Insight into the mechanism of acetonitrile hydrogenation in liquid phase on Pt/Al 2 O 3 by ATR-FTIR

Abstract

The mechanism of the acetonitrile hydrogenation to amines over a platinum/alumina catalyst was investigated by in situ infrared spectroscopy. The reaction was studied under realistic conditions -liquid phase using toluene as solvent- using a flow-through cell-microreactor in Attenuated Total Reflection (ATR) mode. Acetonitrile linearly chemisorbed on platinum sites is stepwise hydrogenated to form an imine surface intermediate (CH 3 CH = NH), which in turn is hydrogenated to ethylamine. Using deuterium, the sequential formation of C?D and N?D bonds was observed. Then, imine intermediate can condense producing diethylamine and triethylamine, giving ammonia as a by-product. The temporal evolution of the IR signals was modeled using a proposed microkinetic mechanism and intrinsic kinetic constants were obtained under chemical control.