EPR study on the mechanism of H2O2-based oxidation of alkylphenols over titanium single-site catalysts

✍ Scribed by Olga V. Zalomaeva; Natalia N. Trukhan; Irina D. Ivanchikova; Alexander A. Panchenko; Emil Roduner; Eugenii P. Talsi; Alexander B. Sorokin; Vladimir A. Rogov; Oxana A. Kholdeeva

• Book ID: 104057282
• Publisher: Elsevier Science
• Year: 2007
• Tongue: English
• Weight: 576 KB
• Volume: 277
• Category: Article
• ISSN: 1381-1169
• DOI: 10.1016/j.molcata.2007.07.047

✦ Synopsis

The selective oxidation of 2,3,6-trimethylphenol (TMP) and 2-methyl-1-naphthol (MNL) with H 2 O 2 catalyzed by titanium single-site catalysts, TiO 2 -SiO 2 aerogel and mesostructured hydrothermally stable titanium-silicate, Ti-MMM-2, have been studied by means of EPR spectroscopic technique with spin traps. The formation of phenoxyl (naphthoxyl) and hydroxyl radical intermediates during the oxidation process have been detected using 3,5-dibromo-4-nitrosobenzene-sulfonic acid (DBNBS) and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) spin traps, respectively. The character of the EPR spectra of the DBNBS adducts strongly depends on the nature of the organic substrate and the reaction temperature. A compilation of the EPR and by-product studies strongly supports a homolytic oxidation mechanism. Study by DR-UV-vis spectroscopy has confirmed the previously suggested chemical adsorption of phenol on the titanium center.