Carbon isotope kinetics of gaseous hydrocarbons generated from different kinds of vitrinites

Kinetics study of gaseous hydrocarbons generated from vitrinites based on pyrolysis of gold tube closed system shows that the activation energies of methane generated from telocollinite are higher than that from desmocol-linite due to structure differences. But carbon isotope ratios of generated methane in pyrolysates of vitrinites at the same temperature points are similar. Carbon isotope ratio of methane may decrease in the early stage of gas generation and then increase in the later stage. But at higher temperature, δ13C1 decreases slightly or almost keeps stable with increasing temperature. Since it is known that carbon isotope distillation is controlled by time, temperature and carbon isotope ratio of bulk organic matter, the character of side chains connected to macromolecule of vitrinite and distribution of activation energies have no obvious effect on carbon isotope fraction. Decreasing trend of δ13C1 in the early stage may be caused by contagious structure of vitrinite or differences of activation energies between 12C-12C and 12C-13C are not strictly constant at different ranges of activation energy area.