Application of a Dual-Solvent Method in Separating Paraffin from a Shale Oil: A Combined Experimental and DFT Study

An effective dual-solvent (DS) extraction combined with recrystallization was designed for refined paraffin (RP) separation from a shale oil (SO). The content of wax enriched with acetonitrile (AN)/petroleum ether is higher than that with other DSs. The maximum recovery of RP is 22.1 wt % obtained by regulating the DS/SO ratio, extraction time (ET), and extraction times (ETs). The corresponding total relative content of oil obtained by controlling solvent polarity during the recrystallization is 1.9% based on the analysis with a gas chromatograph/mass spectrometer. Long-chain n-alkanes are predominant in RPs, which is consistent with Fourier transform infrared analysis. In addition, the mechanisms for synergic DS extraction were revealed by quantum chemistry calculation with density functional theory, i.e., C-H center dot center dot center dot pi and X-H center dot center dot center dot Y bonds exist between AN and selected model compounds according to the analyses of electrostatic potential and average local ionization energy. The low boiling point and immiscibility of DS are beneficial for recycling the solvents. The synergic DS extraction approach has a potential to facilitate further separation of RP from SO.