EXPERIMENTAL STUDY ON SUPERCRITICAL EXTRACTION OF CHINESE OIL SHALES TO YIELD LIQUID PRODUCTS.

Eight Chinese oil shales were extracted under nonisothermal conditions with supercritical toluene and toluene-tetralin mixtures. Optimum extraction conditions for high liquid yield and high conversion were determined by systematic variation of extraction parameters: pressure, final extraction temperature, oil shale particle size, solvent flow rate, and H-donor content of the solvent. The results indicate that supercritical extraction of oil shale with toluene gives about twice as much oil yield as conventional retorting. With supercritical hydroextraction, where an H-donor is added to the supercritical toluene, nearly complete recovery of organic matters in the oil shale is possible with a high proportion of liquid products. From the concentration of extract in solution at different temperatures, the kinetics of supercritical extraction of oil shale was shown to be first order in rate, divided into two regions, with corresponding activation energies of about 120 and 180 kJ/mol, respectively.