One-pot synthesis of alanine from glycerol without additional H2 over a rutile-supported Ru catalyst

We successfully demonstrate the synthesis of alanine from glycerol and NH 3 without additional H 2 , using a novel Ru-catalyst with optimized metal-support interactions. Three heterogeneous catalysts (Ru/TiO 2 -Anatase, Ru/TiO 2 -Rutile, and Ru/TiO 2 -P25) were compared, with Ru/TiO 2 -Rutile showing superior performance, giving complete glycerol conversion with 37 % alanine and 26 % lactate yield after 6 h at 220 °C. This performance matches that of state-of-the-art catalysts, but with lower Ru loading (leading to an approximately three-fold higher turnover number) and without external H 2 supply. Catalyst characterization revealed that the metal-support interactions in Ru/TiO 2 -Rutile lead to smaller, well-dispersed Ru nanoparticles ( d ̅ = 2.3 nm) and lower degree of overlayer TiO 2-x formation compared to Ru/TiO 2 -Anatase, which together contribute to higher Ru accessibility (A Ru = 22 %) and thus higher number of active sites per unit mass of Ru, despite the lower surface area of rutile. The reusability of Ru/TiO 2 -Rutile is strongly influenced by the amount of NaOH utilized in the reaction, with a low NaOH: glycerol ratio (1.1) allowing to recycle the catalyst while largely preserving its activity. • One-pot synthesis of alanine from glycerol over a Ru/TiO 2 -Rutile catalyst. • No additional H 2 required to convert glycerol into alanine • Much higher TON (107 mol/mol Ru ) compared to the state-of-the-art catalysts. • Small, well-dispersed Ru nanoparticles with high accessibility are crucial for the activity.