Platinum Metals Review - Volume 52, Issue 3, 2008

A novel palladium-based catalyst has been developed for use in a miniature fuel cell power source for portable applications, incorporating a polymer electrolyte membrane (PEM) fuel cell. Hydrogen, which is the fuel for the cell, is produced in a ceramic microreactor via the catalytic reaction of methanol steam reforming: CH3OH + H2O → 3H2 + CO2. The need for a new catalyst in this application is driven by the limitations of traditional particulate catalysts based on copper oxide, zinc oxide and alumina (Cu-Zn-Al catalysts), which have low thermal stability and high sensitivity towards air and condensing steam. These features result in a declining activity and mechanical integrity of Cu-Zn-Al catalysts under the frequent start-stop conditions typical of the operational mode of the miniature power source. The new Pd-based catalyst has activity and selectivity similar to those of Cu-Zn-Al catalysts, but is more durable and stable under the duty cycle conditions of a portable power source. In the microreformer, the catalyst is washcoated directly on the walls of the steam reforming section, providing favourable conditions for efficient heat transfer between the heat-generating catalytic combustion section of the microreformer and its heat-consuming steam reforming section.

The use of noble metals as catalysts for mercury oxidation in flue gas remains an area of active study. To date, field studies have focused on gold and palladium catalysts installed at pilot scale. In this article, we introduce bench-scale experimental results for gold, palladium and platinum catalysts tested in realistic simulated flue gas. Our initial results reveal some intriguing characteristics of catalytic mercury oxidation and provide insight for future research into this potentially important process.

Following Part I, previously published in this Journal (1), the present paper discusses new routes for immobilisation of ruthenium alkylidene complexes through their ligands. Systematically addressed as suitable participants for immobilisation are Schiff bases, arenes, anionic ligands and specifically tagged (ionic liquid tag, fluoro tag) substituents.

A series of novel lipophilic platinum(II) compounds containing salicylate derivatives as the leaving group have been designed, synthesised and characterised. Most of the platinum compounds exhibit high solubility and have a partition coefficient suited to liposomal encapsulation. Some of the compounds are more pharmacologically active and/or less toxic than carboplatin and oxaliplatin. The liposomal formulation of the most promising compound has been successfully prepared with long stability and high encapsulation rate, showing great potential to be developed as a new tumour-target drug.

Electrochemical water disinfection is a rarely used but convenient and highly efficient way to produce germ-free water. The technique works without the addition of chemical compounds to the water to be treated, but is nevertheless based on the biocidal action of various chemical substances. Electrodes with platinum group metals (pgms) or their oxides as active coatings are generally the best suited to electrochemical water disinfection. In special cases, novel doped diamond electrodes can be applied. A short historical and technical overview of the process is given, augmented by some application examples.

Iridium and its alloys have been considered to be difficult to fabricate due to their high melting temperatures, limited ductility, sensitivity to impurity content and particular chemical properties. The variety of processing methods used for iridium and its alloys are reviewed, including purification, melting, forming, joining and powder metallurgy techniques. Also included are coating and forming by the methods of electroplating, chemical and physical vapour deposition and melt particle deposition.