VOx-SBA-15 modified with AI and Ga in ODS of DBT.

Abstract

In order to adapt current processes to the strict regulatory requirements, several technologies have been developed for deep desulfurization of diesel fuel. The major portion of sulfur compounds in light cycle oils (LCO) are dibenzothiophene (DBT) and alkyl-dibenzothiophenes, which are not easily removable by hydrotreating. Vanadium oxides supported on mesoporous SBA-15 catalysts with different vanadium loadings were studied in the oxidative desulfurization (ODS) of dibenzothiophene. The catalytic activity was improved when SBA-15 framework was modified with Al and Ga as heteroatom substituting Si. Structural and textural characterization of the catalysts were performed by means of XRD, N2 adsorption, UV–Vis–DRS, XPS, NMR, TEM, Raman, TPR and Py-FTIR. UV–Vis–DRS and Raman demonstrated that highly dispersed vanadium VO4-3 species are responsible for the high activity in the sulfur removal. The Ga modified support with an intermediate V/Si ratio was the most active catalyst, using hydrogen peroxide as oxidant and acetonitrile as solvent. 100% of DBT elimination was attained at a short time in mild conditions. Gallium and aluminum incorporation modified successfully the nature of the SBA-15 surface by generating Bronsted and Lewis acidity. The interaction between the acid sites with the vanadium active sites improved the activity of the catalysts. The more acidic support allowed better dispersion of the vanadium species due to stronger interaction metal-support. The reusability of the catalysts indicates that vanadium oxide supported on mesoporous SBA-15 modified with Ga and Al are potential catalysts for the ODS of dibenzothiophene.