Oxidation of toluene in humid air by metal oxides supported on γ-alumina.

Monometallic and bimetallic supported metal oxides catalysts on γ-alumina were prepared by heterogeneous deposition-precipitation. The γ-alumina used as a support was synthesized by the sol-gel and the co-precipitation methods. Supports and catalysts were characterized by Brunauer-Emmett-Teller (BET) surface area, X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The performance of the prepared catalysts was studied for total oxidation of toluene in air at different relative humidity and oxidation temperatures. Efficiency of bimetallic catalysts for deep oxidation of toluene was higher than copper oxide supported on γ-alumina. Although increasing the lanthanum, cobalt, and nickel loading on the support led to a modified catalyst surface and morphology, the catalytic activity of bimetallic catalysts decreased with increasing lanthanum, cobalt, and nickel content due to the reduced amount of copper oxide which has a higher activity for oxidation of volatile organic compounds. The γ-alumina prepared by the sol-gel method using ethanol as a solvent (AlSE) was the best support and La-Cu/AlSE had the best performance (toluene removal efficiency >90%). In addition, the presence of water vapor in the feed had a negative effect on toluene conversion.