(387c) Influence of Titania Structure and Particle Size on the Catalytic Activity of IrOx-Based Catalysts in the Complete Oxidation of Methane

Reducing methane emissions is crucial for mitigating global warming, so developing highly efficient catalysts for low-temperature methane combustion is of great importance. Low temperature activation also has potential to facilitate selective oxidation of methane to higher value chemicals. Several noble or precious metals supported on various metal oxides, such as Pd/CeO₂ and Pd/TiO₂, are active in the methane combustion reaction and have been extensively studied. In contrast, despite the facile CH₄ activation observed over rutile IrO₂(110) surfaces, only a limited number of literature studies has focused on IrO₂-based methane activation catalysts. Our work has focused on TiO₂-supported IrO_x catalysts, and how the TiO₂ structure or crystal phase, namely rutile, anatase, and brookite, and titania particle size influence the activity in the methane oxidation. The different IrO₂/TiO₂ catalysts were synthesized using the urea deposition-precipitation method, followed by calcination in air at 350 °C. The catalytic performance of the IrO₂/TiO₂ in the methane combustion was then evaluated under excess oxygen conditions. Under these conditions, the activity is dependent not only on the titania structure, but also the titania particle size and of course the iridium loading. The best performing catalyst is IrO_x supported on the 10-nm anatase TiO₂ (Figure 1), and we will also show that this catalyst is surprisingly stable with time on stream. This reveals that the structure and particle size of the support can significantly affect the catalytic performance in heterogeneous catalysts, and is very important in catalyst development by rational design.