Designing polyoxometalate based hybrid catalysts for efficient removal of hazardous sulfur from fuel via heterogeneous oxidative desulfurization

Hydrodesulfurization is a common but less effective technique to remove sulfur content of oils due to severe operating conditions of temperature, pressure and cost. Oxidative desulfurization(ODS) is preferable due to low cost and mild operating conditions. Coupling of the extractive catalytic desulfurization with the ODS give rise to extractive catalytic oxidative desulfurization(ECODS), a more promising for the elimination of sulfur contents of fuel oil. Herein we present by polyoxometalate based hybrids, [H₂TPP][K₅BVW₁₁O₄₀]•2CH₃CN•2H₂O (1), [H₂TPP]₂[K₃BVW₁₁O₄₀]•CH₃CN•3H₂O (2), and [H₂TPP]₃[KBVW₁₁O₄₀]•2CH₃CN (3) for efficient ECODS of hazardous model fuel. These were synthesized by facile method and characterized by elemental analysis, inductive couple plasma, powder X-ray diffraction analysis, thermo-gravimetric/differential thermal analysis, fourier transform infrared, and UV–visible analysis. These polyoxometalate based hybrids contain cations [H₂TPP]²⁺(organic) and [BVW₁₁O₄₀]⁷⁻(inorganic) with stoichiometric ratios(i.e., 1:1, 2:1, 3:1). The stoichiometry of these hybrids was also established by Job's analysis which agreed well with the results of TG-DTA and elemental analyses. Interestingly, an increase in catalytic efficiency is observed with increase of organic cations. The maximum ∼99.5 % conversion of dibenzothiophene at 60 °C after 2 h has been achieved with hybrid 3 which could be employed up to ten cycles without a significant decrease in efficiency.