ZnO–CuO nanoparticles supported on activated carbon for biogas purification from H2S at room temperature

Biogas deriving from the anaerobic digestion of different biomasses and wastes is mainly composed of CH4 (50–70%vol.) and CO2 (30–45%vol.).It represents a valuable energy carrier, which can be used in combined heat and power generation unitspossibly with fuel cells systems, or further upgraded to biofuels. H2S is the most harmful and commonly occurring contaminant present in biogas, highly toxic even at low concentration, corrosive for engines, poisoning for catalysts in downstream fuel cells or fuel processors. The purification step represents one of the main operational costs of the whole process. A lot of in-situ and ex-situ purification technologies have been proposed. Adsorption has the advantage to couple high selectivity and capture efficiency to process ease. Among the commonly adopted sorbents, Activated Carbons (AC) have been proposed when the target sulphur exit concentration must be of few ppm, thanks to the AC large surface area and pore volume and to the presence of surface functional groups, which can also promote H2S oxidation. The impregnation of different porous supports with transition metal oxides, hydroxides, and carbonates, in particular those of Zn, Fe and Cu, is widely used to produce highly performing H2S sorbents for natural gas processing or, more in general, to reformate gas streams. In particular, promising results were reported for the functionalization of mesoporous silica with a combination of ZnO–CuO, which determined significant synergistic effects in terms of H2S adsorption capacity. In this work, AC-supported ZnO–CuO sorbents were investigated for room temperature H2S removal, exploring the effect of the Cu:Zn atomic ratio while keeping the total metal loading fixed at 10%wt.