Influence of the Crystal Structure of Titanium Oxide on the Catalytic Activity of Rh/TiO₂ in Steam Reforming of Propane at Low Temperature

Solid oxide fuel cells (SOFCs) with liquefied petroleum gas (LPG) reduce CO₂ emissions due to their high-energy-conversion efficiency. Although SOFCs can convert LPG directly, coking occurs easily by decomposition of hydrocarbons, including C−C bonds on the electrode of fuel cell stacks. It is therefore necessary to develop an active steam pre-reforming catalyst that eliminates the hydrocarbons at low temperature, in which waste heat of SOFCs is used. Herein, we show that the crystal structure of the TiO₂ that anchors Rh particles is crucial for catalytic activity of Rh/TiO₂ catalysts for propane pre-reforming. Our experimental results revealed that strong metal support interaction (SMSI) induced during H₂ pre-reduction were optimized over Rh/TiO₂ with a rutile structure; this catalyst catalyzed the reaction much more effectively than conventional Rh/γ-Al₂O₃. In contrast, the SMSI was too strong for Rh/TiO₂ with an anatase structure, and the surface of the Rh particles was therefore covered mostly with partially reduced TiO₂. The result was very low activity.