Ru/TiO2 Catalysts with Size-Dependent Metal/Support Interaction for Tunable Reactivity in Fischer–Tropsch Synthesis

The Ru/TiO2 catalyst serves as a representative metal/support interaction system with tunable reactivity in catalytic processes. Herein, by varying the metal loadings of Ru from 0.5 to 4 wt % to regulate the size of Ru on support, the catalytic performances of Ru/TiO2 catalysts in Fischer–Tropsch synthesis (FTS) can be further refined. An improved FTS activity is acquired when metal size increases, while long carbon-chain products (C5+ hydrocarbons) prefer to be generated from the small-sized Ru catalyst. With intensive characterizations, it is indicated that the coating of TiOx on Ru greatly depends on the size of Ru, with the TiOx overlayer being enhanced on small Ru metal particles. This size-dependent metal/support interaction on Ru/TiOx therefore leads to a varied reduction degree of Ru, which possesses an alterable capability toward CHx transformation on Ru. As a result, the small-sized Ru/TiOx catalyst shows a preference toward the chain growth in FTS by suppressing the competitive methanation on Ru/TiOx. Our results demonstrate that the size-dependent metal/support interaction plays an important role on determining the catalytic performance of Ru/TiOx in FTS, and it can be used as an effective method to tune the reactivity of metal nanoparticles in catalytic processes.