Abstract
Vanadium catalysts supported on Al(Zr)-MCM-41-type materials were prepared by impregnation. Textural and structural properties, elemental composition and electronic structure were determined by N2 physisorption, small-angle XRD, SEM–EDX and UV–vis DRS, respectively. Al-containing materials showed mostly of Al framework and a small fraction of Al extra-framework species. Zr-containing materials presented almost exclusively small clusters of ZrxOy covering the MCM-41 matrix. Vanadium catalysts, showed the presence of isolated V5+ species and to a lesser extent polymeric chains likely as small crystallites of V2O5. The catalytic results revealed that VAlM30 catalyst, characterized by a Si/Al atomic ratio of 30, was the most active in thiophene hydrodesulfurization, which could be associated to better textural properties and high dispersion of the vanadium species.
Highlights
The demand for crude oil worldwide has generated a reduction of light crude oil reserves and an increase of heavy and extra-heavy crude oils production
Vanadium impregnation resulted in a decrease of specific surface area and a decrease of pore volume, which becomes more pronounced in materials containing zirconium. These results suggest the presence of some metal species covering the structure of the MCM-41 that can cause pore plugging
The modified supports presented a bimodal distribution of pore sizes, with pore sizes prevailing around 30 Å. These results show that there is a decrease in the hexagonal-type mesopores arrays density, due to the development of a new family of extra-structural pores of size above 40 Å, which can be generated by the presence of small metal oxide crystals dispersed in the matrix of MCM-41 [22]
Summary
The demand for crude oil worldwide has generated a reduction of light crude oil reserves and an increase of heavy and extra-heavy crude oils production. It is reported a facile synthesis and characterization of some vanadium-based catalysts supported on MCM-41, pure and structurally modified with Al and Zr. The catalytic tests on thiophene HDS at atmospheric pressure were carried out because, to our best knowledge, these metal combinations have not been evaluated in sulfur removal reactions.
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