Extracting hydrocarbons from Huadian oil shale by sub-critical water

The possibility of extracting hydrocarbons from Huadian oil shale by sub-critical water was found in a stainless steel vessel. The effects of temperature and pressure on the extraction of hydrocarbons were studied. After extraction experiments, the residual solid, liquid and gas phase samples were collected and characterized, respectively. The extract yield could reach 7 wt.% (ad) when the extraction of oil shale was conducted at 260 °C for 2.5 h with the pressure of 15 MPa. The results of thermogravimetry (TG) showed that the weight loss of residual solid samples was much smaller than that of the original oil shale. It indicated that kerogen components had been decomposed partly by treatment with sub-critical water. Gas chromatography–mass spectrometry (GC–MS) analysis showed that there were more than 300 recognizable peaks in the extracting solution following processing at 330 °C and 18 MPa. Large amounts of high molecular weight hydrocarbons were gradually decompounded by the increase in types and levels of low molecular weight hydrocarbons, and polycyclic and heterocyclic compounds with the rising of pressure and temperature. These indicated that sub-critical water is capable of cracking kerogen into smaller hydrocarbon compounds at relatively low temperatures.