Amination of Polyethylene Glycol to Polyetheramine over the Supported Nickel Catalysts

Abstract

Surface nickel (NiOx) species, surface NiAlxOy compound, and NiO crystallites are present on the Ni/Al2O3 catalysts, and the ratio of these nickel species is dependent on the nickel loading. Surface nickel interacts with the TiO2 support to form a surface nickel titanate compound (NiTiOx) which has a lower reducibility. The weak interaction between the surface nickel and the silica support results in the formation of NiO crystallites on the SiO2 surface. The Ni/Al2O3 and Ni/TiO2 catalysts contain new surface Lewis acid sites and the amount of surface Lewis acid sites increases with increasing nickel concentration. The Ni/SiO2 catalysts have no sign of the presence of the surface Lewis acid sites. Only the Ni/Al2O3 catalysts have shown the ammonia adsorption at temperature of 200°C. Supported nickel on alumina catalysts possess the highest amination conversion, and the amine yield increases with increasing nickel loading up to ∼15% and starts to level off. By comparing amination catalysis with quantitatively TPR studies of the H2 consumed of the Ni/Al2O3 catalysts, it appears that the dispersed nickel species are the active sites for amination. In addition, the amination product is mainly the secondary amine due to the presence of water.