Desulphurization of Fuel Oil with Tubular-Polyoxometalates based Catalyst: Optimization Using Response Surface Methodology

Abstract

A facile catalyst termed H4SiW12O40@fHNTs was synthesized and optimized for the oxidative desulphurization of model fuel oil. Halloysite nanotubes (HNTs) were subject to functionalization with 3-aminopropyltriethoxysilane (APTES) and subsequently utilized as a substrate to immobilize H4SiW12O40. The electrostatic interaction between H4SiW12O40 and the functionalized halloysite nanotubes was characterized using UV, FTIR, XRD, and Raman spectroscopy. The oxidative desulphurization process was conducted using an oxidant i.e., hydrogen peroxide and acetonitrile as the extractant. The optimization of process variables, including reaction temperature, catalyst amount, and oxidant concentration, using the Box-Behnken method. The optimal conditions were determined to be 70°C, 70 mg, and 8 ml oxidant concentration, resulting in a desulfurization efficiency of 92.17%. Furthermore, the effectiveness of H4SiW12O40@fHNTs was demonstrated in real fuel samples, reducing dibenzothiophene content from 354 ppm to 224 ppm. The catalyst exhibited excellent recyclability, maintaining a stable desulphurization rate over five consecutive cycles. This research underscores the potential of H4SiW12O40@fHNTs as an effective and reproducible catalyst for the process of oxidative elimination of sulphur, offering promise for the development of cleaner and more sustainable fuel technologies. ix