Green Extraction of Oil from Oil Shale Using Supercritical CO ₂ and Water as a Modifier

Supercritical CO2 (SC-CO2) extraction is a promising alternative to conventional pyrolysis for recovering oil from shale due to its mild critical properties and environmental advantages. In this study, oil was extracted from Jordanian El-Lajjun oil shale using SC-CO2 with 10 vol % H2O, followed by ultrasonic-assisted recovery. The shale was characterized by thermogravimetric analysis, FTIR, and X-ray diffraction prior to extraction. Experiments were systematically performed across a temperature range of 35–100 °C, pressures of 4–10 MPa, and times of 1–3 h to evaluate the effects of these parameters on oil yield and composition. Pressure was identified as the dominant factor, followed by temperature, while extraction time had only a minor influence. The maximum yield (∼8.9 wt %) was achieved at 7.4 MPa and 75 °C, comparable to yields obtained from Fischer assay pyrolysis at >500 °C. GC–MS and 1H NMR analyses revealed that higher temperatures promoted lighter fractions and increased oxygen- and sulfur-containing compounds. These results demonstrate that water-modified SC-CO2 enables efficient oil recovery at significantly lower temperatures, providing a green and energy-efficient extraction route compared to conventional thermal methods.