Calcium-promoted catalytic activity of potassium carbonate for steam gasification of coal char: Effect of hydrothermal pretreatment

► We proposed the hydrothermal pretreatment (HT) with Ca(OH)2 for K2CO3-catalyzed coal gasification. ► HT had a promoting effect on the rate of catalytic char gasification depending on coal type. ► The alkalized mineral matter in coal became inactive for deactivating the potassium catalyst.