Platinum Metals Review - Volume 23, Issue 1, 1979

The unique high temperature and corrosion resistant properties of the platinum group metals can best be utilised if the mechanisms which may result in the degrading of these properties are acknowledged and understood. This article reviews the more important of these mechanisms, thus enabling the conditions which promote them to be avoided, and the nobility of the platinum metals to be maintained in everyday practice.

Over three hundred participants met in Louvain-la-Neuve, Belgium, at the beginning of September 1978 to attend a Second International Symposium, sponsored by the International Union of Pure and Applied Chemistry and the Division de Catalyse of the Société Chimique de Belgique, to discuss the scientific bases for the preparation of heterogeneous catalysts. Papers described the preparation of active oxides, carbides and metals; a considerable fraction concerned the platinum group metals and a brief review of some of these is now presented.

The catalytic reforming of crude oils has been considerably improved during the last ten years by the addition of a second metal, generally rhenium or iridium, to the small amounts of platinum present in alumina supported catalysts. A most important question, from a scientific point of view, is to differentiate between the various possible states of the metal phase, which may range from a mixture of platinum and the second metal particles to homogeneous bimetallic aggregates. This differentiation is extremely difficult because of the very small size of the metallic particles. It is reported that hydrogen-oxygen titration provides evidence of the presence of small particles of pure rhenium, iridium or ruthenium in platinum bimetallic alumina supported catalysts.

The platinum metals feature distinctly in a class of highly anisotropic compounds exhibiting one-dimensional properties. An understanding of their molecular structure and their physical and electronic properties permits the synthesis of anisotropic insulators, semiconductors and metals. The possibility of room temperature superconductivity continues to be a focal point of current research.