Effect of a mixed precursor over monolith MnOx/La-Al2O3catalyst for toluene oxidation

Monolithic MnOx/La-Al(2)O(3)catalysts were prepared using manganese nitrate, manganese acetate and their mixed precursor for the catalytic oxidation of toluene. The activity results indicated that the MNMA catalyst prepared with the mixed precursor exhibited the best catalytic activity and that complete conversion of toluene was achieved at 270 degrees C under a GHSV of 12 000 h(-1), which was 35 degrees C lower than the conversion of the MN catalyst prepared by manganese nitrate. N(2)adsorption-desorption, X-ray diffraction (XRD), Raman spectroscopy, high resolution trans-mission electron microscopy (HRTEM), H(2)temperature-programmed reduction (H-2-TPR), O(2)temperature-programmed desorption (O-2-TPD), X-ray photoelectron spectroscopy (XPS) andin situinfrared diffuse reflectance spectroscopy (in situDRIFTS) techniques were employed for the characterization of the catalysts' properties. It was shown that the MNMA catalyst has better MnO(x)dispersion and more active alpha-MnO(2)species as well as higher concentrations of Mn4+, surface adsorbed oxygen species and active Mn-O bonds. Therefore, this catalyst possessed better reducibility and the best oxygen mobility, which were conducive to the catalytic oxidation of toluene. In addition, the DRIFT spectra results showed that more benzoic acid intermediate was deeply oxidized to carbonate species at a lower temperature on the surface of MNMA catalyst, which improved the low temperature activity for toluene oxidation.