Microwave Aquathermolysis of Oil Shales: Enhancement of Light Hydrocarbon Yield and Modification of Gaseous Product Composition

The growing global demand for energy and the depletion of conventional light hydrocarbon resources necessitate the development of alternative and hard-to-recover feedstocks, among which oil shales represent a strategically important resource due to their vast reserves. In this study, the efficiency of conventional microwave thermolysis in an inert atmosphere is compared with an innovative microwave aquathermolysis approach employing activated steam for oil shale samples from three Azerbaijani deposits (Diyally, Guba, and Jangichay). The experiments were conducted under microwave irradiation (2.45 GHz, 600–800 W) at 300–400 °C with a treatment duration of 20 minutes, ensuring rapid and uniform heating. Microwave aquathermolysis was shown to enhance heat and mass transfer, promoting deeper degassing and partial kerogen conversion. Steam activation led to an increased yield of light hydrocarbons, a marked reduction of heavy resins and asphaltenes, and significant changes in gaseous product composition. Gas chromatographic and SARA analyses confirmed accelerated thermochemical reactions, suppression of secondary coking, steam-assisted conversion of carbon oxides, and partial hydrogenation of unsaturated compounds. Overall, the results indicate that microwave aquathermolysis is more efficient and energy-saving than conventional microwave thermolysis, demonstrating strong potential for processing Azerbaijani oil shales and other kerogen-rich unconventional resources.