Innovative Synthesis of YF3-TiO2 Acid–Base Catalysts with High Surface Area by Embedding Yttrium Trifluoride Nanoparticles in TiO2 Metallogel

Abstract

Combining a water-tolerant oxide such as TiO₂ with yttrium fluoride is expected to provide catalysts with enhanced acid–base properties for catalytic applications in water. We present here a new strategy of incorporating preformed YF₃ nanoparticles (NPs) in a TiO₂-based metallogel, followed by its soft drying at room temperature to produce YF₃-TiO₂ xerogel with high surface area. The as-synthesized YF₃-TiO₂ materials were calcinated at 300 and 400°C and characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), ¹⁹F NMR spectroscopy and N₂ physisorption, calorimetry of NH₃ adsorption, and FT-IR of pyridine adsorption. These studies indicate that the fluorine is present under a stable form of YF₃ for the catalysts calcined at 300°C. The acid–base properties of these YF₃-TiO₂ catalysts were investigated in a model reaction, that is, dihydroxyacetone (DHA) conversion in water, and compared with the blank TiO₂ and YF₃ NPs alone. The incorporation of YF₃ in the TiO₂ matrix leads to enhanced initial rate of DHA dehydration into pyruvaldehyde, which is slowly converted to lactic acid as the reaction progresses. This suggests that the Brønsted acidity was boosted by the presence of YF₃ species via water adsorption in a dissociative form.