Gas generation and its isotope composition during coal pyrolysis: The catalytic effect of nickel and magnetite

In experiments without added water, addition of magnetite enhanced CO2 yield at all temperatures but only enhanced methane yield slightly at high temperature (430-550 °C). The increased CO2 and methane yields can be attributed to the oxidative decomposition of long-chain hydrocarbons via redox reactions between magnetite and hydrocarbons. In experiments with added water, addition of magnetite only caused a slight increase of methane and CO2 yields at 500 °C and 550 °C but did not influence their yields at 370-450 °C, indicating that water inhibited the effect of magnetite on methane and CO2 generation at low temperature. The addition of magnetite did not have systematic influence on carbon and hydrogen isotopes of hydrocarbon gases and carbon isotopes of CO2. Generally, the influence of magnetite on gas generation was very small.