(19)
(11)EP 1 624 948 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
14.03.2012 Bulletin 2012/11

(21)Application number: 04751527.5

(22)Date of filing:  07.05.2004
(51)Int. Cl.: 
B01D 53/04  (2006.01)
F02M 25/08  (2006.01)
F02M 35/10  (2006.01)
(86)International application number:
PCT/US2004/014163
(87)International publication number:
WO 2004/101115 (25.11.2004 Gazette  2004/48)

(54)

VOLATILE HYDROCARBON ADSORBER UNIT

ADSORBEREINHEIT FÜR FLÜCHTIGE KOHLENWASSERSTOFFE

MODULE D'ADSORPTION D'HYDROCARBURES VOLATILES


(84)Designated Contracting States:
AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IT LI LU MC NL PL PT RO SE SI SK TR

(30)Priority: 12.05.2003 US 435860
22.04.2004 US 830351

(43)Date of publication of application:
15.02.2006 Bulletin 2006/07

(73)Proprietor: BASF Catalysts LLC
Florham Park, NJ 07932 (US)

(72)Inventors:
  • FOONG, John, S.
    Piscataway, NJ 08854 (US)
  • HOKE, Jeffrey, B.
    North Brunswick, NJ 08902 (US)

(74)Representative: Fisher, Adrian John et al
Carpmaels & Ransford One Southampton Row
London WC1B 5HA
London WC1B 5HA (GB)


(56)References cited: : 
EP-A- 1 110 593
WO-A-2004/033889
US-A- 5 051 244
US-A1- 2002 043 156
US-A1- 2004 069 146
US-B1- 6 432 179
WO-A-97/11769
DE-A- 10 102 604
US-A- 5 125 231
US-A1- 2004 050 252
US-B1- 6 171 556
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    Field of the Invention



    [0001] This invention relates to a unit for adsorbing volatile hydrocarbon fuel vapors in the air induction system of an automobile. These vapors are generated after epguic shut-off and, if not adsorbed, will flow out of the air cleaner into the atmosphere.

    The Related Art



    [0002] Systems and methods fur trapping volatile hydrocarbon fuel vapors, fmm the fuel tank of an automobile are well known. Such systems are typically referred to as evaporative loss control systems and rely on a canister containing a regenerable adsorbent such as activated charcoal. The adsorbent adsorbs the volatile hydrocarbons and when engine operating conditions arc appropriate for combusting the trapped hydrocarbons, a stream of air is passed through the adsorbent to desorb the adsorbent and the hydrocarbon-laden air stream is passed into the engine where the desorbed hydrocarbons are combusted. Exemplary U.S. patents disclosing evaporative loss control systems include the following: 4,877,001; 4,750,465; and 4,308,841.

    [0003] Systems and methods for adsorbing uncombusted hydrocarbons in the exhaust gas stream of an automobile are also well known. These systems and methods are particularly useful for adsorbing uncombusted hydrocarbons emitted during the cold start of the automobile engine.

    [0004] For example, U.S. Patent No. 4,985,210 is directed to an exhaust gas purifying apparatus for an automobile employing a three-way catalyst with either a Y-type zeolite or a mordernite used in a hydrocarbon trap upstream of the three-way catalyst. In the embodiment of FIG. 2 of U.S. Patent No. 4,985,210, a bed of activated carbon is disposed upstream of an adsorbent zone. A solenoid-operated valve mechanism serves to direct the exhaust gas stream either through or around the activated carbon bed, depending on the temperature of the exhaust gas stream, and then through the adsorbent zone and the three-way catalyst.

    [0005] U.S. Patent No. 5,051,244 is directed to a process for treating an engine exhaust gas stream in which the gas stream is directed through a molecular sieve in an adsorbent zone during the cold-start phase of engine operation. When the hydrocarbons begin to desorb, the adsorbent zone is by-passed until the catalyst is at its operating temperature, at which point the gas stream is again flowed through the adsorbent zone to desorb hydrocarbons and carry them to the catalyst zone. A paper by M. Heimrich, L. Smith and J. Kotowski entitled Cold-Start Hydrocarbon Collection for Advanced Exhaust Emission Control, SAE Publication Number 920847, discloses an apparatus which functions in a manner similar to that of U.S. Patent No. 5,051,244.

    [0006] U.S. Patent No. 5,125,231 discloses an engine exhaust system for reducing hydrocarbon emissions, including the use of beta zeolites as hydrocarbon adsorbents. Zeolites having a silica/alumina ratio in the range of 70/1 to 200/1 are preferred adsorbents. The apparatus includes by-pass lines and valves to direct exhaust gases from a first converter directly to a second converter during cold-start operation and when the first converter reaches its light-off temperature, to either by-pass the second converter or recycle effluent from it to the first converter.

    [0007] U.S. Patent No. 5,158,753 discloses an exhaust gas purifying device comprising: a catalyst device installed in the exhaust gas path of an internal combustion engine for treating the exhaust gas of the engine; an adsorbing device installed in the exhaust gas path between the catalyst device and the internal combustion engine, for treating the exhaust gas of the engine. One embodiment includes a heat exchanger for performing heat transfer between the exhaust gas flowing from the internal combustion engine to the adsorbing device and the exhaust gas flowing from the adsorbing device to the catalyst device. Alternatively, the catalyst device includes a catalyst secured in the low-temperature-side gas flow path of a heat exchanger, and the exhaust gas flowing from the internal combustion engine to the adsorbing device is allowed to flow to the high-temperature-side gas flow path of the heat exchanger.

    [0008] U.S. Patent No: 6,171,556 discloses a method and apparatus for treating an exhaust gas stream containing hydrocarbons and other pollutants. The method comprises the steps of flowing the exhaust gas stream through a catalytic member comprising a monolith body having a first catalyst zone and a second catalyst zone therein to contact a catalyst in a first catalyst zone to convert at least some of the pollutants in the exhaust gas stream into innocuous products. The exhaust gas stream is then discharged from the catalytic member and flowed through an adsorbent zone to adsorb at least some of the hydrocarbon pollutants with an adsorbent composition. The exhaust gas stream is discharged from the adsorbent zone and flowed to the second catalyst zone to convert at least some of the pollutants into innocuous products. The exhaust gas stream, so treated, is then discharged to the atmosphere through suitable discharge means. A preferred adsorbent is a zeolite, having a relatively high silica to alumina ratio and a low relative Bronsted acidity. The preferred adsorbent compositions comprise beta zeolites. WO97/11769 discloses the use of a zeolite-binder coating to the external surface of a vehicle to trap hydrocarbon.

    [0009] Systems for adsorbing vapors which would other wise be emitted into the atmosphere from the vehicle's air induction system when the vehicle is shut-off are also well known. U.S. Patent Application Publication US2002/0043156 A1 discloses a housing securing an air filter having an air stream inlet and an air stream outlet. The air filter comprises a filter media disposed on a support that is disposed within, or secured to, the housing and an air permeable hydrocarbon adsorbing material comprising activated carbon e.g. fixed by a binder to the filter media and the support at the air stream outlet end of the filter. The preferred hydrocarbon adsorbent is an activated carbon cloth.

    [0010] EP 1 110 593 A1 is similar to the U.S. Patent Application Publication. The EP Patent Application discloses an air filter assembly including a housing and a plurality of filter layers disposed in the housing. One of the filter layers is a carbon impregnated polyurethane foam layer to remove hydrocarbon vapors diffusing through an air inlet to the filter when the engine is shut-off.

    Object of the Invention



    [0011] It has been found that a significant amount of volatile hydrocarbons from several sources collect in the air induction system of the automobile engine after the engine has been shut off: These hydrocarbons are then discharged into the atmosphere after the engine has been shut off. Prior art systems and methods devote relatively little attention to prevention of the emissions of such hydrocarbons through the air induction system of the engine since the amounts of such emissions are relatively small as compared to the emissions of hydrocarbons from the fuel system and the exhaust gas stream which would pass into the atmosphere if left untreated. Nevertheless, in view of the increasingly stringent federal and state regulations mandating the elimination of all emissions of uncombusted hydrocarbons in the atmosphere to the extent technically feasible, it is desirable to provide equipment to adsorb such hydrocarbons.

    [0012] Accordingly, it is the object of this invention to provide a unit for adsorbing volatile hydrocarbons emitted after the engine his been shut-off, in the air induction system upstream of the engine and thereby prevent the emission of such hydrocarbons into the atmosphere.

    Summary of the Invention



    [0013] The invention provides a system as set out in claim 1 and comprises a unit for adsorbing hydrocarbons emitted into the air induction system of a vehicular engine during engine shut-off.

    Detailed Description of the Invention



    [0014] The system of this invention is particularly suited for adsorbing volatile hydrocarbon fuel vapors that would otherwise be emitted into the atmosphere through the air induction system of an automobile engine after the engine has been shut off. Such fuel vapors emanate from several sources, e.g., residual fuel, puddle, post-run injector, leakage, blowby, hydrocarbons from exhaust gas recycle, oil hydrocarbons from the PCV. etc. It is the goal of this invention to adsorb such fuel vapors to the extent that no more than 0.001 g/day of such fuel vapors are emitted, thereby helping to meet the LEV II and PZEV limits which will he imposed by the California Air Resource Board and the Tier II limits which will but imposed by the Federal government in respect to the 2004 model year automobiles.

    [0015] The volatile hydrocarbon adsorber unit for controlling the emission of volume hydrocarbons from the air inlake system of an engine is positioned in the air intake system such that all air flowing through the engine passes through the unit. The unit comprises a housing having an air inlet and an air outlet. The housing contains a substrate and a defined volatile hydrocarbon adsorber material coated on the surface of the substrate. The material contains a binder that will cause the material to adhere to the surface of the substrate.

    [0016] Desorption of the volatile hydrocarbons adsorbed by the material occurs by passing a clean air stream through the unit and combusting the desorbed hydrocarbons when the engine is in an operating mode, i.e., when the vehicle is in motion and/or is in an idling mode. The adsorption of the volatile hydrocarbons in the unit of the invention will occur at relatively low temperatures, e.g., about -18°C to about 176°C (about 0 to about 350°F) (higher temperatures tend to favor desorption rather than adsorption).

    [0017] The housing for the volatile hydrocarbon adsorbent material may he comprised of a variety of metals or polymers. The selected metal or polymer should, of course, be resistant to the temperatures existing in the air induction system during various engine operating conditions, especially prolonged idling, and preferably have light weight. Of course, the housing must be resistant to oils, fuels, greases, etc. which arc commonly employed for engine operation. The dimensions of the housing is not critical but is dictated by the dimensions of the conduit leading from the air cleaner to the air intake manifold of the engine, since the housing should tightly fit within such conduit (typical oil and hydrocarbon-resistant gaskets may be employed at the end(s) of the housing to insure a vapor tight seal between the outside of the body and the inner wall of the conduit).

    [0018] The housing will have an air inlet and an air outlet and will typically be open at both its ends. The shape of the housing is not critical, i.e., it may be in the shape of a cylinder, triangle, square, rectangle, polygon, etc. The length of the housing is not critical, but typically it will have a length of about 2.64 to about 12.7 cm (about 1 to about 5 inches), a width or diameter of about 2.64 to about 12.7 cm (about 1 to about 5 inches) and a wall thickness of about 0.5 to about 2 mm.

    [0019] Suitable materials for construction of the housing include thermoplastic polymers, thermoset polymers and metals, especially aluminum, a Fe-Cr alloy or a Cr-Al-Fe alloy which are resistant to the temperatures and materials present within the engine compartment (e.g. liquid fuels, fuel vapors, oils, greases, etc.).

    [0020] The adsorption material used for the process of the present invention comprises a hydrocarbon adsorbent disposed on a substrate. The hydrocarbon adsorbent preferably is hydrophobic as well as organophilic (i.e., highly absorptive for organic chemicals). Preferably, the substrate comprises a polymer or a metal such as aluminum, titanium, stainless steel, a Fc-Cr alloy or a Cr-Al-Fc alloy in the form of a sheet, mesh, foil, etc. In order to increase the surface area of the adsorbent, it is desirable that the metal substrate be present in a corrugated mode. Typically, the hydrocarbon adsorbent will be disposed on the substrate in a loading of about 0.012 to about 0.183g/cm3, e.g., 0.076g/cm3 (about 0.2 to about 3 p/in3, e.g., 1.25 g/in3).

    [0021] The hydrocarbon adsorbent comprises a molecular sieve in the form of a natural or synthetic zeolite or a mixture of a natural and a synthetic zeolite, and optionally silica gel, activated carbon or mixtures thereof. The material may be disposed within the housing as a single layer or separate layers of zeolite and silica gel and/or activated carbon. Preferably the material comprises zeolite alone or in admixture with about 5 to about 50 wt.% of an activated carbon having a pore size of about 5 to about 500 angstroms.

    [0022] The molecular sieve is a natural or synthetic zeolite such as faujasite, chabazite, clinoptilolite, mordenite, silicalite, zeolite X, zeolite Y, ultrastable zeolite Y, ZSM zeolite, offretite, of a beta zeolite.

    [0023] Typically, the substrate is initially coated with a slurry of a high surface area refractory metal oxide, dried for about 0.5 to about 2 hours at about 90 to about 120°C and thereafter calcined at about 450 to about 650°C for 0.5 to about 2 hours. High surface area refractory metal oxides are well known in the prior art. Typically, the refractory metal oxide will have a specific surface area of about 60 to about 300 m2/g. Useful refractory metal oxides include alumina, titania, zirconia and mixtures of alumina with one or more of titania, zirconia, coria, baria and a silicate. Preferably the refractory metal oxide comprises gamma-alumina.

    [0024] Thereafter, the refractory metal oxide-coated substrate is coated with a slurry of the desired adsorbent and dried (e.g., at about 105°C). Alternatively, the refractory metal oxide-coated substrate may he coated with separate slurries of zeolite and the silica gel and/or activated carbon to create layers, with drying between each layer occurring as described above.

    [0025] If desired, a further top coat layer of the high surface urea refractrory metal oxide may be applied on top of the adsorbent, thereafter drying as described above after the application of each layer.

    [0026] It should also be noted that each layer need not extend to the entire layer of the substrate. For example, the entire length of the substrate may be coated with gamma alumina, dried and calcined. The entire length of the alumina-coated substrate is then coated with the selected zeolite plus binder and dried. Thereafter, only a portion of the zeolite plus binder layer may be coaled with a layer of activated carbon followed by drying. Alternatively, a front section of the alumina-coated substrate is coated with the selected zeolite plus binder and a rear section is concurrently coated with activated carbon plus binder, followed by drying. As a further alternate, the alumina-coated substrate containing a middle layer of the selected zeolite may then he coated with a mixture of gamma alumina and activated carbon (20-80wt.% alumina and the balance being activated carbon), followed by drying.

    [0027] A preferred adsorbent material is a zeolite having a high silica to alumina ratio. The particularly preferred adsorbent comprises a beta zeolite of the type disclosed in U.S. Patent Nu. 6,171,556.

    [0028] Generally, sieve materials having so-called three-dimensional pore configurations are preferred over sieve materials having one- or two dimensional pore configurations, although some of the latter function acceptably well. Acceptable materials typically have a micropore diameter of from about 3 to 8 angstroms. Unexpectedly, zeolites (especially beta zeolites) having silica/alumina ratio ranges of about 25/1 to 300/1, and preferably from about 100/1 to about 250/1, have been shown to be particularly effective adsorbents. The preferred beta zeolites arc ion-exchanged beta zeolites, such as H/beta zeolite and Fc/beta zeolite.

    [0029] Preferred zeolites include ZSM-5, Y and beta zeolites, with beta zeolites particularly preferred. The preferred zeolites can be treated to reduce the number of acid sites. This can he accomplished by leaching the zeolite with an organic or inorganic acid, Preferred acids include strong inorganic acids, such as sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid and the like, and carboxylic acids such as trifluoroacetic acid, and dicarboxylic acids such as oxalic, malonic, succinic, glutaric, adipic, maleic, fumaric, phthalic and the like. Useful acids preferably include polyacids, preferably difunctional acids, more preferably dicarboxylic acids with oxalic acid most preferred. The acid use is at a concentration of 0.02 to 12N, preferably 0.1 to 10N, and a solid zeolite concentration of 0.01 to 1.0 g/ml and preferably 0.05 to 0.5 g/ml. The leaching is conducted at a suitable temperature range, typically of from 10 to 100°C; for example, preferably at 70 to 100°C when using sulfuric acid and from 10 to 50°C when using oxalic acid. The leaching is conducted for a sufficient time to achieve the desired silica to alumina ratio attainable at the leach conditions and concentrations, and is typically from about 0.5 to 5 hours, and preferably 0.5 to 3 hours.

    [0030] The zeolite may be used as is or it may be treated with steam at about 350 to about 900°C. Preferably, the stream treatment is conducted at 400 to 800°C, and more preferably 500 to 750°C with a most preferred range being from 550 to 750°C. The steam temperature can be increased at a suitable rate such as from 100 to 600"C per hour. Typical steam concentration is from 10 to 100% and preferably 30 to 100% with a preferred concentration at from about 50 to 100% with the balance being air. The steaming is preferably conducted at atmospheric pressure. The duration of the steam treatment is sufficient to treat the zeolite and is typically from 0.5 to 48 hours, preferably 0.5 to 24 hours, more preferably from 0.5 to 8 hours and most preferably 0.5 to 5 hours. The steam treatment does not significantly increase the silica to alumina ratio. However, it is believed to reduce the acidity of the zeolite by removing at least some of the aluminum from the framework of the zeolite. Steam treated zeolites have been found to increase the durability of zeolites when used to adsorb hydrocarbons in gaseous streams and to resist coke formation. Preferably, the zeolite is treated with both acid (e.g., sulfuric acid) leaching and steam treatment.

    [0031] In a particularly preferred process, the zeolite is first acid leached followed by steam treatment. Optionally, the steps of steam treatment and acid leaching may be repeated in any desired order. For example, leached and steamed zeolite may be repeatedly leached followed by steaming. In a specific embodiment, the zeolite may be leached, steamed and leached again.

    [0032] A useful method to treat beta zeolite is disclosed in CN 1059701A, published March 25, 1992. This reference discloses a high Si beta zeolite produced hy calcining to remove nitrogen compounds from a beta zeolite made through an organo-amine template process. Leaching the beta zeolite is accomplished with an organic or inorganic acid solution having a concentration of 0.02 to 12N, preferably 0.1 to 10N, and a solid zeolite concentration of 0.01 to 1.0 g/ml and preferably 0.05 to 0.5 g/ml at from 10 to 100°C for 0.5 to 5 hours, and preferably 1 to 3 hours. The leaching is followed by treating the zeolite with steam at from 400 to 900°C with the steam temperature increasing at from 100 to 600°C per hour. Disclosed steam concentration is 100% at a system pressure of 50 to 500 KPa. The duration of the steam treatment is from 0.5 to 5 hours.

    [0033] In accordance with a preferred embodiment of the present invention, zeolites can be used which are treated to increase the silica to alumina ratio supplemented by steam treatment. Methods to increase the silica to alumina ratio result in removal of the alumina from the zeolite. Leaching for example removes aluminum from the framework of the zeolite structure. The removed aluminum in the form of aluminum ion salt is removed with the leaching liquor.

    [0034] Of particular interest with regard to the present invention is the acidity which is imparted by the alumina in the zeolite framework. It is believed that the high silica to alumina ratio attained by leaching is related to the acidity of the zeolite. The acidity of the zeolite is believed to affect the durability of the zeolite when used to adsorb hydrocarbons from exhaust streams such as automotive and industrial exhaust steams which are typically' at temperatures in the range of from 300 to 800°C and more typically from 350 to 600°C. The zeolite, when used in such environments tends to lose adsorption efficiency due primarily to clogging of the pores and/or collapse of the zeolite framework. Maintenance of the stable zeolite framework can be attained by controlling the conditions under which the zeolite is treated. Such conditions include acid concentrations, steam temperatures and the like. Milder conditions reduce the tendency for the zeolite framework to deteriorate during treatment and permit the framework to be stabilized at the location where the alumina was removed.

    [0035] Additionally, it is believed that steam treatment removes aluminum from the zeolite framework. The affected aluminum continues to reside in the zeolite, probably in the pores. The zeolite framework is believed to stabilize without the aluminum and the aluminum ions in the pores becomes alumina. The remaining alumina in the pores is believed not contribute to the acidity of the zeolite which is reduced. The alumina in the pores can remain or be washed or leached out in a subsequent leaching step.

    [0036] The zeolite, non-steamed or steamed, has been found to have improved coking resistance, i.e., the formation of coke during engine testing has been significantly reduced. While acid leaching methods to increase the silica to alumina ratio of a zeolite are known to decrease acidity, such methods are believed to remove aluminum atoms from zeolite particles indiscriminately. Methods such as steaming remove the aluminum from the framework of the zeolite preferentially at the Bronsted acid sites. The importance of this can be recognized by both more effective resistance to coking and by the knowledge of how to treat a zeolite to attain such performance with minimizing deterioration of the framework. In essence, leaching a zeolite to death will result in reduced Bronsted acidity; but using a method such as steam treatment alone, or more preferably balanced with leaching results in a more durable zeolite for use as a hydrocarbon adsorber in accordance with the present invention.

    [0037] The volatile hydrocarbon adsorbent material will also include a binder that will cause the material to adhere to the surface of the substrate. Such a binder is also referred to as a washcoat binder. Washcoat binders typical for use in the formulation of slurries include, but are not restricted to, the following: organic polymers; sols of alumina, silica or zirconia; inorganic salts, organic salts and/or hydrolysis products of aluminum, silica or zirconium; hydroxides of aluminum, silica or zirconium; organic silicates that are hydrolyzable to silica; and mixtures thereof.

    [0038] The preferred binder is an organic polymer used in amounts of from 0.5 to 20, preferably 2 to 10, percent by weight of binder based on the weight of the material. The organic polymer may be a thermosetting or thermoplastic polymer and may be plastic or elastomeric. The polymeric binder may contain suitable stabilizers and age resistors known in the polymeric art. Most preferred are thermosetting, elastomeric polymers introduced as a latex into the adsorbent composition, preferably as an aqueous slurry. Upon application of the composition and drying, the binder material fixes the adsorbent particles to themselves and the substrate, and in some cases, can crosslink with itself to provide improved adhesion. This enhances the integrity of the coating, its adhesion to the substrate and provides structural stability under vibrations encountered in motor vehicles. The use of a binder enables the material to adhere to the substrate without the necessity of an undercoat layer. The binder can comprise additives to improve water resistance and improve adhesion.

    [0039] Useful organic polymer binder compositions include polyethylene, polypropylene, polyolefin copolymers, polyisoprene, polybutadiene, polybutadiene copolymers, chlorinated rubber, nitrile rubber, polychloroprene, ethylene-propylene-diene elastomers, polystyrene, polyacrylate, polymethacrylate, polyacrylonitrile, poly(vinyl esters), poly(vinyl halides), polyamides, cellulosic polymers, polyimides, acrylics, vinyl acrylics and styrene acrylics, polyvinyl alcohol, thermoplastic polyesters, thermosetting polyesters, poly(phenylene oxide), poly(phenylene sulfide), fluorinated polymers such as poly(tetrafluoroethylene) polyvinylidene fluoride, poly(vinylfluoride) and chloro/fluoro copolymers such as ethylene chlorotrifluoroethylene copolymer, polyamide, phenolic resins and epoxy resins, polyurethane, and silicone polymers. A most preferred polymeric binder is an acrylic/styrene acrylic copolymer latex .

    [0040] It is also preferred to use a dispersant in conjunction with the binder. The dispersant may be anionic, non-ionic or cationic and is typically utilized in an amount of about 0.1 to about 10 wt.%, based on the weight of the material. Suitable dispersants include polyacrylates, alkoxylates, carboxylates, phosphate esters, sulfonates, taurates, sulfosuccinates, stearates, laureates, amines, amides, imidazolines and mixtures thereof. A preferred dispersant is a low molecular weight polyacrylic acid in which many of the protons on the acid are replaced with sodium. A preferred composite comprises about 90 wt.% beta zeolite, about 9 wt.% acrylic polymer latex and about 1 wt.% dispersant.

    [0041] The following nonlimiting examples illustrate the invention. Unless otherwise indicated, all parts and percentages are on a weight basis.

    Example 1



    [0042] Sulfuric acid-leached ("SAL") beta zeolite was prepared in accordance with the procedure set forth in Example 5 of U.S. Patent.No. 6,171,556. The SAL beta zeolite was then steamed in an atmosphere of air with 60% of steam at 650°C for 24 hours to give a final product having a SiO2 Al2O3 ratio of about 200.

    [0043] 500g of the steamed-SAL final product were dispersed in 521 g of deionized water to form a slurry having a 48% solid content. The slurry was then ball milled such that 90% of the particles had a particle size of less than 9.5 microns. A final slurry was achieved by adding the slurry with 21 g of a colloidal polyacrylic diapersant and 154 g of a polyacrylic latex binder having a solids content of about 50wt.%, a pH of about 6 and a maximum viscosity of 400 cps.

    Example 2



    [0044] A unit comprising a Cr-Al-Fe alloy tube of 7.62 cm (3") diameter and 7.62 cm (3") length was fitted with a Fe-Cr alloy fluted band of 5.08cm (2") height, with the flutes extending about 0.3175 cm (½") from the inner wall of the tube (the band was reccessed about 1.27 cm (½") from each end of the tube). This band was coated with tho final slurry obtained from Example 1. The coated band was dried and placed in a programmable oven and the temperature was slowly raised to 105°C and maintained at such temperature for 1 hour. The washcoat dry gain was 6.4 g. The band was again coated by the same procedure resulting in a coated band having a final dry gain of 12.1 g.

    Example 3



    [0045] Example 2 was repeated with a Cr-Al-Fe alloy tube of 7.62 (3") cm diameter and 7.62m (3") length which was fitted with a Fe-Cr alloy fluted ribbon of 5.08cm (6") height, with the flutes having peak heights of about 0.476 cm (6/32") arranged in a serpentine manner; the ribbon was recessed 1.27 cm (½") from each end of the tube. This ribbon was coated with the final slurry prepared in Example 1. The coated ribbon was dried and placed in a programmable oven and the temperature was slowly raised to 105°C and maintained at such temperature for 1 hour. The washcoat dry gain was 8.5 g. The ribbon was again coated by the same procedure resulting in a coated ribbon having n final dry gain of 19.5g.

    Example 4



    [0046] The units of Example 2 and Example 3 were tested for effectiveness in trapping hydrocarbons. The test vehicle was a 2000 model year vehicle having four cylinders and an engine displacement of 2.3 liters. The total mass of emitted hydrocarbons was measured over a 2-day test period under identical condition. The baseline, i.e., with no housing present in the air induction system of the vehicle, was measured as 10.1 mg/day of hydrocarbons on day 1 and 16.4 mg/day of hydrocarbons on day 2. The unit of Example 2 was installed in the conduct downstream of the air cleaner and upstream of the intake manifold and the cumulative mass of hydrocarbons was measured as 2.1 mg/day on day 1 and 4.1 mg/day on day 2. The test was repeated using the unit of Example 3 (instead of the unit of Example 2) installed in the conduit downstream of the air cleaner and upstream of the intake manifold and the cumulative mass of hydrocarbons was measured as 1.12 mg/day on day 1 and 0.59 mg/day on day 2. These results clearly show that the volatile hydrocarbon adsorbent unit of the invention is effective in reducing the emissions of hydrocarbons through the air induction system of the engine to the extent that much less than 10 mg/day of such hydrocarbons are emitted, thereby helping to meet the LEV II Evaporative Hydrocarbon regulation limit which will be imposed by the Federal Government in respect to the 2004 model year automobiles.

    Example 5



    [0047] 500 g of gamma-alumina having a surface area of 150m2/g were dispersed in 521 g of deionized water to form a slurry having a 48% solids content. 60 g of acetic acid were added to the slurry which was thereafter ball milled such that 90% of the particles had a particle size of less than 9 microns. A final slurry was then achieved by adding 55 g of an alumina binder. The final slurry was further ball milled such that 90% of the particles had a particle size of less than 7 microns. The pH of the resultant slurry was then adjusted with acetic acid to a pH of about 4 and a viscosity of 80 cps. The fluted aluminum band of the type described in Example 2 was then coated with the slurry for a target dry gain of 0.32 g. The coated fluted band was dried in an oven for 1 hour at 105°C and then calcined at 550°C for 1 hour.

    [0048] The coated fluted band was thereafter further coated with the slurry of the beta zeolite as set forth in Example 2. The resultant coated fluted band was coated with an alumina slurry overcoat for a target dry gain of 0.8 g. The coated fluted band was then again dried at 105°C.

    Example 6



    [0049] 400 g of the beta zeolite employed in Example 1 was mixed with 100 g of an activated carbon having a pore size distribution ranging from 10 to 250 angstroms. A slurry of the mixed powder was then prepared as described in Example 1 in respect to the zeolite slurry. The mixed powder slurry was then coated onto a fluted band that had previously been coated with alumina as described in Example 5.

    Reference Example 7



    [0050] A slurry of the activated carbon employed in Example 6 was prepared in the same manner as described in Example 1 in respect to the zeolite slurry. The activated carbon slurry was then coated onto a fluted band that had been previously coated with alumina and a beta zeolite in the manner described in Example 5.

    Example 8



    [0051] A slurry of unsteamed SAL beta zeolite was prepared in the manner set forth in Example 1. This slurry was then coated onto a ribbon in the same manner as set forth in Example 3. The adsorber unit was then evaluated for n-butane trapping capacity in a laboratory bench unit.

    [0052] The laboratory bench unit contained a stream of n-hutaue flowing at the rate of 25 cc/min, and another stream of nitrogen flowing at the rate of 25 cc/min. The two gas streams were combined and then flowed into a test chamber with the absorbent unit as prepared above mounted within the chamber. The gas stream exiting the test chamber was further dilated with 10 liters/min of nitrogen. A split stream of two liers/min was sampled through a sampling pump and sent to a flame ionization detector unit in order to monitor the breakthrough of n-butane. The test was allowed to continue until the inlet concentration of n-butane equaled the outlet concentration, at which point the adsorbent unit was fully saturated.

    [0053] The test chamber was disconnected from the test bench and weighed. The amount of adsorbed n-butane was obtained by subtracting the initial weight of the test chamber. The weight was found to be 1.47 grams.

    Example 9



    [0054] Example 8 was repeated using an adsorbent unit prepared with steamed SAL beta zeolite. The amount of n-butane trapped in the unit was 1.02 grams.


    Claims

    1. A system for controlling the emission of volatile hydrocarbons from an automobile engine having an intake manifold the system including an air cleaner and comprising a volatile hydrocarbon adsorber unit including a housing having an air inlet and an air outlet, said housing containing a substrate and a volatile hydrocarbon adsorber material coated on the surface of the substrate, said volatile hydrocarbon adsorber material comprising a natural zeolite, a synthetic zeolite or a mixture of a natural and a synthetic zeolite, said material further containing a binder that will cause the material to adhere to the surface of the substrate, the adsorber unit being located in a conduit downstream from the air cleaner and suitable for being positioned upstream of the intake manifold, the adsorber unit being operative, in use, to control the emission of volatile hydrocarbons when the engine is shut off.
     
    2. The system of claim 1 wherein the housing is comprised of a metal or a polynter.
     
    3. The system of claim 2 wherein the housing is comprised of a metal selected from the group consisting of aluminum, a Fe-Cr alloy and a Fe--Cr--Al alloy.
     
    4. The system of claim 1 wherein the material comprises a mixture of a natural zeolite or synthetic zeolite and an activated carbon.
     
    5. The system of claim 4 wherein the material comprises separate layers of zeolite and activated carbon.
     
    6. The system of claim 1 wherein the natural or synthetic zeolite is selected from the group consisting of faujasite, chabazite, clinoptilolite, mordenite, silicalite, zeolite X, zeolite Y, ultrastable Y, ZSM zeolite, offretite and a beta zeolite.
     
    7. The system of claim 6 wherein the beta zeolite has a silica:alumina molar ratio of 25:1 to 1000; 1.
     
    8. The system of claim 7 wherein the beta zeolite comprises acid-lowhed beta zeolite.
     
    9. The system of claim 7 wherein the beta zeolite comprises beta zeolite steam-treated at 350 to 900 °C.
     
    10. The system of claim 1 wherein the substrate comprises a polymer or a metal and is present in a corrugated mode.
     
    11. The system of claim 10 wherein the metal is selected from the group consisting of aluminum, titanium, stainless steel, Fe--Cr alloy and Fe--Cr--Al alloy.
     
    12. The system of claim 1 wherein the material is deposited on a high surface refractory metal oxide that in turn is deposited on the surface of the substrate.
     
    13. The system of claim 12 wherein the metal oxide comprises gamma alumina.
     
    14. The system of claim 1 wherein the binder is selected from the group consisting of organic polymer latices; sols of alumina, silica or zirconia; inorganic salts, organic salts and/or hydrolysis products of aluminum, silica or zirconium; hydroxides of aluminum, silica or zirconium; organic silicates that are hydrolyzable to silica; and mixtures thereof.
     
    15. The system of claim 14 wherein the binder comprises an acrylic polymer latex.
     
    16. The system of claim 14 wherein the material further contains a dispersant.
     


    Ansprüche

    1. System zum Steuern der Emission flüchtiger Kohlenwasserstoffe aus einem Automobilmotor mit einem Ansaugkrümmer, wobei das System einen Luftreiniger aufweist und eine Adsorbereinheit für flüchtigen Kohlenwasserstoff umfasst, die ein Gehäuse mit einem Lufteinlass und einem Luftauslass aufweist, wobei das Gehäuse ein Substrat und ein Adsorbermaterial für flüchtigen Kohlenwasserstoff enthält, das auf der Oberfläche des Substrats beschichtet ist, wobei das Adsorbermaterial für flüchtigen Kohlenwasserstoff einen natürlichen Zeolith, einen synthetischen Zeolith oder eine Mischung eines natürlichen und eines synthetischen Zeoliths umfasst, wobei das Material ferner ein Bindemittel enthält, das bewirkt, dass das Material an der Oberfläche des Substrats haftet, wobei sich die Adsorbereinheit in einer Leitung stromabwärts des Luftreinigers befindet und geeignet ist, um stromaufwärts des Ansaugkrümmers angeordnet zu werden, wobei die Adsorbereinheit während des Gebrauchs betätigt werden kann, um die Emission flüchtiger Kohlenwasserstoffe zu steuern, wenn der Motor abgeschaltet ist.
     
    2. System nach Anspruch 1, wobei das Gehäuse aus einem Metall oder einem Polymer besteht.
     
    3. System nach Anspruch 2, wobei das Gehäuse aus einem Metall besteht, das ausgewählt ist aus der Gruppe, bestehend aus Aluminium, einer Fe-Cr-Legierung und einer Fe-Cr-Al-Legierung.
     
    4. System nach Anspruch 1, wobei das Material eine Mischung eines natürlichen Zeoliths oder eines synthetischen Zeoliths und einer Aktivkohle umfasst.
     
    5. System nach Anspruch 4, wobei das Material getrennte Schichten von Zeolith und Aktivkohle umfasst.
     
    6. System nach Anspruch 1, wobei der natürliche oder synthetische Zeolith ausgewählt ist aus der Gruppe, bestehend aus Faujasit, Chabazit, Clinoptilolit, Mordenit, Silicalit, Zeolith X, Zeolith Y, ultrastabilem Y, ZSM Zeolith, Offretit und einem beta-Zeolith.
     
    7. System nach Anspruch 6, wobei der beta-Zeolith ein Molverhältnis von Silica zu Aluminiumoxid von 25:1 bis 1000:1 aufweist.
     
    8. System nach Anspruch 7, wobei der beta-Zeolith säureausgelaugten beta-Zeolith umfasst.
     
    9. System nach Anspruch 7, wobei der beta-Zeolith bei 350 bis 900 °C behandelten beta-Zeolith umfasst.
     
    10. System nach Anspruch 1, wobei das Substrat ein Polymer oder ein Metall umfasst und in einer gewellten Form vorliegt.
     
    11. System nach Anspruch 10, wobei das Metall ausgewählt ist aus der Gruppe, bestehend aus Aluminium, Titan, Edelstahl, Fe-Cr-Legierung und Fe-Cr-A1-Legierung.
     
    12. System nach Anspruch 1, wobei das Material auf ein Metalloxid mit hoher Oberflächenfeuerfestigkeit aufgebracht ist, das wiederum auf die Oberfläche des Substrats aufgebracht ist.
     
    13. System nach Anspruch 12, wobei das Metalloxid gamma-Aluminiumoxid umfasst.
     
    14. System nach Anspruch 1, wobei das Bindemittel ausgewählt ist aus der Gruppe, bestehend aus organischen Polymer-Latices; Solen von Aluminiumoxid, Silica oder Zirkoniumoxid; anorganischen Salzen, organischen Salzen und/oder Hydrolyseprodukten von Aluminium, Silica oder Zirkonium; Hydroxiden von Aluminium, Silica oder Zirkonium; organischen Silikaten, die zu Silica hydrolysierbar sind; und Mischungen davon.
     
    15. System nach Anspruch 14, wobei das Bindemittel einen Acrylpolymerlatex umfasst.
     
    16. System nach Anspruch 14, wobei das Material ferner ein Dispergiermittel enthält.
     


    Revendications

    1. Système de régulation de l'émission d'hydrocarbures volatils provenant d'un moteur d'automobile comportant une tubulure d'admission, le système contenant un dispositif de nettoyage de l'air et comprenant une unité d'adsorbeur d'hydrocarbures volatils comportant un logement doté d'une entrée d'air et d'une sortie d'air, ledit logement contenant un substrat et un matériau adsorbeur d'hydrocarbures volatils appliqué sur la surface du substrat, ledit matériau adsorbeur d'hydrocarbures volatils comprenant une zéolithe naturelle, une zéolithe synthétique ou un mélange d'une zéolithe naturelle et d'une zéolithe synthétique, ledit matériau contenant en outre un liant qui permettra de faire adhérer le matériau à la surface du substrat, l'unité d'adsorbeur étant située dans une conduite en aval du dispositif de nettoyage de l'air et pouvant être placé en amont de la tubulure d'admission, l'unité d'adsorbeur étant opérante, en service, pour réguler l'émission d'hydrocarbures volatils lorsqu'on arrête le moteur.
     
    2. Système selon la revendication 1 dans lequel le logement est composé d'un métal ou d'un polymère.
     
    3. Système selon la revendication 2 dans lequel le logement est composé d'un métal choisi dans le groupe constitué par l'aluminium, un alliage Fe-Cr et un alliage Fe-Cr-Al.
     
    4. Système selon la revendication 1 dans lequel le matériau comprend un mélange d'une zéolithe naturelle ou d'une zéolithe synthétique et d'un charbon actif.
     
    5. Système selon la revendication 4 dans lequel le matériau comprend des couches séparées de zéolithe et de charbon actif.
     
    6. Système selon la revendication 1 dans lequel la zéolithe naturelle ou synthétique est choisie dans le groupe constitué par la faujasite, la chabazite, la clinoptilolite, la mordénite, la silicalite, la zéolithe X, la zéolithe Y, la Y ultrastable, la zéolithe ZSM, l'offrétite et une zéolithe bêta.
     
    7. Système selon la revendication 6 dans lequel la zéolithe bêta possède un rapport molaire silice/alumine de 25:1 à 1000:1.
     
    8. Système selon la revendication 7 dans lequel la zéolithe bêta comprend une zéolithe bêta lixiviée à l'acide.
     
    9. Système selon la revendication 7 dans lequel la zéolithe bêta comprend une zéolithe bêta traitée à la vapeur d'eau à 350 à 900 °C.
     
    10. Système selon la revendication 1 dans lequel le substrat comprend un polymère ou un métal et est présent en mode ondulé.
     
    11. Système selon la revendication 10 dans lequel le métal est choisi dans le groupe constitué par l'aluminium, le titane, l'acier inoxydable, un alliage Fe-Cr et un alliage Fe-Cr-Al.
     
    12. Système selon la revendication 1 dans lequel le matériau est déposé sur un oxyde métallique réfractaire de grande surface spécifique qui est quant à lui déposé sur la surface du substrat.
     
    13. Système selon la revendication 12 dans lequel l'oxyde métallique comprend de l'alumine gamma.
     
    14. Système selon la revendication 1 dans lequel le liant est choisi dans le groupe constitué par les latex de polymère organique ; les sols d'alumine, de silice ou de zircone ; les sels minéraux, les sels organiques et/ou les produits d'hydrolyse d'aluminium, de silice ou de zirconium ; les hydroxydes d'aluminium, de silice ou de zirconium ; les silicates organiques qui sont hydrolysables en silice ; et des mélanges de ceux-ci.
     
    15. Système selon la revendication 14 dans lequel le liant comprend un latex de polymère acrylique.
     
    16. Système selon la revendication 14 dans lequel le matériau contient en outre un dispersant.
     




    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description