Non-hydrolytic sol-gel synthesis of mesoporous iron-aluminum oxide and their properties in the oxidation of hydrocarbons by hydrogen peroxide

Iron-containing alumina materials were prepared by the non-hydrolytic sol-gel method in the presence of surfactants and their use as catalysts in the oxidation of hydrocarbons was studied. The solids were mesoporous, with large specific surface areas, > 250 m2/g for the solids treated at 500 °C, depending on the surfactant used (cetyltrimethylammonium bromide, sodium dodecyl sulfate or hexadecylamine), and the calcination treatment applied (500 or 1000 °C). Iron was well distributed on the alumina surface, as confirmed by the EPR signals at 4.3 and 2.0 G and SEM imaging. The catalytic activity in the oxidation of cyclooctene, cyclohexane, and n-hexane was evaluated. After reaction for 48 h, the solid prepared with cetyltrimethylammonium bromide and calcined at 1000 °C showed a 25% conversion of cyclohexane with 51% selectivity to cyclohexanone. These were promising results, considering the mild reaction conditions, using a non-polluting oxidant at room temperature or 50–55 °C. [Display omitted] •Iron-containing alumina catalysts were prepared by a non-hydrolytic sol-gel method.•Surfactants played a fundamental role in pore structuring in situ.•Iron-aluminas were effective oxidation catalysts, using H2O2 as oxidant.•Cyclooctene, cyclohexane, and n-hexane were successfully oxidized.•Oxidation was effective under mild, environmentally friendly conditions.