Reactivities of Various Alkyl Dibenzothiophenes in Oxidative Desulfurization of Middle Distillate with Cumene Hydroperoxide

Abstract

The oxidation reactivities of various alkyl dibenzothiophenes (DBTs) were evaluated and compared by measuring the rate constant of each alkyl DBT in oxidative desulfurization of a hydrotreated middle distillate (HMD) with cumene hydroperoxide at 75 °C over a MoO 3 /Al 2 O 3 catalyst. It was found that the major sulfur compounds with higher abundance in HMD are the DBTs with alkyl substituents at the 4- and/or 6-positions, and the oxidative reaction of each alkyl DBT follows a pseudo-first-order reaction. The measured rate constants indicate that the oxidation reactivity of these alkyl DBTs decreases in the order of 4-MDBT > 2,4,6-TMDBT ≈ 3,4,6-TMDBT > 1,4,6-TMDBT ≈ 4,6-DMDBT > 4-E,6-MDBT. Comparison of the molecular structures of these sulfur species with their reactivities implies that the oxidation activity of alkyl DBTs with oil-soluble oxidant over a solid catalyst is mainly dependent on the steric hindrance around the central sulfur atom caused by the alkyl substituents at the 4- and/or 6-positions.