Osmium asbestos

Zelinsky and Turowa-Pollak141 describe the specific properties of an osmium catalyst. Hydrogenation on osmium catalysts usually occurs at lower temperatures than on platinum, palladium, or nickel catalysts. Osmium asbestos is a very resistant catalyst that can be used for months on end without loss in activity disadvantages are that osmium catalysts that are not supported on carriers must be frequently regenerated and that when the temperature exceeds 150° osmium tends to decompose the material under hydrogenation. 

A support-effect such as demonstrated in the classical case of platinum asbestos is of negligible importance with ammonia catalysts except with osmium and ruthenium. 

The most active catalyst is platinum applied in finely divided form, for example platinised asbestos. Certain elements, especially arsenic and mercury, have a powerful effect in reducing the activity of the platinum, a quantity of arsenic equal to 0-2 per cent, of the weight of the platinum reducing the activity by 50 per cent.5 These poisons, as they are termed, also include less harmful substances such as antimony, lead, bismuth, etc. The presence of small quantities of rhodium, iridium or osmium in the platinum also causes diminished yields of trioxide, but the presence of palladium or ruthenium has the opposite effect.6... 

Addition of aluminium-strip effects the precipitation of metallic osmium, which is collected in an asbestos-packed tube and dried at dull red heat in hydrogen, cooled in carbon dioxide, and weighed. 

In 1913, the Badische Anilin und Soda-Fabrik (1) disclosed that hydrogen and carbon monoxide would react at 100-200 atmospheres pressure in the presence of alkali-activated cobalt or osmium oxide supported on asbestos to form a liquid product containing alcohols, aldehydes,... 

Caution. The end of the tube containing sodium chlorate and osmium must not be heated during the sealing procedure. This can be prevented by immersing the lower 5 cm of the tube in a beaker of water or by wrapping such a length in wet asbestos. 

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