Energy & Fuels, Vol.11, No.5, 945-950, 1997
Determination of Volatile Hydrocarbons in Coals and Shales Using Supercritical-Fluid Extraction and Chromatography
Conventional analytical techniques, such as headspace gas chromatography and Soxhlet extraction, can provide compositional information for the gaseous (C1-5) and heavy (C15+) hydrocarbon constituents, respectively. The volatile (C6-14) hydrocarbons, if present, usually go undetected because of volatility fractionation and loss. In this study, supercritical CO2 was used to extract the C-6-C-14 volatile hydrocarbons from pulverized coal samples. Capillary column gas chromatography/mass spectrometry was used to identify the mixture components, and packed capillary column supercritical fluid chromatography was used to separate and quantify the aliphatic and aromatic hydrocarbon class fractions. It was found that the compositions of the light hydrocarbon fractions included several homologous series of normal and branched aliphatic hydrocarbons, cyclic and aromatic hydrocarbons, and alkyl-substituted benzenes and naphthalenes; the concentrations of these volatile hydrocarbons ranged between 0.01 and 0.2 wt % of the bulk material for different coal and shale samples.