Nickel and Iron-Doped Biocarbon Catalysts for Reverse Water-Gas Shift Reaction

Biocarbon catalysts for reverse water-gas shift reaction (RWGS) were produced from pyrolyzed fern and willow impregnated with iron and nickel nitrates. This reaction can partake during Fischer-Tropsch synthesis (FTS) by consuming CO2 and lowering both the H-2/CO ratio and the efficiency in the production of fuels. RWGS has attracted much attention to widespread utilization of CO2 through the production of syngas. The catalysts were therefore tested in a fixed-bed reactor at 400 degrees C as it is the maximal temperature for FTS and high RWGS. They showed high selectivity towards CO (>84 %) and fair conversion (<17 %) compared to rust (81 %, 30 %, respectively) and Fe-impregnated alumina (100 %, 8 %). No loss in selectivity and conversion was observed for a longer residence time (288 h). Biomass inherent metals could provide reactive gas adsorption sites that improve conversion by dispersing electrons which reduces adsorption and dissociation energy barriers. K, Mg and Ca in fern biocarbon catalysts may be related to the higher CO2 uptake compared to willow catalysts. Electron deficient sites produced by reduction of biocarbon oxygen functional groups may facilitate CO2 uptake and activation. Ni-impregnated fern-based biocarbon showed the highest activity, due to the synergetic effect of the inherent metals, O vacancies and strong metal-carbon interactions.