Kinetics and mechanism of the preparation of Raney® copper

Raney(R) copper is an active hydrogenation catalyst formed by the selective dissolution of aluminium from a Cu-Al alloy. The structure of Raney(R) copper is presented in a series of images taken using a focussed ion beam miller (FIB). The images show a structure consisting of a uniform three-dimensional network of fine copper ligaments. A rotating disc electrode, used to control the diffusion layer, enabled a study of the kinetics of the leaching reaction at 269-303 K in 2-8 m NaOH. Under these conditions, the reaction rate was constant and independent of hydroxide concentration. The activation energy for leaching was determined as 69 +/- 7 kJ mol(-1). The mixed corrosion potential of the dissolving alloy has been related to the exposed copper surface area, which in turn is dependent on the leaching rate and the mechanism of rearrangement. The overall mechanism of formation/rearrangement of the Raney(R) copper structure was found to be mainly dissolution/redeposition of copper atoms, with surface or volume diffusion, or possibly both, playing a minor role.