Liquid phasw hydrogenation of acetonitrile ot ethylamine over the Co-B amorphous alloy catalyst

摘要

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 actonitrile and the effects of various factors,such as the reaction time,acetonitrile concentration,hydogen pressure,reation temperature,and solvent,were investigated.The following results were obtained: (1) The mazimum ethlamine yield of 69% was obtined 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 ot ethylamine increased slightly with the increase of eigher hydrogen pressure or acetonitrile concentration.(3)Increaes reaction temperature resulted in a great enhancement in the activity (the apparent activation energy was determined as 46kJ/mol)but a slight decreased in the selectivity ot ethylamine.(4)Addition of a little H_2O may result in an increase in the activity.All these effects are discussed based on the rection mechanism.In comparison with other Co-based catalysts,such as Raney Co,pure Co powedr 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 cnsidering both the sturtural characteristics and the electronic intraction between the Co and the alloying B.