patent application entitled "Method and Apparatus for Filtering Volatile Organic Compounds" (Moore), Serial No.

Unknown, filed October 23, 1996, which is a file wrapper continuation of U.S. patent application Serial No.

08/557,375, filed November 13, 1995, which is a file wrapper continuation of U.S. patent application Serial No.

08/292,461, filed August 17, 1994, now abandoned. The disclosures of the above applications are incorporated herein in their entirety by reference.

FIELD OF THE INVENTION This invention relates generally to a method and apparatus for rejuvenating contaminated filter elements, and particularly to a method and apparatus for rejuvenating contaminated filter elements laden with contaminants from air streams.

BACKGROUND OF THE INVENTION Volatile organic compounds (e.g., benzene, toluene, trichloroethylene, and the like) found in the air streams of paint spray or other coating operations and in corrosion control operations are harmful to the environment. Due to high cost, many operations do not have apparatus for effectively removing volatile organic compounds from airstreams and thus are forced to discharge contaminated air to atmosphere rather than recirculating the air. When air is discharged to atmosphere, energy must be expended in heating or cooling make-up air.

Volatile organic compounds also are present in air circulated in buildings which experience so-called building related illness and sick building syndrome and also in air which is brought into or recirculated in vehicle passenger compartments. See e.g., Collins et al.,

Ventilation '85, 859-870 (1986); Turk, ASHRAE Journal, 35- 37 (1993). Previously, there has been no satisfactory provision in these applications for economical removal of the volatile organic compounds and the odor resulting therefrom.

Air in an automobile cabin can be contaminated with volatile organic or inorganic compounds such as carbon monoxide, methane, butane, hydrogen sulfide, sulfur dioxide, formaldehyde, toluene, benzene, and the like.

Whether the air in the automobile cabin is being recirculated or brought in from outside, the quality of the air in the cabin can deteriorate very rapidly leading to the discomfort and ill health of the occupants.

Consumers are demanding better cabin environments in their automobiles. Automakers are attempting to address this demand by providing cabin air filters.

Odor control cabin air filters generally contain a sorbent such as activated carbon, zeolites, or oxidizing catalysts. Once this air filter gets saturated with contaminants from the outside or within the cabin environment, the sorption efficiency and capacity of the filter is diminished. Therefore, there is a need for a method and apparatus for efficient regeneration of the used or spent sorbent of the filter. Regeneration is generally carried out by applying heat to the sorbent.

Thus, the sorbent either releases the contaminants when heated to elevated temperatures or oxidizes them to harmless products such as carbon dioxide and water vapor.

One possible way of regenerating the sorbent is to carry out the heating in situ by directing power to the filter element when the filter has been saturated. This method, however, has the disadvantage that it puts a heavy power demand on the automobile battery or alternator. See e.g., Gadkaree et al., Amer. Filtr. Sep. Soc. Annual Mtg., Valley Forge, 89-92 (April 24, 1996). A more convenient method is therefore needed so that all types of automobiles can enjoy the benefits of clean cabin air.

SUMMARY OF THE INVENTION The foregoing needs have been fulfilled to a great extent by the present invention which provides an apparatus and a method for the efficient regeneration of air filters such as automobile cabin air filters, paint spray air filters, and the like.

The present invention provides an apparatus or a device for rejuvenating a contaminated filter element containing a sorbent laden with one or more contaminants, the device comprising in combination a housing to accommodate the filter element and an oxidizing means to oxidize the contaminants to oxidized products, the housing having an inlet for supplying a carrier gas, an outlet for releasing the oxidized products, a heating means to supply heat to the sorbent and a means for flowing the carrier gas through the inlet to the filter element and flowing the oxidized by-products from the filter element to the outlet.

The present invention further provides a device for rejuvenating a contaminated filter element containing an oxidizing catalyst or sorbent laden with contaminants, the device comprising a housing to accommodate the filter element, the housing having an inlet for supplying a carrier gas and an outlet for releasing the oxidized products resulting from the oxidation of said contaminants, and a means for flowing the carrier gas through the inlet to the filter element and flowing the oxidized by-products from the filter element to the outlet.

The present invention further provides methods of rejuvenating the filter elements using the devices of the present invention.

These and other objects and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. While the invention is

susceptible of various modifications and alternative constructions, certain illustrated embodiment hereof has been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific form disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions and equivalents falling within the spirit and scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a top plan view of a new and improved filter incorporating the unique features of the present invention with successive layers of the filter being broken away to show underlying layers.

Figure 2 is a fragmentary cross-section taken substantially along the line 2-2 of Figure 1.

Figure 3 is a schematic of an embodiment of the rejuvenating device used in a single option process wherein desorbing is accomplished by current directed through the filter element.

Figure 4 is a schematic of another embodiment of the rejuvenating device wherein (i) in a single option process, the desorbing is accomplished by air heated by a heater placed in the duct or (ii) in a double option process, the desorbing is accomplished by air heated by a heater placed in the duct or by current directed through the filter element.

Figure 5 depicts an embodiment of the filter element that can be rejuvenated using the rejuvenating device of the present invention.

Figure 6 depicts another embodiment of the rejuvenating device of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS This invention relates to certain methods and devices for rejuvenating filter elements which have been

contaminated with certain volatile contaminants such as volatile organic and inorganic compounds.

This invention also relates to a method and apparatus for filtering contaminants from air. More particularly, the invention relates to the filtration of airstreams through the use of a room temperature adsorbent capable of adsorbing certain odoriferous components in the air.

The present invention also provides a filter for filtering contaminants present in a gas such as air comprising a matrix made of high temperature-resistant material and defining a plurality of cells, an adsorbent at least partially filling the cells, screens made of high temperature-resistant material on opposite sides of the matrix and retaining the adsorbent in the cells while permitting the gas to flow through the matrix whereby the contaminants are captured by the adsorbent when the latter is at ambient temperature, and a means for periodically heating in situ the adsorbent to a predetermined temperature ranging between 250 degrees F and 1000 degrees F.

The air filter 10 of the present invention illustrated in Figures 1-2 utilizes a matrix 11 made of high temperature-resistant material and defining a plurality of cells 12. A particularly advantageous matrix structure is the so-called honeycomb in which a substantial majority of the cells are six-sided, three sides of each cell being defined by one strip of material while the remaining three sides are defined by a second strip abutting the first strip at spaced locations. The ends of the strips are connected, e.g., by welding, to frame members 14. Preferred materials for the strips and the frame members include stainless steel, copper, or nichrome, or alloys thereof.

In accordance with the invention, the cells 12 of the honeycomb matrix 11 are at least partially filled with an adsorbent 15 which is capable of adsorbing volatile

organic compounds in an ambient temperature airstream and which, when heated, purges itself of the captured compounds. When the air being filtered is brought in from outside, recirculated, or when conditions dictate that air discharged to atmosphere be free of volatile organic compounds, the adsorbent that is used can be a catalyst which is capable when heated of propagating catalytic oxidation of the captured compounds and releasing the contaminants as harmless carbon dioxide and water vapor.

When the adsorbent 15 is a catalyst, various precious metal catalysts such as palladium, platinum, gold, silver, or the like may be employed. From an economical standpoint, however, a preferred catalyst can be a base metal catalyst and more specifically is a mixture of manganese dioxide and copper oxide. Other base metal catalysts include iron oxide, cobalt oxide, nickel oxide, and silver oxide, which may be used alone or in combination. One particularly well-suited catalyst of this type is that sold under the trade designator HOPCALITEa by the Callery Chemical Division of Mine Safety Appliance, Inc. HOPCALITE is granular in nature, and that which is used is 4 x 8 or 8 x 14 U.S. sieve size or mixtures thereof.

After the honeycomb matrix 11 has been fabricated, a gas pervious and high temperature-resistant sheet or screen 17 of sufficient mesh to retain the catalyst 15 or other adsorbent is brazed to the underside of the frame members 14 of the honeycomb. The cells 12 then are filled with the adsorbent, after which a second screen 18 is brazed to the top sides of the frame members to retain the catalyst in the cells.

When the filter 10 is used, for example, as a filter in a paint spray operation, a paint-laden airstream is directed through the screens 17 and 18 and the intervening catalyst 15. When the filter is at room temperature, the catalyst adsorbs volatile organic components such as toulene, benzene, methyl ethyl ketone, ethyl alcohol and

isooctane in the airstream. Periodically, the catalyst is typically heated to a temperature ranging between 250 and 1000 degrees F, and preferably between 250 and 600 degrees F, and in certain embodiments more preferably between 360 and 600 degrees, to cause the catalyst to propagate catalytic oxidation of the captured volatile organic components and to cause the components to be driven from the catalyst as carbon dioxide and water vapor. One preferred way of heating the catalyst is to apply a voltage directly to the honeycomb 11 to cause the grids of the honeycomb to act as electrical resistance heating elements around the catalyst. The filter 10 is maintained at the purge temperature (preferably about 500 degrees F) for a short period of time, e.g., for a period of from about five to about ten minutes, and then is allowed to cool to ambient temperature. Upon cooling, the rejuvenated catalyst again becomes effective to adsorb volatile organic components. The frequency with which the catalyst is heated depends upon the flow rate of the airstream and the concentration of contaminants therein and may be controlled by appropriate sensors acting in conjunction with a microprocessor. The catalyst can also be heated by induction or radiant heating.

By virtue of the catalyst 15 converting the volatile organic compounds into their basic constituents, the air which is cleaned by the filter 10 may be recirculated in the building and need not be exhausted to atmosphere.

Accordingly, heating and cooling costs are reduced while avoiding atmospheric pollution. Also, the filter reduces the lower explosive limit in paint spray and corrosion control operations and thus promotes a safer working environment.

The filter 10 of the invention may be used in commercial building HVAC systems in OEM units and also is useful for filtering the air (either fresh or recirculated) in the passenger compartment of a vehicle.

When the filter is used in a vehicle, it resides at

ambient temperature and in an adsorption stage during the majority of time. When the filter requires rejuvenation, a damper is closed to shut off the flow of air through the filter and then the filter is heated, either electrically by the electrical system of the vehicle or by means of the exhaust or other heat generated by the engine. After the filter is allowed to cool, the damper is re-opened to resume the flow of air to the passenger compartment via the filter. The filter thus is very effective to remove odor from the air introduced into or recirculated in the passenger compartment.

In certain instances, the adsorbent 15 need not be a catalyst but may, for example, be a room temperature adsorbent such as activated carbon. The latter material will adsorb volatile organic compounds at ambient temperature and, when heated to a temperature of at least 250 degrees F, will drive off the contaminants in order to rejuvenate itself. In the case of activated carbon, however, the volatile organic compounds are not oxidized but instead are merely driven from the adsorbent in their original volatile form when the adsorbent is heated.

Accordingly, activated carbon is effective as an adsorbent only in those cases where the air may be exhausted to atmosphere or to another filtration system during the purging cycle. In an embodiment of the present invention, the activated carbon can be contained in a tray made of a high temperature-resistant material or may be a carbon impregnated honeycomb on a ceramic or carbonized monolith.

See e.g., Gadkaree et al., supra. In a preferred embodiment, the activated carbon is contained in a galvanized steel tray having the dimension of about 24 x 24 x 1 inches, such as the media tray shown in Figure 5.

The present invention further provides a method of filtering contaminants from a contaminated gas, the method comprising the steps of: (A) flowing the gas through a filter comprising (i) a matrix made of high temperature- resistant material defining a plurality of cells, (ii) a

catalyst at least partially filling the cells, the catalyst being capable of oxidizing the contaminants to carbon dioxide and water vapor, and (iii) gas pervious sheets of high temperature-resistant material on opposite sides of the matrix, and retaining the catalyst in the matrix; (B) closing off the flow of the gas through the filter while the catalyst is at ambient temperature whereby the contaminants are adsorbed by the catalyst; (C) heating the catalyst to a temperature of at least 250 degrees F to cause the catalyst to release the adsorbed contaminants; and (D) reopening the flow of the gas through the filter. In certain embodiments of the invention, the catalyst may be heated to a temperature of at least 360 degrees F to cause the catalyst to release the adsorbed contaminants.

The present invention further provides a method of filtering contaminants from a contaminated gas, the method comprising the steps of (A) providing a filter comprising (i) a matrix made of high temperature-resistant material and defining a plurality of cells, wherein a substantial majority of the cells are six-sided and three of the six sides are made of one strip of high-temperature resistant material, (ii) a granular activated carbon adsorbent at least partially filling the cells, and (iii) pervious sheets of high-temperature resistant material on opposite sides of the matrix; (B) flowing the gas through the filter while the adsorbent is at ambient temperature whereby the contaminants are adsorbed by the adsorbent; and (C) periodically heating the adsorbent to a temperature of at least 250 degrees F to cause the adsorbent to release the adsorbed contaminants, wherein the periodical heating is carried out by applying a voltage directly to the high-temperature resistant material. In certain embodiments, the adsorbent should be heated to a temperature of at least 360 degrees F to cause the adsorbent to release the adsorbed contaminants.

The present invention further provides a method of filtering contaminants from a contaminated gas, the method comprising the steps of: (A) flowing the gas through the filter comprising (i) a matrix made of high temperature- resistant material and defining a plurality of cells, wherein the cells can be up to six-sided, (ii) a granular activated carbon absorbent at least partially filling the cells, and (iii) pervious sheets of high temperature- resistant material on opposite sides of the matrix; (B) flowing the gas through the filter while the absorbent is at ambient temperature whereby the contaminants are adsorbed by the adsorbent; and (C) heating the adsorbent to a temperature of at least 2500 F, in certain embodiments to at least 3600 F, to cause the adsorbent to release the adsorbed contaminants. The periodic heating can be carried out by radiant, induction, or resistive heating.

In a preferred embodiment, the matrix is four-sided.

An embodiment of the filter that can be used to filter contaminants from a contaminated gas by the method of the present invention includes a media tray shown in Figure 5. In Figure 5 is shown a substantially rectangular media tray designed to hold an adsorbent medium such as activated carbon or an oxidizing medium such as potassium permanganate. The channel frame member 51 holds the gas pervious sheets 54 and the adsorbent together.

The frame members are provided with spacers 52 and 53. The spacers are provided, among others, to prevent the filter element from buckling under the weight of the adsorbent. The gas pervious sheets have perforations 55 suitable for the passage of a gas stream through and for holding the adsorbent particles 50. The perforations are preferably arranged so that the centers of the perforations on the first sheet are staggered with respect to those on the second sheet.

The filter element can be of any suitable size. For example, the element could be substantially rectangular

having the dimensions of approximately 28 inch x 24 inch x 1 inch. The spacers can be of any suitable thickness.

For example, the spacer can be about 0.018 inch thick.

The material of construction can be any suitable material and of any suitable thickness. For example, the material of construction can be stainless steel or galvanized rolled steel. The frame member can have any suitable thickness, e.g., about 20 gauge to about 30 gauge. In some embodiments of the present invention, the frame member can have a thickness of about 26 gauge. The perforations can be of any suitable size and would depend on the particle size of the adsorbent. The adsorbents are typically sized in 4x6, 4x8, 6x12, or 8x16 U.S. Sieve sizes, or combinations thereof, according to ASTM D2862- 92, Standard Test Method for Particle Size Distribution of Granular Activated Carbon, vol. 15.01 (1994). The filter element of the present invention can be employed in combination with other filter elements, for example, a prefilter. Thus, it is preferred to prefilter the contaminated gas stream so that it is substantially free of particulates. The gas stream can be prefiltered using known filters to at least below about 30% ASHRAE.

The present invention further provides a device for rejuvenating a contaminated filter element containing a sorbent laden with one or more contaminants, the device comprising in combination a housing to accommodate the filter element and an oxidizing means to oxidize the contaminants to oxidized products, the housing having an inlet for supplying a carrier gas, an outlet for releasing the oxidized products, a heating means to heat the sorbent and a flowing means for flowing the carrier gas through the inlet to the filter element and flowing the oxidized products from the filter element to the outlet. It is preferred that the contaminants are substantially oxidized products, and it is further preferred that the contaminants are completely oxidized to oxidized products, such as carbon dioxide and water vapor or oxidized to a

degree that any desorbed contaminant is below the OSHA personal exposure limit (PEL) for the contaminant. For example, the PELs for benzene and toluene are, respectively, 1 ppm and 200 ppm.

The present invention further provides a device for rejuvenating a contaminated filter element containing an oxidizing catalyst laden with contaminants, the device comprising a housing to accommodate the filter element, the housing having an inlet for supplying a carrier gas and an outlet for releasing oxidized products resulting from the oxidation of the contaminants.

The contaminants that can be captured in the filter element includes volatile organics and inorganics. The volatile organics can include a large number of absorbable materials. For example, they can be hydrocarbons, cyclic, branched, or linear alkanes, alkenes, and acetylenes.

Preferred examples of alkanes include benzene, toluene, xylenes, and isooctane The organic compound may be aromatic, aliphatic, or combinations thereof. The organics may also include oxygenated hydrocarbons such as alcohols, ethers, aldehydes, ketones, glycols, or complex carbohydrates. Particular examples of alcohols include methanol and ethanol. Particular examples of ketones include methyl ethyl ketone and methyl isobutyl ketone.

The organics may also include nitrogen containing compounds such as amines and ammonia, and sulfur containing compounds such as mercaptans and sulfides, and sulfites.

The filter element containing a sorbent or oxidizing catalyst laden with contaminants, such as the car cabin filter element, can be rejuvenated off-line by the device of the present invention.

The above devices can be placed in rejuvenating stations such as service stations, and, when the automobile is brought in for any repair or maintenance service at suitable time intervals such as after 12,000 miles or 18,000 miles, the filter element can be removed

from the automobile, rejuvenated, and replaced in the automobile. The off-line rejuvenation method is further advantageous in that the high energy demand required to rejuvenate the filter element is not charged to the engine or the battery of the automobile as in the in situ method.

Embodiments 30 and 40 of the rejuvenating device are schematically shown in Figures 3 and 4, respectively. The device comprises a housing 37 or 43, having an intake 31 or 41 for taking in the carrier gas. The direction of flow of the carrier gas is indicated by arrow 35 or 46.

Any suitable carrier gas can be used. Examples of carrier gas include gases such as filtered air, nitrogen, or inert gases such as helium, argon, neon, and the like and combinations thereof. An advantage of the rejuvenating method of the present invention is that the gases are diluted by the carrier gas and therefore the concentration of any residual contaminant in the effluent is minimal. A further advantage results when air is used as the carrier gas, in which case the effluent is diluted by air which is acceptable to the environment, and not by a gas which could cause an environmental concern.

The rejuvenating device preferably includes a flowing means to deliver the carrier gas to the filter element.

Any suitable flowing means to deliver the carrier gas can be employed. In certain embodiments, a blower 32, 42 or a fan and motor can be used. In some other embodiments, a fan and motor can be arranged in a draw-through arrangement at the outlet 36, 47.

The filter elements 33, 44 can be heated by applying a voltage to the elements directly, or by providing a heated gas. The gas can be heated, e.g., by a heater 48 placed in the duct.

Figure 6 depicts the schematic of another embodiment 60 of the rejuvenating device of the present invention.

The device comprises an intake 61 for the carrier gas whose flow direction is indicated by arrow 66. The device accommodates the filter element to be rejuvenated 64 and

the oxidizing catalytic filter element 65. The device includes one or more heaters 62 placed in the duct to produce suitable high temperatures, preferably up to at least 500 degrees F. The device also includes temperature sensors, e.g., a temperature sensor 63 placed upstream of the filter element to be rejuvenated. The rejuvenating device further includes one or more heaters that can produce high temperatures, preferably up to about 1000 degrees F and more preferably up to about 1200OF, in the oxidizing catalytic filter element and suitable temperature sensors. Optionally, an effluent quality monitor such as a photoionization detector 67 can be placed downstream of the oxidizing catalytic filter element.

The filter element to be rejuvenated can be of any suitable size or shape known to those of ordinary skill in the art. For example, it can be a rectangular filter element with a matrix of hexagonal cells filled with a sorbent. An example of the filter is shown in Figure 5.

Alternatively, the filter element can be a porous ceramic honeycomb impregnated with a sorbent, or the filter element can be a honeycomb material which is composed of the sorbent itself. See, e.g., Gadkaree et al., supra.

Other shapes, sizes, and designs known to those of ordinary skill in the art also can be employed. See, e.g., U.S. Patents 5,308,457, 3,675,394, 3,925,248, 3,568,416, 3,590,561, and 3,747,308, the disclosures of which are hereby incorporated by reference in their entirety.

Any suitable sorbent material can be used in the filter element. Examples of sorbents include activated carbons, molecular sieves such as carbon molecular sieves and zeolites, oxidizing catalysts such as catalysts containing noble metals or metal oxides of Groups IB, IIB, VB, VIB, VIIB, and VIII, and preferably of Group VIII.

Particular examples include platinum, palladium, rhodium, and combinations thereof, gold, silver, or combinations

thereof, and base metal catalysts such as those containing manganese, copper, or combinations thereof. In some embodiments, the catalyst can comprise KMnO4. Any suitable zeolite can be used. Examples of zeolites include the mordenite type, Beta PB type, Y type, USY type, L type, and ZSM-5 type zeolites.

In certain embodiments of the present invention, in order to carry out the oxidation of the contaminants, sufficient oxygen must be present in the catalyst environment. Therefore, the carrier gas typically contains at least about 10% by volume oxygen, typically in the range of about 10 to about 30% by volume, and preferably in the range of about 20% by volume. It is further preferred that there is an excess of oxygen to insure complete oxidation of the contaminants. Oxygen also may be needed during the heat up.

The rejuvenating device is constructed so that the filter element to be rejuvenated 33 or 44 and an oxidizing catalytic filter element 34 or 45 can be accommodated in the duct of the housing. The housing can be constructed out of any suitable material capable of withstanding the elevated temperatures encountered in the rejuvenation.

Typically, the housing can be built out of stainless steel, aluminum, copper, galvanized steel, fiberglass, and preferably, stainless steel. The housing can be constructed out of about 0.10-0.30 inch thick metal or alloy. The housing can have any suitable cross-section.

For example, it can have a substantially circular, oval, triangular, square, rectangular, trapezoidal, pentagonal, hexagonal, and the like cross-section.

The rejuvenating device of the present invention can further include insulation to prevent heat loss, probes such as thermocouples, pressure gages, and flow meters, for monitoring temperatures, pressures, and gas flow rates, as well as probes for measuring the extent of completion of oxidation of the volatile organic contaminants. Any suitable probe for monitoring the

conversion of volatile organic compound to carbon dioxide can be used, for example, a gas chromatograph, a mass spectrometer, or a combination thereof. Any suitable detector can be employed, for example, a flame ionization or a photoionization detector can be employed. The device can further include suitable provisions for opening and closing of the device to permit ingress and egress of the filter elements.

The carrier gas supplied to the filter element can be heated to a temperature suitable for desorbing the adsorbed contaminants. For example, when activated carbon is used as the adsorbent, the carrier gas can be at a temperature of from about 1300F to about 1000OF, preferably at a temperature of from about 1300F to about 600OF, and more preferably at a temperature of from about 250"F to about 500OF.

The rejuvenating device of the present invention can be operated in any suitable manner, for example, a single option process or a double option process. In a single option process, the desorber can be heated by passing over a heater 48 provided within the rejuvenating device. In an alternative single option process, unheated carrier gas is supplied to the filter element which is heated by applying a voltage directly to the filter element.

In a double option process, the filter rejuvenating device shown in Figure 4 can be constructed so that either of the aforesaid two single option processes can be practiced. The filter element can be heated by resistive heating or induction heating using any suitable arrangement known in the art, e.g., a buss bar arrangement. For a discussion of radiant and induction heating, see Hottel et al., Radiative Heat Transfer; and Lewis, Induction Heating; both from Mark's Standard Handbook for Mechanical Engineers, McGraw Hill (1967).

The contaminants desorbed thus are captured and oxidized by the adsorbing catalytic filter element 34 or 45. If the filter element to be rejuvenated contains an oxidizing

catalyst, then the rejuvenating device need not be equipped with an oxidizing catalyst filter.

The oxidizing catalytic filter element 34 or 45 can include any suitable catalytic material such as a noble metal catalyst or a base metal catalyst, as discussed earlier. Heat to the catalytic filter element can be provided by any of the methods discussed above, including resistive and induction heating of the filter itself directly, by flowing a heated carrier gas, or by heating the carrier gas by a heater placed within the housing of the device. The contaminants, which have been substantially or fully oxidized to an effluent stream that contains carbon dioxide and water vapor can be released to the atmosphere through outlets 36 and 47. Or alternatively, the effluent can be sent to a heat exchanger to recover any residual heat prior to releasing to the environment. If desired, the carbon dioxide can be removed by using scrubbers known to those of ordinary skill in the art including alkali or amine scrubbers. In certain instances, it may be possible to reuse or recycle the effluent, thereby taking advantage of the residual heat present in the effluent gas stream.

The present invention further provides a method of rejuvenating a filter element containing a sorbent laden with contaminants comprising (a) placing the filter element in a rejuvenating device comprising in combination a housing to accommodate the filter element, a heating means to supply heat to the sorbent, a flowing means for supplying a carrier gas to the filter element, and an oxidizing catalytic filter element which is adapted to catalytically oxidize the contaminants; (b) flowing a carrier gas to the filter element; (c) catalytically oxidizing the contaminants; (d) releasing the oxidized products; and (e) recovering the rejuvenated filter element.

The present invention further provides a method of rejuvenating a filter element containing an oxidizing

catalyst laden with contaminants comprising (a) placing the filter element in a rejuvenating device comprising in combination a housing to accommodate the filter element, a heating means to supply heat to the sorbent, a flowing means to supply a carrier gas to the filter element; (b) flowing a carrier gas to the filter element; (c) catalytically oxidizing the contaminants to oxidized products; (d) releasing the oxidized products; and (e) recovering the rejuvenated filter element.

The present invention further provides a method of removing volatile organic compounds from an airstream comprising (a) providing a filter element so as to adsorb the contaminants from the airstream; (b) removing the filter element after a predetermined period of time; (c) rejuvenating the filter element in a rejuvenating device comprising in combination a housing to accommodate the filter element, a means to supply heat to the filter element, a means for supplying a carrier gas to the filter element so as to release the contaminants from the filter element, and an oxidizing catalytic filter element which is adapted to catalytically oxidize the contaminants released from the filter element to oxidized products; (d) flowing a carrier gas through the filter element; (e) catalytically oxidizing the contaminants; and (f) releasing the oxidized products.

The filter element to be rejuvenated can originate from an automobile as discussed above, or it can originate from a HVAC facility, a paint spray booth or operation, bake oven, dry-cleaning exhaust filtering operation, print shops, and other industrial and domestic applications.

All of the references cited herein including patents, patent applications, and publications are hereby incorporated in their entireties by reference.

While this invention has been described with an emphasis upon the preferred embodiment, it will be obvious to those of ordinary skill in the art that variations of the preferred embodiment may be used and that it is

intended that the invention may be practiced otherwise than as specifically described herein Accordingly, this invention includes all modifications encompassed within the spirit and scope of the invention as defined by the following claims.