Hydrogenation of Acetophenone in the Presence of Ru Catalysts Supported on Amine Groups Functionalized Polymer

Liquid phase hydrogenation of acetophenone (ACT) is studied over ruthenium catalysts (1-4 wt% Ru) supported on gel-type methacrylate-styrene resin (FCN) functionalized with C=O, -NH, and -NH2 groups. Microscopic studies (SEM, STEM) show that the nature of Ru particles depends on the level of Ru doping. At low Ru content (1-2 wt%) ruthenium nano-clusters are formed, while at 4 wt% Ru, metal crystallites of few nanometers in size are observed. Catalytic reactions are performed at mild conditions (atmospheric pressure of hydrogen, 40 degrees C) in biphasic isooctane-water (IO/H2O) solvent system, and, for comparison, in a single component solvent (isooctane or ethanol). The use of biphasic IO/H2O solvent system results in a dramatic improvement of selectivity. The hydrogenation of C=O in acetophenone dominates over the hydrogenation of aromatic ring, yielding 1-phenylethanol with ca. 80% selectivity. Ru/FCN catalysts exhibit higher selectivity than the reference Ru/Al2O3. This is tentatively assigned to the steric effects induced by the polymer network on migrating reactant molecules. Advantageous influence of biphasic IO/H2O solvent system has been attributed to the solvation of phenyl ring of acetophenone by non-polar isooctane, which facilitates the interaction with the catalyst surface via carbonyl group and leads to the preferential reduction to 1-phnenylethanol.