DETERMINATION OF ORGANIC SULFUR FORMS IN SOME COALS AND KEROGENS BY HIGH-PRESSURE TEMPERATURE-PROGRAMMED REDUCTION

The principal inherent drawbacks associated with temperature-programme d reduction (TPR), for specifying the distribution of organic sulfur f orms in solid fuels, in that first, thiophenic sulfur is largely undet ectable and second, sulfides interconvert readily into thiophenes, hav e been overcome by the use of a well-swept, fixed-bed reactor, operati ng at relatively high hydrogen pressure (15 MPa). The high pressure te chnique was applied previously to two high sulfur lignites, Rasa (Croa tia) and Mequinenza (Spain), and indicated that thiophenic forms accou nt for approximately 70% of the total organic sulfur. The study has no w been extended successfully to samples of varying organic sulfur cont ent which include three of the Argonne Premium coals i.e. Wyodak-Ander son, Illinois No. 6 and Upper Freeport; a UK bituminous coal i.e. Gedl ing; two kerogens i.e. Goynuk (Type I, Turkey) and Kimmeridge Dorset-C uddle (Type II, UK); and a liptinite concentrate of Mequinenza lignite . For those samples in which pyritic sulfur represents a significant p roportion of the total sulfur, treatment with lithium aluminium hydrid e was necessary, in order to obtain any meaningful information on the organic sulfur forms present. From the subsequent H2S evolution profil es, the relative contributions from thiophenic and non-thiophenic form s have been resolved satisfactorily. In common with other pyrolysis te chniques and X-ray techniques (XPS and XANES), high pressure TPR indic ates that thiophenic sulfur increases with rank. However, the proporti ons of thiophenic sulfur derived from high pressure TPR are consistent ly higher than by other techniques.