WO2000051713A1

WO2000051713A1 - Decontamination methods and compositions

Info

Publication number: WO2000051713A1
Application number: PCT/US2000/004907
Authority: WO
Inventors: Graeme Duncan Cruickshank; Barry Stoddart; Gordon Robert Davison
Original assignee: The Procter & Gamble Company
Priority date: 1999-02-27
Filing date: 2000-02-25
Publication date: 2000-09-08
Also published as: AU3708000A; GB9904440D0

Abstract

Use of a large pore molecular sieve incorporating a dπ-donor guest material and having a pore diameter greater than about 4-Angstroms as agent for the non-catalytic sorptive decontamination of a non-π-acceptor gas or gaseous mixture comprising π-acceptor gas-phase pollutant. Preferred guest materials include Cu and Ag. The methods, compositions and devices of the invention are applicable to the decontamination of a range of non-πacceptor gases or gaseous mixtures such as air, oxygen, nitrogen, carbon dioxide, hydrogen, the inert gases, saturated hydrocarbon gases, and mixtures thereof, and containing a range of π-acceptor gas phase pollutants such as carbon monoxide, oxides of nitrogen, oxides of sulfur, ethylene, and mixtures thereof.

Description

DECONTAMINATION METHODS AND COMPOSITIONS

TECHNICAL FIELD The present invention relates to compositions and methods for decontamination of gases or gaseous mixtures comprising gas-phase pollutants. In particular, the invention relates to compositions and methods for decontamination of non-π-acceptor gases or gaseous mixtures comprising π-acceptor gas-phase pollutants such as carbon monoxide and oxides of nitrogen.

BACKGROUND OF THE INVENTION

The effective control of pollutants in general and of air pollutants in particular is an important goal of late-20¹¹¹ Century society. Air pollution, as the term is generally understood, is the presence in the atmosphere of any substance at a concentration sufficiently high to produce an objectionable effect on humans, non-human animals, vegetation and other materials, or to significantly alter the natural balance of the ecosystem. Although there are a large number of natural and man-made materials that meet the pollution criteria, among the most important are gas-phase pollutants such as carbon monoxide and the oxides of nitrogen and sulfur, all of which are generated to varying degrees during combustion of fossil and other fuels. While emission control regulations have had a marked effect in reducing or controlling overall levels of gas-phase pollutants in the environment, nevertheless it remains an important goal to improve the quality of the air we breathe, not least in offices and residential buildings and other so- called 'indoor' situations.

In addition to the above man-made pollutants, naturally-occurring gases can also meet the general pollution criteria, if not being objectionable to the same degree. For example, ethylene is emitted naturally by fruit such as bananas, tomatoes, apples, pears, etc and plays an important role in the ripening of the fruit. Excess or uncontrolled ethylene production can be objectionable, however, in that it can lead to over-ripening. It would accordingly be advantageous to provide methods and compositions for controlling ethylene contamination in the headspaceof storage and transport containers in order to prevent over-ripening of fruit.

The use of sorbent materials for controlling gas-phase pollution is of course well-known. Activated carbon, for example, will sorb a wide range of organic compounds but unfortunately, the heterogeneous nature of activated carbon makes selective sorption of low molecular weight pollutant gases impossible. Sorbents of a more selective nature, for example zeolites, are also known. However, typical gas-phase pollutants are not strongly bound inside conventional zeotypes structures and so they can diffuse out and recontaminate the system being purified. Oxidative removal of carbon monoxide, on the other hand, (e.g. using platinum-palladium catalysts) normally requires a high reaction temperature (up to 250 °C) and its use is therefore is limited to specialist situations.

The present invention therefore provides novel non-catalytic sorptive methods, compositions and devices for decontaminating gases or gas mixtures comprising gas- phase pollutants.

SUMMARY OF THE INVENTION

In its broadest aspect, the present invention relates to the use of a large pore molecular sieve incorporating a dπ-donor guest material and having a pore diameter greater than about 4 Angstroms as agent for the non-catalytic sorptive decontamination of a non-π- acceptor gas or gaseous mixture comprising π-acceptor gas-phase pollutant.

Preferably, the dπ-donor guest material is selected from Group lb elements, Group VIII elements having filled outer d⁸ to d¹⁰ shells and mixtures thereof. Highly preferred herein are the Group lb elements, especially Cu, Ag, and mixtures thereof. Suitable Group VIII elements include Pt, Pd, Ni and Rh. The oxidation state of the dπ-donor guest material ranges generally from about -1 to about +2, and is preferably 0 or +1.

The invention herein is primarily directed to the decontamination of gases comprising gas-phase pollutants, i.e., gas components which are undesirable for environmental reasons, for example because they are toxic or have an adverse impact on health, or are objectionable for other environmental reasons. The gas-phase pollutants are referred to herein as π-acceptor gas-phase pollutants as they are capable of acting as π-acceptor ligands with electron-rich dπ-donor transition and heavy metal centres, the resulting complexes being stabilized by strong σ-π bonding. It has now been found that large pore molecular sieves incorporating dπ-donor guest materials such as Cu or Ag are particularly effective decontaminant materials and are capable of lowering and maintaining the concentration of π-acceptor gas-phase pollutants in a gas stream or in a closed or relatively closed space, for example, residential buildings, factories, shops, offices, greenhouses or other 'indoor' situations, storage containers e.g., for vegetables, fruit etc, to an environmentally-acceptable level.

In general terms, the methods, compositions and devices of the invention are applicable to the decontamination of a range of non-π-acceptor gases or gaseous mixtures such as air, oxygen, nitrogen, carbon dioxide, hydrogen, the inert gases, saturated hydrocarbon gases, and mixtures thereof, and containing a range of π-acceptor gas phase pollutants such as carbon monoxide, oxides of nitrogen, oxides of sulfur, ethylene, and mixtures thereof. Naturally, however, the optimum guest material for a given pollutant gas will depend sensitively on nature of the pollutant, the manner in which it interacts with the guest material, and the nature of the gas materials which are to be decontaminated.

The invention herein relates to methods, compositions and devices which are based on so- called non-catalytic sorption principles. In other words, the pollutant gas is absorbed or adsorbed within the pores of the molecular sieve and is trapped therein by strong σ-π complexation with the dπ-donor guest material. Importantly, the dπ-donor guest material acts purely as a sorbent for the pollutant gas, not as a catalyst for further chemical reaction. Accordingly, the non-catalytic sorptive decontamination is generally undertaken at temperature and pressure conditions at or close to ambient, e.g., temperatures from about -10°C to about 45 °C, preferably from about 0°C to about 30°C; pressures form about 0.5 to about 1.5 atmospheres, preferably from about 0.9 to about 1.1 atmospheres.

The dπ-donor guest material is incorporated in the large pore molecular sieve by methods well-known in the art, for example, ion exchange, incipient wetness impregnation, framework exchange, functionalisation reactions, etc. In addition, the guest material is incorporated in a decontamination-effective amount, for example, in an amount from about 0.1% to about 20% , preferably from about 0.5% to about 15%, and especially from about 1% to about 10% by weight of the final molecular sieve material.

Preferred molecular sieves herein are selected from: a) mesoporous molecular sieves having a pore diameter of at least 13, preferably at least 15, and more preferably at least 20 Angstroms; b) phosphate-containing molecular sieves, especially those selected from aluminophosphates, silicoaluminophosphates, metalloaluminophosphates and metallosilicoaluminophosphates wherein 'metallo' represents an additional metallic element selected from Mg, Ti, Mn, Co, Fe, Ga, and Zn; and c) mixtures therof.

Of these, highly preferred are the mesoporous molecular sieves designated M41S which consist essentially of crystalline, inorganic material exhibiting after calcination an X-ray diffraction pattern with at least one peak at a d-spacing of at least 18 Angstroms. A highly preferred material under the M41S designation is MCM-41 which can be described as a mesoporous molecular sieve consisting essentially of inorganic, porous, crystalline material having, after calcination, a hexagonal arrangement of uniformly-sized pores having a pore diameter of at least about 13 Angstrom and exhibiting a hexagonal electron diffraction pattern that can be indexed with a d₁₀₀ value greater than about 18 Angstrom units.

In a method aspect, the present invention provides a method for the non-catalytic sorptive decontamination of a non-π-acceptor gas or gaseous mixture comprising π-acceptor gas- phase pollutant comprising treating the gas or gaseous mixture with a large pore molecular sieve incorporating a dπ-donor guest material and having a pore diameter greater than about 4 Angstroms.

The present invention also provides a composition for the non-catalytic sorptive decontamination of a non-π-acceptor gas or gaseous mixture comprising π-acceptor gas- phase pollutant, the composition comprising a) a large pore molecular sieve incorporating a dπ-donor guest material and having a pore diameter greater than about 4 Angstroms, and b) an environmentally-acceptable carrier therefor.

The compositions herein can take various forms including optionally agglomerated particulate solids, membranes, encapsulates, bars, liquids, gels and aerosols.

The present invention also provides a control device for the non-catalytic sorptive decontamination of a non-π-acceptor gas or gaseous mixture comprising π-acceptor gas- phase pollutant, the control device comprising as active ingredient a large pore molecular sieve incorporating a dπ-donor guest material and having a pore diameter greater than about 4 Angstroms. The control devices of the invention can be applied in a variety of consumer and retail products designed for personal, household, industrial and institutional use, for example, filtration systems based on fabrics, fine fibres, and granular and fluidised beds; air conditioning systems; throw-away or regenerable canisters or cartridges; food storage containers, e.g., for preventing over-ripening of fruit; air purification systems for controlling build-up of toxic gases in automobiles, bedrooms, kitchens, etc; secondary emission control systems for use in conjunction with the primary catalytic emissions control system of an internal combustion engine, etc DETAILED DESCRIPTION OF THE INVENTION

The compositions herein comprise an amount of a large pore molecular sieve incorporating a dπ-donor guest material effective for the non-catalytic sorptive decontamination of a non-π-acceptor gas or gaseous mixture comprising π-acceptor gas- phase pollutant, preferably in an amount of at least about 0.001%, more preferably from about 0.001 % to about 20%, and most preferably from about 0.05% to about 10% by weight of composition.

As used herein, the term "large pore molecular sieve" refers to a range of microporous and mesoporous crystalline materials built around an inorganic charged or neutral framework and possessing pores having a relatively uniform size distribution. In general, the pore diameter of the molecular sieves herein should be greater than about 4, preferably greater than about 8, and especially greater than about 10 Angstroms. Preferred herein, however, are molecular sieves falling within the class of mesoporous materials wherein the pore diameter is preferably at least about 13, more preferably at least about 15 and especially at least about 20 Angstroms. Mesoporous molecular sieves of this type can be generally described as crystalline, inorganic materials which exhibit after calcination an X-ray diffraction pattern with at least one peak at a d-spacing of at least about 18 Angstroms. As used herein, the term 'crystalline' indicates that the molecular sieve has sufficient order to provide, following calcination, a diffraction pattern such as, for example, by X- ray, electron or neutron diffraction with at least one peak It should also be noted that the molecular sieve may exist as a mixture of physically distinct phases. Also, defects and imperfections can cause significant deviations from an ideal regular structure. Generally, however, the pore size distribution within a single phase will be within about 25%, usually within about 15% of the average pore size for that phase. The pore diameter of the molecular sieves can be determined in known manner, for example, by transmission electron microscopy (TEM), x-ray diffraction or argon physisorption. TEM is the preferred technique herein. Suitable methods for determining pore diameter by argon physisorption are disclosed in US-A-5,098,684.

Molecular sieves suitable for use herein include large pore natural and synthetic zeolites, i.e., molecular sieves based on a crystalline silicate or aluminosilicate framework, as well as phosphate-containing molecular sieves and zeolite analogs such as aluminophosphates, silicoaluminophosphates, metalloaluminophosphates and metallosilicoaluminophosphates wherein 'metallo' represents an additional metallic element such as Mg, Ti, Mn, Co, Fe, Ga, or Zn. Large pore silicate molecular sieves (essentially aluminium-free) are also suitable for use herein. For a general discussion of zeoilite-type molecular sieves, see D.W. Breck, Zeolite Molecular Sieves, Structure, Chemistry and Use, John Wiley & Sons, Inc., New York, 1974.

Molecular-sieves of the aluminosilicate variety (zeolites) can be represented by the empirical formula M_2/11O . Al₂O ₃ . ySiO₂. wH₂O, where y is 2 or greater, M is the charge balancing cation, such as sodium, potassium, ammonium, magnesium, and calcium, n is the cation valence, and w represents the moles of water contained in the zeolitic voids. The zeolite framework is made up of SiO₄ tetrahedra linked together by sharing of oxygen ions. Substitution of a Group IIIB metal such as Al for Si generates a charge imbalance, necessitating the inclusion of a cation. The structures contain channels or interconnected voids that are occupied by the cations and water molecules. The water may be removed reversibly, generally by the application of heat, which leaves intact the crystalline host structure permeated with micropores that may account for >50% of the microcrystal's volume. In some zeolites, dehydration may produce some perturbation of the structure, such as cation movement, and some degree of framework distortion.

There are two basic types of zeolite structures: one provides an internal pore system comprising interconnected cage- like voids; the second provides a system of uniform channels which, in some instances, are one-dimensional and in others intersect with similar channels to produce two- or three-dimensional channel systems. The preferred type has two- or three-dimensional channel systems to provide rapid intracrystalline diffusion in adsorption and catalytic applications. Substitution of phosphorus for some or all of the framework silicon not only makes it possible to extend the range of molecular sieves to higher pore sizes but it also has significant impact on the residual framework charge, hydrophobicity, and the binding/complexing character of the molecular sieve.

Molecular sieves of the phosphate-containing class are well-known and are disclosed in a number of documents. Suitable aluminophosphates, for example, include those disclosed in US-A-4,310,440 and US-A-4,385,994. These aluminophosphates have essentially electroneutral lattices. US-A-3,801,704 discloses an aluminophosphate treated in a certain way to impart acidity.

An early reference to a hydrated aluminophosphate which is crystalline until heated at about 110 °C, at which point it becomes amorphous or transforms, is the "H ' phase or hydrate of aluminium phosphate of F. dYvoire, Memoir Presented to the Chemical Society, No. 392, "Study of Aluminium Phosphate and Trivalent Iron", July 6, 1961 (received), pp.1762- 1776. This material, when crystalline, is identified by the JCPDS Internal Center for Diffraction Data card number 15-274. Once heated at about 110 °C, however, the dΥvoire material becomes amorphous or transforms to the aluminophosphate form of tridymite.

Compositions comprising crystals having a framework topology after heating at 110 °C or higher giving an X-ray diffraction pattern consistent with a material having pore windows formed by 18 tetrahedral members of about 12-13 Angstroms in diameter are disclosed in US-A-No. 4,880,611.

A naturally occurring, highly hydrated basic ferric oxyphosphate mineral, cacoxenite, is reported by Moore and Shen, Nature, Vol. 306, No. 5941, pp. 356-358 (1983) to have a framework structure containing very large channels with a calculated free pore diameter of 14.2 Angstroms.

Silicoaluminophosphates of various structures are disclosed in US-A-4,440,871, US-A-3,355,246 (ZK-21) and US- A-3, 791,964 (ZK-22). Other disclosures of silicoaluminophosphates and their synthesis include US-A-4,673,559 (two-phase synthesis method); US-A-4,623,527 (MCM 10); US-A-4,639,358 (MCM-1); US-A- 4,647,442 (MCM-2); US-A-4,664,S97 (MCM-4); US-A-4,638,357 (MCM-5); and US-A- 4,632,811 (MCM-3). A method for synthesizing crystalline metalloaluminophosphates is disclosed in US-A- 4,713,227, while an antimonophosphoaluminate and its synthesis are disclosed in US-A- 4,619,818. US-A-4,567,029 discloses metalloaluminophosphates, while titaniumaluminophosphate and its synthesis are disclosed in US-A-4,500,651.

Other suitable phosphate-containing molecular sieves include the phosphorus substituted zeolites of CA-A-911,416; CA-A-911,417; and CA-A-911,418. US-A-4,363,748 describes a combination of silica and aluminium-calcium-cerium phosphate as a low acid activity catalyst for oxidative dehydrogenation. GB-A-2,068,253 discloses a combination of silica and aluminium-calcium-tungsten phosphate as a low acid activity catalyst for oxidative dehydrogenation. US-A-4,228,036 discloses an alumina-aluminium phosphate-silica matrix as an amorphous body to be mixed with zeolite for use as cracking catalyst. US-A-3,213,035 teaches improving hardness of aluminosilicate catalysts by treatment with phosphoric acid. The catalysts are amorphous.

Other patents teaching aluminophosphates include US-A-4,365,095; US-A-4,361,705; US-A- US-A-4,222,896; US-A-4,210,560; US-A-4, 179,358; US-A-4, 158,621; US-A- 4,071,471; US-A-4,014,945; US-A-3,904,550; and US-A-3,697,550.

Other pertinent references on phosphate-containing molecular sieves include S.T. Wilson and co-workers, J. Amer. Chem. Soc. 104, 1146 (1982); S.T. Wilson, B.M. Lok, CA. Messina, and E.M. Flanigen, ACS Symp. Ser. 218,79 (1983); B.M. Lok and co-workers, J. Amer. Chem. Soc. 106, 6092 (1984); U.S. Pat. 4,554,143; U.S. Pat. 4,567, 029 S.T. Wilson and E.M. Flanigen, ACS Symp. Ser. 398,329 (1989); and E.M. Flanigen, B.M. Lok, R.L. Patton, and S.T. Wilson, Pure & Appl.Chem.58,1351 (1986).

A number of specific synthetic routes to large pore phosphate-containing molecular sieves have been reported in the literature, for example, AlPO₄-8 ( R.M. Dessau, J.L. Schlenker, and J.B. Higgins, Zeolites 10,522 (1990)); VPI-5 ( M.E. Davis, C. Montes, and J.M.

Garces, ACS Symp. Ser. 398, 291 (1989)); cloverite (J. Patarin and co-workers, Proc. 9^th Intern. Zeolite Conf. I, 263 (1993)); and JDF-20 (Q. Huo and co-workers, J. Chem. Soc, Chem. Commun. 875 (1992)). Cacoxenite, a natural large pore ferroaluminophosphate has also been structurally characterised (P.B. Moore and J. Shen, Nature 306, 356 (1983)). Of all the above, molecular sieves of the phosphate-containing type preferred for use herein include AlPO₄-5, AlPO₄-8, SAPO-5, SAPO-37, VPI-5, Cloverite (an 18-membered ring gallophosphate), and JDF-20.

Another class of large pore molecular sieves suitable for use herein are the liquid crystal template-synthesised M41S range of mesoporous molecular sieves reported by C.T. Kresge and co-workers, Nature 359, 710 (1992) and by Beck and co-workers, J. Amer. Chem. Soc. 114, 10834 (1992). See also US-A-5,102,643, US-A-5,250,282, US-A- 5,264,203, US-A-5,145,816, US-A-5,098,684, US-A-5,378,440, US-A-5,098,684, US-A- 5,108,725 and US-A-5,057,296.

In general terms, the M41S mesoporous molecular sieves can be described (see US-A- 5,378,440) as inorganic, porous, non-layered crystalline phase materials which exhibit, after calcination, an X-ray diffraction pattern with at least one peak at a d-spacing greater than about 18 Angstrom Units with a relative intensity of 100 and a benzene adsoφtion capacity of greater than 15 grams benzene per 100 grams of anhydrous crystal at 50 torr and 25 °C.

Highly preferred M41S molecular sieves herein are mesoporous molecular sieves which consist essentially of inorganic, porous, crystalline material having, after calcination, a hexagonal arrangement of uniformly-sized pores having a pore diameter of at least about 13 Angstrom and exhibiting a hexagonal electron diffraction pattern that can be indexed with a d_]00 value greater than about 18 Angstrom units. Such materials have been given the designation MCM-41 (see US-A-5,378,440).

Preferred large pore molecular sieves for use herein have a pore diameter of about 13 Angstroms or greater, more preferably of about 20-200 Angstroms, and most preferably about 30-100 Angstroms. Also preferred molecular sieves herein have surface area of at least about 300 m² /g, more preferably at least about 400 m²/g and most preferred being at least about 500 m²/g. In addition, the molecular sieves preferred for use herein are relatively hydrophobic, being either aluminium-free or having an Si:Al molar ratio of at least about 10:1, preferably at least about 30:1, more preferably at least about 60:1, and especially at least about 100:1

The molecular sieves can be used in colloidal or micron-sized form (with a primary particle size of less than about 10 microns, preferably less than about 1 micron, more preferably less than about 0.1 micron) or they can be used as larger sized particles (compositions at risk of inhalation, for example, will generally have a particle size in excess of 10 microns, preferably greater than 15 microns) or they can be shaped or agglomerated into a wide variety of particle sizes. Generally speaking, shaped/agglomerated particles can be in the form of a powder, a granule, or a molded product, such as an extrudate having particle size sufficient to pass through a 2 mesh (Tyler) screen and be retained on a 400 mesh (Tyler) screen.

It may be desirable to incoφorate the molecular sieves with a binder or a porous matrix material or to use the molecular sieve in conjunction with another sorbent material.

Suitable binders include inorganic materials such as sodium sulphate, clays, silica and/or metal oxides, such as alumina, titania, and/or zirconia. The latter may be either naturally occurring or in the form of gelatinous precipitates or gels, including mixtures of silica and metal oxides. The clays may be naturally occurring clays, e.g., bentonite and kaolin. Suitable organic binders include cellulose derivatives such as carboxymethyl cellulose and water-soluble polymers such as sodium polyacrylate. Porous matrix suitable herein include silica-alumina, silica-magnesia, silica zirconia, silica-thoria, silica-beryllia, silica- titania as well as ternary compositions such as silica-alumina-thoria, silica-alumina- zirconia, silica-alumina-magnesia and silica-magnesia-zirconia. Other sorbent materials suitable for admixture herein include activated carbon inclusive of virgin, regenerated and chemically treated granular activated carbon, zeolites other than those prescribed herein, polymeric adsorbents, activated alumina, ion exchange resin, manganese oxide, magnesium oxide, calcite, dolomite and mixtures thereof;

The guest material can be introduced into the pores of the molecular sieve in a number of ways including ion-exchange. In a preferred method, the molecular sieve is contacted with a solution or colloidal dispersion of the guest material using so-called incipient wetness impregnation. The guest material will generally be incoφorated in the molecular sieve at a weight ratio (guest materia sieve) in the range from about 1 : 1000 to about 1 :1, preferably from about 1 :200 to about 1 :4, more preferably from about 1 :50 to about 1:10.

Control devices containing the molecular sieve material are manufactured in known ways. For example, the molecular sieve material can be incoφorated in particulate form as an inner layer of a cartridge-type filtration device with outer layers as appropriate to provide additional filtration (particulates, moisture, etc) or structural support characteristics. Suitable other layers include compacted polyester urethane foam, glass fibre pads and filter papers, cellulosic layers, etc. Alternatively, the molecular sieve material can be suspended within a suitable carrier layer such as a relatively coarse glass fibre pad.

Claims

What is claimed is:

1. Use of a large pore molecular sieve incoφorating a dπ-donor guest material and having a pore diameter greater than about 4 Angstroms as agent for the non-catalytic soφtive decontamination of a non-π-acceptor gas or gaseous mixture comprising π- acceptor gas-phase pollutant.

2. Use according to claim 1 wherein the dπ-donor guest material is selected from Group lb elements, Group VIII elements having filled outer d^δ to d¹⁰ shells, and mixtures thereof.

3. Use according to claim 1 or 2 wherein the dπ-donor guest material is selected from Group lb elements and mixtures thereof.

4. Use according to claim 3 wherein the dπ-donor guest material is selected Cu, Ag, and mixtures thereof.

5. Use according to any of claims 1 to 4 wherein the non-catalytic soφtive decontamination is undertaken at ambient or near-ambient temperature and pressure conditions.

6. Use according to any of claims 1 to 5 wherein the π-acceptor gas phase pollutant is selected from carbon monoxide, oxides of nitrogen, oxides of sulfur, ethylene, and mixtures thereof.

7. Use according to any of claims 1 to 6 wherein the non-π-acceptor gas or gaseous mixture is selected from air, oxygen, nitrogen, carbon dioxide, hydrogen, the inert gases, saturated hydrocarbon gases, and mixtures thereof.

8. A method for the non-catalytic soφtive decontamination of a non-π-acceptor gas or gaseous mixture comprising π-acceptor gas-phase pollutant comprising treating the gas or gaseous mixture with a large pore molecular sieve incoφorating a dπ-donor guest material and having a pore diameter greater than about 4 Angstroms.

9. A composition for the non-catalytic soφtive decontamination of a non-π-acceptor gas or gaseous mixture comprising π-acceptor gas-phase pollutant, the composition comprising a) a large pore molecular sieve incoφorating a dπ-donor guest material and having a pore diameter greater than about 4 Angstroms, and b) an environmentally- acceptable carrier therefor.

10. A composition according to claim 9 wherein the dπ-donor guest material is selected from Cu, Ag, and mixtures thereof.

11. A composition according to claim 9 or 10 wherein the oxidation state of the dπ-donor guest material is from about -1 to about +2, preferably 0 or +1.

12. A composition according to any of claims 9 to 11 wherein the dπ-donor guest material is incoφorated in the large pore molecular sieve by ion exchange, incipient wetness impregnation, framework exchange, or functionalisation.

13. A composition according to any of claims 9 to 12 in the form of an optionally agglomerated particulate solid, membrane, encapsulate, bar, liquid, gel or aerosol.

14. A composition, method or use according to any of claims 1 to 13 wherein the molecular sieve is selected from mesoporous molecular sieves having a pore diameter of at least 13, preferably at least 15, more preferably at least 20 Angstroms.

15. A composition, method or use according to claim 14 wherein the mesoporous molecular sieve consists essentially of crystalline, inorganic material exhibiting after calcination an X-ray diffraction pattern with at least one peak at a d-spacing of at least 18 Angstroms.

16 A composition, method or use according to claim 14 or 15 wherein the mesoporous molecular sieve consists essentially of inorganic, porous, crystalline material having, after calcination, a hexagonal arrangement of uniformly-sized pores having a pore diameter of at least about 13 Angstrom and exhibiting a hexagonal electron diffraction pattern that can be indexed with a d₁₀₀ value greater than about 18 Angstrom units.

17 A composition, method or use according to any of claims 1 to 13 wherein the molecular sieve is a phosphate-containing molecular sieve, preferably selected from aluminophosphates, silicoaluminophosphates, metalloaluminophosphates and metallosilicoaluminophosphates wherein 'metallo' represents an additional metallic element selected from Mg, Ti, Mn, Co, Fe, Ga, and Zn.

18. A control device for the non-catalytic soφtive decontamination of a non-π-acceptor gas or gaseous mixture comprising π-acceptor gas-phase pollutant, the control device comprising as active ingredient a large pore molecular sieve incoφorating a dπ-donor guest material and having a pore diameter greater than about 4 Angstroms.