Gas separation: processes – Solid sorption – Inorganic gas or liquid particle sorbed
Patent
1997-04-07
1998-11-17
Spitzer, Robert
Gas separation: processes
Solid sorption
Inorganic gas or liquid particle sorbed
95144, 95146, 96132, 96135, B01D 5304
Patent
active
058370366
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a process and the associated filter system in which a gas stream loaded with organic substances and ozone is first contacted with an ozone-binding polymer and then with activated carbon.
DESCRIPTION OF THE PRIOR ART
Activated carbon is used as an adsorbent for removing undesirable organic substances such as gasoline or solvent vapors from gases (Rompp Chemie 9th Edition, Volume 1, Georg Thieme Verlag, Stuttgart--New York 1989, p. 83). Activated carbon can degrade ozone and is used as a filter material for removing ozone from gases.
If activated carbon is used for purifying gases which contain ozone and organic substances such as hydrocarbons, in the event of advanced loading of the activated carbon with organic substances, the undesirable effects listed below occur (see "Comparison of adsorption characteristics for VOC on activated carbon and oxidized activated carbon", J. H. You, H. L. Chiang, P. C. Chiang, Environ. Progr. 13 (1994) 31-36): organic substances already adsorbed and partially chemically degrades these, in particular if these are unsaturated compounds. organic substances desorb from the activated carbon so that the purification action of the activated carbon is impaired in the presence of ozone. Some of the desorbed decomposition products (e.g. formaldehyde) are more toxic than the originally adsorbed organic substances. igniting the activated carbon, in particular if the exhaust airstreams to be purified have relatively high concentrations of ozone or organic substances.
Other conventional ozone-degrading materials lead to difficulties in the purification of gases which contain ozone and organic substances: containing noble metals very rapidly lose their ozone-degrading activity in the presence of hydrocarbons. atmospheric humidity. gases (H.sub.2 S, SO.sub.2, formaldehyde) which act as catalyst poisons.
The object of the invention was therefore to develop a suitable filter for removing organic substances and ozone from gases which does not have the disadvantages of known filter systems and nevertheless utilizes the favorable properties of activated carbon for removing organic substances.
SUMMARY OF THE INVENTION
It has been found that certain polymers such as poly(phenylene sulfide) or poly(2,6-dimethylphenylene oxide) react with ozone without their filter action being impaired by organic substances such as hydrocarbons or other volatile organic compounds. It is therefore possible to decouple the purification of gases which contain ozone and organic substances by first contacting the gas with the ozone-binding polymer and then with activated carbon.
The invention therefore relates to a process for removing ozone and organic substances from gases, the gas first being contacted with an ozone-binding polymer and then with activated carbon.
BRIEF DESCRIPTION OF THE DRAWING
preferred filter structure having a single filter element comprising an ozone-binding polymer zone and an activated carbon zone.
DETAILED DESCRIPTION
The ozone-binding polymer preferably comprises poly(arylene ethers) and sulfur-containing polymers.
Poly(arylene ethers) designate polymers which contain methyl-substituted arylene ether units. Poly(2,6-dimethylphenylene oxide) or poly(2,6-dimethylphenylene ether) is preferably used as poly(arylene ether) (for properties and preparation see Ullmann's Encyclopedia of is Industrial Chemistry, Vol. A21, 5th Edition, B. Elvers, S. Hawkins and G. Schulz (Editors), VCH Publishers, Weinheim-New York 1992, p. 605 ff.).
The expression sulfur-containing polymers comprises all polymers which contain at least one arylene thioether unit (--Ar--S--; Ar: arylene). The arylene groups can be composed of mononuclear or polynuclear aromatics. The arylene groups are composed of at least one 5- or 6-membered ring which can contain one or more heteroatoms and can be unsubstituted or substituted. Heteroatoms are, e.g. nitrogen or oxygen, substituents are, e.g. linear or branched alkyl groups. The sulfur-containing polymers, apart from sulfur
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Frank Georg
Schleicher Andreas
Von Eysmondt Jorg
Spitzer Robert
Ticona GmbH
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