Highly catalytic activity of Mn/SBA-15 catalysts for toluene combustion improved by adjusting the morphology of supports.

Abstract

Rod-like, hexagonal and fiber-like SBA-15 mesoporous silicas were synthesized to support MnOx for toluene oxidation. This study showed that the morphology of the supports greatly influenced the catalytic activity in toluene oxidation. MnOx supported on rod-like SBA-15 (R-SBA-15) displayed the best catalytic activity and the conversion at 230°C reached more than 90%, which was higher than the other two catalysts. MnOx species consisted of coexisting MnO2 and Mn2O3 on the three kinds of SBA-15 samples. Large amounts of Mn2O3 species were formed on the surface and high oxygen mobility was obtained on MnOx supported on R-SBA-15, according to the H2 temperature programmed reduction (H2-TPR) and X-ray photoelectron spectroscopy (XPS) results. The Mn/R-SBA-15 catalyst with greater amounts of Mn2O3 species possessed a large amount of surface lattice oxygen, which accelerated the catalytic reaction rate. Therefore, the surface lattice oxygen and high oxygen mobility were critical factors on the catalytic activity of the Mn/R-SBA-15 catalyst.