Effect of Supercritical Water Temperature on Pyrolysis Characteristics of Oil Shales

Temperature is an important factor affecting the pyrolysis of oil shale, and it is of great significance to study the effect of supercritical water at different temperatures on the pyrolysis characteristics of oil shale. In this experiment, a semi-open reaction system was used to study the effect of temperature on the pyrolysis of Balikun oil shale under a supercritical water pressure of 23 MPa. The semi-open reaction system allows for the continuous injection of water and discharge of products, which is different from previous closed systems and batch reaction systems. This setup can promptly discharge products, reducing the likelihood of secondary reactions and making it more suitable for industrial production models and the study of pyrolysis mechanisms. Results show that the higher the temperature, the closer the time point at which oil and gas peak production occurs, the higher the total gas yield, but the lower the total oil yield. Hydrocarbon gas, CO2, and H2 yields increase with increasing temperature. Higher temperatures increase aromatics and resins but reduce saturated hydrocarbons and asphaltenes. The research shows that about 400 °C is optimal for the maximum oil yield under supercritical water conditions, and higher temperatures only marginally increase organic matter conversion. This study provides critical insights for future in situ extraction of deep oil shale deposits using supercritical water.