Catalyst to reduce carbon monoxide and nitric oxide from the mainstream smoke of a cigarette

[0001] The present invention generally relates to methods for reducing the amount of components such as carbon monoxide in a mainstream smoke from a cigarette during smoking. More specifically, the invention relates to cut filler compositions, cigarettes, methods of making cigarettes, and methods of smoking, which include the use of additives, in the form of nanoparticles, capable of reducing the amount of various components in tobacco smoke.

BACKGROUND OF THE INVENTION [0002] The following description refers to certain structures and methods, however, such references should not be construed as assuming that these structures and methods fall within the prior art according to the applicable statutory conditions. Applicants reserve the right to demonstrate that none of the subjects in question constitutes prior knowledge.

[0003] Smoking articles, such as cigarettes or cigars, produce both the mainstream smoke when puffing and the side smoke when puffing static. One of the components of both the main smoke stream and the side smoke stream is carbon monoxide (CO). Reducing the amount of carbon monoxide in smoke is desirable.

[0004] Catalysts, sorbents, and / or oxidants for smoking articles are disclosed in the following documents: U.S. Patent No. 6,371,127 to Snider et al., U.S. Patent No. 6,286,516 to Bowen et al., U.S. Patent No. 6,138,684 to Yamazaki et al., U.S. Patent No. 5,671,758 to Rongved, U.S. Patent 5,386,838 to Quincy, III et al., US Patent No. 5,211,684 to Shannon et al., US Patent No. 4,744,374 to Deffeves et al., US Patent No. 4,453,553 to Cohn, US Patent No. 4,450,847 to Owens, US Patent No. 4,182,348 to Seehofer et al., US Patent No. 4,108,151 to Martin et al., US Patent No. 3,807,416, and US Patent 3,720,214. Published patent applications WO 02/24005, WO 87/06104, WO 00/40104 and

EP 1 635 656 B1, U.S. Patent Application Publication Numbers 2002/2979 A1, 2003/0037792 A1 and 2002/0062834 A1 also relate to catalysts, sorbents and / or oxidants.

[0005] Iron and / or iron oxide have been described for use in tobacco products (see, e.g., US Patent No. 4,197,861; US ​​4,489,739 and US 5,728,462). Iron oxide has been described as a coloring agent (e.g., US Patent Nos. 4,119,104; US 4,195,645; US 5,284,166) and as a smoking control agent (e.g. U.S. Patent Nos. 3,931,824; US 4,109,663 and US 4,195,645) and was used to improve the taste, color and / or appearance (e.g., US patents US 6,095,152; US 5,598,868; US 5,129,408; US 5,105,836 and US 5,101,839).

[0006] Despite the development to date, there is still a need for improved and more effective methods and compositions for reducing the amount of carbon monoxide in a mainstream smoke from a smoking article during its smoking.

Summary [0007] Cut tobacco filler compositions, cigarette filters and / or cigarette paper, cigarettes, methods of making cigarettes and methods of smoking are provided that include the use of catalysts for converting carbon monoxide in the mainstream smoke to carbon dioxide and / or converting nitric oxide into main stream of smoke in nitrogen.

[0008] An embodiment provides a cigarette comprising a cut filler and a catalyst capable of converting carbon monoxide in the mainstream smoke to carbon dioxide and / or nitric oxide in the mainstream smoke to nitrogen, wherein the catalyst contains metal nanoparticles and / or metal oxide nanoparticles deposited on a substrate fiber.

[0009] A further embodiment provides a method of making a cigarette, comprising (i) adding a catalyst to a tobacco cut filler, cigarette paper wrapper and / or a cigarette filter, wherein the catalyst comprises metal nanoparticles and / or metal oxide nanoparticles deposited on a fibrous substrate; (ii) providing the cut filler to a cigarette making machine to produce a tobacco rod; (iii) placing a cigarette paper wrapper around a tobacco column to form a tobacco rod; and (iv) optionally attaching a cigarette filter to the tobacco column to form a cigarette. Cigarettes made according to the invention preferably contain up to about 200 mg catalyst per cigarette or more.

[0010] In a preferred embodiment, metal nanoparticles and / or metal oxide nanoparticles

EP 1 635 656 B1 contain metal elements selected from the group consisting of elements of group IB-VIIB,

VIII, IIIA and IVA of the periodic table, and mixtures thereof. For example, metal oxide nanoparticles may contain iron oxide, iron oxyhydroxide and copper oxide, and mixtures thereof.

Metal nanoparticles and / or metal oxide nanoparticles may have a specific surface area from ₂ between about 20 to 2500 m²/ g, average particle size less than about 50 nm, preferably less than about 10 nm. While the metal nanoparticles and / or metal oxide nanoparticles may further contain carbon, preferably the metal nanoparticles and / or metal oxide nanoparticles contain no carbon.

[0011] The fibrous support may contain hard-melting carbides and oxides selected from the group consisting of silicon carbide bonded, boron (III) oxide, alumina, silica, aluminosilicates, titanium dioxide, yttrium oxide, cerium dioxide, glasses, zirconium dioxide optionally stabilized with calcium oxide or magnesium oxide, and mixtures thereof. ₂

The fibrous support can have a specific surface from about 0.1 to 200 m²/ gi can contain millimeter, micron, submicron and / or nanofibers.

[0012] According to a preferred embodiment, the metal oxide nanoparticles comprise iron oxide, iron oxyhydroxide, copper oxide, and mixtures thereof. The catalyst can be added to the cigarette in an amount effective to convert at least 10% of carbon monoxide in the mainstream smoke to carbon dioxide and / or at least 10% of nitric oxide in the mainstream smoke to nitrogen. Preferably, less than the nanoparticle monolayer is deposited in and / or on the fibrous support. For example, the catalyst may contain from 0.1 to 50% by weight of nanoparticles deposited on a fibrous support, the catalyst being present in the cut filler, cigarette paper and / or cigarette filter.

[0013] According to a preferred method, the catalyst is formed by (i) combining metal nanoparticles and / or metal oxide nanoparticles and liquids to form a dispersion; (ii) combining the dispersion with a fibrous support; and (iii) heating the fibrous support to remove liquid and depositing nanoparticles in and / or onto the fibrous support.

[0014] According to another preferred method, the catalyst is formed by (i) combining a metal precursor and a solvent to form a solution of the metal precursor; (ii) contacting the fibrous support with the metal precursor solution; (iii) drying the fibrous support; and (iv) heating the fibrous support to a temperature sufficient to

The thermal decomposition of the metal precursor to form nanoparticles in and / or on a fibrous substrate. For example, the dispersion of nanoparticles or a metal precursor solution may be sprayed onto a fibrous support, preferably a heated fibrous support. Optionally, the dispersion of nanoparticles can be added to the metal precursor solution.

[0015] The metal precursor may be one or more of metal β-diketonates, metal dionates, metal oxalates and metal hydroxides, and the metal in the metal precursor may contain at least one element selected from groups IB-VIIB, VIII, IIIA and IVA of the periodic table elements, and mixtures thereof. The liquids used to make the nanoparticle dispersion, and the solvents used to make the metal precursor solution may include distilled water, pentanes, hexanes, aromatic hydrocarbons, cyclohexanes, xylenes, ethyl acetate, toluene, benzenes, tetrahydrofuran, acetone, carbon disulphide, dichlorobenzenes, nitrobenzenes , methyl alcohol, ethyl alcohol, butyl alcohol, aldehydes, ketones, chloroform, white spirit, and mixtures thereof. The metal precursor can be broken down into metal nanoparticles and / or metal oxide by heating to a temperature of about 200 to 400 ^aboutC.

[0016] Still another embodiment provides a method of smoking a cigarette as described above, which includes lighting the cigarette to form smoke and drawing smoke from the cigarette, wherein during smoking the catalyst acts as a catalyst for converting carbon monoxide to carbon dioxide and / or nitric oxide to nitrogen.

Brief Description of the Drawings [0017] Figure 1 shows SEM images of a catalyst obtained according to an embodiment in which iron oxide nanoparticles are deposited on a fibrous quartz wool substrate.

[0018] Figure 2 shows a comparison between the catalytic activity of Fe2O3 nanoparticles (NANOCAT® Superfine Iron Oxide (SFIO) from MACH I, Inc., King of Prussia, PA) having an average particle size of about 3 nm and powdered Fe2O3 (from Aldrich Chemical Company ) having an average particle size of about 5 μm.

[0019] Figure 3 shows the temperature dependence of the conversion rate for CuOi Fe2O3 nanoparticles as catalysts for oxidizing carbon monoxide with oxygen to form carbon dioxide.

Detailed Description of Preferred Embodiments [0020] Tobacco cut filler compositions, cigarettes, methods of making cigarettes and methods of smoking are provided that include the use of catalysts

EP 1 635 656 B1 having metal nanoparticles and / or metal oxide nanoparticles on a fibrous support capable of acting as a catalyst for the conversion of carbon monoxide (CO) to carbon dioxide (CO2) and / or nitrogen oxide (NOx) to nitrogen (N2).

[0021] The catalyst is able to affect the rate of a chemical reaction, e.g., by increasing the rate of oxidation of carbon monoxide to carbon dioxide and / or increasing the rate of reduction of nitric oxide to nitrogen without taking part in the reaction as its substrate or product. The oxidant is able to oxidize the substrate, e.g., by transferring oxygen to the substrate so that the oxidant itself is reduced.

[0022] "Smoking" a cigarette means heating or burning a cigarette to produce smoke that can be inhaled through the cigarette. Generally, smoking involves lighting one end of the cigarette and, while the tobacco it contains undergoes a combustion reaction, drawing smoke from the cigarette end in the mouth. You can also smoke in a different way. For example, a cigarette can be smoked by heating the cigarette and / or heating with an electric heater as described in US Patent Nos. 6,053,176; US 5,934,289; US 5,591,368 and US 5,322,075.

[0023] The term "mainstream" smoke refers to a mixture of gases passing through the tobacco rod and emitted through the end of the filter, that is, the amount of smoke emitted or drawn by the cigarette end placed in the mouth while smoking the cigarette.

[0024] In addition to the ingredients in tobacco, the temperature and concentration of oxygen inside the cigarette during smoking are factors that influence the formation and reaction of carbon monoxide, nitric oxide and carbon dioxide. For example, the total amount of carbon monoxide formed during smoking comes from a combination of three main sources: thermal decomposition (about 30%), combustion (about 36%) and reduction of carbon dioxide on charred tobacco (at least 23%). The formation of carbon monoxide from thermal decomposition, which is largely controlled by chemical kinetics, begins at about 180 ^aboutC and ends in about 1050 ^aboutC. The formation of carbon monoxide and carbon dioxide during combustion is controlled to a large extent by the diffusion of oxygen into the surface (ka) and by the surface reaction (kb). In 250^aboutC, ka and kb are approximately the same. In 400^aboutC, the reaction becomes controlled by diffusion. Finally, the reduction of carbon dioxide on charred tobacco or charcoal occurs at temperatures around 390^aboutC and higher.

[0025] During smoking, there are three clearly visible areas in the cigarette: combustion zone,

EP 1 635 656 B1 pyrolysis / distillation zone, and condensation / filtration zone. Without being limited by any theory, it is believed that the catalyst of the invention can accelerate the various reactions that occur in different areas of the cigarette during smoking.

[0026] First, the combustion zone is a cigarette burning zone produced during cigarette smoking, typically at the lit end of a cigarette. The temperature in the combustion zone is in the range of about 700^aboutC to about 950 ^aboutC, and the heating rate can be as high as 500 ^aboutC / second. Because oxygen is consumed in the combustion of tobacco to produce carbon monoxide, carbon dioxide, nitrogen oxide, water vapor, and various organic compounds, the oxygen concentration in the combustion zone is low. Low oxygen levels combined with high temperatures lead to a reduction of carbon dioxide to carbon monoxide on charred tobacco. In this area, the catalyst can convert carbon monoxide to carbon dioxide by both catalysis and oxidation, and the catalyst can convert nitric oxide into nitrogen by both catalysis and reduction. The combustion zone is highly exothermic and the heat generated is transferred to the pyrolysis / distillation zone.

[0027] The pyrolysis zone is the area behind the combustion zone where temperatures range from about 200 ^aboutC to about 600 ^aboutC. The pyrolysis zone is where most of the carbon monoxide and nitric oxide are produced. The main reaction is the pyrolysis (i.e., thermal decomposition) of tobacco, which produces carbon monoxide, carbon dioxide, nitrogen oxide, smoke constituents, and charcoal, using the heat generated in the combustion zone. There is a certain presence of oxygen in this area, and therefore the catalyst can act as a catalyst for the oxidation of carbon monoxide to carbon dioxide and / or the reduction of nitric oxide to nitrogen. The catalytic reaction starts at 150^aboutYou achieve a maximum activity of around 300 ^aboutC.

[0028] In the condensation / filtration zone, the temperature ranges from ambient temperature to about 150 ^aboutC. The main process in this zone is the condensation / filtration of smoke constituents. A certain amount of carbon monoxide, carbon dioxide and nitrogen oxide diffuses out of the cigarette and some oxygen diffuses into the cigarette. The oxygen partial pressure in the condensation / filtration zone generally does not return to atmospheric pressure.

[0029] The catalyst contains metal and / or metal oxide nanoparticles deposited on a fibrous support. Nanoparticles may contain metallic elements selected from the group consisting of elements of Group IB-VIIB, VIII, IIIA and IVA of the periodic table, and mixtures thereof, e.g.,

EP 1 635 656 B1

B, C, Mg, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Sn, Ce, Hf, Ta, W, Re, Os, Ir, Pt and Au. The fibrous support may contain oxide-bonded silicon carbide, boron (III) oxide, alumina, silica, aluminosilicates, titanium dioxide, yttrium oxide, cerium dioxide, glasses, zirconia, or stabilized with calcium oxide or magnesium oxide, and mixtures thereof. While direct placement of the catalyst in the tobacco cut filler is preferred, the catalyst can be placed in a cigarette filter or included in a cigarette paper. The catalyst can also be placed in the cut tobacco filler and elsewhere.

[0030] Nanoparticles are a new class of materials whose distinguishing feature is that their average diameter, particle size or other structural domain is less than about 100 nanometers. The nanoparticles may have an average particle size less than about 100 nm, preferably less than about 50 nm, most preferably less than about 10 nm. Nanoparticles have very large surface area to volume ratios, which makes them attractive from the point of view of catalytic applications.

[0031] Due to the dispersion of nanoparticles on a fibrous support, the particles are easier to handle and combine with the cut tobacco filler than with the non-embedded particles. In the method, the nanoparticles can be combined with the tobacco cut filler before and / or during the introduction of the tobacco cut filler into a cigarette. The fibrous support can act as a separator that inhibits clumping or sintering of particles during the burning of the cut filler. Sintering particles can adversely extend the combustion zone, which can result in excessive CO and NOx production. The fibrous support minimizes particle sintering, and thus minimizes the elongation of the combustion zone and the loss of active surface area.

[0032] To maximize the amount of surface area of ​​the nanoparticles available for catalysis, preferably less than a nanoparticle monolayer is deposited inside and / or on the fibrous support. For example, the catalyst may contain from about 0.1 to 50% by weight of nanoparticles deposited on a fibrous support. By adjusting the charge of nanoparticles on a fibrous support, the activity of the catalyst / oxidant can be regulated. Due to the deposition of less than monolayers of nanoparticles, adjacent nanoparticles will be less sintered.

[0033] The synergistic combination of catalytically active nanoparticles with a catalytically active fibrous support can produce a more efficient catalyst. So nanoparticles

Disposed on the fibrous support preferably allow the use of small amounts of catalyst to catalyze, for example, oxidation of CO to CO2 and / or reduction of NOx to N2. [0034] According to a preferred method, metal nanoparticles and / or metal oxide nanoparticles, such as copper oxide nanoparticles and / or iron oxide nanoparticles can be dispersed in a liquid and thoroughly contacted with a fibrous support that is dried to produce a good dispersion of nanoparticles inside or on a fibrous medium.

[0035] According to another preferred method, nanoparticles can be formed in situ after heating a fibrous support that has been contacted with a metal precursor compound. For example, a metal precursor such as copper acetylacetonate can be dissolved in a solvent such as alcohol and contacted with a fibrous support. The soaked substrate can be heated to a relatively low temperature, for example 200-400^aboutC, in which the thermal decomposition of the metal precursor results in the formation and deposition of metal nanoparticles or metal oxide within or on a fibrous support.

[0036] An example of metal oxide nanoparticles are iron oxide particles. For example, MACH I, Inc.,

King of Prussia, PA sells Fe2O3 nanoparticles under the trade names NANOCAT®

Superfine Iron Oxide (SFIO) and NANOCAT® Magnetic Iron Oxide. NANOCAT® Superfine Iron

Oxide (SFIO) is an amorphous ferric oxide in the form of a free flowing powder, o ₂ particle size about 3 nm, specific surface area about 250 m²/ g, and a bulk density of about 0.05 g / ml. NANOCAT® Superfine Iron Oxide (SFIO) is synthesized in a gas-phase process, making it free of impurities that may be present in conventional catalysts, and is suitable for use in food, medicine and cosmetics. NANOCAT® Magnetic Iron Oxide is a free flowing powder of the size₂ approximately 25 nm and a specific surface area of ​​approximately 40 m²/ G.

[0037] The fibrous support may contain a mixture of hard-melting carbides and oxides, including amorphous and crystalline forms of such fibrous materials.

Exemplary classes of ceramics that can be used as a fibrous support include molten quartz and fused silica. Molten quartz and molten silica are ultra-pure one-component glasses. Both molten quartz and fused silica are inert to most substances. Molten quartz is made using powdered quartz crystal as feed material and is usually transparent,

While fused silica products are generally made of high purity silica sand. In both cases, the melting process is carried out at high temperature (over 2 ° C) using any suitable heating technique, such as an electric furnace or flame melting process.

[0038] The specific surface area of ​​the fibers used as the fibrous support is preferably low, usually less than about 200 m²/ g, but greater than about 0.001 m²/ g, preferably between about ₂

0.1 to 200 m²/ G. The fiber length is preferably greater than about 1 cm, e.g., greater than about 2.5 cm, but usually less than about 25 cm. Preferably, the fibers are not woven like a fabric, but instead are randomly woven like a non-woven mat or rug. Preferably, the fibers are catalytically active fibers.

[0039] A method for decomposing organic particles (Molecular organic decomposition (MOD)) can be used to produce nanoparticles. The MOD process starts with a metal precursor containing the desired metallic element dissolved in a suitable solvent. For example, the method may include a single metal precursor carrying one or more metal atoms, or the method may include multiple individual metal precursors that are combined in solution to form a mixture of solutions. As described above, MOD can be used to produce metal nanoparticles and / or metal oxide nanoparticles before adding the particles to the fibrous support, or in situ, by contacting the fibrous support with a metal precursor solution and thermal decomposing the metal precursor to obtain nanoparticles.

[0040] The decomposition temperature of the metal precursor is the temperature at which the ligands substantially dissociate (or volatilize) from the metal atoms. During this process, the bonds between the ligands and the metal atoms are broken so that the ligands are evaporated or otherwise separated from the metal. Preferably all ligands (ligand) are broken down. However, nanoparticles may also contain carbon obtained from partial decomposition of organic or inorganic constituents present in the metal precursor and / or solvent.

[0041] The metal precursors used in the MOD treatment are preferably high purity, non-toxic, and easy to handle and store (with long shelf life). Desirable physical properties include solubility in solvent systems, compatibility with other precursors for multi-component synthesis, and volatility for low temperature treatment.

[0042] Multi-component nanoparticles can be obtained from mixtures of single metal (homo-metallic) precursors or a single-source mixed metal (hetero-metallic) precursor molecule in which one or more metallic elements are chemically bonded. The desired stoichiometry of the resulting particles may match the stoichiometry of the metal precursor solution.

[0043] In the preparation of multi-component nanoparticles, the use of various single metal precursors has the advantage of flexibility in the design of precursor rheology as well as product stoichiometry. Hetero-metal precursors, on the other hand, may offer access to metal systems whose single metal precursors have undesirable solubility, volatility or compatibility.

[0044] Mixed metals can be obtained by Lewis acid-base reaction or substitution reaction by mixing metal alkoxides and / or other metal precursors such as acetates, β-diketonates or nitrates. Because the binding reactions are thermodynamically controlled, however, the stoichiometry of the hetero compound after isolation may not reflect the ratio of the components in the mixture from which it was isolated. On the other hand, most metal alkoxides can be combined to form hetero-metals, which are often more soluble than the substrates.

[0045] An aspect of the method described in the present patent for the preparation of the catalyst is that commercially desired stoichiometry can be obtained in nanoparticles. For example, the desired atomic ratio in nanoparticles can be obtained by choosing a metal precursor or a mixture of metal precursors having a ratio of first metal atoms to second metal atoms that is equal to the desired atomic ratio.

[0046] The metal precursor compounds are preferably organometallic compounds that have a central atom from the main group, a transition group, a lanthanide metal, or an actinide or non-metal atom or atoms associated with a bridging atom (e.g., N, O, P or S), which turn is associated with an organic substituent. Examples of the metal or non-metal as the central atom include, but are not limited to, B, C, Mg, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Sn, Ce, Hf, Ta, W, Re, Os, Ir, Pt and Au. Such metal compounds may include alcoholates, β-diketonates, carboxylates, oxalates; citrates, hydrides, thiolates, amides, nitrates, carbonates, cyanates, sulfates, bromides, chlorides, and their hydrates. The metal precursor can also be like this

EP 1 635 656 B1 called an organometallic compound in which a central metal atom is attached to one or more carbon atoms of an organic group. Aspects of processing with these metal precursors are considered below.

[0047] Precursors for the synthesis of nanoxides are molecules having already existing metal-oxygen bonds, such as metal alkoxides M (OR) n or oxoalkoxides MO (OR) n R = saturated or unsaturated organic group, alkyl or aryl), β-diketonates (e-diketonate)_n (β-diketonate = RCOCHCOR ') and metal carboxylates M (O2CR) n. Metal alkoxides have both good solubility and volatility and can easily be used in the MOD treatment. In general, however, these compounds are highly hygroscopic and require storage in an inert atmosphere. Unlike silicon alkoxides, which are liquids and are monomeric, most metal-based alcoholates are solids. On the other hand, high metalalkoxide binding reactivity can make these metal precursor substances useful as substrates for various compounds with heteroleptic linkages (i.e. compounds of different types of ligands) such as M (OR)_nxFROM_x (Z = β-diketonate or O₂CR).

[0048] M (OR) n metal alcoholates react readily with protons of a wide variety of molecules. This allows easy chemical modification and thus control of stoichiometry by using, for example, organic hydroxy compounds such as alcohols, silanols (R3SiOH), OH glycols (CH2) nOH, carboxylic and hydroxycarboxylic acids, hydroxyl surfactants, etc.

[0049] Fluorinated alcoholates M (ORF) n (RF = CH (CF3) 2, C6F5, ...) are easily soluble in organic solvents and less sensitive to hydrolysis than non-fluorinated alcoholates. These substances can be used as precursors for fluorides, oxides or oxides of fluorine, such as fluorine doped tin oxide, which can be used as metal oxide nanoparticles.

[0050] The modification of metal alkoxides reduces the amount of M-OR bonds available for hydrolysis and thus hydrolytic susceptibility. Thus, it is possible to control solution chemistry in situ by using, for example, metal β-diketonates (e.g. acetylacetone) or carboxylic acids (e.g. acetic acid) as modifiers for or instead of alcoholate.

[0051] Metal β-diketonates [M (RCOCHCOR ')_n]_m they are attractive precursors for MOD processing due to their volatility and high solubility. Their volatility is managed mainly by

The size of the R and R 'groups, as well as the nature of the metal, which will determine the degree of association, m, is shown in the above formula. Acetylacetonates (R = R '= CH3) are preferred because they can provide good yields.

[0052] Metal β-diketonates are susceptible to chelating behavior, which may lead to a reduction in the number of cores of these precursors. These ligands can act as surface coating reagents and polymerization inhibitors. Thus, after M (OR) hydrolysis_nx(E-diketonate)_x small particles can be obtained. Acetylacetone can, for example, stabilize nanocolloids. Thus, metal β-diketonate precursors are preferred in the production of nanoparticles.

[0053] Metal carboxylates such as acetates (M (O2CMe) n) are commercially available in the form of hydrates, which can be made anhydrous by heating with acetic anhydride or with 2-methoxyethanol. Many metal carboxylates generally show poor solubility in organic solvents, and because carboxylate ligands act mainly as bridging-chelating ligands, they easily form oligomers or polymers. However, 2-ethylhexanoates (M (O2CCHEtnBu) n), which are carboxylates with the least carbon atoms, are generally soluble in most organic solvents. A large number of carboxylate derivatives are available for aluminum. Macromolecules and aluminum-oxygen clusters (alumoxanes) at nanoscale can be used as nanoparticles. For example, Al (O2CH) 3 (H2O) and carboxylate [AlOx (OH) y (O2CR) z] m formate alumoxanes can be prepared from inexpensive gibsite or boonite minerals.

[0054] The solvents (solvent) used in the MOD treatment are selected based on a number of criteria, including the high solubility of metal precursor compounds; chemical inertness towards precursor compounds; rheological compatibility with the deposition technique used (e.g., desired viscosity, wettability and / or compatibility with other rheology affecting agents); melting point; steam pressure and evaporation rate; and economic factors (e.g. cost, recoverability, toxicity, etc.).

[0055] Solvents that can be used in the MOD treatment include distilled water, pentanes, hexanes, aromatic hydrocarbons, cyclohexanes, xylenes, ethyl acetates, toluene, benzenes, tetrahydrofuran, acetone, carbon disulfide, dichlorobenzenes, nitrobenzenes, pyridine, methyl alcohol, alcohol ethyl, butyl alcohol, aldehydes, ketones, chloroform, white spirit, and mixtures thereof.

[0056] Metal nanoparticles can be introduced into the fibrous support by known methods such as ion exchange, soaking, or physical mixing. For example, nanoparticles and / or a metal precursor may be suspended or dissolved in a liquid, and the fibrous support may be contacted, mixed or dewatered with a liquid containing the dispersed particles and / or dissolved metal precursor. The fibrous support may be dried and / or heat treated during or after the coating step.

[0057] According to a first embodiment, the liquid dispersion of nanoparticles can be combined with a fibrous support. The nanoparticles can be suspended or dissolved in a liquid, and the fibrous support can be mixed or watered with a liquid having dispersed particles. The liquid can be substantially removed from the fibrous support, such as by heating the fibrous support at a temperature higher than the boiling point of the liquid, or by reducing the pressure of the atmosphere surrounding the fibrous support, so that the particles remain on the support. The liquid used to make the nanoparticle dispersion may contain distilled water, pentanes, hexanes, aromatic hydrocarbons, cyclohexanes, xylenes, ethyl acetates, toluene, benzenes, tetrahydrofuran, acetone, carbon disulfide, dichlorobenzenes, nitrobenzenes, pyridine, methyl alcohol, ethyl alcohol, butyl alcohol , aldehydes, ketones, chloroform, white spirit, and mixtures thereof.

[0058] Generally, nanoparticles and fibrous support can be combined in any suitable ratio to achieve the desired packing degree of the metal particles on the support. For example, iron oxide nanoparticles or copper oxide particles can be combined with ceramic fibers to produce from about 0.1% to 50% by weight, e.g., 10% by weight or 20% by weight of iron oxide or copper oxide nanoparticles on ceramic fibers.

[0059] For example, 5% by weight of the mixture of NANOCAT® iron oxide particles was dispersed in distilled water by sonication. The dispersion was sprayed onto 200 mg of quartz wadding, which was heated to about 50^aboutC during the coating step and then air dried to obtain a catalyst containing 100 mg of iron oxide at the nanoscale on quartz wool. SEM images of the resulting catalyst are shown in Figure 1. The catalyst was introduced into the experimental cigarette cut filler which was smoked under continuous puffing at a flow rate of 500 ml / min. A multi-gas analyzer was used to measure CO and NO. The amount of CO and NO inhaled by the experimental cigarette was compared to the amount consumed by the control cigarette without catalyst. Data

EP 1 635 656 B1 in Table 1 illustrate the improvement obtained by using a nanoparticle / quartz wool catalyst.

<td>Table 1. CO and NO reduction for</td><td colspan="2">using a NANOCAT / quartz wadding catalyst.</td>

<td></td><td>CO (mg)</td><td>NO (mg)</td>

<td>control</td><td> 23,7</td><td> 0,233</td>

<td>experimental</td><td> 10,5</td><td> 0,167</td>

<td>reduction(%)</td><td> 55,7</td><td> 28,3</td>

[0060] According to a second embodiment, nanoparticles can be produced in situ on a fibrous support by thermal decomposition of the metal precursor compound. Suitable precursor compounds for metal nanoparticles or metal oxide are those that thermally degrade at relatively low temperatures, such as those discussed above. The concentration of the metal precursor in the solvent generally ranges from about 0.001 molar (M) to 10 M, preferably from about 0.1 to 1 M. The metal precursor solution and the fibrous support can be combined at about ambient temperature, e.g., by spraying or immersion coating, or at higher temperatures, e.g., at reflux temperature. The mixing temperature usually ranges from about ambient temperature, e.g., 23^aboutC to about 50 ^aboutC. Mixing is preferably carried out at ambient pressure.

[0061] After contacting the fibers with a solution containing the metal precursor, the fibrous support material can be dried in air at a temperature ranging from about 23 ^aboutC to a temperature below the decomposition temperature of the metal precursor, usually a temperature between about 23 ^aboutC and 100 ^aboutC. According to one preferred embodiment, the dried fibrous substrate precursor may be heated (e.g., above 100 ^aboutC) to break down the metal precursor and form a catalyst substance containing nanoparticles on a fibrous support. According to another embodiment, the dried fibrous substrate precursor can be combined with cut filler.

[0062] The metal precursor can be decomposed to form nanoparticles that are dispersed in or on the fibrous support by thermally treating the metal precursor at a temperature above

EP 1 635 656 B1 its decomposition temperature. Thermal treatment breaks down the metal precursor to dissociate the metal atoms, so that the metal atoms can combine to form metal or metal oxide nanoparticles. Where the metal precursor contains more than one metallic element, the nanoparticles may have an atomic ratio approximately equal to the stoichiometric ratio of the metals in the metal precursor solution.

[0063] Thermal treatment can be carried out in different atmospheres. For example, the fibrous support may be contacted with a metal precursor solution and the contacted support may be heated in the presence of an oxidizing atmosphere and then heated in the substantial absence of the oxidizing atmosphere to produce metal oxide nanoparticles. The oxidizing atmosphere may contain air or oxygen. Otherwise, the fibrous support can be contacted with a metal precursor solution and the contacted support can be heated in an inert or reducing atmosphere to form metal nanoparticles. The reducing atmosphere may contain hydrogen, nitrogen, ammonia, carbon dioxide and mixtures thereof. The preferred reducing atmosphere is mixed hydrogen-nitrogen (e.g., forming gas).

[0064] The substrate contacted with the metal precursor is preferably heated to a temperature equal to or greater than the decomposition temperature of the metal precursor. The preferred heating temperature will depend on the specific ligands used, as well as the metal (s) decomposition temperature and any other desired groups that are to remain. However, the preferred temperature is from about 200^aboutC to 400 ^aboutC, for example 300 ^aboutC or 350 ^aboutC. The thermal decomposition of a homogeneously dispersed metal precursor preferably results in uniform deposition of nanoparticles in and / or on the surface of a fibrous support.

[0065] For example, copper oxide nanoparticles were formed on quartz wadding by homogeneously mixing the quartz wadding with a 0.5 M solution of copper acetylacetonate in alcohol to the point of initial humidity. The medium was dried at room temperature overnight and then heated to 400^aboutC in the air to form a catalyst substance containing copper oxide nanoparticles that thoroughly coated / mixed with quartz wool.

[0066] Generally, the metal precursor and the fibrous support can be combined in any suitable ratio to achieve the desired packing degree of the metal particles on the support. For example, iron oxalate or copper acetylacetonate can be combined with quartz wadding to produce from about 0.1% to 50% by weight, e.g., 10% by weight or 20% by weight

EP 1 635 656 B1 nanoparticles of iron oxide, iron oxyhydroxide or copper oxide on quartz wool. [0067] The fibrous support may contain any thermally stable / refractory substance that, when heated to a temperature at which the metal precursor is converted to metal on its surface, does not melt, evaporates completely, or otherwise becomes unable to be a carrier of nanoparticles .

[0068] During the conversion of CO to CO2, oxide nanoparticles may be reduced. For example, Fe2O3 nanoparticles can be reduced to Fe3O4, FeO or Fe during the CO to CO2 transition reaction. The fibrous support preferably acts as a separator between nanoparticles and prevents them from fusing, which would result in a loss of surface area and catalytic activity. [0069] Iron oxide is the preferred component in the catalyst because it can have a dual effect as a CO catalyst in the presence of oxygen, and as a CO and / or NO oxidant for direct CO oxidation in the absence of oxygen and / or NO reduction. A catalyst that can also be used as an oxidant is particularly useful in certain applications, such as inside a burning cigarette, where the partial pressure of oxygen can be very low.

[0070] Figure 2 shows a comparison between the catalytic activity of Fe2O3 nanoparticles (50 mg samples) (NANOCAT® Superfine Iron Oxide (SFIO) from MACH I, Inc., King of Prussia, PA) having an average particle size of about 3 nm (curve A ) relative to powdered

fe₂ABOUT₃ (from Aldrich Chemical Company) having an average particle size of about 5 μm (curve B). The gas flow rate (3.4% CO, 20.6% O2, He equilibrium) was 1 ml / min, and the temperature change rate was 12 K / min. Fe2O3 nanoparticles have a much higher percentage of carbon monoxide to carbon dioxide conversion than larger Fe2O3 particles.

[0071] As mentioned above, Fe2O3 nanoparticles are able to act as both an oxidant for the conversion of carbon monoxide to carbon dioxide and as a catalyst for the conversion of carbon monoxide to carbon dioxide and / or nitrogen oxide to nitrogen. For example, Fe2O3 nanoparticles can act as catalysts in pyrolysis zones and can act as an oxidant in the combustion zone.

[0072] Iron oxide nanoparticles can act as a catalyst in the conversion of CO to CO2 according to the 2CO + O reaction equation₂ &gt; 2CO₂ and in the conversion of NO to N₂ according to the CO + equation

2NO »N₂ + CO₂. Iron oxide nanoparticles can act as an oxidant in the conversion of CO to CO₂ according to the CO + Fe equation₂ABOUT₃ WHAT₂ + 2FeO.

[0073] To illustrate the effectiveness of the metal oxide at the nanoscale, Figure 3 shows a comparison between the temperature relationship of the conversion rate for CuO nanoparticles (curve A) and Fe2O3 (curve B) using 50 mg CuO particles and 50 mg Fe2O3 nanoparticles as a catalyst in a quartz tubular reactor. The gas flow rate (3.4% CO, 21% O2, equilibrium He) was 1 ml / min, and the heating rate was 12.4 K / min. Although CuO nanoparticles have higher conversion rates at lower temperatures, at higher temperatures CuO and Fe2O3 have comparable conversion rates.

[0074] Table 2 shows a comparison between the carbon monoxide to carbon dioxide ratio, and the percentage of oxygen consumption when CuOi Fe2O3 nanoparticles were used.

Table 2. Comparison of CuO and Fe nanoparticles₂ABOUT₃

<td>nanoparticle</td><td>CO / CO2</td><td>Oxygen consumption (%)</td>

<td>lack</td><td> 0,51</td><td> 48</td>

<td>CuO</td><td> 0,29</td><td> 67</td>

<td>Fe2O3</td><td> 0,23</td><td> 100</td>

[0075] In the absence of nanoparticles, the carbon monoxide to carbon dioxide ratio is about 0.51 and oxygen consumption is about 48%. The data in Table 2 illustrate the improvement obtained by using nanoparticles. The carbon monoxide to carbon dioxide ratio drops to 0.29 and 0.23 dlanano particles of CuO and Fe2O3, respectively. Oxygen consumption increases to 67% and 100% respectively for CuOi Fe2O3 nanoparticles.

[0076] The catalysts will preferably be distributed throughout the tobacco rod forming part of the cigarette. By providing catalysts throughout the tobacco rod, it is possible to reduce the amount of carbon monoxide and / or nitric oxide drawn by the cigarette, and in particular in both the combustion area and the pyrolysis zone.

[0077] Catalysts that contain nanoparticles deposited on a fibrous support can be provided along the length of the tobacco rod by spreading the catalysts in tobacco or including them in the tobacco cut filler. The catalysts can also be added to the supply of cut tobacco filler fed to the cigarette making machine, or added to the tobacco rod before the tobacco rod is wrapped in cigarette paper. According to a preferred embodiment, when the nanoparticles are formed in situ by MOD processing,

As described above, heating the fibrous support containing the metal precursor solution to a temperature sufficient to thermally disintegrate the metal precursor into the nanoparticles can be carried out before adding the wetted substrate to the cigarette.

[0078] The amount of catalyst can be selected such that the amount of carbon monoxide and / or nitric oxide in the mainstream smoke is reduced while smoking a cigarette. Preferably, the amount of catalyst will be a catalytically effective amount, e.g., from about a few milligrams, e.g., 5 mg / cigarette, to about 200 mg / cigarette or more.

[0079] One embodiment provides a cut filler composition comprising tobacco and at least one catalyst as described above that is able to convert carbon monoxide to carbon dioxide and / or nitrogen oxide to nitrogen, wherein the catalyst is in the form of metal nanoparticles and / or metal oxide nanoparticles deposited on a fibrous support.

[0080] Any tobacco mixture may be used as the cut filler. Examples of suitable types of tobacco substances include flue-cured tobacco, Burley, Maryland or Oriental, rare or special tobacco, and mixtures thereof. Tobacco substances can be provided in the form of tobacco leaf blades, processed tobacco substances such as expanded or fluffed tobacco, processed tobacco lines such as cut-rolled or cut-fluffed lines, reconstituted tobacco substances, or mixtures thereof. Tobacco may also contain tobacco substitutes.

[0081] In the production of cigarettes, tobacco is usually used in the form of cut filler, i.e. in the form of scraps or cut leaf veins cut in widths ranging from about 1/10 inch to about 1/20 inch or even 1/40 inch. Line lengths range from about 0.25 inches to about 3.0 inches. The cigarette may further contain one or more known flavors or other additives (e.g. additives affecting smoking, combustion modifiers, dyes, binders, etc.).

[0082] Another embodiment provides a cigarette comprising a tobacco rod, wherein the tobacco rod comprises a cut tobacco filler having at least one catalyst, as described above, which is able to convert carbon monoxide to carbon dioxide and / or nitrogen oxide to nitrogen. In addition to being placed in the cut tobacco filler, the catalyst may be placed in the cigarette paper and / or cigarette filter.

[0083] A further embodiment provides a method of making a cigarette, comprising (i) adding

Catalyst for cut tobacco filler, cigarette paper and / or cigarette filter;

(ii) providing the cut filler to a cigarette making machine to make a tobacco column; (iii) placing a paper wrap around the tobacco column to form a tobacco rod; and (iv) optionally attaching a cigarette filter to the tobacco rod to form a cigarette.

[0084] Cigarette making techniques are known. Any conventional or modified cigarette making technique can be used to incorporate the catalysts. The resulting cigarettes can be made to any known specifications using standard or modified techniques and equipment for making cigarettes. Usually, the cut filler composition is optionally combined with other cigarette additive agents, and provided with a cigarette making machine to form a tobacco rod which is then wrapped in cigarette paper, and optionally terminated with filters.

[0085] Cigarettes may have a length of from about 50 mm to about 120 mm. Generally, a typical cigarette is about 70 mm long, and "King Size" is about 85 mm long, "Super King Size" is about 100 mm long, and "Long" is usually about 120 mm long. The circumference is from about 15 mm to about 30 mm, and preferably about 25 mm. The tobacco packing density is usually in the range

3 3 3 from about 100 mg / cm³ about 300 mg / cm³and preferably 150 mg / cm³ about 275 mg / cm³.

[0086] Still another embodiment provides a method of smoking a cigarette as described above, which includes lighting a cigarette to produce smoke and puffing smoke in a cigarette, in which, while smoking, the catalyst acts as a catalyst for converting carbon monoxide to carbon dioxide and / or nitrogen oxide to nitrogen .

[0087] While the invention has been described with reference to preferred embodiments, it should be understood that changes and modifications can be resorted to, as will be apparent to those skilled in the art. Such changes and modifications are to be considered within the scope of the invention as defined by the claims appended hereto.

EP 1 635 656 B1