The effect of TiO2 crystal phase on CH3Br catalytic combustion over Ru/TiO2 catalyst

Supported Ru catalysts over TiO2 with various crystal phases were prepared, which involved rutile, anatase, and their mixed phase. And their catalytic activities for CH3Br complete oxidation were investigated. Results showed Ru/TiO2-700-4 that TiO2-700-4 is sourced from anatase TiO2 calcined at 700 °C for 4 h is the most active catalyst among these catalysts. The content of rutile phase on the surface is lower than the bulk. Strong metal support interaction occurs owing to lower lattice mismatch between RuO2 and rutile TiO2. It was further verified by H2-temperature programmed reduction, ultraviolet-Raman and transmission electron microscopy. Especially mixed-phase TiO2 is more conductive to higher dispersion of RuO2 than pure phase TiO2, which is easier to form epitaxial growth. The catalytic activity for CH3Br complete oxidation was not in exact accord with the dispersion of Ru. It is possibly attributed to the combination of arguably favorable physico-chemical properties of more Ru active sites, electron transfer, and appropriate surface acidity. At the low reaction temperature, more Ru active sites are beneficial for the total oxidation of CH3Br. With the increase of temperature, higher activity is prone to strong surface acidity and electron transfer, as was confirmed by X-ray photoelectron spectra and NH3-temperature programmed desorption analysis.