Deep Oxidative Desulfurization of Refractory Sulfur Compounds with Cesium Salts of Mono-Substituted Phosphomolybdate as Efficient Catalyst

Abstract

Catalytic oxidation desulfurization (ODS) of model oil containing refractory sulfur compounds, dibenzothiophene (DBT), benzothiophene (BT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT), have been investigated with a series of cesium salts of the transition metal mono-substituted phosphomolybdates [PMo11M(H2O)O39]5− (M = Co2+, Ni2+, Zn2+, and Mn2+) as heterogeneous catalysts using H2O2 as the oxidant and acetonitrile as the extractant. The catalysts were characterized by Fourier transform infrared, DRS, scanning electron microscopy and X-ray diffraction. The main factors affecting the desulfurizing efficiency including catalyst dosage, and O/S (H2O2/DBT) molar ratio, temperature and reaction time were explored in detail. The results show that these catalysts are high efficient for sulfur removal of model oil under mild conditions, and CsPMo11Co is the most efficient with the sulfur-removal of 99.8, 92.9 and 85.3% for DBT, 4,6-DMDBT and BT, respectively at 60 °C for 100 min. Two probable reaction mechanisms was proposed for the oxidative desulfurization. Moreover, the catalysts could be recycled and maintained stability and high catalytic activity for consecutive desulfurization.