Compositions for abatement of volatile organic compounds and apparatus and methods using the same

Apparatus for abatement of volatile organic compound pollution in an air stream defines an air flow path through the apparatus for such air stream and comprises:

• (a) an abatement composition for abatement of volatile organic compounds (“VOCs”) comprising (i) a protective adsorbent selected from the group consisting of zeolites having a minimum pore aperture of at least about 6.5 Ångstroms and which are effective within an adsorption temperature range (A) to adsorb first VOCs and (B) to pass therethrough second VOCs of smaller molecular dimensions than the first VOCs, but excluding from the group zeolites containing one or both of silver and copper cations in a mounts effective to enhance adsorption of the second VOCs on the protective adsorbent;
• (ii) a second adsorbent selected from the group consisting of one or more of silver-containing zeolites and copper-containing Y zeolite and effective, within the adsorption temperature range, to adsorb, at least in the absence of moisture, the second VOCs;
• (iii) a catalytically effective amount of a protective oxidation catalyst disposed relative to the protective and second adsorbents so as to contact and, under oxidation conditions as defined below, promote the oxidation of first VOCs prior to the first VOCs' contacting the second adsorbent;
• and (iv) a second oxidation catalyst intimately intermingled with the second adsorbent, and present in an amount effective to promote, under the oxidation conditions, oxidation of second VOCs retained on the second adsorbent, the intermingled second oxidation catalyst and second adsorbent being disposed to contact the effluent from the protective adsorbent and protective oxidation catalyst;
• the oxidation conditions comprising an oxidation temperature range which is hotter than the adsorption temperature range, both the adsorption and oxidation temperature ranges lying in an operating temperature range of between about 20 to 500° C.;
• (b) a treatment zone within which the abatement composition is disposed;
• (c) a heat exchanger disposed in heat exchange relationship with one or both of (i) such air stream at or upstream of the treatment zone;
• and (ii) the abatement composition, and
• (d) a temperature control device operatively associated with the heat exchanger to periodically vary, between the adsorption temperature range and the oxidation temperature range, the temperature of one or both of (i) the air stream in the treatment zone and (ii) the abatement composition.

A method for abatement of volatile organic compound pollution comprises treating an air stream containing volatile organic compounds (“VOCs”) by contacting the air stream with an abatement composition comprising (i) a protective adsorbent selected from the group consisting of zeolites having a minimum pore aperture of at least about 6.5 Ångstroms and which are effective, within an adsorption temperature range, (A) to adsorb first VOCs and (B) to pass therethrough second VOCs of smaller molecular dimensions than the first VOCs, but excluding from the group zeolites containing one or both of silver and copper cations in amounts effective to enhance adsorption of the second VOCs on the protective adsorbent;

• (ii) a second adsorbent selected from the group consisting of one or more of silver-containing zeolites and copper-containing Y zeolite and effective, within the adsorption temperature range, to adsorb, at least in the absence of moisture, the second VOCs;
• (iii) a catalytically effective amount of a protective oxidation catalyst disposed relative to the protective and second adsorbents so as to contact and, under oxidation conditions defined below, promote the oxidation of first VOCs prior to the first VOCs' contacting the second adsorbent;
• and (iv) a second oxidation catalyst intimately intermingled with the second adsorbent, and present in an amount effective to promote, under the oxidation conditions, containing oxidation of second VOCs retained on the second adsorbent, the intermingled second oxidation catalyst and second adsorbent being disposed to contact the effluent from the protective adsorbent and protective oxidation catalyst;
• the oxidation conditions comprising an oxidation temperature range which is hotter than the adsorption temperature range, both the adsorption and oxidation temperature ranges lying in an operating temperature range of between about 20 to 500° C., and the method comprising the steps of:
• (a) flowing the air stream in series to first contact it with the protective adsorbent and then to contact it with the second adsorbent;
• and
• (b) periodically varying between the adsorption temperature range and the oxidation temperature range the temperature at which the air stream contacts the protective and second adsorbents;
• whereby, during the oxidation conditions, oxidation of desorbed first VOCs is promoted by the first catalytic composition and second VOCs migrate from adsorption sites on the second adsorbent to catalytic sites on the second adsorbent, at which catalytic sites oxidation of the second VOCs is promoted.