Catalytic oxidative desulfurization of thio-compounds by employing χ-Anderson-type polyoxometalates-porphyrin covalent organic framework (COF)

Abstract

Severe environmental sulfur contents due to the consumption of fuels in automobiles and industries resulted in serious health hazards and pollution because of it, desulfurization of diesel become inevitable. Targeting the profound desulfurization of diesel, we performed experiments to deeply desulphurized the thio-compounds by catalytic-oxidative desulfurization technique. We synthesized new metalloporphyrin (C52H36N4O8Sn)4MeO-SnPor which after conversion into (C64H64N8O16Sn)4Tris-SnTP leading towards the synthesis of covalent organic framework [(N(C4H9)4]12[HNC(CH2O)3]4[(CO)4C44H24N4Sn] [NiMo6O18]4(SnTP@NiAdCOF). SnTP@NiAd COF showed the outstanding catalytic property for deep desulfurization of thio-compounds above than 96% of thiobenzoic acid (TB) and 99% of 2-aminothiophenol (2-ATP) sulfur contents were oxides after 100 min of reaction using H2O2 as an oxidant at room temperature with constant stirring. During desulfurization percentage desulfurization efficiency was checked for different time intervals by TLC and further confirmed by reverse phase high-performance liquid chromatography (RP-HPLC). Reverse-phase high-performance liquid chromatograms indicated that the peak area and peak height of thio-compounds decrease gradually with the passage of reaction time which confirmed the removal of thio-compounds from the reaction mixture. Sulfur contents removed up to 5 ppmw showed excellent catalytic characteristics of synthesized SnTP@NiAdCOF. The exceptional catalytic efficiency of prepared catalyst SnTP@NiAdCOF was because of the existence of active oxidizing centers of χ-NiAd and metalloporphyrin that are MoO and [(Por)SnII], respectively. The potential mechanism appeared to be the formation of Mo(O2) and [(Por)SnII–OOH] from MoO and [(Por)SnII], respectively that act as active oxidizing centers and efficiently converted the thio-group into oxides and sulfones. Effective removal of sulfur grants the desulfurization of fuels by using SnTP@NiAdCOF catalyst to lessen the energy expenditure and also to enhance the production of environmentally-safe fuels.