Asphaltenes and preasphaltenes in direct coal liquefaction - changes in heteroatom content

The oxygen, nitrogen and sulphur heteroatom contents of four asphaltenes (isolated from different stages of a direct coal liquefaction process) decline as a function of the severity of hydrocracking. Subsequent hydropyrolysis of these asphaltenes further reduces the sulphur content to zero, but oxygen and nitrogen contents appear to reach limiting (but significant) values. The conversion of the asphaltenes to pentane-soluble material (oils) includes inter alia, the formation of alkylphenols and alkylindoles. A related set of four preasphaltenes have been hydropyrolysed in the presence and in the absence of a hydrogen donor (9,10-dihydroanthracene): large differences were observed in the yields of products, and the fate of nitrogen and sulphur during these processes has been, to a large extent, charted. © 1987.