Liquid phase hydrogenation of acetonitrile to ethylamine over the CoB amorphous alloy catalyst

Abstract

The CoB amorphous alloy catalyst was prepared by chemical reduction of Co 2+ ions with BH 4 − in aqueous solution. Its activity and selectivity were measured during the liquid phase hydrogenation of acetonitrile and the effects of various factors, such as the reaction time, acetonitrile concentration, hydrogen pressure, reaction temperature, and solvent, were investigated. The following results were obtained: (1) The maximum ethylamine yield of 69% was obtained at the total conversion of acetonitrile. (2) The acetonitrile hydrogenation was zero-order with respect to acetonitrile and first-order with respect to hydrogen. Meanwhile, the selectivity to ethylamine increased slightly with the increase of either hydrogen pressure or acetonitrile concentration. (3) Increased reaction temperature resulted in a great enhancement in the activity (the apparent activation energy was determined as 46 kJ/mol) but a slight decrease in the selectivity to ethylamine. (4) Addition of a little H 2O may result in an increase in the activity. All these effects are discussed based on the reaction mechanism. In comparison with other Co-based catalysts, such as Raney Co, pure Co powder catalyst, and the crystallized CoB catalyst, the amorphous CoB catalyst exhibited much higher activity and better selectivity to ethylamine. Although Ni-based catalysts had higher activity, their poorer selectivity to ethylamine suggested that they were not suitable for the title reaction under the present conditions. Based on the reaction mechanism and various characterizations, including SAED, XRD, SEM, TEM, EXAFS, XPS, hydrogen chemisorption, and DSC, the promoting effects on the activity and selectivity of the CoB amorphous catalyst are discussed briefly by considering both the structural characteristics and the electronic interaction between the Co and the alloying B.