SELECTIVE HYDROGENATION OF ACETOPHENONE ON CHROMIUM PROMOTED RANEY-NICKEL CATALYSTS .2. CATALYTIC PROPERTIES IN THE HYDROGENATION OF ACETOPHENONE, DETERMINATION OF THE REACTIVITY RATIOS AS SELECTIVITY CRITERIA

The hydrogenation of acetophenone has been investigated in cyclohexane , with chromium promoted Raney nickel. The preparation and the physico -chemical properties of these catalysts have been described in part I. The reaction was carried out in a static receptor and its progress wa s followed by measuring the concentration of the components in the liq uid phase. The ratios k(i)b(M)/k(j)b(N) where k(i), k(j) are the rate constants and b(M), b(N) are the adsorption equilibrium constants for two competitive parallel reactions or two consecutive reactions, have been computed and used as selectivity criteria. These selectivity crit eria allow to compare the activity of the different sites of hydrogena tion. In the presence of chromium the hydrogenation of the C-O bond is favoured with respect to the two side reactions: the hydrogenation of the aromatic ring and the hydrogenolysis of the C-OH bond. Catalysts prepared by soaking Raney nickel in an aqueous chromium chloride solut ion gave the highest selectivity in 1-phenylethanol.