An Efficient Extraction-Free Method for Oxidative Desulfurization of Model Fuels Employing Cross-Linked Polyionic Liquid Phosphotungstate Catalysts

An efficient extraction-free oxidative desulfurization (ODS) process using a series of cross-linked polyionic liquid phosphotungstate (CLPIL-PW) catalysts is reported. The cross-linked PILs were prepared with DVB and 1-n-alkyl-3-vinyl imidazole hydrobromide (alkyl = ethyl, butyl, octyl, dodecyl), and were then assembled with phosphotungstic acid (H3PW12O40) to form the catalysts. The CLPIL-PWs have been applied to the oxidative removal of dibenzothiophene (DBT) from model oil with H2O2 as an oxidant. The effects of ionic liquid (IL) cationic species, varying the DVB/IL molar ratio in the polymerization process, and varying operating conditions were investigated. The CLPIL-PWs were characterized by inductively coupled plasma (ICP) mass spectrometry, elemental analysis, scanning electron microscopy (SEM), Fourier transform infra-red (FTIR) spectroscopy, X-ray diffraction (XRD), 13C and 31P nuclear magnetic resonance (NMR) spectroscopy. The polydivinylbenzene-co-1-n-octyl-3-vinyl imidazole phosphotungstate (P(DVB-OVIm)PW) exhibited the highest DBT removal efficiency (99.9％) and remarkable recyclability, and could be reused eight times without reducing its activity. Finally, an extraction-free ODS mechanism is proposed.