Pore structure characteristics and gasification reactivity under CO2 of char from catalytic depolymerization of low-rank coal

The catalytic depolymerization technology of low rank coal aims to obtain more tar through the promotion of depolymerization coal macromolecular structure at low temperatures. The addition of catalyst in the catalytic depolymer- ization process can not only increase the yield and quality of tar,but also reduce the polymerization degree of char. This study is mainly to investigate the gasification performance of the chars with the variation of pore structure. The effect of Fe based catalyst and Mo based catalyst on the pore structure and CO2 gasification reactivity of the respective chars were investigated by TG analyzer and N2 adsorption. The results showed that the catalyst promoted the bond breaking of the oxygen-containing groups in coal,reduced the oxygen content in char,and changed the surface proper- ties,and finally caused the change of adsorption isotherm of Inner Mongolia char with catalyst from type I of raw coal pyrolysis semi-coke to type V,and the change of adsorption isotherm of Xinjiang char of raw coal pyrolysis from type II to type IV after Mo based catalyst addition and to type V after Fe based catalyst addition. The catalyst inhibited the polycondensation of char in the process of catalytic depolymerization,which increased the number of mesopores,sur- face area and pore volume of char,especially for the Mo catalyst addition. The pore volume of Inner Mongolia char with Mo catalyst was 2. 14 times of that of raw coal char,and the pore volume of Xinjiang coal with Mo catalyst was 16. 5 times of that of raw coal char. The catalyst addition had no obvious effect on the gasification reactivity of the char, while with intervening the pyrolysis process of coal,the char formed more mesopores,and the specific surface area and pore volume of char increased,thus the gasification performance of char improved significantly. The change of isotherm ad-sorption line and the increase of pore volume of char also provided the possibility to expand the utilization of the obtained char. As a porous material,the influence of coal depolymerization catalyst on the adsorption perfor-mance of the char could be further investigated,which has an application possibility in sewage treatment and gas purification.