Effect of acid and heat treatments on surface area and porosity of a Spanish coal with high mineral matter content

Abstract

The main components of the mineral matter of a Spanish coal (ASTM classification as high volatile A bituminous) were shown, by X-ray diffraction studies and ash analyses, to be quartz, kaolin and mica. The textural characterization of the raw coal and samples prepared from it by acid and heat treatments was effected by gas adsorption at low temperatures, mercury porosimetry and density measurements. The treatment of raw coal with HCl brought about the largest development of the surface area accessible to nitrogen at 77 K and to the carbon dioxide at 273 K. Heat treatment resulted in the highest value of the total open pore volume. Acid treatments produced an enlargement of the mesopores, while heat treatment resulted in a loss of mesopores of smaller size and a high development of macroporosity.