A simple and cost-effective extractive desulfurization process with novel deep eutectic solvents

Deep eutectic solvents (DESs), a new class of ionic liquid (IL) analogues, are easily produced through mixing Lewis or Bronsted acid and base. In this study, a class of DESs was prepared by mixing low cost triethylamine and organic acid with different molar ratios. It was found that the base/acid molar ratio (B/A) played an outstanding role in the solubility and extractive ability of DESs. When B/A was 1 : 3 and 1 : 5, the loss of DESs in model oil was even less than 0.003%. Take the DES with B/A = 1 : 3 for example, the extraction ability of DESs showed the following order [TEtA][Pr] > [TEtA][Ac] > [TEtA][Fo], which could be explained by H-1 NMR analysis. The extractive mechanism was also discussed by density functional theory (DFT) calculations. The sulfur partition coefficient (KN) was 2.14 using [TEtA][Pr] as the extractant, and the sulfur content could be reduced from 500 ppm to 10 ppm after four times extraction.