Effective separation of organic species from a shale oil sludge

Exhaustively separating organic matter (OM) from shale oil sludge (SOS) not only facilitates the value-added utilization of the OM, but also is capable of avoiding the pollution by discharging or combusting SOS. The OM in the SOS was sequentially extracted under ultrasonic irradiation using petroleum ether (PE), methanol, carbon disulfide (CDS), and isometric mixture (IMM) of acetone and carbon disulfide. As a result, over 99.8% of the OM in the SOS was extracted. According to the analysis with a gas chromatograph/mass spectrometer, the extracts primarily consist of alkanes, alkenes, and arenes. The interaction energies between model compounds (MCs, e.g., dodecane and naphthalene were used to represent alkanes and arenes, respectively) and a solvent were investigated via quantum chemical calculations. The results show that n-hexane exhibits the binding energy (BE) towards dodecane (-35.08 kJ mol^-1) and naphthalene (-33.55 kJ mol^-1). Methanol has significantly stronger BE towards naphthalene (-18.57 kJ mol^-1) than towards dodecane (-14.91 kJ mol^-1), while CDS shows near BEs for naphthalene (-16.71 kJ mol^-1) and for dodecane (-15.93 kJ mol^-1). As the weak intermolecular interaction, based on the Independent Gradient Model according to Hirshfeld Partition and Atoms in Molecules Theories, the alkane dissolution is primarily dominated by dispersion forces. For arenes, the enhanced adsorption occurs due to C-H ^… π interactions with the solvents. In the case of IMM, the synergic effect between acetone and CDS significantly increases the solubility of aromatics in the SOS. This is achieved through strong π-π interactions between > C=O in acetone and S=C=S in CDS. IMM proves to be very effective for extracting OM from SOS because of the synergic effect and the easy recovery of IMM due to its low boiling point.