Abstract

Three well-characterized coal samples of varying rank were extracted with supercritical CO₂ to determine the amount of polycyclic aromatic hydrocarbons (PAHs) that could be mobilized during simulated CO₂ injection/sequestration in deep coal beds. The supercritical CO₂ extractions were conducted at 40°C and 100 bars, roughly corresponding to a depth of 1 km. The greatest amount of PAHs was extracted from the high-volatile C bituminous coal sample. Extracts from the subbituminous C and anthracite coal samples contained lower concentrations of these compounds. The effectiveness of supercritical CO₂ in liberating PAHs from the coal sample was evaluated in a comparison with a parallel series of Soxhlet extractions using 100% dichloromethane. More PAHs were extracted from the lower rank coal samples with dichloromethane than with supercritical CO₂. The results from this investigation indicate that, regardless of coal rank, CO₂ injection into deep coal beds may mobilize PAHs from the coal matrix. However, more PAHs could be mobilized during CO2 sequestration in a high-volatile C bituminous coal bed than in either of the other two coal ranks studied.