Handbook on the Physics and Chemistry of Rare Earths

The oldest use of rare earths in catalysis deals with the structural and chemical stabilization of the zeolites for petroleum cracking applications. For a long time this has been an area of application for non-separated rare earths. The addition of several percent of rare earths in the pores of the zeolite results in a strong surface acidity, which is essential for an efficient conversion of high-weight molecules into lighter species, like low-octane fuel, even in the very aggressive conditions of the petroleum industry.

The popular demand for high-quality air in spite of the traffic congestion in large cities resulted in larger and larger constraints in the emission exhaust from cars. Thus highly efficient catalysts have had to be designed, and due to the combination of its redox properties and very good thermal stability, cerium oxide has been since the beginning, early in the 1980s, a major component of the three-way catalysts (TWC) now used in all modern gasoline cars.

The future of rare earths in catalysis is probably bright. The fact that approximately 400 patents are applied for yearly in the area since 1992 is an illustration of a very active area. Usage of rare earths in catalysis is expected to grow due to their highly specific properties. Instead of the physical properties used in electronic applications, one deals now with redox properties, water and thermal stability, coordination numbers and so forth. The rare earths are so specific in these properties that their use can hardly be avoided, not only for the beauty of academic studies but also for the development of industrial applications with immediate influence on everyday life.

Careful control of the synthesis conditions and the definition of optimum composition in each case are the keys to the preparation of highly performing compounds for catalytic applications. They must actually be considered as high performance products with functional properties, and not just chemical species.

Chapters devoted primarily to catalysis have been published in earlier volumes of the Handbook. In this volume several more are added. The first is an extension of the earlier chapter 43, on interactions at surfaces of metals and alloys, to reactions such as hydrogenation, methanation, ammonia synthesis, saturated hydrocarbon reactions, dehydrogenation of hydrogenated materials, hydrodesulfurization, and carbon monoxide oxidation. The second chapter reports on the wide variety of catalyzed reactions involving metals and alloys in the innovated form of metal overlayers or bimetallic compounds with some transi...