Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Nitrogen or nitrogenous component
Patent
1994-02-28
1997-03-18
Bos, Steven
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Nitrogen or nitrogenous component
B01J 800
Patent
active
056120095
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a supported silver-containing catalyst and to a process for the selective catalytic decomposition of dinitrogen monoxide in pure form or in admixture with other gases, using said supported silver catalyst.
The catalytic decomposition of dinitrogen monoxide (nitrous oxide, ie, laughing gas) has been known for many years and is described in numerous publications referring to kinetic experiments. As long ago as 1936, a paper in Gmelins Handbuch der anorganischen Chemie, Stickstoff 8th Edition, pp 573 et seq, describes experiments on the decomposition of dinitrogen monoxide in a quartz vessel in the presence and absence of various catalysts such as SiO.sub.2, platinum foil, titanium dioxide, platinum black, Al.sub.2 O.sub.3, charcoal, and thorium dioxide, at various temperatures. Kinetic tests on pure silver and on silver/gold and silver/calcium alloys are described by K. E. Hayes in Canad. J. Chem. 37, 583 (1959). R. Larsson presents an overview of the activating energies of nitrous oxide decompositions using oxidic catalysts, particularly mixed oxides, in Catalysis Today 4, 235-251 (1989).
Commercial interest in the decomposition of dinitrogen monoxide to nitrogen and oxygen was instigated by NASA, who wanted to utilize the decomposition of nitrous oxide (derived from ammonium nitrate) into its elements, in order to obtain respiratory air for astronauts from a compound which is easy to handle (Chem. Abstracts 6, 1481 (1965)). Catalysts described as being suitable are: platinum on various inorganic supports, rhodium on aluminum oxide, and the oxides of nickel, cobalt, and molybdenum.
Another technical field of application is the destruction of anesthetic gases present, for example, in operating theatres. A number of Japanese patents relate to this field, and the following catalyst systems have been described: activated charcoal (JP 54/11090), elements in the iron group in conjunction with rare-earth metals (JP 61/45487), platinum, palladium, rhodium, indium, and/or ruthenium (JP 55/31463), and oxides of copper and chromium on aluminum oxide (JP 61/50650). The dinitrogen monoxide is usually decomposed in a 1:1 mixture of dinitrogen monoxide and air. JP 61/53142 describes the removal of dinitrogen monoxide from off-gases by contacting the same with oxides of cobalt, copper, and manganese on .gamma.-aluminum oxide.
DE-OS 3,543,640 discloses palladium-containing catalysts for the decomposition of dinitrogen monoxide.
JP 63/07826 describes the removal of dinitrogen monoxide from off-gases by contact with, inter alia, palladium or copper oxide on a .gamma.-aluminum support. In the example, the N.sub.2 O concentration in the gas is 26 ppm.
Finally, SU 1,011,238 describes the decomposition of dinitrogen monoxide by contact with carbides on CaCl.sub.2 as support.
In all of the publications cited above, either mixtures of dinitrogen monoxide and air or mixtures of dinitrogen monoxide and oxygen are reacted. DE-OS 3,543,640 describes a method in which mixtures with 430 ppm of nitrogen oxides and 4% of water (as steam) are reacted in contact with palladium catalysts.
DE-P 40 29 061.1, which is not a prior publication, describes supported silver-containing catalysts, in which the Al.sub.2 O.sub.3 used as support has a specific surface area of from 5 to 25 m.sup.2 /g.
SUMMARY OF THE INVENTION
It is thus an object of the invention to provide a process and a catalyst for the catalytic decomposition of dinitrogen monoxide in pure form or in admixture with other gases, by means of which dinitrogen monoxide can be decomposed to the elements nitrogen and oxygen even in the presence of higher concentrations of nitric oxides and other gases which are not oxygen or nitrogen (particularly off-gases such as are obtained in the synthesis of adipic acid by, eg, the oxidation of cyclohexanol and cyclohexanone using nitric acid). Another object of the invention is to provide means of selectively degrading dinitrogen monoxide without decomposing other nitric oxides to their elements.
BRIEF DESCRIPTION OF THE
REFERENCES:
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patent: 4314913 (1982-02-01), Derrien et al.
patent: 4529718 (1985-07-01), Dupin
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Hayes, "The metal-catalyzed decomposition . . . ", Can. J. Chem., vol. 37, 1959, pp. 583-589.
Larsson, "On the catalytic decomposition . . . ", Catalysis Today, vol. 4, 1989, pp. 235-251.
Banchero, "Apparatus, plant equipment, and unit . . . ", Chem. Abst. vol. 63, No. 16, 1965.
Lewis, Hawley's Condensed Chemical Dictionary, 10th ed. 1981 (no month) p. 777.
Translation of '940 patent publication.
Buechele Wolfgang
Buerger Gert
Fetzer Thomas
Herrmann Guenter
Wistuba Hermann
BASF - Aktiengesellschaft
Bos Steven
Dunn Jr. Thomas G.
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