Activity enhancement of Ru/TiO2 catalysts for catalytic hydrogenation of amides to amines through controlling strong metal–support interactions†

Abstract

Efficient and selective catalytic hydrogenation of amides to amines is highly significant but extremely challenging. Here, a series of Ru/TiO₂ catalysts were prepared with the impregnation method at different calcination and reduction temperatures. Multiple characterization tools were used to characterize the physicochemical properties of the catalysts. The hydrogenation of butyramide to butylamine as a model reaction was used to evaluate the catalytic performance. The catalytic activity of the Ru catalyst supported on rutile TiO₂ was superior to that on anatase TiO₂. As the calcination temperature increased from 200 °C to 600 °C, the catalytic performance of Ru/rutile catalysts monotonously decreased. With the reduction temperature increasing from 200 °C to 600 °C, Ru/rutile catalysts displayed a volcano-like trend of catalytic activity. The Ru/rutile catalyst calcined at 200 °C and reduced at 500 °C exhibited the highest catalytic performance, with 93% butyramide conversion and 65% selectivity to butylamine at 150 °C with 5 MPa H₂. The evaluation and characterization results suggested that the lattice match between RuO₂ and rutile TiO₂ prevented Ru particle aggregation under high-temperature calcination, and smaller Ru particles were in favor of the amide hydrogenation reaction. The coverage of the TiO_x overlayer on Ru nanoparticles and the Ru–TiO_x boundary perimeter were effectively modulated by the strong metal–support interaction under different catalyst reduction temperatures, resulting in the optimization of the amide hydrogenation reactivity over Ru/rutile catalysts. This study facilitates the understanding of the influence of strong metal–support interaction on the catalytic hydrogenation of amide.