Total oxidation of toluene over noble metal based Ce, Fe and Ni doped titanium oxides

The catalytic oxidation of toluene over macro-mesoporous titania loaded with noble metals (Au, Pd) and doped with three different metal oxides has been investigated. Doping of titania proved to offer a better reducibility for titania and greater activity towards toluene total oxidation, with a decrease of approximately 80°C in T₅₀ values for 5wt% ceria (5CeTi) and iron (5FeTi) doped titania. After gold loading, 5CeTi supported material demonstrated the highest performance in the removal of toluene, with a total selectivity for CO₂ and formation of traces of benzene. Since CeTi support (unloaded and noble metal loaded) proved to be the most effective material in the oxidation of toluene, an investigation of the effect of dopant content of this material has been conducted. Higher ceria content resulted in higher surface area values, higher noble metal-support interaction (observed in DR-UV-VIS results) and consequently a greater activity. Moreover, palladium loaded catalysts (T₅₀ around 219°C) proved to be the best performing ones in terms of catalytic behaviour. Consequently, Pd5CeTi was tested for its durability under low toluene conversion rates in order to determine its stability and possible structural changes under these conditions. Doping and noble metal loading offered a stable activity of the catalysts in the conversion of toluene at low temperatures and for a long period of time, even though changes in TiO₂ crystal sizes were detected. Carbonaceous compounds were formed onto the used catalyst and their quantity was investigated by DTA-TGA experiments.