Experimental study and life cycle assessment of CO2 methanation over biochar supported catalysts

With the existing natural gas pipeline network, methane can be easily transported and utilized. Catalytic conversion of CO2 into fuels can provide an attractive solution to convert greenhouse gas to valuable products. Thus, it is of great significance to synthesize CH4 from CO2 for the replacement of fossil fuels to relieve energy and environment issues. A novel Ni-based catalyst (Ni/Ce-ABC, where ABC referred to activated biochar) using biomass as raw materials was designed for CO2 methanation reaction in this study. The biochar modified by highly dispersed CeO2 was obtained from pyrolysis of Pinus sylvestris combined with in-situ activation with NaHCO3 and Ce doping and then was assessed as a catalyst support (Ce-ABC). A series of characterization methods were employed to study the detailed physicochemical properties of the catalyst. The Ni/Ce-ABC catalyst exhibited better activity than Ni/ABC for CO2 methanation, achieving a CO2 conversion of 88.6% at 360 °C with a CH4 selectivity of 92.3% at 1 MPa. In addition, the Ni/Ce-ABC catalyst showed fantastic activity at relatively low temperature. The highly dispersed Ce species on the biochar were found to be beneficial for the dispersion of the nickel species and enhancement of the CO2 adsorption capacity of biochar. Life cycle assessment suggested that the biochar-based catalysts were more environmentally friendly than the metal oxides catalysts. This study therefore developed an environmentally benign and catalytically efficient biochar-based catalyst to achieve the reduction and valorization of CO2.