Heraeus Deutschland Gmbh & Co Kg

Heraeus Precious Metals Gmbh & Co. Kg

Dirk Maier

Martin Schlott

Annette Lukas

Nicole Staudt

Willi Boll

Stephan Humm

Pascal Hirschel

Verena Wald

Known catalyst systems for the catalytic combustion of ammonia to form nitrogen oxides consist of a plurality of single- or multilayer catalyst gauzes warp-knitted, weft-knitted or woven from platinum-based noble metal wire, which, when arranged one behind the other in a fresh gas flow direction, form a front group of gauze layers and at least one downstream group of gauze layers arranged after the front group. To provide from this starting point a catalyst system for use in a medium-pressure plant for ammonia oxidation, with which a high service life and a high yield of the main product NO can be achieved, it is proposed that the front group comprises a gauze layer or a plurality of gauze layers made of a first, rhodium-rich noble metal wire, wherein the gauze layer or one of the gauze layers made of the rhodium-rich noble metal wire is a front gauze layer facing the fresh gas, and that the downstream group comprises gauze layers made of a second, rhodium-poor noble metal wire, wherein the rhodium content in the rhodium-rich noble metal wire is at least 7 wt. % and no more than 9 wt. % and is at least 1 percentage point higher than the rhodium content in the rhodium-poor noble metal wire.

Catalyst system and method for the catalytic combustion of ammonia to form nitrogen oxides in a medium-pressure system

Known catalyst systems for the catalytic combustion of ammonia to form nitrogen oxides consist of a plurality of catalyst gauze layers which are knitted, woven or braided from platinum-based precious metal wire, which form a catalyst package when arranged after one another when viewed in a fresh gas flow direction. In order to provide a catalyst system on this basis for use in a medium-pressure system, with which a yield of the main product NO comparable to the industry standard can be achieved despite the reduced precious metal use, according to the invention, the catalyst package is formed from a front assembly with three catalyst gauzes with a first average mass per unit area and a downstream assembly of catalyst gauze layers arranged after the front assembly and having a second average mass per unit area, wherein the average mass per unit area of the front assembly has a short weight in the region of 1.5% to 29% in relation to the second average mass per unit area, and the first average mass per unit area lies in the regions of 410 to 30 g/mand the second average mass per unit area lies in the region of 540 to 790 g/m.

The present invention relates to a powder composed of spherical noble-metal particles having a particle size distribution with a dvalue of &#x2265;10.0 &#x3bc;m and a dvalue of &#x2264;80.0 &#x3bc;m.

Noble-metal powder and the use thereof for producing components

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Hanau, Germany

Dirk Maier