Fate of sulfur compounds in coal during oxidative dissolution in perchloric acid

Abstract

The sulfur forms in coal (sulfate, pyrite and organic) have been clearly delineated by oxidation with perchloric acid. Perchloric acid was chosen as an oxidizing agent because its oxidizing power can be varied by changing its concentration and subsequent boiling point. Using this property, the stepwise oxidation of an Illinois No. 6 coal, a coal-derived pyrite, and a New Zealand coal (in which almost all of the sufur was organic) was effected. At low temperatures, sulfate was removed without oxidizing the pyrite or organic material. At a moderate temperature (155°C), the pyrite was oxidized to sulfate and a sulfur-containing gas. Little or no organic sulfur was oxidized at 155°C. Boiling concentrated perchloric acid (203°C) converted all the sulfur to sulfate and a sulfur-containing gas. The sulfur-containing gas was produced primarily from the pyrite; organic sulfur produced very small amounts of a sulfur-containing gas as an oxidation product.