CHARACTERIZATION OF THE CHEMICAL FRAGMENTATION PRODUCTS OF AIR-OXIDIZED COALS BY GAS CHROMATOGRAPHY AND GAS CHROMATOGRAPHY/MASS SPECTROMETRY

A major problem in coal technology is air oxidation and weathering. These processes are at least responsible for ignition on storage and loss of coking properties. In the present work, the problem has been approached by subjecting a variety of coals to air oxidation followed by oxidatively degrading the material with trifluoroperoxyacetic acid (TFPA). The products were identified and the yields determined. Twenty-five coals have been selected to include a wide range of percent carbon, type, and rank. Selections of these coals were heated in vacuum at 85, 140 and 200 degrees centigrade and oxidized in air at 25, 85, 110, 140 and 200 degrees centrigrade. The weight gains or losses were recorded. The residues were oxidized by TFPA and the products interpreted.;Gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) techniques were employed for analysis of the TFPA coal fragmentation products. It was necessary in analyzing the complex mixtures of products to improve the usual GC/MS interface and these improvements are described.;Changes in the dihydroaromatic, phenolic, and aliphatic structures of coal, and the introduction of carboxyl groups, were detected by alterations in the TFPA product distributions. Heating coals in vacuum up to 200 degrees centigrade caused little chemical change. Coals of varying rank did not react in the same way during air oxidation; this technique was not found to be applicable to the study of anthracite coals. The results of this work are related to other studies on the oxidation of coals by air.