Catalytic performance of CoMo/Al2O3-MgO-Li(x) formulations in DBT hydrodesulfurization

In this work, it is reported the catalytic performance of low acidity catalysts in the hydrodesulfurization reaction of dibenzothiophene. Catalytic CoMo formulations supported on materials based on Al2O3-MgO modified with several amounts of lithium oxide (x=1, 5 and 10 wt.% of Li2O) were used. It was correlated the effect of the atomic lithium content on the dispersion of the Mo and Co phases in their oxidized and sulfided forms, in order to explain their catalytic performance. Elemental chemical composition on the catalyst surface as well as sulfurization degree and the interaction of sulfided Co and Mo phases with the support were determined by X-ray photoelectron spectroscopy (XPS). Textural properties were measured by N-2 physisorption technique; the identification of the crystalline phases was studied by X-ray powder diffraction (XRD) and Raman spectroscopy (RS). The chemical coordination state was determined from diffuse reflectance spectroscopy (DRS) measurements. Reducibility was determined by temperature programmed desorption (TPR). Dispersion of MoS2 crystallites was revealed by high resolution transmission electron microscopy (HRTEM). Catalytic activity of the formulations was evaluated using a pressurized batch reaction system through the hydrodesulfurization reaction of dibenzothiophene as a model molecule, selectivity toward direct desulfurization reaction route was studied following the biphenyl and cyclohexylbenzene reaction products identified by using gas chromatography; results show that there is an optimal amount of 3.7 at.% of Li, which maintains hydrodesulfurization function and decrease the hydrogenation function compared to the conventional CoMo catalyst. (C) 2015 Elsevier B.V. All rights reserved.