Novel synthesis route for egg-shell, egg-white and egg-yolk type of cobalt on silica catalysts

A novel method for the preparation of egg-shell, egg-white and egg-yolk type of catalysts was developed. The synthesis procedure utilizes the hydrophobic nature of silica. Egg-shell catalysts with a sharp boundary can be prepared by covering the inside of the pellet with a defined amount of n-undecane prior to the impregnation procedure. A partial coverage of silica pellets with a hydrocarbon, n-undecane, protects that part of the pellet yielding an egg-shell type of catalyst. Egg-yolk type of catalysts can be prepared by leaching the shell of a homogeneously impregnated, reduced catalyst with nitric acid followed by neutralisation. Egg-white type of catalysts can be prepared by selective leaching of a reduced, egg-shell catalyst. (c) 2005 Elsevier B.V. All rights reserved.