Investigation of solvent dewaxing of straight-run diesel: Combination of quantum chemical calculations and experimental condition optimization

Separation of the paraffin contained in straight-run diesel is important to alleviate the surplus and achieve high value utilization of diesel. The differences in the dewaxing effect of straight-run diesel under different solvent systems were investigated using ethanol-butanone (EA-MEK), acetone-butanone (AC-MEK) and ethyl formate (EF) as dewaxing solvents. The differences can be able to explain by the different trends in the magnitude of the forces between the solvent and model components calculated from quantum chemical calculations. The relationship between the solvent-model compound interaction and the solvent dewaxing effect was obtained by combining the results of analytical experiments and quantum chemical calculations. It was also found that the main force between the solvent and the diesel model components is van der Waals (VDW). The stronger the interaction between solvent and paraffin, the higher the dewaxing ratio. AC-MEK exhibits the highest dewaxing ratio of 85.8% owing to the strongest solvent-paraffin interaction. Theoretical guidance is provided for the in-depth understanding of the dewaxing process and the subsequent rapid screening of efficient dewaxing solvents. In addition, the process conditions of solvent dewaxing were studied and optimized. Under optimized conditions, EA-MEK could reach a dewaxing ratio of 73.0% with a wax purity of 86.0 wt%. The condition of dewaxing temperature was also studied in detail and the relationship between the dewaxing temperature and the carbon number of paraffin in the dewaxed oil was obtained.