Mechanisms governing the effects of thermal oxidation on hydrogen production during in-situ combustion gasification of heavy oil

This study combines thermogravimetric analysis with high-temperature and high-pressure reactor experiments to reveal the mechanisms governing the effects of heavy-oil thermal oxidation on hydrogen production and investigates the effects of water and clay minerals. Heavy-oil oxidation comprises low-temperature oxidation (28.5–402 °C), coke formation (402–496 °C), and high-temperature oxidation (496–682 °C). Low-temperature oxidation primarily involves light-component volatilization and oxidative addition, with limited hydrogen production. During coke formation, deep pyrolysis, dehydrogenation, and polycondensation reactions become dominant, enhancing hydrogen production. High-temperature oxidation significantly promotes hydrogen production through the synergistic effects of coke oxidation, coke gasification, and the water-gas shift reaction. Both water and clay minerals increase the hydrogen production efficiency. This study underscores that hydrogen production is significantly influenced by thermal oxidation, which provides more comprehensive insights into hydrogen production mechanisms during in-situ combustion gasification of heavy oil.