Extraction of Huadian oil shale in subcritical FeCl2 solution

Abstract The combination of subcritical water and catalyst was proposed for oil shale extraction. The extraction of Huadian oil shale in FeCl2 solution was performed at 350 °C to evaluate the combined method. At 20 h, a high yield of bitumen 1 (the bitumen discharged from shale matrix) was obtained in FeCl2 solution with an optimal concentration of 0.08 mol/L, which was 50.5% higher than that obtained in pure water. The bitumen 1 reached a maximum yield of 18.98 wt% at 40 h in subcritical FeCl2 solution and 19.14 wt% at 70 h in subcritical water, respectively. The time needed for a maximum yield of bitumen 1 was reduced by 43% after the addition of FeCl2. The results indicated that FeCl2 played an important role in the promotion of the cleavage of hetero-atomic bonds in kerogen and the transportation of bitumen 2 (the bitumen remaining in the shale matrix) in the shale matrix. It showed the addition of FeCl2 did not significantly affect the variation trends of the relative content of the major components in bitumen 1 and bitumen 2 with the time. The subcritical FeCl2 solution extraction should be a highly efficient method for in situ extraction of oil shale.