WO2000013773A1 - Ozone destroying compositions of improved tolerance to sulfur poisoning - Google Patents

Ozone destroying compositions of improved tolerance to sulfur poisoning Download PDF

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Publication number
WO2000013773A1
WO2000013773A1 PCT/US1999/017632 US9917632W WO0013773A1 WO 2000013773 A1 WO2000013773 A1 WO 2000013773A1 US 9917632 W US9917632 W US 9917632W WO 0013773 A1 WO0013773 A1 WO 0013773A1
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composition
binder
manganese oxide
weight percent
particle size
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PCT/US1999/017632
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French (fr)
Inventor
Jeffrey B. Hoke
Ronald M. Heck
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Engelhard Corporation
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Priority to AU52544/99A priority Critical patent/AU5254499A/en
Publication of WO2000013773A1 publication Critical patent/WO2000013773A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
    • B01J23/56—Platinum group metals
    • B01J23/64—Platinum group metals with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/656—Manganese, technetium or rhenium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8671—Removing components of defined structure not provided for in B01D53/8603 - B01D53/8668
    • B01D53/8675—Ozone
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/32—Manganese, technetium or rhenium
    • B01J23/34—Manganese
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/40—Catalysts, in general, characterised by their form or physical properties characterised by dimensions, e.g. grain size
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst

Definitions

  • the present invention is directed toward compositions and methods of treating the atmosphere to remove ozone.
  • the invention is more tolerant of sulfur-containing compounds whose presence in the atmosphere poisons catalytic performance.
  • References are known which disclose proactively cleaning the environment, wherein the environment contains pollutants which may adversely affect performance of a catalyst used to clean the environment.
  • U.S. Patent No. 3,738,088 discloses an air filtering assembly for cleaning pollution from the ambient air by utilizing a vehicle as a mobile cleaning device.
  • a variety of elements are disclosed to be used in combination with a vehicle to clean the ambient air as the vehicle is driven through the environment.
  • the filter means can include filters and electronic precipitators.
  • Catalyzed postfilters are disclosed to be useful to treat nonparticulate or aerosol pollution such as carbon monoxide, unburned hydrocarbons, nitrous oxide and/or sulfur oxides, and the like.
  • U.S. 4,551,304 discloses a method of cleaning air supplied to a cabin (e.g., to serve a space occupied by a human) having been purified to remove sulfur dioxide, nitrogen monoxide, nitrogen dioxide, carbon monoxide and hydrocarbons therefrom.
  • the method involves providing an ozonizer to generate ozone to react with, e.g., sulfur dioxide to produce sulfur trioxide.
  • Sulfur trioxide is disclosed to be taken up in part on sorption masses to permit the air to be heated before introduced to a catalyst mass to react carbon monoxide to form carbon dioxide. The carbon dioxide is then absorbed and the purified air after cooling, is fed to the cabin.
  • the present invention relates to compositions and methods of use of these compositions as ozone decomposition compositions which are surprisingly resistant to the poisoning effects of sulfur containing compounds.
  • the invention relates to an ozone decomposition composition comprising a manganese oxide wherein the median particle size diameter of the manganese oxide is equal to or less than about 1 micrometer thereby enabling the composition to be resistant to sulfur poisoning.
  • the invention relates to a method of decomposing ozone in an atmosphere containing sulfur compounds comprising contacting the atmosphere with a composition comprising a manganese oxide wherein the median particle size diameter of the manganese oxide is equal to or less than about 1 micrometer thereby enabling the composition to be resistant to sulfur poisoning.
  • the invention clearly demonstrates the use of manganese oxide of median particle size equal to or less than 1 micrometer as an atmospheric ozone decomposition composition resistant to sulfur poisoning.
  • Advantages of this invention include improved tolerance to sulfur poisoning of the catalyst without having separate and/or additional sulfur sorption or treatment means as required by the prior act.
  • compositions and methods of this invention relate to advances in the treatment of the atmosphere which have improved tolerance to sulfur-containing compounds.
  • sulfur-containing compounds include SO 2 , SO 3 , H 2 S, thiols, dithiols, sulfides, and disulfides.
  • the catalytic materials useful in the present invention are those which contain manganese and particularly those which contain manganese dioxide as explained in detail hereinafter. Such catalytic materials are especially suitable for treating ozone.
  • Ozone treating catalyst compositions comprise manganese compounds including manganese dioxide, non stoichiometric manganese dioxide (e.g., XMnO (1 5 . 20) ), and/or XMn 2 O 3 wherein X is a metal ion, preferably an alkali metal or alkaline earth metal (e.g. sodium, potassium and barium).
  • X is a metal ion, preferably an alkali metal or alkaline earth metal (e.g. sodium, potassium and barium).
  • Variable amounts of water H 2 O, OH " ) can be incorporated in the structure as well.
  • Preferred manganese dioxides which are nominally referred to as MnO 2 have a chemical formula wherein the molar ratio of manganese to oxide is about from 1.5 to 2.0. Up to 100 percent by weight of manganese dioxide MnO 2 can be used in catalyst compositions to treat ozone.
  • Alternative compositions which are available comprise manganese dioxide and compounds such as copper oxide alone or copper oxide and alumina. In accordance with the present invention, the most dramatic improvement in catalytic efficiency with higher pore size distribution is seen with catalyst containing manganese dioxide alone.
  • Useful and preferred manganese dioxides are alpha-manganese dioxides nominally having a molar ratio of manganese to oxygen of from 1 to 2. Useful alpha manganese dioxides are disclosed in U.S.
  • the preferred alpha- manganese dioxide is selected from hollandite (BaMn 8 O 16 .xH 2 O), cryptomelane (KMn 8 O 16 .xH 2 O), manjiroite (NaMn 8 O 16 .xH 2 O) or coronadite (PbMn 8 O, 6 .xH 2 O).
  • the manganese dioxides useful in the present invention preferably have a surface area as high as possible while maintaining a pore size distribution of at least 10 nm. A preferred surface area is at least 100 m 2 /g.
  • the composition preferably comprises a binder as of the type described below with preferred binders being polymeric binders.
  • the composition can further comprise precious metal components with precious metal components being the oxides of precious metal, including the oxides of platinum group metals and oxides of palladium or platinum also referred to as palladium black or platinum black.
  • precious metal components being the oxides of precious metal, including the oxides of platinum group metals and oxides of palladium or platinum also referred to as palladium black or platinum black.
  • the amount of palladium or platinum black can range from 0 to 25%, with useful amounts being in ranges of from about 1 to 25 and 5 to 15% by weight based on the weight of the manganese component and the precious metal component.
  • compositions comprising the cryptomelane form of alpha manganese oxide, which also contain a polymeric binder can result in greater than 50%, preferably greater than 60% and typically from 75-85% conversion of ozone in a concentration range of up to 400 parts per billion (ppb).
  • the preferred cryptomelane manganese dioxide can be calcined at a temperature range of from 250°C to 550°C and preferably below 500°C and greater than 300° for least 1.5 hours and preferably at least 2 hours up to about 6 hours.
  • the preferred cryptomelane can be made in accordance with methods described and incorporated into U.S. Patent Application Serial No. 08/589,182 filed January 19, 1996 (Attorney Docket No. 3777C), incorporated herein by reference.
  • the cryptomelane can be made by reacting a manganese salt including salts selected from the group consisting MnCl 2 , Mn(NO 3 ) 2 , MnSO 4 and Mn (CH 3 COO) 2 with a permanganate compound.
  • Cryptomelane is made using potassium permanganate; hollandite is made using barium permanganate; coronadite is made using lead permanganate; and manjiroite is made using sodium permanganate.
  • the alpha-manganese dioxide useful in the present invention can contain one or more of hollandite, cryptomelane, manjiroite or coronadite compounds. Even when making cryptomelane minor amounts of other metal ions such as sodium may be present. Useful methods to form the alpha-manganese dioxide are described in the above references which are incorporated herein by reference.
  • the preferred alpha-manganese dioxide for use in accordance with the present invention is cryptomelane.
  • the preferred cryptomelane is "clean" or substantially free of inorganic anions, particularly on the surface. Such anions could include chlorides, sulfates and nitrates which are introduced during the method to form cryptomelane.
  • An alternate method to make the clean cryptomelane is to react a manganese carboxylate, preferably manganese acetate, with potassium permanganate.
  • the carboxylates are burned off during the calcination process.
  • inorganic anions remain on the surface even during calcination.
  • the inorganic anions such as sulfates can be washed away with the aqueous solution or a slightly acidic aqueous solution.
  • the alpha manganese dioxide is a "clean" alpha manganese dioxide.
  • the cryptomelane can be washed at from about 60°C to 100°C for about one-half hour to remove a significant amount of sulfate anions.
  • the nitrate anions may be removed in a similar manner.
  • the "clean" alpha manganese dioxide is characterized as having an IR spectrum as disclosed in U.S. Patent Application Serial No.
  • a preferred method of making cryptomelane useful in the present invention comprises mixing an aqueous acidic manganese salt solution with a potassium permanganate solution.
  • the acidic manganese salt solution preferably has a pH of from 0.5 to 3.0 and can be made acidic using any common acid, preferably acetic acid at a concentration of from 0.5 to 5.0 normal and more preferably from 1.0 to 2.0 normal.
  • the mixture forms a slurry which is stirred at a temperature range of from 50°C to 110°C.
  • the slurry is filtered and the filtrate is dried at a temperature range of from 75°C to 200°C.
  • the resulting cryptomelane crystals have a surface area typically in the range of at least 100 m 2 /g.
  • compositions comprise manganese dioxide and optionally copper oxide and alumina and at least one precious metal component such as a platinum group metal supported on the manganese dioxide and where present copper oxide and alumina.
  • Useful compositions contain up to 100, from 40 to 80 and preferably 50 to 70 weight percent manganese dioxide, and 10 to 60 and typically 30 to 50 percent copper oxide.
  • Useful compositions include hopcalite (supplied by, for example, Mine Safety Applications, Inc.) which is about 60 percent manganese dioxide and about 40 percent copper oxide; and Carulite ® 200 (sold by Cams Chemical Co.) which is reported to have 60 to 75 weight percent manganese dioxide, 11 to 14 percent copper oxide and 15 to 16 percent aluminum oxide.
  • the surface area of Carulite ® 200 is reported to be about 180 m 2 /g. Calcining at 450°C reduces the surface area of the Carulite ® by about fifty percent (50%) without significantly affecting activity. It is preferred to calcine manganese compounds at from 300°C to 500°C and more preferably 350°C to 450°C. Calcining at 550°C causes a great loss of surface area and ozone treatment activity. Calcining the Carulite ® after ball milling with acetic acid and coating on a substrate can improve adhesion of the coating to a substrate. Other compositions to treat ozone can comprise a manganese dioxide component and precious metal components such as platinum group metal components.
  • the manganese dioxide can also support the precious metal component.
  • the platinum group metal component preferably is a palladium and/or platinum component.
  • the amount of platinum group metal compound preferably ranges from about 0.1 to about 10 weight percent (based on the weight of the platinum group metal) of the composition. Preferably, where platinum is present it is present in amounts of from 0. 1 to 5 weight percent, with useful and preferred amounts on pollutant treating catalyst volume, based on the volume of the supporting article, ranging from about 0.5 to about 70 g/ft 3 .
  • the amount of the palladium component preferably ranges from about 2 to about 10 weight percent of the composition, with useful and preferred amounts on pollutant treating catalyst volume ranging from about 10 to about 250 g/ft 3 .
  • Useful amounts of the catalytic material can range from 70 to 95, preferably from 75 to 90 weight percent of the catalytic coating based on dry weight of the catalytic coating.
  • the pollutant treating compositions of the present invention preferably comprise a binder which acts to adhere the composition and to provide adhesion to the atmosphere contacting surface.
  • a preferred binder is a polymeric binder used in amounts of from 3 to 20, more preferably from 5 to 15 percent by weight of binder based on the weight of the composition.
  • the binder is a polymeric binder which can be a thermosetting or thermoplastic polymeric binder.
  • the polymeric binder can have suitable stabilizers and age resistors known in the polymeric art.
  • the polymer can be a plastic or elastomeric polymer.
  • thermosetting, elastomeric polymers introduced as a latex into a slurry of the catalyst composition, preferably an aqueous slurry.
  • the binder material can crosslink providing a suitable support which enhances the integrity of the coating, its adhesion to the atmosphere contacting surface and provides structural stability under vibrations encountered in motor vehicles.
  • the use of preferred polymeric binder enables the pollutant treating composition to adhere to the atmosphere contacting surface without the necessity of an undercoat layer.
  • the binder can comprise water resistant additives to improve water resistance and improve adhesion.
  • additives can include fluorocarbon emulsions, silicone polymers, and petroleum wax emulsions.
  • Useful polymeric 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, poly vinyl 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,
  • Preferred binders are selected from the group consisting of polymers and copolymers of acrylics, vinyl acrylics, styrene acrylics, ethylene vinyl acetates, vinyl acetates, fluorinated polymers and silicones.
  • Particularly preferred polymers and copolymers are vinyl acrylic polymers and ethylene vinyl acetate copolymers.
  • a preferred vinyl acrylic polymer is a cross linking polymer sold by National Starch and Chemical Company as Xlink 2833. It is described as a vinyl acrylic polymer having a Tg of -15°C, 45% solids, a pH of 4.5 and a viscosity of 300 cps. In particular, it is indicated to have vinyl acetate CAS No. 108-05-4 in a concentration range of less than 0.5 percent. It is indicated to be a vinyl acetate copolymer.
  • Other preferred vinyl acetate copolymers which are sold by the National Starch and Chemical Company include Dur-O-Set E-623 and Dur-O-Set E- 646.
  • Dur-O-Set E-623 is indicated to be an ethylene vinyl acetate copolymer having a Tg of 0°C, 52% solids, a pH of 5.5 and a viscosity of 200 cps.
  • Dur-O-Set E-646 is indicated to be an ethylene vinyl acetate copolymer with a Tg of -12 °C, 52% solids, a pH of 5.5 and a viscosity of 300 cps.
  • a useful and preferred binder is a crosslinking acrylic copolymer sold by National Starch and Chemical Company as X-4280.
  • polymeric dispersants may be added to enhance or promote slurry stability between the binder and catalyst. Binder/catalyst compatibility may be achieved by adding a polymeric aery late derived dispersant (ca. 3% solids basis). The dispersant can be added during the ball milling operation or after. Despite generating a large negative charge on the catalyst particles, not all dispersants work equally as well.
  • Preferred dispersants comprise polymers containing carboxylic acid groups or derivatives thereof such as esters and salts.
  • Preferred dispersants include Accusol 445 (from Rohm & Haas) and Colloid 226/35 (from Rhone-Poulenc).
  • Useful dispersants and a review of dispersion technology are presented in, Additives for Dispersion Technology, published by Rhone-Poulenc, Surfactants & Specialties hereby incorporated by reference.
  • Useful polymeric dispersants include but are not limited to polyacrylic acid partial sodium salts (i.e., at least partially contains a sodium salt of polyacrylic acid) and anionic copolymer sodium salts sold by Rhone-Poulenc as Colloid TM polymeric dispersants. Again, although surface charge is an important factor in determining catalyst/binder compatibility, it is not the only factor.
  • the dispersant (particularly Colloid 226) does a good job of stabilizing the slurry since a greater variety of latex binders (e.g. acrylics, styrene acrylics, and EVA's) are compatible. Long term compatibility problems may be addressed by increasing the quantity of dispersant, raising the pH somewhat, or both.
  • Useful amounts of dispersant range from 2 to 10, preferably from 2 to 6 weight percent of dispersant based on the dry weight of the composition.
  • the polymeric slurries of the present invention can contain conventional additives such as thickeners, biocides, antioxidants, antifoamants and the like.
  • the pollutant treating composition can be applied to the atmosphere contacting surfaces by any suitable means such as spray coating, powder coating, or brushing or dipping the surface into a catalyst slurry.
  • Milling of the catalytic composition may be done in any of a number of conventional particle milling devices in order to reach the desired particle size .
  • One suitable device is a ball mill.
  • the degree of particle milling can conveniently be measured by devices using light scattering techniques and the milling is stopped once the desired particle size is reached.
  • One such suitable particle size measuring device is the Horiba LA-500 Laser Diffraction Particle Size Distribution Analyzer.
  • the final slurry pH is approximately 4.5.
  • the resulting composition contained approximately 83.3% MnO 2 , and 12.5% latex binder and 4.2% acetic acid residue (e.g., in the form of acetate) based on dry weight of the composition.
  • 6000g of high surface area MnO 2 (220-250 m 2 /g cryptomelane) is combined in a 9 gallon ball mill with 9000g of deionized water and 514.3g of Rhone-Poulenc Colloid 226/35 polyacrylate dispersant (3% solids based on MnO 2 weight).
  • the resulting mixture is milled for approximately 22 hours to a median particle size ⁇ 1.0 ⁇ m.
  • An additional 342.8g of Colloid 226 dispersant (2% solids based on MnO 2 weight) is added, the slurry is rolled for 10 minutes, and the mill is drained into a suitable mixing container. The resulting slurry is reduced to 25% solids overall with the addition of deionized water.
  • catalyst particle size was measured with a
  • the smallest 50% of particles in the entire distribution have a particle size less than the median particle size value.
  • Reproducibility in the measurement due to variability in the sampling is on the order of +/-0.1 ⁇ m.
  • Example E-l picks up significantly less sulfur than Example C-l after aging for up to 24 hours in a stream of 1 ppm SO 2 .
  • the effect of this is a measurable and significant improvement in ozone conversion efficiency of E-l relative to C-l after aging. This result is quite unexpected since at roughly equivalent binder loadings one would expect the smaller particle size E-l coating to pick up more sulfur than a larger sized particle due to the much higher overall particle geometric surface area (i.e., smaller particles gives higher total surface area).

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Abstract

Manganese oxide ozone destroying catalyst compositions of median particle size equal to or less than about 1 micrometer are surprisingly more resistant to poisoning by sulfur-containing compounds compared with manganese oxide catalyst compositions of larger particle size.

Description

OZONE DESTROYING COMPOSITIONS OF IMPROVED TOLERANCE TO SULFUR POISONING
BACKGROUND OF THE INVENTION
1.1 Field of the Invention The present invention is directed toward compositions and methods of treating the atmosphere to remove ozone. The invention is more tolerant of sulfur-containing compounds whose presence in the atmosphere poisons catalytic performance.
1.2 Related Art Co-pending, commonly assigned patent applications, 08/588,972, 08/589,030,
08/589,032, 08/589,182, 08/682,174, 08/695,687, 09/046,103, the disclosures of which are incorporated by reference, address various aspects of atmospheric pollutant treatment. However, these applications do not address the problem of long term catalyst activity in view of the poisoning effects of sulfur-containing compounds on catalytic materials, particularly manganese dioxides.
References are known which disclose proactively cleaning the environment, wherein the environment contains pollutants which may adversely affect performance of a catalyst used to clean the environment.
U.S. Patent No. 3,738,088 discloses an air filtering assembly for cleaning pollution from the ambient air by utilizing a vehicle as a mobile cleaning device. A variety of elements are disclosed to be used in combination with a vehicle to clean the ambient air as the vehicle is driven through the environment. In particular, there is disclosed ducting to control air stream velocity and direct the air to various filter means. The filter means can include filters and electronic precipitators. Catalyzed postfilters are disclosed to be useful to treat nonparticulate or aerosol pollution such as carbon monoxide, unburned hydrocarbons, nitrous oxide and/or sulfur oxides, and the like. While US 3,738,088 discloses catalyzed postfilters to treat nonparticulate or aerosol pollution such as carbon monoxide, unburned hydrocarbons, nitrous oxides, and/or sulfur oxides, and the like, it does not address the catalytically deactivating effects of sulfur-containing compounds on manganese dioxides. Furthermore, applicants are not aware of any catalysts capable of destroying sulfur oxides that may alleviate any poisoning problems of manganese oxides.
U.S. 4,551,304 discloses a method of cleaning air supplied to a cabin (e.g., to serve a space occupied by a human) having been purified to remove sulfur dioxide, nitrogen monoxide, nitrogen dioxide, carbon monoxide and hydrocarbons therefrom. The method involves providing an ozonizer to generate ozone to react with, e.g., sulfur dioxide to produce sulfur trioxide. Sulfur trioxide is disclosed to be taken up in part on sorption masses to permit the air to be heated before introduced to a catalyst mass to react carbon monoxide to form carbon dioxide. The carbon dioxide is then absorbed and the purified air after cooling, is fed to the cabin. As with 3,738,088, the issue of catalyst tolerance to sulfur-containing compounds is not addressed and requires ozone generating means and sorptive means to treat the air prior to contain with the catalyst. Applicants' invention provides a significant advance in providing catalytic compositions which are of improved tolerance to sulfur-containing compounds such as SO2. Such improved catalytic performance is achieved without providing additional devices or sulfur-containing compound sorptive or destructive compositions and is achieved by use of catalytic compositions containing manganese oxides of adjusted particle size.
SUMMARY OF THE INVENTION
The present invention relates to compositions and methods of use of these compositions as ozone decomposition compositions which are surprisingly resistant to the poisoning effects of sulfur containing compounds.
In one embodiment, the invention relates to an ozone decomposition composition comprising a manganese oxide wherein the median particle size diameter of the manganese oxide is equal to or less than about 1 micrometer thereby enabling the composition to be resistant to sulfur poisoning. In another embodiment, the invention relates to a method of decomposing ozone in an atmosphere containing sulfur compounds comprising contacting the atmosphere with a composition comprising a manganese oxide wherein the median particle size diameter of the manganese oxide is equal to or less than about 1 micrometer thereby enabling the composition to be resistant to sulfur poisoning.
The invention clearly demonstrates the use of manganese oxide of median particle size equal to or less than 1 micrometer as an atmospheric ozone decomposition composition resistant to sulfur poisoning.
Advantages of this invention include improved tolerance to sulfur poisoning of the catalyst without having separate and/or additional sulfur sorption or treatment means as required by the prior act.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
The compositions and methods of this invention relate to advances in the treatment of the atmosphere which have improved tolerance to sulfur-containing compounds. Examples of sulfur-containing compounds include SO2, SO3, H2S, thiols, dithiols, sulfides, and disulfides. The present invention will become more apparent from the following definitions and accompanying discussion.
The catalytic materials useful in the present invention are those which contain manganese and particularly those which contain manganese dioxide as explained in detail hereinafter. Such catalytic materials are especially suitable for treating ozone. Ozone treating catalyst compositions comprise manganese compounds including manganese dioxide, non stoichiometric manganese dioxide (e.g., XMnO(1 5. 20)), and/or XMn2O3wherein X is a metal ion, preferably an alkali metal or alkaline earth metal (e.g. sodium, potassium and barium). Variable amounts of water (H2O, OH") can be incorporated in the structure as well. Preferred manganese dioxides, which are nominally referred to as MnO2 have a chemical formula wherein the molar ratio of manganese to oxide is about from 1.5 to 2.0. Up to 100 percent by weight of manganese dioxide MnO2 can be used in catalyst compositions to treat ozone. Alternative compositions which are available comprise manganese dioxide and compounds such as copper oxide alone or copper oxide and alumina. In accordance with the present invention, the most dramatic improvement in catalytic efficiency with higher pore size distribution is seen with catalyst containing manganese dioxide alone. Useful and preferred manganese dioxides are alpha-manganese dioxides nominally having a molar ratio of manganese to oxygen of from 1 to 2. Useful alpha manganese dioxides are disclosed in U.S. Patent No. 5,340,562 to O'Young, et al.; also in O'Young, Hydrothermal Synthesis of Manganese Oxides with Tunnel Structures presented at the Symposium on Advances in Zeolites and Pillared Clay Structures presented before the Division of Petroleum Chemistry, Inc. American Chemical Society New York City Meeting, August 25-30, 1991 beginning at page 342; and in McKenzie, the Synthesis of Birnessite, Cryptomelane, and Some Other Oxides and Hydroxides of Manganese, Mineralogical Magazine, December 1971, Vol. 38, pp. 493-502. For the purposes of the present invention, the preferred alpha- manganese dioxide is selected from hollandite (BaMn8O16.xH2O), cryptomelane (KMn8O16.xH2O), manjiroite (NaMn8O16.xH2O) or coronadite (PbMn8O,6.xH2O). The manganese dioxides useful in the present invention preferably have a surface area as high as possible while maintaining a pore size distribution of at least 10 nm. A preferred surface area is at least 100 m2/g. The composition preferably comprises a binder as of the type described below with preferred binders being polymeric binders. The composition can further comprise precious metal components with precious metal components being the oxides of precious metal, including the oxides of platinum group metals and oxides of palladium or platinum also referred to as palladium black or platinum black. The amount of palladium or platinum black can range from 0 to 25%, with useful amounts being in ranges of from about 1 to 25 and 5 to 15% by weight based on the weight of the manganese component and the precious metal component.
It has been found that the use of compositions comprising the cryptomelane form of alpha manganese oxide, which also contain a polymeric binder can result in greater than 50%, preferably greater than 60% and typically from 75-85% conversion of ozone in a concentration range of up to 400 parts per billion (ppb). The preferred cryptomelane manganese dioxide can be calcined at a temperature range of from 250°C to 550°C and preferably below 500°C and greater than 300° for least 1.5 hours and preferably at least 2 hours up to about 6 hours. The preferred cryptomelane can be made in accordance with methods described and incorporated into U.S. Patent Application Serial No. 08/589,182 filed January 19, 1996 (Attorney Docket No. 3777C), incorporated herein by reference. The cryptomelane can be made by reacting a manganese salt including salts selected from the group consisting MnCl2, Mn(NO3)2, MnSO4 and Mn (CH3COO)2 with a permanganate compound. Cryptomelane is made using potassium permanganate; hollandite is made using barium permanganate; coronadite is made using lead permanganate; and manjiroite is made using sodium permanganate. It is recognized that the alpha-manganese dioxide useful in the present invention can contain one or more of hollandite, cryptomelane, manjiroite or coronadite compounds. Even when making cryptomelane minor amounts of other metal ions such as sodium may be present. Useful methods to form the alpha-manganese dioxide are described in the above references which are incorporated herein by reference.
The preferred alpha-manganese dioxide for use in accordance with the present invention is cryptomelane. The preferred cryptomelane is "clean" or substantially free of inorganic anions, particularly on the surface. Such anions could include chlorides, sulfates and nitrates which are introduced during the method to form cryptomelane. An alternate method to make the clean cryptomelane is to react a manganese carboxylate, preferably manganese acetate, with potassium permanganate.
It is believed that the carboxylates are burned off during the calcination process. However, inorganic anions remain on the surface even during calcination. The inorganic anions such as sulfates can be washed away with the aqueous solution or a slightly acidic aqueous solution. Preferably the alpha manganese dioxide is a "clean" alpha manganese dioxide. The cryptomelane can be washed at from about 60°C to 100°C for about one-half hour to remove a significant amount of sulfate anions. The nitrate anions may be removed in a similar manner. The "clean" alpha manganese dioxide is characterized as having an IR spectrum as disclosed in U.S. Patent Application Serial No. 08/589,182 filed January 19, 1996. A preferred method of making cryptomelane useful in the present invention comprises mixing an aqueous acidic manganese salt solution with a potassium permanganate solution. The acidic manganese salt solution preferably has a pH of from 0.5 to 3.0 and can be made acidic using any common acid, preferably acetic acid at a concentration of from 0.5 to 5.0 normal and more preferably from 1.0 to 2.0 normal. The mixture forms a slurry which is stirred at a temperature range of from 50°C to 110°C. The slurry is filtered and the filtrate is dried at a temperature range of from 75°C to 200°C. The resulting cryptomelane crystals have a surface area typically in the range of at least 100 m2/g. Other useful compositions comprise manganese dioxide and optionally copper oxide and alumina and at least one precious metal component such as a platinum group metal supported on the manganese dioxide and where present copper oxide and alumina. Useful compositions contain up to 100, from 40 to 80 and preferably 50 to 70 weight percent manganese dioxide, and 10 to 60 and typically 30 to 50 percent copper oxide. Useful compositions include hopcalite (supplied by, for example, Mine Safety Applications, Inc.) which is about 60 percent manganese dioxide and about 40 percent copper oxide; and Carulite® 200 (sold by Cams Chemical Co.) which is reported to have 60 to 75 weight percent manganese dioxide, 11 to 14 percent copper oxide and 15 to 16 percent aluminum oxide. The surface area of Carulite® 200 is reported to be about 180 m2/g. Calcining at 450°C reduces the surface area of the Carulite® by about fifty percent (50%) without significantly affecting activity. It is preferred to calcine manganese compounds at from 300°C to 500°C and more preferably 350°C to 450°C. Calcining at 550°C causes a great loss of surface area and ozone treatment activity. Calcining the Carulite® after ball milling with acetic acid and coating on a substrate can improve adhesion of the coating to a substrate. Other compositions to treat ozone can comprise a manganese dioxide component and precious metal components such as platinum group metal components. While both components are catalytically active, the manganese dioxide can also support the precious metal component. The platinum group metal component preferably is a palladium and/or platinum component. The amount of platinum group metal compound preferably ranges from about 0.1 to about 10 weight percent (based on the weight of the platinum group metal) of the composition. Preferably, where platinum is present it is present in amounts of from 0. 1 to 5 weight percent, with useful and preferred amounts on pollutant treating catalyst volume, based on the volume of the supporting article, ranging from about 0.5 to about 70 g/ft3. The amount of the palladium component preferably ranges from about 2 to about 10 weight percent of the composition, with useful and preferred amounts on pollutant treating catalyst volume ranging from about 10 to about 250 g/ft3.
Useful amounts of the catalytic material can range from 70 to 95, preferably from 75 to 90 weight percent of the catalytic coating based on dry weight of the catalytic coating.
The pollutant treating compositions of the present invention preferably comprise a binder which acts to adhere the composition and to provide adhesion to the atmosphere contacting surface. It has been found that a preferred binder is a polymeric binder used in amounts of from 3 to 20, more preferably from 5 to 15 percent by weight of binder based on the weight of the composition. Preferably, the binder is a polymeric binder which can be a thermosetting or thermoplastic polymeric binder. The polymeric binder can have suitable stabilizers and age resistors known in the polymeric art. The polymer can be a plastic or elastomeric polymer. Most preferred are thermosetting, elastomeric polymers introduced as a latex into a slurry of the catalyst composition, preferably an aqueous slurry. Upon application of the composition and heating the binder material can crosslink providing a suitable support which enhances the integrity of the coating, its adhesion to the atmosphere contacting surface and provides structural stability under vibrations encountered in motor vehicles. The use of preferred polymeric binder enables the pollutant treating composition to adhere to the atmosphere contacting surface without the necessity of an undercoat layer. The binder can comprise water resistant additives to improve water resistance and improve adhesion. Such additives can include fluorocarbon emulsions, silicone polymers, and petroleum wax emulsions.
Useful polymeric 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, poly vinyl 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.
Preferred binders are selected from the group consisting of polymers and copolymers of acrylics, vinyl acrylics, styrene acrylics, ethylene vinyl acetates, vinyl acetates, fluorinated polymers and silicones.
Particularly preferred polymers and copolymers are vinyl acrylic polymers and ethylene vinyl acetate copolymers. A preferred vinyl acrylic polymer is a cross linking polymer sold by National Starch and Chemical Company as Xlink 2833. It is described as a vinyl acrylic polymer having a Tg of -15°C, 45% solids, a pH of 4.5 and a viscosity of 300 cps. In particular, it is indicated to have vinyl acetate CAS No. 108-05-4 in a concentration range of less than 0.5 percent. It is indicated to be a vinyl acetate copolymer. Other preferred vinyl acetate copolymers which are sold by the National Starch and Chemical Company include Dur-O-Set E-623 and Dur-O-Set E- 646. Dur-O-Set E-623 is indicated to be an ethylene vinyl acetate copolymer having a Tg of 0°C, 52% solids, a pH of 5.5 and a viscosity of 200 cps. Dur-O-Set E-646 is indicated to be an ethylene vinyl acetate copolymer with a Tg of -12 °C, 52% solids, a pH of 5.5 and a viscosity of 300 cps. A useful and preferred binder is a crosslinking acrylic copolymer sold by National Starch and Chemical Company as X-4280. It is described as a milk white aqueous emulsion having a pH of 2.6; a boiling point of 212°F, a freezing point of 32°F; a specific gravity of 1.060; a viscosity of 100 cps. Polymeric dispersants may be added to enhance or promote slurry stability between the binder and catalyst. Binder/catalyst compatibility may be achieved by adding a polymeric aery late derived dispersant (ca. 3% solids basis). The dispersant can be added during the ball milling operation or after. Despite generating a large negative charge on the catalyst particles, not all dispersants work equally as well. Preferred dispersants comprise polymers containing carboxylic acid groups or derivatives thereof such as esters and salts. Preferred dispersants include Accusol 445 (from Rohm & Haas) and Colloid 226/35 (from Rhone-Poulenc). Useful dispersants and a review of dispersion technology are presented in, Additives for Dispersion Technology, published by Rhone-Poulenc, Surfactants & Specialties hereby incorporated by reference. Useful polymeric dispersants include but are not limited to polyacrylic acid partial sodium salts (i.e., at least partially contains a sodium salt of polyacrylic acid) and anionic copolymer sodium salts sold by Rhone-Poulenc as Colloid ™ polymeric dispersants. Again, although surface charge is an important factor in determining catalyst/binder compatibility, it is not the only factor. In general, the dispersant (particularly Colloid 226) does a good job of stabilizing the slurry since a greater variety of latex binders (e.g. acrylics, styrene acrylics, and EVA's) are compatible. Long term compatibility problems may be addressed by increasing the quantity of dispersant, raising the pH somewhat, or both. Useful amounts of dispersant range from 2 to 10, preferably from 2 to 6 weight percent of dispersant based on the dry weight of the composition.
The polymeric slurries of the present invention, particularly polymer latex slurries, can contain conventional additives such as thickeners, biocides, antioxidants, antifoamants and the like. The pollutant treating composition can be applied to the atmosphere contacting surfaces by any suitable means such as spray coating, powder coating, or brushing or dipping the surface into a catalyst slurry.
Milling of the catalytic composition may be done in any of a number of conventional particle milling devices in order to reach the desired particle size . One suitable device is a ball mill. The degree of particle milling can conveniently be measured by devices using light scattering techniques and the milling is stopped once the desired particle size is reached. One such suitable particle size measuring device is the Horiba LA-500 Laser Diffraction Particle Size Distribution Analyzer.
The particle size referred to in the following examples and in the claims in the median particle size is based on the total number of particles in the measured sample. The invention will become more apparent with reference to the accompanying examples.
EXAMPLES Preparative Examples Q=l lOOOg of high surface area MnO2 (220-250 m2/g cryptomelane) is combined in a 1 gallon ball mill with 1500g of deionized water and 50g of acetic acid (5% solids based on MnO2 weight). The resulting mixture is milled for approximately 15 minutes to a median particle size of approximately 3.5 μm. The slurry is drained from the mill, and the solids are reduced to 25% with the addition of deionized water. Using an overhead stirrer, 288.5g of National Starch E-646 EVA latex binder (15% solids based on MnO2 weight) are added with stirring. The mixture is stirred a minimum of 30 minutes. The final slurry pH is approximately 4.5. The resulting composition contained approximately 83.3% MnO2, and 12.5% latex binder and 4.2% acetic acid residue (e.g., in the form of acetate) based on dry weight of the composition.
E-l
6000g of high surface area MnO2 (220-250 m2/g cryptomelane) is combined in a 9 gallon ball mill with 9000g of deionized water and 514.3g of Rhone-Poulenc Colloid 226/35 polyacrylate dispersant (3% solids based on MnO2 weight). The resulting mixture is milled for approximately 22 hours to a median particle size <1.0 μm. An additional 342.8g of Colloid 226 dispersant (2% solids based on MnO2 weight) is added, the slurry is rolled for 10 minutes, and the mill is drained into a suitable mixing container. The resulting slurry is reduced to 25% solids overall with the addition of deionized water. Using an overhead stirrer, 13% of National Starch x- 4280 acrylic latex binder, 3.5% of Rohm & Haas RM-8W polymeric thickener, and 0.25% of Nopco NXZ defoamer are added sequentially with mixing (percentage amounts added are calculated on a solids basis compared to weight of MnO2). The mixture is stirred a minimum of 30 minutes and then packaged for transport to a coating facility. The final slurry pH is approximately 5.5. The resulting composition contained approximately 82.3 % MnO2, 4.1% dispersant, and 10.7 % latex binder, and
2.9 % thickener based on dry weight of the composition.
In each of the foregoing examples, catalyst particle size was measured with a
Horiba LA-500 Laser Diffraction Particle Size Distribution Analyzer. Specifically each catalytic material was ultrasonicated in the analyzer test chamber for approximately 20-30 seconds prior to the particle size measurement. The particle size is reported as a median based on the total number of particles in the measured sample.
In other words, the smallest 50% of particles in the entire distribution have a particle size less than the median particle size value. Reproducibility in the measurement due to variability in the sampling is on the order of +/-0.1 μm.
Comparative Examples
Resistance to sulfur poisoning for the C-l and E-l compositions are set forth in Table 1. Coating compositions of C-l and E-l were applied to separate 7/8" x 1/2" x 1 " 1997 Ford Taurus aluminum radiator samples in coat weights of approximately 0.35 g/in3.
TABLE 1
Figure imgf000013_0001
Aging Conditions: 1.0 ppm S02; 600,000/h Space Velocity; 75°C Reaction Temperature, 15°C
Dewpoint; No Ozone.
Conversion Measurement Conditions: ca. 250 ppb 03; 600,000/h Space Velocity; 75°C Reaction
Temperature; 15°C Dewpoint; No S02; + 3% Reproducibility.
The amount of sulfur absorbed into the coating after aging was measured by IR. Referring to Table 1 , the sulfur absorption results clearly indicate that Example E-l picks up significantly less sulfur than Example C-l after aging for up to 24 hours in a stream of 1 ppm SO2. The effect of this is a measurable and significant improvement in ozone conversion efficiency of E-l relative to C-l after aging. This result is quite unexpected since at roughly equivalent binder loadings one would expect the smaller particle size E-l coating to pick up more sulfur than a larger sized particle due to the much higher overall particle geometric surface area (i.e., smaller particles gives higher total surface area).
The results are clearly advantageous from a sulfur poisoning durability standpoint. For a point of reference, exposure of 1 ppm SO2 for 24 hours is roughly equivalent to the amount of SO2 which would come into contact with a catalyst coating on an automobile radiator after driving 100,000 miles in air containing the US national ambient SO2 level of 6 ppb. Thus, comparing the difference in the amount of sulfur absorbed for the 24 hour test between the E-l and C-l coatings, one sees that E- 1 collects only approximately 70 percent (3.9/5.6 x 100%) of the sulfur that C-l collected which translates to approximately an additional 43,500 miles (100,000 x 5.6/3.9) of catalyst durability.
The principles, preferred embodiments, and modes of operating of this invention have been described in the foregoing specification. However, the invention which is intended to be protected herein is not to be construed as limited to the particular forms disclosed, since they are to be regarded as illustrative rather than restrictive. Variations and changes may be made by those skilled in the art without departing from the spirit of the invention.

Claims

What is claimed is:
1. An ozone decomposition composition comprising a manganese oxide wherein the median particle size diameter of the manganese oxide is equal to or less than about 1 micrometer thereby enabling the composition to be resistant to sulfur poisoning.
2. The composition of claim 1, wherein the particle size diameter is about 0.7 micrometer.
3. The composition of claim 1 or 2, further comprising platinum or palladium and a binder.
4. The composition of claim 1 or 2, wherein the binder is a polymeric binder.
5. The composition of claim 4, wherein the binder is selected from the group consisting of polymers and copolymers of acrylics, vinyl acrylics, styrene acrylics, ethylene vinyl acetates, vinyl acetates, fluorinated polymers and silicones.
6. The composition of claim 5, wherein the manganese oxide comprises 70-95 weight percent of the composition based on dry weight.
7. The composition of claim 6, wherein the binder is from 3 to 20 weight percent of the composition based on dry weight.
8. The composition of claim 7 further comprising a polymeric dispersant in an amount from 2 to 10 weight percent of the compostion based on dry weight.
9. The composition of claim 8, wherein the manganese oxide is an alpha-manganese dioxide.
10. The composition of claim 9, wherein the alpha-manganese dioxide is cryptomelane.
11. The composition of claim 10, wherein the cryptomelane comprises from 75 to 90 weight percent of the composition, the binder is an acrylic polymer or an ethylene vinyl acetate copolymer comprising from 5 to 15 weight percent of the composition, and the dispersant is a polymer containing carboxylic acid groups or derivatives thereof such as esters and salts comprising from 2 to 6 weight percent of the composition.
12. The composition of claim 11, wherein the dispersant comprises at least a partial sodium salt of a polyacrylic acid.
13. The composition of claim 12, further comprising platinum or palladium.
14. The method of decomposing ozone in an atmosphere containing sulfur compounds comprising contacting the atmosphere with a composition comprising a manganese oxide wherein the median particle size diameter of the manganese oxide is equal to or less than about 1 micrometer thereby enabling the composition to be resistant to sulfur poisoning.
15. The method of claim 14, wherein the sulfur-containing compounds are SO2, SO3, H2S, thiols, dithiols, sulfides or disulfides.
16. The method of claim 15, wherein the particle size diameter is about 0.7 micrometer.
17. The method of claim 16, wherein the manganese oxide is cryptomelane.
18. The method of claim 17, further comprising a polymeric binder.
19. The method of claim 18, wherein the binder is selected from the group consisting of polymers and copolymers of acrylics, vinyl acrylics, styrene acrylics, ethylene vinyl acetates, vinyl acetates, fluorinated polymers and silicones.
20. The method of claim 19, wherein the binder is from 3 to 20 weight percent of the composition based on dry weight.
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Publication number Priority date Publication date Assignee Title
US6699529B2 (en) 2002-05-20 2004-03-02 Engelhard Corporation Method for coating vehicular radiators with ozone depleting slurry catalyst
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CN112023685A (en) * 2020-08-04 2020-12-04 汤忠武 Ozone treatment equipment

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