Electrochemical Desulfurization of Dibenzothiophene Sulfone in Sodium Fluoride/Acetonitrile

The oxidative and reductive desulfurization using electrochemical techniques has attracted much attention in the last decade because mild temperature and conditions are needed [1, 2]. It is known that the dibenzothiophene (DBT) can be progressively oxidized to a sulfoxide dibenzothiophene (DBTO) and dibenzothiophene sulfone (DBTO₂).  However, the electrochemical oxidation and reduction DBTO₂ in a liquid-liquid two-phase system of aqueous NaF/acetonitrile has not been reported.  The analysis by Fourier Transformed Infrared Spectroscopy (FTIR) showed partial removal of sulfur from DBTO₂ placed in the electrolytic medium at 18.6 ppm or 108 ppm. The FTIR spectrum of the samples diluted in KBr after cathodic electrolysis at -8.0 V on Pt or Ti as cathode and Pt as anode in an undivided cell showed the absence of the characteristic bands of DBTO₂: 1288 cm^-1, 1166 cm^-1 and 758 cm^-1. This suggests a transformation of  DBTO₂ with the electrochemical treatment (Fig. 1). The oxidation and reduction products of DBTO₂ were analyzed by GC-MS and LC-MS.

Figure 1 FTIR spectra of DBTO₂ before electrochemical treatment (a) and after cathodic treatment using Pt electrode (b and c). IR spectra of the acetonitrile (b) and the aqueous (c) phases.