Full Text for Volume 49 Number 3 (July 2005)

 

This issue contains the following:

Optimising Performance of Platinum Jewellery Alloys
Two commercially available general purpose alloys that are commonly used by manufacturing platinum jewellers are platinum-5%copper and platinum-5%ruthenium. In order to provide a scientific basis to the differences in finish and workability of these alloys, as experienced by jewellers, Duncan Miller and his colleagues from the University of Cape Town, South Africa, compare casting characteristics of the Pt-Cu and Pt-Ru alloys and factors affecting them. They also suggest how working conditions can be manipulated to optimise the performance of each alloy in jewellery manufacture. From a microstructural point of view, it appears the Pt-5%Ru alloy is a superior alloy for casting, if the higher melting temperature required can be met by induction melting, for instance. The greater uniformity in crystal size, shape and composition enhances both the colour and the hardness.

 

Reversible Gelation of Palladium-Based Solvent by Ultrasound
Scientists from Osaka University, Japan, have developed the first molecule that is assembled by brief irradiation with ultrasound (sonication) using an association-inert dinuclear Pd complex stabilised by an intra-molecular p-stacking. When the Pd complex was placed in various solvents and irradiated with sound (0.45 W cm^–2, 40 kHz) for a few seconds, the stable sol state was completely converted to gel. The resulting gels can easily be converted back to the original solution by heating at above T_gel, followed by cooling to room temperature. The aggregation rate can be controlled between ‘no gelation’ and ‘instant gelation’ by tuning the sonication time.

 

Latest Development in Diesel Engine Technology
A specialist course run by the University of Leeds, U.K., entitled "Diesel Particulates and NOx Emissions" is reviewed by John Pignon, Johnson Matthey Technology Centre, Sonning Common, U.K. The course was very informative covering the latest developments in diesel technology, such as engine design, fuel injection systems, fuel, lubricants, turbochargers, aftertreatment, and emissions and health effects, that impact on particulate and NOx emissions.

 

Highly Active Platinum Homogeneous Catalysts
Phosphinito Pt complex catalysts are known as being highly active and versatile for nitrile hydrations. Now scientists at Harvard University, U.S.A., have used [PtH(PMe₂OH)(PMe₂O)₂H] to transform the nitrile group of an epimerised product into the corresponding primary amide. In the synthesis of Stephacidin B, the complex was indispensable in a step where a nitrile group of a Strecker-like HCN addition product became a primary amide under neutral conditions.

 

Platinum Group Metal Nanoparticles with Narrow Size Distribution
In structure sensitive catalytic reactions there is an ideal size and morphology for the metal particles for optimum reaction conditions. A narrow particle size distribution gives them a very high surface area, better for catalytic activity and good order. Recent reports in the literature describe various way to produce uniform, well-ordered optimised Pt nanoparticles, stable Pt clusters (1 to 3 nm), monodisperse Pd nanoparticles and novel Pt-Ru nanoparticles.

 

Ruthenium Complexes Having N-Heterocyclic Carbene Ligands
A large number of ruthenium complexes with nucleophilic N-heterocyclic carbene ligands is selectively discussed by Valerian Dragutan and Ileana Dragutan, from the Institute of Organic Chemistry, Romanian Academy, Bucharest, Romania, and Albert Demonceau, from the University of Liege, Belgium. The survey covers work done to-date on the ruthenium alkylidene, vinylidene, allenylidene and indenylidene complexes, bearing imidazolin-2-ylidene and dihydroimidazolin-2-ylidene carbenes, as well as a number of immobilised ruthenium complexes having these types of ligands. These new ruthenium complexes were found to display higher activity and thermal stability than the parent diphosphane ruthenium complexes, but their activity was strongly dependent on the nature of the complex, the solvent and the olefinic substrate. Therefore, activity can be finely tuned by changing the electronic and steric properties of the imidazolin-2-ylidene ligands.

 

Obtaining High Purity, Porous Platinum Films
A simple low cost hydrothermal method for producing thin films of porous platinum is described by J. Wrzyszcz and his team from the Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Wroclaw. The high purity films are formed from [Pt(NH₃)₄]Cl₂ solution and comprise platinum agglomerates ~ 200 to 300 nm in size with internal grains of ~ 20 to 60 nm. Grain sizes sizes in Pt films produced by this route appear to be independent of film thickness.

 

Revised Data for the Themodynamic Properties of Platinum
The thermodynamic properties of platinum were previously first published here by J. W. Arblaster, now at Coleshill Laboratories, U.K., in 1994. However, the use of superior values for the enthalpy of liquid Pt have resulted in a major revision of the thermodynamic values for the liquid phase. One consequence of the revision is that the boiling point at one atmosphere pressure is altered from 4125 K, as calculated in the 1994 paper, to 4149 K. Previously accepted values for solid Pt are not altered, and there are only very minor changes to the gaseous phase values as a result of using a new atomic weight for Pt and the CODATA 2002 recommended values of the fundamental constants.

 

PGM Market Survey, and Patent and Literature Selection
The issue also contains a summary of the main features in "Platinum 2005", which is a survey of the supply and demand for the platinum group metals in 2004, and a selection of abstracts based on recently published patent and scientific literature.

 

Final Analysis: Elimination of Fouling in Catalyst Beds
In order in improve performance in operating catalyst beds used in many refinery and chemical processes, fouling in catalyst beds must be avoided. John Dunleavy of the Oil & Gas Section, Johnson Matthey PCT, U.K., provides specific criteria to achieve this. John has over 20 years’ experience working in the catalyst industry.

Susan V. Ashton
Editor

Contact
The Editor, Platinum Metals Review, Johnson Matthey PLC, Orchard Road, Royston, Hertfordshire SG8 5HE, United Kingdom; Fax +44 (0) 1763 256359; Email jmpmr@matthey.com

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