Interaction mechanism of in-situ catalytic coal H2O-gasification over biochar catalysts for H2O-H2-tar reforming and active sites conversion

The co-gasification of biomass and coal is a promising way to make H-2-rich synthesis gas, to better serve the carbon-neutrality development in China. Decoupling core processes of their thermal conversion, the in-situ catalytic co-gasification and co-pyrolysis of coal over biochar were carried out in a one-stage fluidized-bed/ fixed-bed reactor, with the analysis of interaction effect on gas-liquid-solid products by FTIR, XPS, SEM, TG, and electrochemistry methods. The results show that during co-gasification reaction, biochar and coal have a synergistic effect on the in-situ H2O-H-2-tar reforming, which is reflected in the competitive relationship of H2O between biochar and coal, as well as coal tar and steam. H2O preferentially undergoes gasification reaction with biochar, greatly enhances the H-2 yield (increased by 62.3%) and accelerates the active sites conversion. Biochar enhances the degree of graphitization (C-C) of coal char and increases the ratio of O-/N-groups to provide active sites. The AAEMs in biochar would migrate to the coal char surface, enhancing the gasification reactivity and energy storage characteristics of mixed char product, and promoting the reforming of heavy tar into small molecular substances. The interaction between biochar and coal is of great significance to the "carbon-hydrogen " polygeneration of co-gasification of coal and biomass.