Effect of iron-based catalyst from coal liquefaction on coal char gasification reactivity and kinetics

Abstract

Gasification technology can help the resource recovery of solid product from coal liquefaction, where the iron-based catalyst widely exists. In the present work, the effects of iron-based catalysts from coal liquefaction on the coal structure and reactivity were studied, using the Hami raw coal and demineralized coal. The surface morphology, element distribution and mesoporous characteristics of coal char were investigated by SEM-EDS and physical adsorption analyzer. The gasification reactivity was performed in a thermogravimetric analyzer. The gasification kinetics was studied through the model-fitting and model-free methods. The results showed that the demineralization and catalyst loading had more obvious effect on the surface attachments than the carbon matrix. The coal char with catalyst loading had significant larger specific surface area (SSA). The reactivity improvement by iron-based catalyst could be attributed to the enrichment of Fe and AAEMS and increase of SSA for coal char. More pronounced relative catalytic activity was observed for the catalytic gasification of demineralized coal char, and its activity was not sensitive to the change of heating rate and carbon conversion. The gasification characteristics difference would be reduced with the increase of heating rate. The iron-based catalyst can increase the pre-exponential factor A for the demineralized coal char gasification, and reduce the activation energy Ea for the raw coal char gasification. Under non-isothermal conditions, the Ea decreased with conversion. According to fitting performance and kinetic compensation effect, the random pore model was the best model to describe gasification, especially for the (catalytic) gasification of the demineralized coal char.