Relating the Synthesis Method of VOX/CeO2/SiO2 Catalysts to Red-Ox Properties, Acid Sites, and Catalytic Activity for the Oxidative Dehydrogenation of Propane and n-Butane Article uri icon

abstract

  • Four V-Ce/SiO2 catalysts were synthesized, using V grafting via VO(O-iC3H7)3 on Ce-loaded Aerosil support, with Ce incorporation either by grafting with Ce(O-iC3H7)4 (VOx/CeO2/S-GA and VOx/CeO2/S-GB) or by incipient wetness impregnation with Ce salt (VOx/CeO2/S-IA and VOx/CeO2/S-IB). Vanadium loadings were similar, while Ce was loaded to two different levels. Raman and X-ray diffraction (XRD) analysis indicated significant differences in VOx speciation: Vanadium pentoxide (V2O5) nano-crystals were prevalent on those catalysts synthesized via Ce impregnation, and absent from the catalysts prepared with grafted Ce. Cerium vanadate (CeVO4) phase was detected in catalyst prepared via Ce grafted at one theoretical monolayer coverage. Microcalorimetry results show that V2O5 species found on VOx/CeO2/S-IA are related to acid sites (acid strength > 90 kJ/mol) responsible for the oxidative dehydrogenation (ODH) reaction of n-butane. Catalyst acidity in VOx/CeO2/S-IA, combined with the redox properties of the vanadium species on the same material, promoted a high selectivity to butadiene and cis- and trans-2-butenes, which subsequently reacted in a Diels-Alder addition to produce benzaldehyde and total oxidation products. In contrast, the lack of acidity in VOx/CeO2/S-GA led to very low selectivity (< 20%25) to dehydrogenation products in both the ODH of butane and propane. © 2022, The Author(s), under exclusive licence to Springer Science Business Media, LLC, part of Springer Nature.
  • Four V-Ce/SiO2 catalysts were synthesized, using V grafting via VO(O-iC3H7)3 on Ce-loaded Aerosil support, with Ce incorporation either by grafting with Ce(O-iC3H7)4 (VOx/CeO2/S-GA and VOx/CeO2/S-GB) or by incipient wetness impregnation with Ce salt (VOx/CeO2/S-IA and VOx/CeO2/S-IB). Vanadium loadings were similar, while Ce was loaded to two different levels. Raman and X-ray diffraction (XRD) analysis indicated significant differences in VOx speciation: Vanadium pentoxide (V2O5) nano-crystals were prevalent on those catalysts synthesized via Ce impregnation, and absent from the catalysts prepared with grafted Ce. Cerium vanadate (CeVO4) phase was detected in catalyst prepared via Ce grafted at one theoretical monolayer coverage. Microcalorimetry results show that V2O5 species found on VOx/CeO2/S-IA are related to acid sites (acid strength > 90 kJ/mol) responsible for the oxidative dehydrogenation (ODH) reaction of n-butane. Catalyst acidity in VOx/CeO2/S-IA, combined with the redox properties of the vanadium species on the same material, promoted a high selectivity to butadiene and cis- and trans-2-butenes, which subsequently reacted in a Diels-Alder addition to produce benzaldehyde and total oxidation products. In contrast, the lack of acidity in VOx/CeO2/S-GA led to very low selectivity (< 20%25) to dehydrogenation products in both the ODH of butane and propane. © 2022, The Author(s), under exclusive licence to Springer Science%2bBusiness Media, LLC, part of Springer Nature.

publication date

  • 2022-01-01