Temperature effects on supercritical carbon dioxide extractions of hydrocarbons from geological samples

Abstract

SummaryThe extraction of aliphatic and aromatic hydrocarbons from New Albany Shale by supercritical carbon dioxide at different extraction temperatures is described. The main goal of this work was to determine the effect of the temperature on the extraction process (ie. relative extraction rate and efficiency). The data suggest that temperature changes of 20 and 40 degrees for the relatively moderate extraction temperatures tested (55, 75, and 95 "C), can have significant effects on both 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, such as the phenanthrenes, showed a linear extraction profile. This behavior 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. Extractions at elevated temperatures (300 "C) resulted in significant increments in the relative recoveries of all compounds, but particularly for the aromatic hydrocarbons. This may be caused by structural rearrangement of the sample matrix with subsequent release of trapped hydrocarbons and possibly by C-S and S-S bond breakage.

Relative Recoveries of Hydrocarbons from Geological Samples Using High Temperature Supercritical Fluid Extraction: Contributions from Thermal Desorption

“…Four fractions of extractions at every extraction temperature were individually collected. 60-minute extractions were chosen based on previous experiments [13,15] to provide exhaustive or near-exhaustive extractions for each temperature studied. A 1899-ppm squalane standard solution was prepared by weighing 0.0959 g of squalane (99%) in a 50-mL volumetric flask, mixing and diluting to volume with methylene chloride.…”

A two‐step supercritical fluid extraction of polycyclic aromatic hydrocarbons from roadside soil samples

“…This substitution can be done by molecules of a modifier and/or by other simple organic molecules mixed with the so-called polarity-shifting modifiers. Molecules of other compounds present in a sample, i. e., traces of water, etc., have also been found to be very helpful in some cases [17]. The removal of analytes bound in a matrix is often a time-consuming process.…”

“…Also, the extraction efficiency of PAH was found to be dependent on pressure and temperature, while that of phenols was not. JaffØ et al [17] observed the influence of temperature on the extraction of PAHs from clay soils. At mild temperatures (55, 75, and 958C), the yield of low-and high-molecular weight PAHs is increased exponentially and linearly, respectively.…”

Recovering Valuable Hydrocarbon Molecules from Used Lubricating Oils via Supercritical CO2 Extraction

“…Consequently, this results in an increase in solubility. However, the extraction efficiency exhibits an inverse relationship with the temperature: increasing the temperature at a constant pressure causes a decrease in CO 2 density. − Additionally, the kinematic viscosity increases with a rising temperature. These lead to a reduction in the mass transfer coefficient, ultimately diminishing the extraction efficiency …”