Detection of Residual Solvent in Solvent-Extracted Unconventional Oil Ore Gangues

Abstract

The solvent extraction technology is a promising method for recovery of unconventional oil resources because of its high efficiency, low energy consumption, and high compatibility. Solvent selection and solvent loss are the main limitations in terms of industrialization of the technology. To evaluate the solvent, efficient detection of the residual solvent content in the extracted-oil gangue is also a problem. A solvent extraction-gas chromatography (GC) combined method is proposed for fast determination of residual organic solvent in extracted-oil ore gangues (mixed with process water). To improve the precision, a combination of the external standard method and the internal standard method (ES&IS method) was applied. This analytical method shows a relative standard deviation (RSD) of less than 2%. The recovery of residual solvent was in the range of 95.4 ~ 102.0 wt% (for a spiked organic solvent content of 0.5 to 25.0 wt%). It is also found that whatever types of solvent (ethanol, tetrahydrofuran, cyclohexane, n-heptane, acetone, ethyl acetate, or toluene) are used, the method detection limit (MDL) can be less than 0.023 mg/mg. The whole procedure of this method, including the pretreatment and instrumental detection, can be finished in-situ in a relatively short time (less than 1.5 hours). On the other hand, due to the simple application of solvent extraction pretreatment and GC detection, this measurement can be a low-cost one. Therefore, it can be applied to solvent selection and solvent recovery method evaluation and propel the industrialization of the solvent extraction technology.