REACTION OF BITUMINOUS COAL WITH CONCENTRATED SULFURIC ACID

Special Research Report SR-21 The most effective utilization of coal requires that a complete knowledge of its chemical constitution be known. And it is for this reason that a large amount of effort has been expended on studying coal in the laboratory. In the present work, bituminous coal has been treated with concentrated sulfuric acid in the range of 50° to 150°C. A small part of the carbon of the coal is eliminated by oxidation to carbon dioxide; however, the majority remains in the solid product" Carboxyl, hydrogen sulfate, and sulfonic acid groups are introduced giving the product acidic properties" These are the groups that give commercial sulfonated coals their water-softening properties" In addition, phenoiic and carbonyl groups are introduced and the percentage of hydrogen has been reduced by about 503" These results show that the sulfuric acid attacks the aliphatic structures in the coal first, forming aliphati.c hydrogen sulfate and sulfonic acid groups. Oxidation or cyclization by the hot sulfuric acid increases the aromaticity of the product: and with higher temperature some of the sulfur-containing groups are replaced by phenolic and ketonic groups. Further work on the b~havior of coals when treated with sulfuric acid would be justified.