Preparation of Raney nickel hydrogenation catalyst

Raney nickel is prepared by reacting nickel-aluminum alloy with sodium hydroxide. This method, known as "activation", dissolves most of the aluminum outside the alloy. This porous structure has a large area and gives a high catalytic activity. A typical catalyst contains about 85% nickel (mass fraction), corresponding to one atom of aluminum for every two atoms of nickel. Aluminum facilitates the maintenance of the pore structure and contributes to the catalyst as a whole.

The alloy is prepared industrially by melting the active metal (nickel catalysts are made in this case, but "skeletal" catalysts such as iron and copper can also be prepared in the same way) and quenching the aluminum in a crucible, resulting in a melt that is then pulverized into a fine powder. This powder is set in a specific particle size range depending on the catalyst required for the actual application.

Temperature has a significant effect on the surface properties of the catalyst and the leaching alloy. The commonly used temperature range is from 70 to 100°C. The surface area of Raney nickel (including skeletal catalysts in general) tends to decrease as the leaching temperature increases. This is due to the structural rearrangement of the alloy similar to that of sintering, where the alloy will begin to adhere to each other at higher temperatures leading to loss of porous structure.

Prior to storage, the catalyst should be washed with distilled water at room temperature to eliminate any remaining impurities such as sodium aluminate solution. Oxygen-free water is the preferred storage solvent to prevent oxidation of the catalyst, which would otherwise accelerate its aging process and consequently reduce the activity of the catalyst.