NIOBIUM-DOPED PHOSPHOMOLYBDIC ACID CATALYST INCLUDED IN SILICA MATRIX: STUDY OF STABILITY AND REACTIVITY USING DIFFERENT LOADS

Heteropolyacids are used as catalysts in numerous reactions because they are inexpensive, nontoxic, have high acid strength and excellent redox properties. They have been used as acid catalyst in different ways, and numerous studies indicate that the incorporation of Nb into the structure of a solid generates an increase in the acidity of the sample, both at Lewis and Brönsted acid sites. Heteropolyacids have low surface area, which makes it necessary to include them in a support to increase the surface area and allow their use as heterogeneous catalysts in liquid phase reactions because they are very soluble in polar solvents. In this work, the synthesis of catalysts containing a niobium-doped heteropolyacid (PMoNb) included in silica at different concentrations is reported. The catalysts were characterized by ICP-MS, FT-IR, XRD, potentiometric titration, and their catalytic activity was tested in the selective oxidation of diphenyl sulfide to diphenyl sulfoxide, showing excellent results.