Abstract: Nitrogen oxides and low molecular weight hydrocarbons are removed from air by subjecting the air to a temperature swing adsorption process using as the adsorbent a composite zeolite product containing both zeolite type A and zeolite type X. The composite zeolite product is prepared by crystallizing a sodium ion- or sodium ion- and potassium ion-containing alumina-silica hydrogel under conditions which result in the production of a zeolitic composite which contains both zeolite type A and zeolite type X crystal domains. In a preferred embodiment, calcium ions constitute a substantial number of the composite's exchangeable cations and the type X portion of the composite zeolite product has a silicon-to-aluminum atomic ratio in the range of 0.9 to less than 1.15. The nitrogen oxide- and hydrocarbon-selective adsorbent can be incorporated into an atmospheric air prepurification plant downstream of a water vapor-selective adsorbent and a carbon dioxide-selective adsorbent.
Type:
Grant
Filed:
August 28, 2000
Date of Patent:
July 9, 2002
Assignees:
The BOC Group, Inc., Chemiewerk Bad Köstritz GmbH
Inventors:
Martin Bülow, Adeola F. Ojo, Frank R. Fitch, Baldur Unger, Alfons Brandt
Abstract: Zeolites exchanged with lithium cations and polyvalent cations are prepared by first partially ion-exchanging a sodium-containing zeolite, a potassium-containing zeolite or a sodium- and potassium-containing zeolite with polyvalent cations, then heat-treating the partially polyvalent cation-exchanged zeolite, then ion exchanging the heat-treated zeolite with ammonium cations, and then reacting the ammonium cation-exchanged zeolite with a water-soluble lithium compound under conditions which result in the removal of ammonia from the reaction zone.
Type:
Grant
Filed:
February 10, 2000
Date of Patent:
June 18, 2002
Assignees:
The BOC Group, Inc., Chemiewerk Bad Köstritz GmbH
Inventors:
Alfons Brandt, Baldur Unger, Hartmut Tschritter, Martin Bülow, Frank R. Fitch, Adeola F. Ojo