Density functional theory study on the mechanism of calcium sulfate reductive decomposition by methane

► Our study investigates reaction mechanism by density functional theory (DFT). ► The reductive decomposition process of CaSO4 in chemical looping combustion (CLC) system has been calculated. ► The DFT method, we used, can be a reliable method for predicting the reaction mechanism. ► A probably mechanism of CaSO4 reacting with CH4 is proposed.