Process for hydrogenating unsaturated compounds

In a process for hydrogenating an hydrogenizable compound having an unsaturated hydrogenatable bond, said compound being an aromatic hydrocarbon, a saturated aldehyde, an unsaturated aldehyde, an unsaturated alcohol, an unsaturated ether, a saturated nitrile, an unsaturated nitrile, an unsaturated amine, a phenol, a polyolefinic hydrocarbon, or vinylacetylene by means of hydrogen, in the homogeneous liquid phase in an inert solvent or in the compound to be hydrogenated in the liquid phase, under hydrogenation conditions at 0.degree.-300.degree. C. and under a pressure of 0.1 to 100 bars, in the presence of a hydrogenation catalyst, said catalyst being soluble in heptane in catalytic quantities and obtained by reacting a metal compound with a reducing agent of the formula Al R.sub.3 wherein each R is an alkyl group of 1-12 carbon atoms, the improvement wherein said metal compound is used as a mixture in synergistic proportions, of (a) at least one alkoxide, acetylacetonate or carboxylate of a metal selected from iron, zinc, zirconium, manganese and molybdenum and (b) at least one alkoxide, acetylacetonate or carboxylate of a metal selected from nickel and cobalt, the ratio of the atomic amount of metal (a) to metal (b) being within about 10:1 to 0.01:1, and the process being conducted under such conditions that the rate of hydrogenation is disproportionately higher compared to the use of (a) or (b) compound taken alone.