Biogas upgrading by transition metal carbides

Abstract

The separation of carbon dioxide (CO2) from methane (CH4) is critical in biogas upgrading, requiring materials with high selectivity toward one of the two gas components. Hereby we show, by means of density functional theory based calculations including dispersive forces description, the distinct interaction of CO2 and CH4 with the most stable (001) surfaces of seven transition metal carbides (TMC; TM = Ti, Zr, Hf, V, Nb, Ta, and Mo). Transition state theory derived ad-/desorption rates suggest a very high CO2 uptake and selectivity over CH4 even at ambient temperature and low partial gas pressures.