Renewable production of methane from woody biomass by catalytic hydrothermal gasification

Production of synthetic natural gas (SNG) from wood by a catalytic hydrothermal process was studied in a laboratory batch reactor suitable for high feed concentrations (10-30 wt %) at 300-410 degrees C and 12-34 MPa with Raney nickel as the catalyst. A maximum methane yield of 0.33 (g of CH4)/(g of wood) was obtained, corresponding to the thermodynamic equilibrium yield. The carbon gasification efficiency was a function of the reaction time, and for reaction times long enough (similar to 90 min), complete gasification was achieved. At supercritical conditions, the remaining liquid phase always was tar-free, was colorless, and contained less than 2 wt % of the feed carbon. Analysis of the spent catalyst revealed a slight increase of carbonaceous deposits on the surface (15 atom % vs 10 atom % for the fresh catalyst).