Platinum Metals Review - Volume 11, Issue 3, 1967

Trickle column reactors combine the advantages of continuous operation at high catalyst efficiency, inherent in gas-phase processes, with the advantages of working under mild conditions, inherent in liquid-phase processes. However, considerable attention has to be given to the design of catalysts for use in such reactors. Studies conducted in the Johnson Matthey Research Laboratories have led to substantial improvements over past practice and several processes of potential industrial interest have been developed.

In the manufacture of ferrite core assemblies for computer memories, small and accurately dimensioned rings of the ferrite must be individually threaded on to copper wires. This article describes a new technique for producing the rectangular array by depositing the ferrite on to a grid of platinum wires

A pronounced yield point effect is sometimes encountered when heavily worked palladium is aged between 500° and 800°C. Such strain-ageing phenomena are usually associated with body centred cubic metals such as iron, and it is surprising to find that palladium, a face centred cubic metal, can exhibit analogous behaviour. In this article it is shown that the effect is caused by the presence of silicon, in concentrations as low as a few parts per million, which can be taken up even from a nominally pure alumina crucible in melting under reducing conditions. The precise mechanism involved is not understood, although the effect, when it occurs, complicates fabrication procedures such as wire drawing, contact manufacture and the production of high quality sheet. Working difficulties of this sort can, however, be avoided by adding small quantities of sodium or calcium to the palladium in the course of melting.

In an ammonia oxidation plant for the manufacture of nitric acid the rhodium-platinum alloy catalyst gauzes must be pickled at intervals to remove accumulated impurities such as iron oxide and so to avoid a reduction in catalytic efficiency. This article outlines a method recently devised to determine the optimum frequency of pickling required to ensure consistent operation at high efficiency.

The study of the carbonyls of most of the platinum metals has led to the preparation of a whole series of new complexes, some of which have potential usefulness in the field of homogeneous catalysis. In the case of osmium carbonyls, however, research has so far been hampered by difficulties in their preparation. The new method of preparation described here now makes it possible to investigate the chemistry of osmium complexes along the same lines.

At a Conference held in April at the University of Leeds, organised by Professor F. E. Hoare and Professor J. S. Dugdale, a number of papers were presented and discussed on the subject of the electronic structure and properties of palladium, platinum and their alloys. The greater part of proceedings dealt with palladium, and in this article the author summarises and reviews the discussion.