Platinum-containing Catalysts Research Articles

Performance of platinum-group metal catalysts for the selective reduction of nitrogen oxides by hydrocarbons

The performances of platinum-group metals, platinum, iridium, palladium, rhodium and ruthenium supported on γ-alumina, as catalysts for the selective reduction of nitrogen oxides by hydrocarbons were investigated. Platinum and rhodium had high nitric oxide conversion activities both in model mixtures and in real diesel exhaust gases, especially at relatively low temperatures between 200 and 350°C. It was confirmed that the platinum-rhodium and platinum catalysts have higher activity and durability than a catalyst composed of copper supported on ZSM-5 under real diesel exhaust conditions. The platinum-containing catalysts, however, produced more nitrous oxide than nitrogen. It is expected that platinum-group metal catalysts will be able to be used for practical purposes if once their selectivity toward nitrogen is improved.

Synthesis of new vinylsilanes containing an asymmetric silicon via platinum catalyzed hydrosilylation of acetylene and monosubstituted alkynes

A series of new racemic vinylsilanes has been obtained by hydrosilylation reaction of acetylene and monosubstituted alkynes with (±)-α-NpPhMeSiH and (±)-N(CH 2CH 2O) 3SiCH 2PhMeSiH in the presence of platinum-containing catalysts.

Catalysts for Fuel Cell Applications

Phosphoric acid fuel cells are approaching commercial reality, especially in the United States of America and Japan. Without exception they are catalysed by platinum-containing catalysts; in view of the probable future development of such cells and the predicted size of the market for them it is necessary to consider the availability of platinum for this purpose. This article is based, in part, upon a paper presented at an international workshop on trends in research and applications of fuel cells, which was organised by Unesco in co-operation with the Commission of the European Communities, held at Ravello, Italy, during June. It examines the scale of this potential requirement against a background of existing applications of the metal and the way in which it will be used and recycled. Having discussed some recent developments it concludes that supplies will be adequate to meet even the most optimistic projections of fuel cell market penetration.

The role of rhenium and sulfur in platinum-based hydrocarbon-conversion catalysts

Chemisorption, ir, and XPS data indicate that rhenium atoms covered with chemisorbed sulfur atoms divide the metal surface of platinum-containing catalysts into ensembles consisting of a small number of contiguous platinum atoms. Data on the catalytic conversion of n-hexane show that it is the combined action of rhenium and sulfur that converts platinum into a catalyst of very high selectivity for mild dehydrogenation. It thus appears that the beneficial effects on catalyst selectivity and stability which are brought about by adding widely different catalyst modifiers (gold, tin, sulfur, carbon) to platinum catalysts are largely due to one common cause, namely, the division of the platinum surface into very small ensembles of platinum atoms.