Catalytic oxidation of toluene over V, Ce and Mo doped Cu/?-Al2O3 in SO2-containing flue gas: Study of metal doping effect and reaction pathway

To efficiently oxidize toluene in SO2-containing flue gas, different non-noble metals (V, Ce and Mo) were suc-cessfully introduced into Cu-based catalysts (Cu-M/gamma-Al2O3). Results show that the temperature corresponding to 90% CO2 generation (T90,C) of CuO/gamma-Al2O3 in toluene oxidation is decreased by ca. 11-46 celcius after introducing an additional metal oxide, which is attributed to a bimetallic synergy. Among the three different metals, V is found to have the most obvious promoting effect, which is mainly connected with the big average pore size, good reducibility and high content of surface adsorbed oxygen (OS). Furthermore, the reaction pathways of the toluene oxidation on both the fresh Cu-V/gamma-Al2O3 and the SO2-treated Cu-V/gamma-Al2O3 are investigated by in-situ DRIFTS. For SO2-treated Cu-V/gamma-Al2O3, we found an additional pathway: toluene-benzene-benzoquinone-maleic anhy-dride-CO2 and H2O. This new pathway can help to explain the decrease of the CO2 generation rate in the presence of SO2.