Effect of O-containing functional groups produced by preoxidation on Zhundong coal gasification

Low-temperature preoxidation is being evaluated as a preprocessing technique in gasification, but the action mechanism of preoxidation is not yet well understood. The influence mechanism of O-containing functional groups formed by preoxidation on Zhundong coal gasification is detailed in this study. The effect of preoxidation on the gasification kinetics was studied using a micro-fluidized-bed reaction analyzer. Graphite oxide was used as a model compound to simulate coal. Chemical characterization and quantum chemistry calculations were combined to analyze the mechanism of action of preoxidation in gasification. The O-containing functional groups formed during preoxidation can significantly enhance the gasification reactivity and reduce the activation energy by 32%. Experiments with coal samples with a single metal added after pickling revealed that these O-containing functional groups facilitate the efficacy of metal catalysts, particularly for the easily deactivated chloride metal salts in Zhundong coal. The results of experiments controlling the O-containing functional groups on graphite, along with density functional theory calculations, indicated that the carbonyl group was most likely responsible for facilitating catalytic gasification. The carbonyl group can combine with the metal to form more catalytic active C–O–M centers, which strengthen the link between the metal and carbon matrix, thus promoting catalytic gasification.