Sustainable and cleaner approach for paraffin wax treatment via CO2-induced polarity transformation of switchable solvents

Abstract

Paraffin wax has caused obvious detrimental consequences to the extraction for fossil fuels, and posed environmental challenge due to the absence of cleaner methods for paraffin wax removal. A cleaner and sustainable approach for paraffin wax removal was developed using the switchable polarity solvents (SPS). Three SPS with low polarity, including dipropylamine (DPA), ethylbutylamine (EBA), and dibutylamine (DNBA) were selected for paraffin wax removal. Compared with bubbling CO2 into SPS straightway, the transformation of the polarity quantified by normalized polarity energy confirms the addition of water is benefit to enlarge the polarity scope. Paraffin wax is removed at the initial state and separated at the final state by CO2-induced polarity transformation of SPS. The dissolution rates for paraffin wax of DPA and EBA reached 0.071 g/min and 0.062 g/min, which surpassed that of traditional solvents, such as o-xylene (0.045 g/min) and Petroleum ether (0.017 g/min), indicating that these selected SPS is suitable for paraffin wax removal. The paraffin wax dissolution behaviors of SPS can be accurately matched using modified Apelblat models with root-mean-square deviation of 1.085%. With the addition of water, more than 99% of paraffin wax is separated from DPA and EBA by introducing CO2 within 10mins, which is a better alternative method for energy-intensive distillation process. The introduction of water is indispensable for improving the separation efficiency, since it enlarged the polarity difference between solvents and paraffin wax. The thermal behavior of separated paraffin wax detected by Differential Scanning Calorimetry remained steady, and there were negligible residual solvents detected indicate the feasible separation of paraffin wax. Both SPS and water are recovered upon N2/80 °C, which retain good recyclability for paraffin wax removal. These findings confirms the applicability of SPS in the sustainable and cleaner removal of paraffin wax. The use of SPS provides an alternative and promising approach for paraffin wax removal for ensuring the demands of low-energy consumption and environment.