Textural study of a coal from villanueva de rio y minas (sevilla, spain) and of samples prepared from it by acid and heat treatments

Abstract

AbstractA coal with high inorganic matter content from the mine of Villanueva de Rio y Minas (Sevilla, Spain) (VRMO) was classified by following the ASTM norms as a high volatile matter A bituminous coal. The starting coal was treated either with HCl (VRMH) or thermally at 1000°C for 2 h (VRMOC), the resultant yield values (referred to as VRMO, dry) being, respectively, 97 and 79%; also VRMH was either treated with HNO3 (VRMN) or HF (VRMF), and the yield values (referred to as VRMH, dry) of the process were then 95 and 59%. The textural characterization of samples was effected by adsorption of CO2 at 273 K and of N2 at 77 K, as well as by mercury porosimetry. VRMN presents the highest value of the apparent surface area (SD‐R=219 m2 g−1) (CO2, 273 K) and of the specific surface area of mesopores and macropores (Sme+ma=5.2 m2 g−1) (N2, 77 K), while the greatest value of the cumulative specific surface area of macropores (Sma=1.2 m2 g−1) (mercury porosimetry) corresponds to VRMOC; S values are expressed on a per gram of original sample basis. The micropore volume accessible to CO2 at 273 K increases in both the HCl and the HNO3 treatment and decreases in the HF and heat treatments. The HCl and HNO3 treatments produce an increase of the mesoporosity; the HF treatment seems to affect in a special way the mesoporous texture. Furthermore, the heat treatment gives rise to a notable development of the macroporosity.