Microcalorimetric adsorption and infrared spectroscopic studies of K—Ni/MgAlO catalysts for the hydrogenation of acetonitrile

Graphical abstract The addition of K2 CO3 significantly increased the heat of adsorption of CH3 CN onto Ni and changed the adsorption structures from that involving the π bond in C[triple bond; length as m-dash]N to di-σ bonded CH3 CN. The strong adsorption of CH3 CN might be an important factor in the decreased activity of Ni doped with K2 CO3 for the hydrogenation of acetonitrile to ethylamine. Display Omitted Highlights Addition of K2 CO3 increased electron density on Ni and strengthened CO adsorption. Addition of K2 CO3 weakened H2 adsorption on Ni and decreased hydrogenation activity. Addition of K2 CO3 weakened adsorption of ethylamine and increased its selectivity. Addition of K2 CO3 changed adsorption structures of CH3 CN on Ni. Addition of K2 CO3 strengthened adsorption of CH3 CN and decreased catalytic activity. Ni/MgAlO and K2 CO3 [single bond]Ni/MgAlO catalysts for the hydrogenation of acetonitrile to primary amine were studied. Microcalorimetric measurements and infrared spectroscopy were used to study the adsorption of CO, H2 , acetonitrile, and ethylamine onto the catalysts. It was found that the addition of K2 CO3 led to an increase in the heat of adsorption of CO on Ni, due to increased surface electron density of Ni. The presence of K2 CO3 weakened the strength of H[single bond]Ni and strengthened the bonding of CH3 CN onto Ni by changing adsorptive states of CH3 CN, which might be two main reasons for the decreased activity of Ni doped with K2 CO3 . Furthermore, the addition of K2 CO3 decreased adsorptive strength of ethylamine on Ni, resulting in an increase in ethylamine selectivity. Finally, infrared spectra of CH3 CN adsorbed onto the Ni surface with preadsorbed hydrogen indicated that the hydrogenation might occur preferentially on carbon atoms in C[triple bond; length as m-dash]N, leading to the formation of surface species Ni[single bond]N[double bond; length as m-dash]CH[single bond]CH3 and Ni[double bond; length as m-dash]N[single bond]CH2 [single bond]CH3 . [PUBLICATION ABSTRACT]