SURFACE STRUCTURAL-CHANGES OF COAL UPON HEAT-TREATMENT AT 200-900-DEGREES-C

Surface properties of the chars obtained from two Australian coals at different temperatures of 200-900-degrees-C were characterized by means of high-pressure mercury porosimetry, adsorptions of CO2 (0-degrees-C), CH3OH (25-degrees-C), and H2O (25-degrees-C), and H2O-immersional microcalorimetry at 25-degrees-C. With increasing temperatures of char preparation, the volume of macropores in a diameter range of 50 nm-10-mu-m increased with a maximum at 600-degrees-C, while the amounts of CO2, CH3OH, and H2O adsorbed, depending on the micro- and mesoporosity of char, changed with a minimum at a temperature (400-600 degrees-C) dependent on the nature of coal. In contrast, surface hydrophilicity of char, estimated from the specific immersional heat of char into water, monotonously decreased with increasing temperatures of char preparation from 200 to 750-degrees-C.