Chemistry of inorganic compounds – Modifying or removing component of normally gaseous mixture – Nitrogen or nitrogenous component
Patent
1996-07-15
1998-08-11
Straub, Gary P.
Chemistry of inorganic compounds
Modifying or removing component of normally gaseous mixture
Nitrogen or nitrogenous component
210749, 210758, 210903, B01D 3700
Patent
active
057924376
DESCRIPTION:
BRIEF SUMMARY
This application is a national stage filing under 35 USC 371 of PCT/EP94/02688 filed 11 Aug. 1994.
The invention relates to a filter material and to a method of removing oxides of nitrogen from gases and liquids, in which the stream of gas or a liquid is brought into contact with a filter material comprising polyarylenethioether or a mixture of polyarylenethioether and oxidative compounds.
It is known that virtually all combustion processes, for example in power stations which operate using fossil fuels and in the engines of motor vehicles, are accompanied by the formation of so-called oxides of nitrogen (NO.sub.x) which pass into the environment. These oxides essentially comprise nitrogen monoxide (NO) and nitrogen dioxide (NO.sub.2) and/or adducts of the two. Because of the readiness of nitrogen monoxide to undergo oxidation with oxygen, it is predominantly nitrogen dioxide which is present in the atmosphere. In an environmental context, oxides of nitrogen give rise essentially to two problems. On the one hand they are seen as a precursor in the formation of ozone, and on the other hand they represent--even in low concentrations--a considerable health risk (Rompp Chemie Lexikon, 9th edition, vol. 5, 4314-6).
In order to remedy this situation a large number of processes have been developed which describe the removal of nitrogen oxides from the stream of air released from devices as described above, such as internal combustion engines. In these processes the oxides of nitrogen are either destroyed or else bound by chemical or physical means.
It is known to pass the stream of gas through a filter in which the oxides of nitrogen are catalytically decomposed and/or reduced at elevated temperatures by the addition of compounds which form free radicals (WO 92/04962). The base material of the filter is impregnated with one or more metallic compounds, metals or alloys, for example compounds of iron, chromium or nickel, a further addition to which is a compound or a metal from the group consisting of the so-called noble metals, for example palladium or platinum. These catalysts are very expensive and generally have only a limited service life, since such heterogenous catalysts are rapidly deactivated by a variety of catalyst poisons. Moreover, the supply of energy required is highly unfavorable.
Activated charcoal can also be used as an adsorbent for the removal of oxides of nitrogen (Rompp Chemie Lexikon, 9th edition, vol. 2, 1181, Table; Ullmann's Encycl. Ind. Chem., 5th edition, vol. A17, 328). However, activated charcoal filters are subject to ageing because of the reduction in their active surface caused by the adsorption of vapors or moisture; see also Kirk-Othmer, 3th edition, 4, 565 ("storage"). Activated carbon filters are used in particular for the removal of gasoline vapors, in cars for example, or of other hydrocarbon compounds; the filters adsorb these compounds from the air with a high degree of efficiency, resulting in a decrease in their additional adsorption capacity for NO.sub.x gases. In addition, only a small proportion of the filter weight is available as active fraction.
EP-A-0 405 265, furthermore, describes the permeation effect of specially prepared polyphenylene sulfide (PPS) films with respect to gases containing oxides of sulfur or of nitrogen. The effect in this case is one more or less of purely physical separation. It is mentioned that the media used for the separation of the waste gases should be inert with respect to the gases to be separated and that they must have a good permeability for this phase. In this case neither a complete filter effect with respect to oxides of sulfur or of nitrogen nor the adsorption of oxides of sulfur or of nitrogen was observed.
The object of the invention was therefore to provide a filter and a method of removing oxides of nitrogen without encountering the abovementioned disadvantages.
The invention relates to a polymer-based filter for removing oxides of nitrogen, especially nitrogen dioxide, from gases and liquids by chemical reaction between the
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Rompp Chemie Lexikon, 9.sup.th Edition, vol. 5, "Stickstoffoxide", pp. 4314-4317 (1992) no month.
Ullmann's Encyclopedia of Industrial Chemistry, Edited by Elvers et al., vol. A17 "Naphthalene to Nuclear Technology", 5th completely revised edition, pp. 327-330 (1991) no month.
Blood, Coagulants and Anticoagulants to Cardiovascular Agents, Third Edition, vol. 4, Kirk-Othmer, "Encyclopedia of Chemical Technology", p. 565 (1979) no month.
Roupp Chemie Lexikon 9.sup.th Edition, vol. 2, ISBN 3-13-734709-2, "Entstickung", pp. 1180-1181 (1990) no month.
Von R. Gabler and J. Studinka, "Neue Polyphenylensulfone Reaktionen an festen Polymeren", Chimia 28 (Sep. 1974) Nr. 9, pp. 567-575.
Fleischer Dietrich
Frank Georg
Kulpe Jurgen
Schleicher Andreas
Hoechst Aktiengesellschaft
Straub Gary P.
Vanoy Timothy C.
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