Char structure dependence on formation enthalpy of parent coal

The aim of this work was to investigate char structure dependency on parent coal rank expressed by the formation enthalpy. For this purpose, a detailed characterization of eleven char samples obtained under the same pyrolysis conditions was performed. The porous structure was investigated in terms of micro-, meso- and macropores by employing nitrogen adsorption at 77 K, carbon dioxide adsorption at 273 K and mercury intrusion porosimetry. In order to assess both the carbon crystalline structure and degree of structure organization, the X-ray diffraction and Raman spectroscopy techniques were employed as well. The found correlations revealed a strong linear dependency of aromaticity index and char rank parameters from the formation enthalpy of parent coal. Other char parameters, like micropore and macropore surface area, average crystalline sizes and band area ratio from Raman spectroscopy demonstrate weaker correlation but still the results suggest a valid relationship with formation enthalpy of parent coal.