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A custom-built, solvent recirculating, supercritical fluid extraction (SFE) apparatus was used to study the extraction of hydrocarbons from a crude oil tank bottom sludge (COTBS) with supercritical ethane. The SFE experiments were carried out varying the pressure (10 MPa and 17.20 MPa) and temperature (358C and 658C). The yield of the extracted hydrocarbon fraction increased with increase in extraction pressure at constant temperature, and decreased with increase in extraction temperature at constant pressure. The maximum extraction yield was obtained at the pressure and temperature conditions that lead to the highest solvent density. The extracted hydrocarbon fraction was a significantly upgraded liquid relative to the original untreated COTBS.

In this work two natural certified soils were extracted with supercritical ethane. One sample was polluted with total petroleum hydrocarbons (THP−soil) and the second one with polycyclic aromatic hydrocarbons (PAH−soil). The extraction studies were carried out using a high-pressure experimental device constructed in our laboratory. The extraction conditions for the TPH−soil were 27.1 MPa and 308.15 K, whereas those for the PAH−soil were 23.7 MPa and 308.15 K. Four independent extractions were performed on each test soil varying the volume of solvent: 10, 20, 30, and 40 L. Infrared spectroscopy was used to quantify the hydrocarbons in the residues after supercritical extraction of the TPH−soil, whereas high-performance liquid chromatography was employed, with a photodiode array detector and a fluorescence detector, to analyze seven polycyclic aromatic hydrocarbons (PAHs) in the residues after supercritical extraction of the PAH−soil. The extraction results show that there is a reduction of hydrocarbons of 76% using 10 L of ethane while the reduction is 90% using 40 L of ethane for the TPH−soil sample. For the sample of PAH−soil there is a reduction greater than 80% for the concentration of six of the seven PAHs studied. Naphthalene behaves as a refractory compound; hence, it presents the lowest reduction in concentration.

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