Characterization of Chinese, American and Estonian oil shale semicokes and their sorptive potential

The primary byproduct of current oil shale oil extraction processes is semicoke. Its landfill deposition presents a potential threat to the environment and represents a waste of a potentially useable byproduct. Here we examine the sorptive characteristics of oil shale semicoke. Oil shale samples from Estonia, China and the United States were pyrolyzed at 500 and 1000 °C and their products analyzed for organic char content, surface area and porosity. Pyrolysis of the oil shales at temperatures of 500–1000 °C yields semicokes with organic char contents from 1.7% to 17.5% and BET surface areas of 4.4–57 m2 g−1, corresponding to 100–550 m2 g−1 of organic char. For comparison, the BET surface areas of class F coal fly ashes (combustion byproducts of bituminous coals) typically range from 2 to 5 m2 g−1, corresponding to 30–60 m2 g−1 of carbon while class C fly ash (from low rank coals) have carbon BET surface areas comparable to oil shale semicoke organic char surface areas.