CARBON SEQUESTRATION IN COAL: PREDICTING THE BEHAVIOR OF ORGANIC CONSTITUENTS DURING CO2 SEQUESTRATION

Flooding coals with carbon dioxide (CO2) is expected to produce an acidic aqueous phase in addition to the supercritical water-saturated CO2 phase. At low pH, organic acids within porewater and within the organic-rich rock matrix preferentially exist in neutral form and are soluble in the supercritical phase. Here we describe the experimental interaction between supercritical CO2, saline water, and thermally immature coal at 60°C and 100 bars. We also describe a protocol to sample both supercritical and aqueous phases for the chemical analyses of dissolved organic acids and volatile aromatic compounds. Short chain monocarboxylic acids are measured by HPLC, whereas longer chain mono and dicarboxylic acids are analyzed as n-propyl esters via conventional gas chromatography and mass spectroscopy. Carbon dioxide-induced liberation of organic acids from natural earth materials could affect mechanisms of mineral surface reactivity. This process could also provide an important, unintended source of labile carbon to the deep biosphere.