Deep oxidative desulfurization of gas oil by iron(III)-substituted polyoxometalate immobilized on nickel(II) oxide, ((n-C(4)H(9))(4)N)(4)H[PW(11)FeO(39)]@NiO, as an efficient nanocatalyst

Sulfur compounds are among the most unfavorable constituents of petroleum derivatives, so stringent regulations have been established to curb their atmospheric emissions. In this regard, a new nanocomposite ((n-C(4)H(9))(4)N)(4)H[PW(11)FeO(39)]@NiO) was synthesized composed of quaternary ammonium bromide salt of iron(III)-substituted Keggin-type polyoxometalate immobilized on nickel(II) oxide nanoceramics via sol–gel method. The assembled (n-C(4)H(9))(4)N)(4)H[PW(11)FeO(39)]@NiO nanocomposite was identified by FT-IR, UV–Vis, XRD, SEM, EDX, and TGA-DTG methods. The characterization results exhibited that ((n-C(4)H(9))(4)N)(4)H[PW(11)FeO(39)] dispersed uniformly over the surface of the NiO nanoceramics. The ((n-C(4)H(9))(4)N)(4)H[PW(11)FeO(39)]@NiO nanocomposite was employed as a heterogeneous nanocatalyst in the extractive coupled oxidation desulfurization (ECOD) of real gas oil and dibenzothiophene (DBT) as a model compound. Under relatively moderate conditions, the catalytic performance of the ((n-C(4)H(9))(4)N)(4)H[PW(11)FeO(39)]@NiO in the ECOD procedure was studied by incorporating acetic acid/hydrogen peroxide as an oxidant system at a volume ratio of 1:2. According to the ECOD results, the ((n-C(4)H(9))(4)N)(4)H[PW(11)FeO(39)]@NiO demonstrated the effectiveness of up to 95% with 0.1 g at 60 °C under optimal operating conditions. Moreover, the ((n-C(4)H(9))(4)N)(4)H[PW(11)FeO(39)]@NiO nanocatalyst could be separated and reused for five runs without a noticeable decrease in the ECOD process. This study provides a promising way to meet the target of ultra-low sulfur as an essential process in oil refineries.