Hydrogenation of quinoline by ruthenium nanoparticles immobilized on poly(4-vinylpyridine)

A series of catalysts composed of ruthenium nanoparticles immobilized on poly(4-vinylpyridine) was prepared by NaBH4 reduction of RuCl3 · 3H2O in methanol in the presence of the polymer; TEM measurements of a 10 wt% Ru/P4VPy material indicate that ruthenium particles of 1–2 nm predominate. This catalyst is efficient for the selective hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline at 100–120 °C and 30–40 bar H2. The activity increases with hydrogen pressure up to 40 bar but is essentially independent of quinoline concentration. Polar solvents, triethylamine, and acetic acid enhance catalytic performance, suggesting an ionic mechanism involving heterolytic hydrogen activation.