Pressure-Differential Scanning Calorimetry of Coals, Organic Compounds, and Polymers

摘要

Pressure differential scanning calorimetry (PDSC) has been found to be a useful technique for the rapid measurement of heat of combustion of coals. A typical experiment involves heating a 1 to 1.5 mg sample at a linear rate of 20 exp 0 C/min over the range of 150 to 500 exp 0 C, in a 3.5 MPa atmosphere of oxygen. For most coals, the resulting thermogram consists of two exothermic peaks, the relative intensity of which varies in a characteristic way with coal rank. The experiments on coal were supplemented with measurements on over 30 model compounds and about 50 polymers. The exotherm occurring at the lower temperature was found to arise from the aliphatic portion of the coal structure and the exotherm at higher temperature, from the aromatic portion. A value of the aromaticity can be deduced from the relative intensities of the two peaks; such values generally agree with data obtained for similar coals by solid state nuclear magnetic resonance. The maximum of the aromatic peak shifts to higher temperatures with increasing ring condensation. Thus, from a single PDSC experiment it is possible to measure the heating value and to deduce rank, aromaticity, and ring condensation. Our current research seeks to use PDSC technique to study variations in aromaticity with depth in the seam, and variations in aromaticity and ring condensation among coal lithotypes. 6 figures. (ERA citation 08:045484)