Palladium catalyzed synthesis of methylamines from carbon dioxide, hydrogen and ammonia

The synthesis of methylamines from carbon dioxide, hydrogen, and ammonia has been studied over two palladium-alumina catalysts with palladium loadings of 2.8 and 7.6 wt%, respectively. Catalytic tests were performed in a fixed-bed microreactor at 0.6 MPa total pressure in the temperature range 473-573 K. The catalysts showed high activity for methylamine formation at low temperatures and produced monomethylamine with selectivities higher than 80%, besides of smaller amounts of di- and trimethylamine. Other carbon containing products observed were carbon monoxide, formed by the reverse water-gas shift reaction, and methane, which was the prevailing product above 573 K. Ln situ diffuse reflectance FTIR studies were performed to identify the species present on the catalyst surface under reaction conditions. Ammonia and methylamines are adsorbed on Bronsted and Lewis acid sites on the catalyst. Evidence is given that surface formate and isocyanate species are present on palladium-alumina under reaction conditions.