Effect of Dimethylformamide Treatment of Coals on Their Thermal Degradation and Elastic-Plastic Properties

Data on the thermal degradation and the elastic-plastic properties of Donetsk hard coals before and after sorption of dimethylformamide (DMF) are reported. It was shown that the sorption parameters and the microhardness of the coals decrease to different extents with an increase in metamorphic maturity for isometamorphic coals of different genetic types in terms of the degree of reduction. It was concluded that it is impractical to use DMF for studying the sorption behavior of coal of different genotypes with a vitrinite reflectance greater than 1.1%. It was found that the interaction of coals of a less reduced genotype with DMF leads to substantial changes in the microhardness and the parameters of thermal degradation of the coals. For coals of a more reduced type, the microhardness and thermal degradation parameters change to a much lesser extent. This finding suggests that DMF sorption by these coals is accompanied by partially reversible processes that do not result in a substantial alteration in the structure of coal matter.