Secondary pyrolysis of the products of the thermal destruction of high-sulfur oil shale

Secondary pyrolysis of products of Israeli oil shale processing was studied in a two-stage bench-scale unit. The gas and oil vapors generated from the primary pyrolysis were sent to the converter for the secondary pyrolysis at temperatures of 650-820 degrees C. The oil yield on kerogen decreased from 35.3% at the pyrolysis temperature of 500 degrees C to 15.4% at 820 degrees C. The gas yield increased in the same temperature range from 10.7 to 25.5%. The yields of hydrogen, methane, ethylene, and carbon monoxide increased with temperature, whereas yields of alkanes decreased. The secondary pyrolysis enables us to simplify substantially the composition of the primary shale oil. The higher the severity of the conversion, the higher the yield of the simplest homologues-thiophene, naphthalene, phenanthrene, anthracene, thionaphthene, and dibenzothiophene-and the lower the yield of alkyl derivatives-toluene, methylthiophenes, styrene, etc. Maximal content of methyl and dimethyl derivatives was observed at a temperature of 730 degrees C. The total thiophenes yield may be as high as 6.4% on oil shale organic matter, and this can be of practical interest because thiophenes are an important source for the production of light- and photoemitting polymers, materials for semiconductors, electrochemical cells, films, sensors, and other high-tech devices.