Co-containing polyoxometalate-based heterogeneous catalysts for the selective aerobic oxidation of aldehydes under ambient conditions

• Published in: Journal of catalysis Vol. 226; no. 2; pp. 363 - 371
• Main Authors: Kholdeeva, O.A., Vanina, M.P., Timofeeva, M.N., Maksimovskaya, R.I., Trubitsina, T.A., Melgunov, M.S., Burgina, E.B., Mrowiec-Bialon, J., Jarzebski, A.B., Hill, C.L.
• Format: Journal Article
• Language: English; Russian
• Published: Amsterdam Elsevier Inc 10.09.2004; Elsevier
• Subjects: Aerobic oxidation; Aldehyde; Cobalt; Supported polyoxometalates; Supported polyoxometalates; Aldehyde; Cobalt; Aerobic oxidation
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2004.05.032

Tetra- n-butylammonium (TBA) salts of the cobalt-monosubstituted Keggin polyoxometalate (Co-POM), TBA 4HPW 11CoO 39 ( I) and TBA 5PW 11CoO 39 ( II), have been prepared and characterized by using elemental analysis, potentiometric titration, IR, UV–vis, 31P NMR, and cyclic voltammetry. Different modes of heterogenization of the Co-POM, including anchoring to both NH 2- and NH 3 +-modified mesoporous silica surfaces and sol–gel synthesis, have been performed. The resulting solid catalysts were characterized by N 2-adsorption measurements, elemental analysis, DR-UV–vis, and FT-IR spectroscopy. The activity of the solid Co-POM materials to catalyze aerobic oxidation of two representative aldehydes, isobutyraldehyde (IBA) in MeCN and formaldehyde in H 2O under mild conditions (20–40 °C, 1 atm of air), was assessed and compared with the catalytic activity of the corresponding homogeneous Co-POMs. An emphasis has been placed on leaching tests and catalyst recycling. The effect of protonation of the amine-modified silica surface or the Co-POM on the loading, stability, and activity of the Co-POM solid catalyst was evaluated.