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Abstract: This research compares the hydrodesulphurization (HDS) activity of supported Co(Ni)-Mo-W ternary catalysts with respect to the nature of the support (hexagonal mesoporous silica (HMS) versus SBA-16 material having cage-like mesoporous structure), the type of promoter (Co vs. Ni) and the nature of Al species formed after support modification with Al. Both Al-HMS and Al-SBA-16 mesoporous silica substrates were prepared by the one-pot sol–gel synthesis method via the neutral templating pathway using dodecylamine and Pluronic F127 as surfactants, respectively. The oxide precursors were characterized by a variety of techniques (N2 adsorption–desorption isotherms, XRD, DRS UV–vis spectroscopy and 27Al NMR), whereas sulphided catalysts were characterized by XPS and HRTEM, and tested in the HDS of DBT conducted in a high-pressure batch reactor at T =350°C and P =3.1MPa. The activity results revealed that NiMoW/Al-HMS catalyst was more active than all Co-promoted catalysts (including a commercial CoMo/Al2O3 catalyst). The HDS activity was found to be markedly influenced by the textural properties of support and the dispersion of the active phases on the catalyst surface. It has been hypothesised that the presence of extraframework AlNO3 phases on the surface of CoMoW/Al-SBA16 compromises its HDS activity because of the formation of a less active “onion-type” Mo(W)S2 structure. [Copyright &y& Elsevier]

Abstract: Phosphate-loaded mesoporous SBA-15 and SBA-16 materials were used as supports of novel ternary Co-Mo-W hydrodesulfurization catalysts. The effects of support morphology (SBA-15 against SBA-16) and its modification with variable amounts of phosphorus were studied. The sulfided catalysts were tested in a reaction of hydrodesulfurization (HDS) of dibenzothiophene (DBT) at 350°C and 3.1MPa of total H2 pressure. The calcined, fresh sulfided and spent catalysts were characterized by a variety of techniques (N2 adsorption–desorption isotherms, XRD, TPR, TPD-NH3, DRS UV–vis, micro-Raman spectroscopy, XPS, HRTEM and TPO/TGA). Regardless of the support, it was found that the presence of phosphorous inhibited the HDS activity, and the catalytic response of both SBA-15- and SBA-16-based systems did not depend on the support morphology. In terms of the reaction rate constants (k), both CoMoW/SBA-15 and CoMoW/SBA-16 catalysts were more active than a CoMo/Al2O3 commercial catalyst containing a small amount of phosphorous in its formulation. In general, the spent CoMoW/(x)P-SBA-16 catalysts showed a lower coke formation than their SBA-15-based counterparts because the phosphate incorporation to the SBA-16 material led to decrease in coke formation in the final catalysts, as opposite to the behavior of SBA-15-based counterparts. [Copyright &y& Elsevier]

A group of hydrodesulfurization (HDS) catalysts, based on transition metal sulfides (Co-Mo-W) and supported on mechanically-mixed mesoporous silicas (SBA-15 and SBA-16), have been synthesized and characterized by physicochemical methods (DRS-UV–vis, Micro Raman spectroscopy, XRD, SEM, HRTEM, EDS and catalytic activity). It has been demonstrated that the use of a mixture of silicas with two different porous structures has an advantage with respect to the use of the SBA-15 and SBA-16 separately for the preparation of supported catalysts for hydrodesulfurization reactions of refractory sulfur compounds, such as dibenzothiophene. This is because the presence of different porous structures has a positive effect over the diffusion processes of the precursors of the active phases on the support, and the whole result is a higher catalytic activity for the HDS reactions of dibenzothiophene, even more than that of the commercial catalyst used as a comparative model; this activity is also related with the stage of the synthesis process in which the mixture is done. [ABSTRACT FROM AUTHOR]