Green Production of Nitriles

Nitriles are an important class of compounds that find applications as solvents, intermediate compounds and pharmaceutical molecules. Current nitrile synthesis methods rely on petrochemical starting materials. This is in itself not ideal in a world where fossil resources are becoming scarcer. The thesis presents an alternative, catalyzed process. An attractive feature of the new process is that it can be run at much milder conditions compared with traditional methods. This reduces energy consumption during manufacture considerably and also carries various practical advantages.

The most important industrial nitrile process is ammoxidation of propene to acrylonitrile. Annual production exceeds 5 million tons of acrylonitrile. The dominant concept is the Sohio process which was introduced in 1960 and soon became successful due to high conversion rates (98 %) and good yields. The process produces both acrylonitrile and acetonitrile, which can be seen as an advantage. However, in the event that acrylonitrile production drops for economic or political reasons, this could lead to a shortage of acetonitrile – as occurred in 2009. Furthermore, the Sohio process relies on petroleum based feedstocks and has relatively harsh operating conditions, including temperatures in the range 400-450 °C. A more energy efficient process is therefore in demand.

The thesis presents a new, alternative path to acetonitrile from ethanol via the oxidative dehydrogenation of ethylamine. High conversion rates (up to 100 %) and selectivities (80-90 %) are reported.

Further, RuO₂/Al₂O₃ catalysts are applied to the oxidative dehydrogenation of benzylamine in air, utilizing a new reaction setup. Moderate benzonitrile yields (up to 62 %) and high conversions (up to 100 %) are reported. After optimization of the catalysts, benzonitrile yields were improved (up to 82 %).

Finally, oxidative dehydrogenation of amines using air and RuO2/Al2O3 catalysts was applied to a range of substituted aromatic amines and longer chain aliphatic amines. Substituent groups of aromatic amines are found to affect both the rate of amine conversion and nitrile production. Novel attempts are made to apply the Hammett relationship to the oxidative dehydrogenation of amines using air and RuO₂/Al₂O₃ catalysts in continuous flow.