DETERMINATION OF VOLATILE HYDROCARBONS IN COALS AND SHALES USING SUPERCRITICAL-FLUID EXTRACTION AND CHROMATOGRAPHY

Conventional analytical techniques, such as headspace gas chromatograp hy and Soxhlet extraction, can provide compositional information for t he gaseous (C1-5) and heavy (C15+) hydrocarbon constituents, respectiv ely. The volatile (C6-14) hydrocarbons, if present, usually go undetec ted because of volatility fractionation and loss. In this study, super critical CO2 was used to extract the C-6-C-14 volatile hydrocarbons fr om pulverized coal samples. Capillary column gas chromatography/mass s pectrometry was used to identify the mixture components, and packed ca pillary 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 hy drocarbons, cyclic and aromatic hydrocarbons, and alkyl-substituted be nzenes and naphthalenes; the concentrations of these volatile hydrocar bons ranged between 0.01 and 0.2 wt % of the bulk material for differe nt coal and shale samples.