Polyethylene glycol oligomers as green and efficient extractant for extractive catalytic oxidative desulfurization of diesel

An efficient and green extractive catalytic oxidative desulfurization (ECODS) process is developed for diesel by using polyethylene glycol (PEG) oligomers, H2O2 and a phosphotungstate based poly ionic liquid (HPW-PIL) as extractant, oxidant and catalyst, respectively. The PEG oligomers with repeating glycol units of 0, 4 and 8 are determined as the best extractants among acetonitrile, methanol, DMF, [BMIM]BF4, and PEG-2000 with comprehensive characteristics like non-toxicity, non-volatility, low cost, easy recycling, and good desulfurization performance. Benzothiophene (BT) and dibenzothiophene (DBT) in model oil can be removed completely within 2 h at the following conditions: PEG oligomer/oil = 0.2 (mass ratio), H2O2 usage of O/S = 20 (mole ratio), HPW-PIL catalyst/oil = 1/100 (mass ratio), at the temperature of 353 K. And the desulfurization ability of the present process can be retained as 99% even after six successive reuses without regeneration. Further, the S-content in real diesel can also be reduced from 110 to 9.3 ppm-S by the ECODS process followed by AlCl3 adsorption for the oxidized diesel. Meanwhile, the PEG extractant and the HPW-PIL catalyst can be facilely regenerated and recycled.