화학공학소재연구정보센터
International Journal of Coal Geology, Vol.107, 141-151, 2013
Extractability of biomarkers from high- and low-vitrinite coals and its effect on the porosity of coal
The influence of two solvents on the degree of bitumen extractability and the porosity of the extracted coals was investigated using two high-volatile bituminous coals with different petrographic composition. The Springfield Coal (vitrinite-rich) and the Lower Block Coal (vitrinite-poor) from the Illinois Basin were Soxhlet-extracted with methanol (CH3OH) and dichloromethane (CH2Cl2). The abundances of three selected groups of biomarkers extracted from both coals were compared: (1) n-alkanes plus pristane and phytane; (2) hopanes; and (3) 3- and 4-ring aromatic hydrocarbons (phenanthrene, anthracene, fluoranthene, and pyrene). Overall, the extracts of the vitrinite-poor Lower Block Coal contained greater amounts of n-alkanes and hopanes, whereas aromatic hydrocarbons were extracted in greater quantities from the vitrinite-rich Springfield Coal. Fourier Transform Infrared Spectroscopy (FUR) and Gas Chromatography/Mass Spectrometry (GC/MS) confirmed that the average lengths of aliphatic chains were greater in CH2Cl2 extracts from both coals. For the Lower Block Coal, the aromaticity of extracted organic matter was greater in the CH2Cl2 extract than in the CH3OH extract. Both coals showed an increase in microporosity (<2 nm; measured by CO2 adsorption) after solvent treatments. In addition, the mesopore surface area (2-50 nm, measured by N-2 adsorption) was reduced likely because of a shift in the size distribution of mesopore diameters towards those of macropores (i.e. >50 nm). Our analyses of compound classes present in the extracts and resultant porosity changes in the extracted coals provide useful insights into the structural and molecular differences in two bituminous coals of different maceral compositions. (C) 2012 Elsevier B.V. All rights reserved.