active pairs tailored by Ga-Al-O spinel for CO2-to-ethanol synthesis

Abstract

• Co 0 -Co 2+ active pairs could be tailored by the ratio of Al/Ga in the spinel precursor of CoGa x Al 2-x O 4 /SiO 2 . • The selectivity to ethanol reached 20.1 % under 270 °C and 3.0 MPa. • The dispersion and the size of Co nanoparticles could be adjusted by the content of Ga in CoGa x Al 2-x O 4 /SiO 2 . • Reaction pathway followed the reverse water gas shift reaction and hydrogenation of CO process. • A dynamic evolution of Co 0 -Co 2+ caused the decrease in the ratio of ethanol to methanol. Direct hydrogenation of CO 2 into ethanol has been considered as an up-and-coming way to achieve CO 2 utilization. Ethanol can be generated by reverse water gas shift as well as CO hydrogenation over Co-based catalysts, where the regulation of Co 0 − Co δ+ is critical. Herein, we designed a supported Co-based catalyst doped with gallium, which was derived from Co-Al-O spinel precursor to facilitate synergistic catalyzing for CO 2 -to-ethanol transformation. The selectivity of ethanol reached 20.1 % in a continuous flow fixed micro-reactor over reduced CoGa 1.0 Al 1.0 O 4 /SiO 2 catalyst at 270 °C and 3.0 MPa. Results of characterization show that the existence of the strong interaction between Ga oxide and cobalt induced the configuration of Co 0 − Co δ+ active pairs, which promotes the process of ethanol synthesis by coupling the dissociation (CH x *)/non-dissociation (CO*) of the intermediates. The strategy by tuning the interaction between cobalt and gallium and/or aluminum oxide brings an avenue to tailor Co 0 − Co δ+ active pairs for the hydrogenation of CO and CO 2 .