Coal properties and their influence on air activation

This research sought to determine how the properties of a raw coal influence the degree to which it may be activated. Twelve coals were analyzed using thermogravimetry, mass spectroscopy, mercury porosimetry, nitrogen sorption and infrared spectroscopy, and activated in air, water-saturated helium and carbon dioxide. The greatest amounts of surface area using air activation were generated for bituminous coals. To investigate possible reasons for the sample-to-sample variation in the amount of surface area generated, a spline-fitting program was used to generate a curve that encloses the surface areas generated for all samples. The differences between measured surface areas and surface areas predicted by the spline-fitting program were determined. Statistical analyses of twenty-two predictor variables suggest that the percent vitrinite present accounts for nearly 73% of the deviation from predicted surface area. The % liptinite + % ash predicts 86% of the deviation and the inclusion of two additional variables, the % pyrite and % organic S, appear capable of predicting nearly 99% of the difference between measured and predicted surface areas. Increasing amounts of vitrinite and pyrite appear to increase the surface area generated, while increasing amounts of liptinite, ash and organic S appear to decrease the surface area generated. Pyrite may act as a catalyst during activation. (C) 1997 Elsevier Science Ltd.