Achieving deep desulfurization with inverse-micellar polyoxometalates and oxygen

Abstract

Designing green and efficient catalytic systems that can operate under mild conditions and utilize molecular oxygen as an oxidant for achieving deep desulfurization is highly desirable. In this study, an inverse-micellar polyoxometalate (POM) (NH₄)₅(CTA)₆PMo₄V₈O₄₀ (CTA = cetyltrimethylammonium), abbreviated as (CTA)PMo₄V₈, was designed and its activity in desulfurization was evaluated. Almost ∼100% of organic sulfur was removed in 8 h at 100 °C, using only flowing oxygen under atmospheric pressure. (CTA)PMo₄V₈ exhibited excellent activity in treating sulfur-containing compounds (dibenzothiophene (DBT), 4,6-dimethyldibenzothiophene (DMDBT), benzothiophene (BT) and thiophene) in real oils, i.e. diesel and FCC gasoline, affording clean oils with super-low sulfur content of 8.77 and 6.17 ppm, respectively. Furthermore, (CTA)PMo₄V₈ showed high activity in the oxidative desulfurization of real oils in the presence of oxygen and nitrogen (volume ratio 1 : 1). Such inverse-micellar POMs could be reused at least six times without significant loss of activity due to their high stability.