Role of ethylenediamine in the preparation of alumina-supported Ni catalysts from [Ni(en)2(H2O)2](NO3)2: from solution properties to nickel particles

A Ni 0 (15 wt %)/Al 2 O 3 catalyst is prepared by impregnation using [Ni(en) 2 (H 2 O) 2 ](NO 3 ) 2 as precursor salt containing the chelating ligand ethylenediamine (en). Due to the low solubility of this salt and the high viscosity of its solution, large crystals of the salt deposit on the support, clogging the porosity of alumina. These crystals split during the thermal treatment in argon; hydrogen produced in situ from organic residues reduces quantitatively nickel (II) to monodisperse small Ni 0 particles, compared with only one half of nickel reduced by hydrogen when catalysts are prepared from [Ni(H 2 O) 6 ](NO 3 ) 2 .