Mesoporous chromia with ordered three-dimensional structures for the complete oxidation of toluene and ethyl acetate.

Mesoporous chromia with ordered three-dimensional (3D) hexagonal polycrystalline structures were fabricated at 130, 180, 240, 280, and 350 degrees C in an autoclave through a novel solvent-free route using KIT-6 as the hard template. The as-obtained materials were characterized (by means of X-ray diffraction, transmission electron microscopy, N(2) adsorption-desorption, temperature-programmed reduction, and X-ray photoelectron spectroscopy techniques) and tested as a catalyst for the complete oxidation of toluene and ethyl acetate. We found that with a high surface area of 106 m(2)/g and being multivalent (Cr(3+), Cr(5+), and Cr(6+)), the chromia (meso-Cr-240) fabricated at 240 degrees C is the best among the five in catalytic performance. According to the results of the temperature-programmed reduction and X-ray photoelectron spectroscopy investigations, it is apparent that the coexistence of multiple chromium species promotes the low-temperature reducibility of chromia. The excellent performance of meso-Cr-240 is because of good 3D mesoporosity and low-temperature reducibility as well as the high surface area of the chromia. The combustion follows a first-order reaction with respect to toluene or ethyl acetate in the presence of excess oxygen, and the corresponding average activation energy is 79.8 and 51.9 kJ/mol, respectively, over the best-performing catalyst.