Tentative study on elementary steps and reaction mechanism of thermochemical sulfate reduction

Thermal simulation experiments on n-heptane and six sulfates including Fe2(SO4)3, Al2(SO4)3, MgSO4, CaSO4, Na2SO4 and K2SO4 were carried out in autoclave in the presence of water to investigate the possibilities of thermochemical sulfate reduction (TSR). It was found that Fe2(SO4)3, Al2(SO4)3 and MgSO4 could intensely react with n-heptane at 400℃ to produce metal oxide and / or metal sulfide, hydrogen sulfide, coke and a series of organic sulfur compounds such as mercaptans, sulfoethers and thiophenes as the main products. Under the same reaction conditions, the extent of reactions of nheptane with CaSO4, Na2SO4 and K2SO4 is very limited. Based on the analysis of the gas-oil-solid 3-phase products of the reactions between n-heptane and six sulfates, the elementary steps and reaction mechanism of TSR were tentatively studied.