Raney Nickel - Properties

Properties

Macroscopically, Raney nickel is a finely divided gray powder. Microscopically, each particle of this powder is a three-dimensional mesh, with pores of irregular size and shape of which the vast majority are created during the leaching process. Raney nickel is notable for being thermally and structurally stable, as well has having a large BET (Brunauer-Emmett-Teller) surface area. These properties are a direct result of the activation process and contribute to a relatively high catalytic activity.

The surface area is typically determined via a BET measurement using a gas that will be preferentially adsorbed on metallic surfaces, such as hydrogen. Using this type of measurement, almost all the exposed area in a particle of the catalyst has been shown to have Ni on its surface. Since Ni is the active metal of the catalyst, a large Ni surface area implies a large surface is available for reactions to occur simultaneously, which is reflected in an increased catalyst activity. Commercially available Raney nickel has an average Ni surface area of 100 m2 per gram of catalyst.

A high catalytic activity, coupled with the fact that hydrogen is absorbed within the pores of the catalyst during activation, makes Raney nickel a useful catalyst for many hydrogenation reactions. Its structural and thermal stability (i.e., it does not decompose at high temperatures) allows its use under a wide range of reaction conditions. Additionally, the solubility of Raney nickel is negligible in most common laboratory solvents, with the exception of mineral acids such as hydrochloric acid, and its relatively high density (about 6.5 g/cm3) also facilitates its separation from a liquid phase after a reaction is completed.