| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 55392 | Catalysis Today | 2012 | 15 Pages |
The immobilization of Fe(III) picolinate and Fe(III) dipicolinate complexes on kaolinite furnished heterogeneous catalysts, whose catalytic activity was evaluated. The precursor materials were kaolinite grafted with picolinic (Ka-pa) and dipicolinic (Ka-dpa) acids obtained by melting of the pyridine carboxylic acids. To obtain the catalysts Fe(Ka-pa)-n and Fe(Ka-dpa)-n (n = 1, 2, or 3 is the ligand/Fe ratio), the precursors were suspended in Fe3+ solutions with cation/ligand ratios of 1:1, 1:2, or 1:3. The resulting materials were characterized by thermal analyses (simultaneous TG/DTA), X-ray diffraction, UV/vis and infrared spectroscopies, and transmission electron microscopy. The grafted complexes were employed as heterogeneous catalysts in the epoxidation of cis-cyclooctene to cis-cyclooctenoxide and in the oxidation of cyclohexane to cyclohexanol and cyclohexanone at ambient temperature and pressure. Hydrogen peroxide was used as oxygen donor at a catalyst/oxidant/substrate molar ratio of 1:300:100. Fe(Ka-pa)-n catalysts were very efficient for cis-cyclooctene epoxidation (38% conversion). For cyclohexane oxidation, Fe(Ka-dpa)-n was 100% selective for cyclohexanone formation, with substrate conversion of 14%. This last series of catalysts was also very effective in the Baeyer–Villiger reaction, with 60% substrate conversion and 100% selectivity for ξ-caprolactone. After reuse (5 times), the catalysts still led to high substrate conversion.
Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (134 K)Download as PowerPoint slideHighlights► Catalysts were prepared by immobilization of Fe(III)–picolinate complexes in kaolinite. ► Catalysts were selective in the oxidation of cis-cyclooctene to cyloocteneoxide. ► Cyclohexane oxidation: 14% conversion, 100% selectivity to cyclohexanone. ► Baeyer–Villiger cyclohexanone: 60% conversion, 100% selectivity to ξ-caprolactone. ► Pseudo tubular kaolinite phase lead to high selectivity on oxidation reactions.
