Optimization study of ultrasound-assisted oxidative desulfurization using a novel magnetic particle supported phosphotungstic acid catalyst

ABSTRACT The primary goal of desulfurization is to remove sulfur compounds from fuels or crude oil, thereby creating a cleaner product. This helps avoid harmful environmental effects, such as particulate matter and acid rain. However, conventional desulfurization methods only have high selectivity for inorganic sulfur compounds. Ultrasound-assisted oxidative desulfurization (UAOD) can address this as it has high selectivity towards organic sulfur compounds and occurs at mild conditions. The present work utilizes a novel heterogeneous catalyst using magnetic particles and phosphotungstic acid. It is then tested under different conditions by varying the active site loading ratio (1:1 to 1:4), catalyst dosage (0.4 g to 1 g), O/S ratio (6:6 mL to 16:8 mL), and ultrasound reaction time (3 min to 10 min) to determine the optimal parameters for this system. Various phase transfer agents (PTAs) are also tested to determine their effectiveness in improving the performance of the oxidation system. This catalyst design addresses the solubility issue with polyoxometalates which are a common catalyst choice for UAOD. It also tests the system using real fuel oils to further establish its application in an industrial setting. This resulted in an oxidation efficiency of 90.04% with the parameters of loading ratio, catalyst dosage, and ultrasound time having the greatest effect on the efficiency. The presence of PTAs was also investigated to determine the effect on desulfurization. As such, this study establishes the reaction conditions necessary to efficiently desulfurize fuel oils using this catalyst.