HIGHLY SELECTIVE AND EFFICIENT LOW-TEMPERATURE OXIDATION OF BENZYL ALCOHOL IN THE PRESENCE OF MOLYBDATE-SUBSTITUTED HYDROXYAPATITE

• Published in: Ceramics international 2024-12
• Main Authors: Goldberg, M.A., Eseva, E.A., Donskaya, N.O., Fomin, A.S., Antonova, O.S., Leonov, A.V., Konovalov, A.A., Murzakhanov, F.F., Kudriavtsev, E.A., Akopyan, A.V., Gafurov, M.R., Barinov, S.M., Komlev, V.S.
• Format: Article
• Language: English
• Subjects: benzaldehyde; hydrogen peroxide; liquid-phase oxidation; mesoporous material; molybdate-substituted hydroxyapatite
• ISSN: 0272-8842
• DOI: 10.1016/j.ceramint.2024.12.463

Our purpose was to develop a highly selective and efficient catalyst based on molybdate-substituted hydroxyapatite for low-temperature liquid-phase oxidation of benzyl alcohol. Catalysts were synthesized by the coprecipitation method while the molybdate anion content was varied from 1 to 10 mol.%. The materials were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, transmission electron microscopy, N2 surface adsorption/desorption isotherm measurement, electron paramagnetic resonance spectroscopy, temperature-programmed reduction of hydrogen, and X-ray photoelectron spectroscopy. In contrast to hydrothermal synthesis, the obtained hydroxyapatite samples are characterized by a large specific surface area of 121 m2/g and high catalytic activity in the oxidation of benzyl alcohol with hydrogen peroxide under mild conditions. It was found that the turnover number (426 h−1) of nanosized mesoporous catalyst HA-2.5%MoO4 (MoHA2) is 5–20 times higher than that of known molybdenum-containing catalysts. In the presence of the obtained nanocatalyst, more than 59% substrate conversion was achieved with 100% selectivity at 30 °C. It was revealed that the key criteria for a nanocatalyst for this purpose are a highly developed surface with well-dispersed molybdate anions and the presence of the Mo(VI)/Mo(IV) redox couple, which ensure improved catalyst–substrate phase contact, the formation of a peroxo complex, and high selectivity for the formation of benzaldehyde as the target product. [Display omitted] •Mesoporous molybdate-containing hydroxyapatite (MoHA) nanopowders were obtained.•The preservation of the single apatite phase was up to 2.5 mol.% MoO42- content.•MoHA showed high selectivity and efficiency as a catalyst for the oxidation of benzyl alcohol.•The process was carried out at low temperature and the only water was a by-product.