Investigation of the nature of V-species on alumina modified by alkali cations: Development of multi-functional DeSOx catalysts Original Research Article

The location of vanadium species on δ-aluminas modified by lithium, sodium or potassium has been thoroughly investigated by means of several techniques. XRD, TPR and textural analyses showed that vanadium species are preferentially located on group I element or in its close vicinity when compared with the non-modified alumina.Vanadium species are localized nearby lithium and potassium cations, whilst vanadium species are partially distributed between sodium and alumina support in the sodium-modified alumina. A detailed XPS study was also carried out over potassium-promoted alumina catalysts and confirmed the vanadium distribution nearby potassium. Experiments of SOx capture and sulfate reduction to H2S were performed under realistic Fluid Catalytic Cracking (FCC) conditions with respect to the temperature of the catalyst regeneration (at 725 °C) and during hydrocarbon reactions (around 575 °C). Among different alkali cation modifiers, alumina modified by potassium exhibited the best performance in the DeSOx reaction (in terms of mole of absorbed sulfur per mole of group I cation) according to the following ratios: 0.74, 0.34 and 0.24 observed for K, Li and Na, respectively. Finally, vanadium largely improved the rate of SO2 oxidation as well as the rate of sulfate reduction to H2S.