Extractions and reactions of coals below 100 °C: 4. Oxidations of Illinois No. 6 coal

✍ Scribed by Frank R. Mayo; Lee A. Pavelka; Albert S. Hirschon; John S. Zevely

• Publisher: Elsevier Science
• Year: 1988
• Tongue: English
• Weight: 842 KB
• Volume: 67
• Category: Article
• ISSN: 0016-2361
• DOI: 10.1016/0016-2361(88)90288-8

✦ Synopsis

This paper summarizes efforts to increase the solubilities of coal fractions, with minimum loss of carbon, by oxidations with aqueous NaOCI, oxygen, and nitric acid, at or below 60°C. The principal products were 'black acids', insoluble in water but sparingly soluble in dilute aqueous base; small proportions of colourless, water-soluble acids were also obtained. The best yields of black acids (60-80'4 on carbon and the lowest losses of carbon (10 to 20%) varied little with the oxidizing agents used. The H/C ratios of black acids obtained with nitric acid (-0.6) were lower than in the starting materials (0.73), indicating loss of more aliphatic than aromatic material. Oxidations with oxygen and NaOCl at pH 13 indicate that somewhat more aromatic than aliphatic carbon was lost during oxidation. The small residues of undissolved coal had H/C ratios -0.9. Some of the black acids were fractionated by size-exclusion and high performance liquid chromatography;

the methods appear to have considerable potential for investigating coal structure. Fractional precipitation of black acids from water with hydrochloric acid over the pH range 64 gave products of only a small range of average compositions.

An effort to find diary1 ketone groups in black acids by oxidation with m-chloroperbenzoic acid, and thus evidence of single methylene groups between groups in coal, found no conclusive evidence of such groups. but the method is insensitive.