MCM-41-supported vanadium catalysts structurally modified with Al or Zr for thiophene hydrodesulfurization

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 N 2 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 Zr x O y covering the MCM-41 matrix. Vanadium catalysts, showed the presence of isolated V 5+ species and to a lesser extent polymeric chains likely as small crystallites of V 2 O 5. 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.

Effect of the Gallium and Vanadium on the Dibenzothiophene Hydrodesulfurization and Naphthalene Hydrogenation Activities Using Sulfided NiMo-V2O5/Al2O3-Ga2O3

“…The XPS spectra in the Ga 3d and V 2p 3/2-1/2 regions (not shown here), the Ga 3+ (20.5 eV) and V 5+ (517.1 eV) signals could be attributable to Ga 2 O 3 and V 2 O 5 with amounts from 0.1 to 0.6 on the surface [43,44]. The previous experimental results may be due to the presence of different V 5+ species on surface, that is, when the support is modified with Ga, small V rich-aggregates on the surface could predominate depending on their dispersion associated to the solubility of the precursors during synthesis [30]. In the synthesis method by impregnation is possible that, in the Al 2 O 3 -Ga 2 O 3 (1%-I) support, a large number of Ga 3+ sites will be available on the surface even after impregnating the V, which is reflected in the good reducing and sulfiding of the Anderson type polyoxomolybdates as seen in the NiMoV-S/Al-Ga(1%-I) catalysts.…”

“…Thus, the introduction of Ga and V to NiMoV-S/Al-Ga(1%-SG) resulted in almost a three-fold increase of the rate constant than their unpromoted analog, while NiMoV-S/Al-Ga(1%-I) was more than half; display that NiMoV-S/Al-Ga(1%-SG) was the most active between the synthesized and tested catalysts. This result suggests that the way to incorporate Ga into the support influences the dispersion of the V 5+ species (structural promoter) [30]. It is well known that Ga-incorporation into A 2 O 3 -framework provides an increased number of acid sites that allow a better dispersion [20].…”

“…Paulino et al have obtained V-based catalysts promoting the HDS and HDN of LCO (7 times greater activities than MoS 2 ) [28,29]. Escalante et al showed that Al-MCM-41-supported V sulfides catalysts presented the highest formation of hydrogenated products in the thiophene HDS due to the support nature with lower Si/Al(Zr) ratios [30].…”