PORE STRUCTURE OF THE ARGONNE PREMIUM COALS

Data are presented that are inconsistent with the accepted model of coal pores existing as an interconnected network of bottlenecked pores. It is proposed that pores in coals are isolated and can be reached only by diffusion through the solid, The fractal dimensionality of the pores in five Argonne Premium Coals were measured by small-angle X-ray scattering and vary between 2.35 and 2.87. The adsorption of the following gases has been measured on all of the Argonne coals: N-2, CO2, ethane, cyclopropane, cyclobutane, cyclopentane, and cyclohexane. Except for Zap lignite, there is a very steep dependence of BET surface area on adsorbate size which is rationalized as being due to the size dependence of the adsorbate diffusion rates through coals.