Total oxidation of VOCs on Pd and/or Au supported on TiO/ZrO followed by "operando" DRIFT

Catalytic performances of nanostructured mesoporous TiO-ZrO mixed oxides impregnated by Pd and/or Au were studied in toluene total oxidation in a fixed bed microreactor and with "operando" DRIFT. Mesoporous TiO-ZrO mixed oxides with various Ti:Zr mole ratio of 80/20, 50/50 and 20/80, high surface areas were synthesised using a mixture of zirconium propoxide and titanium isoporopoxide as Zr and Ti sources and also CTMABr as surfactant. The new supports are impregnated by 0.5 or 1.5 wt% of palladium and 1 wt% of gold using impregnation and Deposition-Precipitation methods. The catalytic activity for the nanostructured mesoporous TiO-ZrO mixed oxides varies depending on the molar ratio of Ti:Zr and also for all series of the studied catalysts impregnated by Pd and/or Au, when the gold is loaded firstly the activity in toluene complete oxidation is higher than when Pd was deposited firstly (PdAu/TZ > 1.5Pd/TZ > AuPd/TZ > Pd/TZ > Au/TZ > TZ). The highest activity of PdAu/TZ (80/20) can be related to the higher acid sites density of the support and also to the presence of a synergetic effect between palladium and gold. "Operando" DRIFT allowed following the VOCs oxidation but also suggesting an interaction between the adsorbed molecule and the catalyst which decreases when the activity for oxidation reaction increases.