Stability and activity of a co-precipitated Mg promoted Ni/Al2O3 catalyst for supercritical water gasification of biomass

We have investigated the stability and activity of a co-precipitated Mg promoted Ni/Al2O3 catalyst (Ni-Mg-Al) for supercritical water gasification (SCWG) of various biomass model compounds and real biomass. Phase stability and activity recovery of the Ni-Mg-Al catalyst were first compared with a catalyst prepared by impregnation method. It was found that the co-participated catalyst showed higher activity recoveries than the impregnated catalyst due to the stable Ni crystal size. Then, effects of SCWG variables including heating up rate, gasification temperature, catalyst loading amount and feedstock concentration, on the non-catalytic and catalytic gas yields and gasification efficiencies of glucose and phenol were evaluated. Results demonstrated that the presence of sufficient amount of Ni catalyst could realize complete carbon gasification of different organics, including phenol and real biomass. Catalyzed by Ni, CH4 was the more favored produced gas at 400-500 degrees C while H-2 yields were more abundant at 500-600 degrees C. Without catalyst, carbon gasification efficiencies of SCWG of different feedstock were in the order: glycerol > glucose > cellulose approximate to corncob approximate to poplar leaf approximate to sawdust > phenol, while those catalyzed by Ni were in the order: glycerol approximate to glucose approximate to cellulose approximate to phenol > corncob approximate to poplar leaf approximate to sawdust, illustrating that the co-precipitated Ni Mg Al catalyst is more active on catalyzing the gasification of water-soluble organics than real biomass. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.