Decrease of the Surface Area of Raney-type Catalysts in the Aluminium dissolution Process

Variations of the surface area in the dissolution process were investigated on a Raney copper catalyst “No. 16” (for dehydrogenation of cyclohexanol) and a Raney nickel catalyst. It has been found that nascent bare atoms of copper or nickel formed at the initial step move rapidly, perhaps particularly in alkali solution, to reconfigurate the surface-structure to a more stable one. That is to say, the surface area reaches a maximum at an initial step, where only a small quantity of aluminium is dissolved out, then rapidly decreases to a stable value in spite of successive dissolution of aluminium. The rate of decrease is much greater than that recognized on reserving the catalyst in its dried state or in water. By calculating reliable “n” values, the number of adsorbed molecular layers on the surface area from the modified B.E.T. equation, it has been deduced that the average catalytic activity per unit area of the surface may be decreased in process of dissolution of aluminium.