Hydrogenation of N,N-dimethyl-2-propenylamine over nickel catalysts supported on various metal oxides

Abstract

Hydrogenation of N,N-diethy1-2-propenylaine was carried out over nickel catalysts supported on various kinds of metal oxides to examine the influence of various types of supports upon catalytic activity. The supports used were MgO, CaO, La 2O 3ThO 2, ZrO 2, Al 2O 3, TiO 2, SiO 2, and Al 2O 3. The activities of catalysts did not correlate with the amounts of hydrogen adsorbed nor the amounts of metallic nickel titrated with I 2. Generally, N1 supported on solid base catalysts such as MgO, CaO, La 2O 3, and ThO 2 exhibited high activities as compared with Ni supported on solid acid catalysts, though Ni/SiO 2-Al 2O 3, showed high activity. In particular, the activity of Ni/MgO was extremely high. The Ni/MgO catalyst was completely poisoned by CO 2, whereas the Ni/SiO 2-Al 2O 3, was not. During hydrogenation, the formation of N.N-dimethyl-l-propenyl-amine was observed over the Ni/MgO catalyst but was not appreciable over the Ni/SiO 2-Al 2O 3, catalyst. In the deuteration, two D atoms were incorporated both with the Ni/MgO catalyst and with the Ni/SiO 2-Al 2O 3 catalyst, with the Ni/SiO 2-AI 2O 3 catalyst, however, one D atom was located on each carbon atom 2 and 3, while with the Ni/MgO catalyst, one D atom was on carbon atom 2 and a half on each carbon atom 1 and 3. It was concluded that over Ni on solid bases, N,N-dimethyl-2-propenylamine was isomerized to yield N.N-dimethyl-1-propenylamine which easily underwent hydrogenation to give N,N-dimethylpropylamine, while over Ni on solid acids, N,N-dimethy1-2-propenyl-amine was directly hydrogenated to produce N,N-dimethylpropylamine. On the basis of this conclusion, a highly active catalyst was prepared by mounting Ni on MgO in a non-aqueous medium.