Abstract: A solid solution for the desulfurization of sulfur containing gases is provided in which the solution contains oxides having oxygen ion vacancies provided therein. The solid solution has a solvent which has at least one lanthanide oxide which crystallizes in the fluorite habit. The solid solution has a solute which contains a second oxide having a valence which differs from the valence of the lanthanide oxide present in the solvent.

Abstract: A process for optimizing the removal of nitrogen oxide (NO.sub.x) and sulfur oxide (SO.sub.X) from flue gases is provided in which the flue gases pass over a lanthanide-oxygen-sulfur catalyst. The catalyst has active sites provided on its surface which promote the dissociation of NO.sub.X and receive and entrap oxygen released during the dissociation of the NO.sub.X. While the flue gases pass over the catalyst, a reducing gas contacts the catalyst to reduce the oxygen on the active sites of the catalyst and permit the catalyst to continue to promote the dissociation of the NO.sub.x in the flue gas. If the flue gases contain SO.sub.X, they are then passed over a solid solution having a solvent of a first lanthanide oxide compound which crystallizes in the fluorite habit and a solute of at least one altervalent oxide of a second lanthanide. The SO.sub.X in the flue gases reacts with the solid solution to form a sulfated lanthanide oxide which is removed from the flue gases.

Abstract: A process for the removal of chlorine from reducing gases is provided wherein the reducing gases are contacted with cerium oxide. The chlorided cerium oxide is regenerated in an oxidizing atmosphere to provide cerium oxide. This cerium oxide regenerated is again capable of reacting with chlorine in reducing gases.