Experiments were conducted to determine whether mild oxidation of Illinois No. 6 coal at 50Β°C might contribute to a liquefaction process and to add to our knowledge of coal structure. Fractions of coal extract, extracted coal, and fractions of solvent-refined coal were used. Many of the oxidations were self-retarding, but refluxing with alcoholic KOH eliminated this retardation and effected considerable breakdown of the coal, even in the absence of oxygen. Oxidations and base treatments of soluble fractions gave more breakdown than extracted coal, a difference attributed to the dissimilarity between branched and network structures.
The ultimate objective of this work is to contribute to an improved liquefaction process. Our immediate objective is to determine the potential of selective oxidation for breaking large coal molecules into smaller, soluble ones and thus contribute to our knowledge of the connecting links between the condensed-ring systems in coal. In this part of the work, we used extracted coal and fractions of soluble extracts of coal and solvent-refined coal (SRC), nearly all derived from Illinois No. 6 coal. In another part of the work' we have oxidized model compounds under similar conditions to provide the fundamental information needed to guide and interpret the coal oxidations. The present paper first compares the rates of oxidation of these fractions and shows that many of the oxidations are self-retarding, an effect that is reduced by pretreatment with refluxing alcoholic KOH. Also described are the individual and successive oxidations and KOH treatments, first on the pyridine-soluble, tolueneinsoluble extract of coal, and then on the insoluble pyridineextracted residue. Our conclusions are summarized in the final Discussion.
EXPERIMENTAL
Materials
The Illinois No. 6 coal was a beneficiated sample obtained from Pennsylvania State University as PSOC-26 (C 76.8, H 5.0, N 1.57, S 2.13,O (diff.) 12.3, ash 2.2); the coal was ground under nitrogen to pass a 60-mesh U.S. sieve and dried. It was extracted exhaustively with refluxing pyridine under nitrogen; use of interposed ballmillings under nitrogen gave a very finely divided residue and an increase in ash (porcelain). The pyridine extract was then fractionated into three fractions, totally soluble in pyridine (P) but not in toluene or hexane, totally soluble in toluene (T) and pyridine but not in hexane, and totally soluble in hexane (H) as well as the other solvents. The insoluble, extracted coal (R) corresponded to 85% of the original coal. Illinois No. 6 SRC was obtained from Mr Everett Huffman of Southern Services, Birmingham, Alabama, and fractionated similarly. Details of these extractions, fractionations and analyses are presented elsewhere . 293 Another SRC, made from coal from 0016-2361179fOI 00P4-0782.00