DE884639C - Recovery of the platinum which evaporates during ammonia combustion - Google Patents

Description

Recovery of the platinum which evaporates during ammonia combustion The subject of patent 747 120 is a process for the recovery of the platinum which evaporates during ammonia combustion with the aid of catalysts made from platinum and platinum alloys, in that the hot combustion gases are passed through a gas-permeable layer, the gold contains in a large surface and / or fine distribution. The gas-permeable layer can, for. B. made of ceramic support material: 1, such as tubes, hollow cylinders with a square cross-section or the like, which are provided with a thin, possibly porous coating of gold of the finely divided platinum in the exhaust gas takes place with the gold. This is e.g. B. at temperatures of 600 to 700 ' the case.

Further tests have shown that the method of the patent mentioned can also be carried out in such a way that the gold is partially or completely through other precious metals or precious metal alloys are replaced. You can z. B. platinum or Use palladium, which is also like gold corrosion resistant -are- and do not oxidize. Due to the higher melting point of platinum and palladium However, the pre-welding of the volatilized platinum is less easy. It is therefore advisable to use l # e, # -:,. V (# rWendu.ng of platinum and / or Palladium to lower the melting point of these metals, what in the simplest way can be done by alloying gold in the required quantities.

Furthermore, it has been found that, instead of gold, alloys which contain gold, platinum or palladium and also silver in certain proportions can advantageously be used. Since silver is not sufficiently resistant to corrosion, its proportion must not exceed certain limits in order to maintain the corrosion resistance of these alloys. Gold should generally contain no more than about 50 atomic percent silver, platinum no more than about 60 atomic percent, and palladium no more than about. 50 atomic percent silver.

Palladium is somewhat less resistant to corrosion than platinum and gold and is therefore somewhat inferior to the latter. The same applies to alloys that contain palladium as a main component. Of course, alloys with more than two components, e.g. B. Gold # -Platinum-Si 1 ber, gold-palladium-silver, platinum-palladium-silver, gold-platinum-palladium-silver, can be used.

The present invention applied precious metals and precious metal alloys -can also untergeofdnete amounts of other Edelineta-Ii # n, b'esondere in # - such - included such as ruthenium, osmium, rhodium, iridium individually, or more of the platinum group, applying the Noble metals or noble metal alloys claimed here on carriers, such as fine tubes, hollow cylinders with a square cross-section or saddle bodies made of ceramic material, can result in the same or a similar way as in the method of the main patent. Alloys can be produced on the base itself. B. first apply silver to the substrate in the manner of (# äa-nz-versilb-eru-ng- or by cathode sputtering and apply the silver base to a top layer of corrosion-resistant metal, e.g. gold, galvanically or in some other way heating to suitable temperatures will alloying by interdiffusion of the metals instead. This alloy'bildung may with advantage in the practical application of the formations -stattfinden. finds during the passage of the exhaust gases of the combustion of ammonia by the gas-permeable layer at temperatures of about 6oo to 700 ', the Alloy formation takes place independently.

Claims (2)

PATENT CLAIMS. i. Modification of the process for the recovery of the platinum which is volatilized during ammonia combustion by means of catalysts made of platinum or platinum alloys by guiding the hot combustion gases through gas-permeable layers containing gold on the surface according to patent 747 i2o, characterized in that to bind the platinum in place of gold or in addition to Gold other precious metals that are present at the temperatures in question, e.g. B. 600 to 7000, are corrosion and oxidation resistant, such as palladium or platinum, can be used individually or in the form of their alloys. 2. The method according to claim i, characterized by the use of corrosion- and oxidation-resistant alloys of silver with corrosion-resistant noble metals such as gold, palladium, silver. 3. The method according to claims i and 2, characterized by the use of corrosion- and oxidation-resistant alloys that are on the documents, for. B. ceramic support bodies, by separate application of the components and diffusion by the effect of heat before or during the application. 4. The method according to claims i to 3, characterized by the use of alloys which have arisen in that silver is first applied to the carrier body, the silver coating is coated with a cover layer of corrosion-resistant noble metals and alloyed with it by the action of heat before or during use is.