Reverse microemulsion synthesis of polyoxometalate-based heterogeneous hybrid catalysts for oxidative desulfurization

Keggin-type heteropoly acids are known as active catalysts for oxidative desulfurization of refractory sulfur compounds from fuels. In this work, cesium salts of phosphotungstic acid (HPW) were synthesized based on three different methods: co-precipitation, reversed emulsion, and reversed microemulsion. For reversed microemulsion procedure, the effect of adding order of cesium ion or phosphotungstic acid in the micelle aggregation of sodium dodecyl sulfate (SDS) surfactant was investigated to synthesize different particle sizes of heterogeneous HPW. Obtained products were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, and N-2 physical adsorption-desorption techniques. It was observed that all materials obtained via reversed microemulsion method are in organic-inorganic hybrid form which origin from the attachment of SDS to cesium salts of HPW. Oxidative desulfurization of dibenzothiophene from hexane was performed to investigate the activity of the prepared catalysts. The best catalytic activity was achieved by the new organic-inorganic hybrid materials obtained via the reversed microemulsion method.