Catalytic properties of nickel/sepiolite promoted with potassium and lanthanum in adiponitrile hydrogenation under mild conditions

Abstract

Ni/sepiolite, potassium and (or) lanthanum doped Ni/sepiolite catalysts were prepared by the incipient impregnation method and characterized by N₂ adsorption–desorption, temperature programmed reduction (TPR), hydrogen chemisorption, powder X-ray diffraction (XRD), ammonia temperature programmed desorption (NH₃-TPD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). It was revealed that the potassium could inhibit the formation of the ACH by-product by neutralizing some acid sites on the catalyst, and the lanthanum could efficiently reduce the diameter and improve the dispersion of the active nickel particles. These catalysts were tested in liquid phase hydrogenation of adiponitrile (ADN). The products include 6-aminocapronitrile (ACN), hexamethylenediamine (HMDA), 1-azacycloheptane (ACH) and C₁₂ compounds. It shows that the catalyst doped with potassium and lanthanum gives the best catalytic performance, the selectivity to ACN and HMDA reaches to 91.32% at 92.56% conversion of adiponitrile under 393 K and 2.0 MPa.