Heterogeneous Hydration of Acrylonitrile over the Metal Oxide Catalysts in Liquid Phase

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Abstract
The liquid-phase hydration of acrylonitrile has been examined over various single metal oxide catalysts at 65 °C. Numerous metal oxides have proved to be active for hydration and have been used to produce three products: acrylamide, ethylene cyanohydrin, and bis(2-cyanoethyl) ether. These oxide catalysts could be divided into two groups with respect to the acrylamide selectivity with 100% or not. A good relationship between the catalytic abilities (activity and selectivity) and the solid acid-base properties of each metal oxide group examined in benzene or in water was observed. Differences in the hydration selectivity to either a C≡N or a C=C bond of acrylonitrile over the catalysts could be explained on the basis of the IR spectra of two adsorbed states of acrylonitrile on the metal oxide surface. It was proved that the liquid-phase hydration of acrylonitrile over the insoluble metal oxide catalysts was an acid-base-catalyzed reaction proceeding on the acidic or basic surface hydroxyl groups.