Oxidation Reactivities of Dibenzothiophene and its Derivative in Model Oil using Polyoxometalates /H2O2 Systems

Abstract

In order to reduce the sulfur level in liquid hydrocarbon fuels for environmental protection and fuel cell applications, deep desulphurization of model sulfur compounds dibenzothiophene (DBT), 4-methyldibenzothiophene (4-MDBT) and 4,6-dmethyldibenzothiophene (4,6-DMDBT), which have the lowest reactivity in hydrodesulfurization process (HDS). The oxidation reaction was performed in biphasic mixtures of n-octane/acetonitrile using different polyoxometalates as catalysts and hydrogen peroxide (H₂O₂) as oxidant. H₃PW₁₂O₄₀ was identified as an effective catalyst for the oxidative removal of DBT under mild reaction conditions of atmospheric pressure and 60 °C. Ranking of catalyst efficiency is as follows: H₃PW₁₂O₄₀ (NPW)> Na₃PW₁₂O₄₀ (NAPW)>H₃PMo₁₂O₄₀ (HPMO)> H₄SiW₁₂O₄₀ (HSIW). The conversion of DBT was nearly 100%. As a result, because of the influence of the electron density and the space steric hindrance, the oxidation reactivity of the different sulfur compounds in simulated oil followed the order DBT > 4-MDBT >4,6-DMDBT.