Characterization and catalytic properties of several La/Ni and Sr/Ni solids

The structural characterization using BET, XRD, TPR, XPS, SEM and TPD, and the catalytic behaviors of several La/Ni and Sr/Ni samples compared with those previously reported on K/Ni and undoped nickel catalysts have been studied for the hydrogenation reaction of adiponitrile. BET and XRD show the increase of area and the sintering inhibition of the nickel particles due to the presence of both lanthanum and strontium, respectively. XPS shows a high lanthanum migration from the bulk to the surface of the nickel catalysts with respect to Sr/Ni and K/Ni samples and also a decrease of the reduction degree of the samples with the increase of lanthanum or strontium content. The latter effect has also been observed by TPR, XRD and BET and is in agreement with those potassium-doped nickel catalysts. According to TPD results lanthanum and strontium do not significantly modify, either the metal-hydrogen, metal-amine and metal-adiponitrile interactions or its blocking capability upon any particular active nickel site, when both are compared with the undoped nickel. These behaviors agree with the catalytic results as lanthanum/nickel and strontium/nickel catalysts show higher conversions and lower selectivities to primary amines than those obtained from the previously reported potassium doped nickel catalysts.