Titania-heteropolyacid composites (TiO2-HPA) as catalyst for the green oxidation of trimethylphenol to 2,3,5-trimethyl-p-benzoquinone

PALACIO, MAGDALENA; ROMANELLI, GUSTAVO P.; PALERMO, VALERIA; VILLABRILLE, PAULA I.

JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY

SPRINGER

Lugar: Berlin; Año: 2020 p. 321 - 331

0928-0707

Newcatalysts containing phosphomolybdic acid (PMA) and vanadophosphomolybdic acid(VPMA) in a titania matrix were synthesized by the sol?gel process withdifferent heteropolyacid loads (5%, 15%, and 30% (w/w): 5PMA-TiO2, 15PMA-TiO2, 30PMA-TiO2,5VPMA-TiO2, 15VPMA-TiO2, and 30VPMA-TiO2). The techniques used to characterizethe materials were XRD, DRS, SEM, FT-IR, 31P MAS-NMR, potentiometric titrationwith n-butylamine, and N2 physisorption at −196 °C. The materials were used asheterogeneous catalysts in the oxidation of 2,3,6-trimethylphenol (TMP) to2,3,5-trimethyl-p-benzoquinone (TMBQ), a key intermediate in vitamin Esynthesis. The catalysts allowed an ecofriendly TMBQ synthesis, using ethanolas solvent and aqueous hydrogen peroxide as a clean oxidizing agent, at roomtemperature. The conversion of TMP reached 90% and 99% for the samples with15PMA-TiO2 and 15VPMA-TiO2, respectively, after 4 h. The amount of Mo and V inthe reaction medium was determined by ICP-MS, which showed leaching of only17?18% Mo, but 48% V. Reuse of the catalysts was performed. For 15PMA-TiO2, theconversion was maintained in the second cycle. A homolytic mechanism wasproposed for TMBQ synthesis, which involved the formation of a peroxometallicspecies through an HPA-Ti center.