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DOE OSTI · 1849443

Creating Brønsted acidity at the SiO 2 -Nb 2 O 5 interface

Wolek, Andrew T. Y.·Ardagh, M. Alexander·Pham, Hien N.·Alayoglu, Selim·Datye, Abhaya K.·Notestein, Justin M.
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Abstract

Catalytically active acid sites associated with the silica-niobia interface were probed with a series of overcoated SiO 2 on Nb 2 O 5 (SiO 2 /Nb 2 O 5 ) mixed oxide materials prepared by deposition of tetraethyl orthosilicate onto niobic acid (Nb 2 O 5 nH 2 O) or calcined niobia (Nb 2 O 5 ). NH 3 TPD and pyridine DRIFTS studies indicated that the speciation of acid sites in the materials evolved as a function of SiO 2 loading, impacting the quantity and stability of Brønsted sites. Catalyst activity was highly dependent on SiO 2 loading in the liquid phase hydroalkoxylation of dihydropyran with n-octanol. At SiO 2 surface densities corresponding to approximately 1 Si per 2 surface Nb, the activity of these catalysts passed through a maximum approximately 20 times higher than the activity of calcined Nb 2 O 5 . We found that apparent reaction barriers measured over the most active SiO 2 /Nb 2 O 5 catalysts were 10 kJ/mol lower than those measured over niobic acid, suggesting that the OH features unique to the SiO 2 -Nb 2 O 5 interface were slightly more reactive than those on niobic acid.

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY42 ENGINEERINGBrønsted AcidsChemistryEngineeringHydroalkoxylationMixed OxidesNiobic AcidOvercoated MaterialsTetrahydropyranylation

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Wolek, Andrew T. Y., Ardagh, M. Alexander, Pham, Hien N., Alayoglu, Selim, Datye, Abhaya K., Notestein, Justin M.. 2020-11-09. Creating Brønsted acidity at the SiO 2 -Nb 2 O 5 interface. https://doi.org/10.1016/j.jcat.2020.10.027

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