(661m) Insights into the Influence of Crystal Structure on Strong-Metal Support Interactions for Ethylene Hydrogenation over Rh/TiO2 Catalysts

Strong metal-support interactions (SMSI), considered as a signature property of TiO₂, have been investigated in the past decades. However, how different TiO₂ crystal phases and shapes affect the interactions with active metals has not been examined in detail.

In this study, several Rh-based catalysts supported on different TiO₂ supports, pure anatase and rutile nanoparticles as well as rutile nanorods, were synthesized and tested for activity in the hydrogenation of ethylene. After a low temperature reductive treatment (200 °C), all catalysts are highly active at room temperature in this probe reaction. A high-temperature reductive treatment (500 °C), induces changes consistent with SMSI, i.e. reduced CO chemisorption and a lower activity due to the decrease in metal surface area. As expected for SMSI, this effect is reversible by an oxidative treatment and another low temperature reduction activity for the Rh supported on anatase nanoparticles or rutile rods. In contrast, the activity of the Rh on the rutile TiO₂ nanoparticles is not recovered, suggesting that this catalyst undergoes irreversible changes during these reduction-oxidation treatments. This is not expected for conventional SMSI, which results in reversible geometric blocking of Rh sites (encapsulation). This suggests that electronic metal-support interactions, i.e. electron transfer between metal and support, is also important in these catalysts.