Catalytic self-sustained combustion of toluene and reaction pathway over CuxMn1-xCe0.75Zr0.25/TiO2 catalysts

The catalytic self-sustained combustion of toluene over CuxMn1-xCe0.75Zr0.25/TiO2 catalysts (x = 1, 0.5, 0) was studied in a microscale combustor. The catalytic activity is determined not only by the temperature with toluene conversion of 90% (T-co), but also by the corresponding lean-combustion limits. It was found that the self-sustained combustion was achieved successfully over the catalysts, with the toluene concentrations of 0.35 con.%, 0.50 con.% and 1.00 con.%. According to T-co,T- the activity decreased in the order of CuCe0.75Zr0.25/TiO2 (234 degrees C) > Cu0.5Mn0.5Ce0.75Zr0.25/TiO2 (238 degrees C) > MnCe0.75Zr0.25/TiO2 (284 degrees C). The excellent activity of CuCe0.75Zr0.25/TiO2 catalyst could be ascribed to the high content of active lattice oxygen, good low-temperature reducibility and homogeneous dispersion, combined with the results of H-2-TPR, O-2-TPD and XPS. Furthermore, the results of in-situ DRIFT and temperature-programmed oxidation (TPO) of toluene in N-2 atmosphere suggested that toluene was adsorbed on the catalyst surface by removing alpha-H from methyl and combining with active oxygen specie to form benzyl group, which was finally oxidized into CO2 and H2O with lattice oxygen.