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In the presence of water, thermal simulation experiments on the reaction between CH4 and MgSO4 were conducted at high temperatures and high pressures. Chemical and carbon isotopic variations were characterized with advanced analytical methods, including microcoulometry, gas chromatography, Fourier transform infrared spectroscopy, X-ray diffraction, and gas chromatograph combustion isotope ratio mass spectrometry. It was found that CH4 can react with MgSO4 to produce H2S, CO2, and MgO as the main products of thermochemical sulfate reduction. The carbon kinetic isotope fractionation was tentatively investigated using quantum chemistry and the kinetic isotope effect was calculated. [ABSTRACT FROM AUTHOR]

Thermal simulation experiments on the reaction between n-C8H18 and CaSO4 were carried out under high temperatures and high pressures. Properties of the reaction products are characterized by advanced analytical methods. Based on the results of simulation experiments, possible reaction pathways and thermodynamic characteristics were tentatively investigated. It was found that n-C8H18 can react with CaSO4 to produce CaCO3, H2S, CO2, H2O, CS2, and a series of organic sulfur compounds (OSCs). The conversion of elemental sulfur in the molecular structure of CaSO4 to small molecule inorganic sulfides and thiophene sulfur increases with the increase of temperature. There is a strong thermodynamic drive for the reaction of n-C8H18 with CaSO4 and high temperature is favorable to the reaction. This study may provide new insights into the origin of OSCs in petroleum. [ABSTRACT FROM AUTHOR]