TEMPERATURE EFFECTS ON SUPERCRITICAL CARBON-DIOXIDE EXTRACTIONS OF HYDROCARBONS FROM GEOLOGICAL SAMPLES

The extraction of aliphatic and aromatic hydrocarbons from New Albany Shale by supercritical carbon dioxide at different extraction temperat ures is described. The main goal of this work was to determine the eff ect of the temperature on the extraction process (i.e. relative extrac tion rate and efficiency). The data suggest that temperature changes o f 20 and 40 degrees for the relatively moderate extraction temperature s tested (55, 75, and 95 degrees C), can have significant effects on b oth relative extraction rates and yields. While lower molecular weight aromatics presented exponential extraction profiles, similar to those of the aliphatic hydrocarbons, higher molecular weight aromatics, suc h as the phenanthrenes, showed a linear extraction profile. This behav ior cannot be explained by solubility differences in the supercritical fluid alone, and are, therefore, most likely based on differences in the speciation of the hydrocarbons within the sample matrix. Extractio ns at elevated temperatures (300 degrees C) resulted in significant in crements in the relative recoveries of all compounds, but particularly for the aromatic hydrocarbons. This may be caused by structural rearr angement of the sample matrix with subsequent release of trapped hydro carbons and possibly by C-S and S-S bond breakage.