PYROLYSIS OF BROWN COALS .2. DECOMPOSITION OF ACIDIC GROUPS ON HEATING IN THE RANGE 100-900-DEGREES-C

The pyrolysis of a Yallourn brown coal in the acid form and several different cation forms has been studied at temperatures up to 900 °C, in regard to the decomposition of acid groups, the relation between oxygen products evolved and these groups, and the fate of cations. The exchange of carboxyl groups changes the amounts of both carbon dioxide and water evolved on pyrolysis, indicating that oxygen-containing groups other than carboxyl are affected by the exchange. The total acid-group content of the acid-form coal heated at different temperatures can be related to the sum of the acid group content of the residual char, and carbon dioxide and carbon monoxide evolved during pyrolysis. The results, in general, confirm the conclusion reached previously in regard to pyrolysis carried out at temperatures up to 300 °C. Pyrolysis in nitrogen at 900 °C releases all oxygen from the acid-form coal. In cation coals the amount of oxygen retained in the char in combination with the cation depends on the type of cation and the extent of reaction with nitrogen in the pyrolysis atmosphere. © 1979.