Title of Invention

A CIGARETTE IN WHICH CARBON MONOXIDE IS CONVERTED TO CARBON DIOXIDE BY A CATALYST COMPRISING NANOSCALE METAL PARTICLES

Abstract Cut filler compositions, cigarette paper, cigarette filters, cigarettes, methods for making cigarettes and methods for smoking cigarettes are provided, which involve the use of a catalyst capable converting carbon monoxide to carbon dioxide. The catalyst comprises nanoscale metal and/or metal oxide particles supported on high surface area support particles. The catalyst can be prepared by combining a metal precursor solution with high surface area support particles to form a mixture, or by combining a metal precursor solution with a colloidal solution to form a mixture, and then heat treating the mixture.
Full Text Field of the Invention
0001 The invention relates generally to methods for reducing constituents such
as carbon monoxide in the mainstream smoke of a cigarette during smoking. More
specifically, the invention relates to cut filler compositions, cigarettes, methods for
making cigarettes and methods for smoking cigarettes, which involve the use of
nanoparticle additives capable of reducing the amounts of various constituents in
tobacco smoke.
Background of the Invention
2 In the description that follows reference is made to certain structures and
methods, however, such references should not necessarily be construed as an
admission that these structures and methods qualify as prior art under the applicable
statutory provisions. Applicants reserve the right to demonstrate that any of the
referenced subject matter does not constitute prior art.
3 Smoking articles, such as cigarettes or cigars, produce both mainstream
smoke during a puff and sidestream smoke during static burning. One constituent of
both mainstream smoke and sidestream smoke is carbon monoxide (CO). The
reduction of carbon monoxide in smoke is desirable.
4 Catalysts, sorbents, and/or oxidants for smoking articles are disclosed in
the following: U.S. Patent No. 6,371,127 issued to Snider et al., U.S. Patent No.
6,286,516 issued to Bowen et al., U.S. Patent No. 6,138,684 issued to Yamazaki et
al., U.S. Patent No. 5,671,758 issued to Rongyed, U.S. Patent No. 5,386,838 issued
to Quincy, III et al., U.S. Patent No. 5,211,684 issued to Shannon et al., U.S. Patent
No. 4,744,374 issued to Deffeves et al., U. S. Patent No. 4,453,553 issued to Cohn,
U.S. Patent No. 4,450,847 issued to Owens, U.S. Patent No. 4,182,348 issued to
Seehofer et al., U.S. Patent No. 4,108,151 issued to Martin et al., U.S. Patent No.
3,807,416, and U.S. Patent No. 3,720,214. Published applications WO 02/24005,
WO 87/06104, WO 00/40104 and U.S. Patent Application Publication Nos.
2002/0002979.A1, 2003/0037792 Al and 2002/0062834 Al also refer to catalysts,
sorbents, and/or oxidants.
5 Iron and/or iron oxide has been described for use in tobacco products (see
e.g., U.S. Patent No. 4,197,861; 4,489,739 and 5,728,462). Iron oxide has been
described as a coloring agent (e.g. U.S. Patent Nos. 4,119,104; 4,195,645;
5,284,166) and as a burn regulator (e.g. U.S. Patent Nos. 3,931,824; 4,109,663 and
4,195,645) and has been used to improve taste, color and/or appearance (e.g. U.S.
Patent Nos. 6,095,152; 5,598,868; 5,129,408; 5,105,836 and 5,101,839).
6 Despite the developments to date, there remains a need for improved and
more efficient methods and compositions for reducing the amount of carbon
monoxide in the mainstream smoke of a smoking article during smoking.WO 03/020058 discloses cut filler compositions, cigarettes, methods for making cigarettes and method for smoking cigarettes involving the use of nanoparticle metal oxides additives, such as Fe2O3, CuO, TiO2, CeO2, Ce2O3, or Al2O3, capable of acting as oxidants for the conversion of carbon monoxide to carbon dioxide and/ or as catalysts for the conversion of carbon monoxide to carbon dioxide.
US 3,292,636 is concerned with the oxidation of organic compounds formed during smoking and discloses a smoking preparation comprising tobacco and a catalyst composition consisting essentially of a crystalline zeolitic molecular sieve adsorbent having pores sufficiently large to receive benzene, and a catalytically active metal having vapor pressure below 1 atmosphere at 1000°C, which is contained in finely divided form in the inner adsorption region of the molecular sieve.
US 4,524,051 discloses a method of preparing a catalyst for the oxidation of carbon monoxide to carbon dioxide, comprising providing a substrate with tin (IV) oxide support material and with catalytically active material comprising a precious metal.
US 4,450,245 discloses a catalyst support made by co-precipitating copper aluminate from a solution containing copper and aluminium ions and converting the precipitate into solid, generally particulate, form.
US 4,317,460 discloses catalysts for the low temperature oxidation of carbon monoxide to carbon dioxide comprising a support and catalytically active metal or metal compound.
about ! 00 mg of the catalyst per cigarette. The catalyst is preferably formed prior to the smoking of the cigarette.
11 A further embodiment provides a method of making a cigarette,
comprising (i) adding a catalyst to a tobacco cut filler, wherein the catalyst
comprises nanoscale metal particles and/or nanoscale metal oxide particles
supported on high surface area support particles; (ii) providing the cut filler to a
cigarette making machine to form a tobacco rod; and (iii) placing a paper wrapper
around the tobacco rod to form the cigarette.
12 1 n a preferred embodiment the nanoscale metal particles and/or metal
oxide particles comprise Group niB and Group 1VB metals and metalloids, high
melting point metals, and transition, refractory, rare earth and precious metals, e.g.,
B, Mg, Al, Si, Ti, Fe, Co, Ni, Cu, Zn, Ge, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Sn, Ce, Hf,
Ta, W, Re, Os, Ir, Pt, Au and mixtures thereof, and the high surface area support
particles comprise silica gel beads, activated carbon, molecular sieves, magnesia,
alumina, silica, titania, zirconia, iron oxide, cobalt oxide, nickel oxide, copper oxide,
yttria optionally doped with zirconium, manganese oxide optionally doped with
palladium, ceria and mixtures thereof.
13 According to another preferred embodiment, the nanoscale metal particles
and/or nanoscale metal oxide particles comprise Cu, Zn, Co, Fe and/or Au and the
high surface area support particles comprise silica gel beads, iron oxide and/or
activated carbon in an amount effective to convert at least about 10%, preferably at
least about 25% of the carbon monoxide to carbon dioxide. For example, the catalyst can comprise from about 0.1 to 25 wt.% Cu, Zn, Co and/or Fe nanoscale particles supported on liigh surface area support particles.
14 According to one method, a cigarette is manufactured by combining a
metal precursor and a solvent to form a metal precursor solution, combining the
metal precursor solution with high surface area support particles to form a mixture,
heating the mixture to a temperature sufficient to thermally decompose the metal
precursor to form nanoscale particles within and/or on the high surface area support
particles, and drying the mixture. Optionally, a dispersion of nanoscale particles can
be added to the metal precursor solution.
15 The nanoscale particles can have an average particle size less than about
100 run, preferably less than about 50 run, more preferably less than about 10 nm,
;uid most preferably less than about 7 nm. Nanoscale particles may also contain
carbon from partial decomposition of the organic or inorganic components present in
the metal precursor and/or solvent. Preferably the nanoscale particles are
substantially carbon free. The nanoscale metal particles and/or nanoscale metal
oxide particles can comprise magnetic particles. The high surface area support
particles preferably have a surface area of about 20 to 2500 m2/g and can comprise
millimeter, micron, submicron and/or nanoscale particles.
16 According to a further method, the metal precursor is one or more of p-
diketonates, dionates, oxalates and hydroxides and the metal comprises at least one
element selected from B, Mg, Al, Si, Ti, Fe, Co, Ni, Cu, Zn, Ge, Zr, Mb, Mo, Ru, Rh, Pd, Ag, Sn, Ce, Hf, Ta, W, Re, Os, IT, Pt and Au. The solvent can comprise at least one of distilled water, methyl alcohol, ethyl alcohol, chloroform, aldehydes, ketones, aromatic hydrocarbons and mixtures thereof. Preferably, the mixture is heated to a temperature of from about 200 to 400EC. The nanoscale particles are preferably deposited within cavities, pores and/or on the surface of the high surface area support particles. The size of the pores in the high surface area support can be less than about 50 nm.
17 The high surface area support particles can be derived from a colloidal
solution and can comprise magnesia, alumina, silica, titania, yttria, zirconia and/or
ceria where the concentration of colloids hi the colloidal solution can be from about
10 to 60 weight percent. The viscosity of the colloidal solution can be increased by
changing the pH of the colloidal solution. The step of increasing the viscosity of the
colloidal solution can comprise adding a dilute acid or a dilute base to the colloidal
solution. The dilute acid can comprise HC1. According to a preferred method, the
viscosity of the colloidal solution is increased to form a gel before the step of
heating the mixture. Preferably the gel is washed. The step of drying the mixture
can comprise air-drying.
18 Yet another embodiment provides a method of smoking the cigarette
described above, which involves lighting the cigarette to form smoke and drawing
the smoke through the cigarette, wherein during the smoking of the cigarette, the catalyst converts carbon monoxide to carbon dioxide.
Brief Description of the Drawings
19 Figures 1 -4 show TEM images of a catalyst prepared according to an
embodiment wherein nanoscale gold particles are deposited on iron oxide support
particles.
20 Figure 5 depicts the temperature dependence of the Gibbs Free Energy and
Enthalpy for the oxidation reaction of carbon monoxide to carbon dioxide.
21 Figure 6 depicts the temperature dependence of the percentage conversion
of carbon dioxide to carbon monoxide.
22 Figure 7 depicts a comparison between the catalytic activity of FeaOs
nanoscale particles (NANOCATD Superfine Iron Oxide (SFIO) from MACH I, hie.,
King of Prussia, PA) having an average particle size of about 3 run, versus Fe2O3
powder (from Aldrich Chemical Company) having an average particle size of about
5(im,
23 Figure 8 depicts the temperature dependence for the conversion rates of
CuO and Pc2O\ nanoscale particles as catalysts for the oxidation of carbon monoxide
with oxygen to produce carbon dioxide.
Detailed Description
24 Tobacco cut filler compositions, cigarette paper, cigarette filter material,
cigarettes, methods for making cigarettes and methods for smoking cigarettes are
provided which use catalysts having nanoscale metal particles and/or nanoscale
metal oxide particles on high surface area support particles capable of converting
carbon monoxide to carbon dioxide.
25 "Smoking" of a cigarette means the heating or combustion of the cigarette
to form smoke, which can be drawn through the cigarette. Generally, smoking of a
cigarette involves lighting one end of the cigarette and, while the tobacco contained
therein undergoes a combustion reaction, drawing the cigarette smoke through the
mouth end of the cigarette. The cigarette may also be smoked by other means. For
example, the cigarette may be smoked by heating the cigarette and/or heating using
electrical heater means, as described in commonly-assigned U.S. Patent Nos.
6,053,176; 5,934,289; 5,591,368 or 5,322,075.
26 The term "mainstream" smoke refers to the mixture of gases passing down
the tobacco rod and issuing through the filter end, i.e., the amount of smoke issuing
or drawn from the mouth end of a cigarette during smoking of the cigarette.
27 In addition to the constituents in the tobacco, the temperature and the
oxygen concentration are factors affecting the formation and reaction of carbon
monoxide and carbon dioxide. 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 with carbonized tobacco (at least 23%). Formation of carbon monoxide from thermal decomposition, which is largely controlled by chemical kinetics, starts at a temperature of about 180Q C and finishes at about 1050D C. Formation of carbon monoxide and carbon dioxide during combustion is controlled largely by the diffusion of oxygen to the surface (ka) and via a surface reaction (kt>). At 250D C, ka and kt>, are about the same. At about 4000 C, the reaction becomes diffusion controlled. Finally, the reduction of carbon dioxide with carbonized tobacco or charcoal occurs at temperatures around 390D C and above.
28 During smoking there are three distinct regions in a cigarette: the
combustion zone, the pyrolysis/distillation zone, and the condensation/filtration
zone. While not wishing to be bound by theory, it is believed that catalysts having
nanoscale metal particles and/or nanoscale metal oxide particles on high surface area
support particles can target the various reactions that occur in different regions of the
cigarette during smoking.
29 First, the combustion zone is the burning zone of the cigarette produced
during smoking of the cigarette, usually at the lighted end of the cigarette. The
temperature in the combustion zone ranges from about 700D C to about 9500 C, and
the heating rate can be as high as 500Q C/second. Because oxygen is being
consumed in the combustion of tobacco to produce carbon monoxide, carbon
dioxide, water vapor, and various organics, the concentration of oxygen is low in the
combustion zone. The low oxygen concentrations coupled with the high temperature leads to the reduction of carbon dioxide to carbon monoxide by the carbonized tobacco. In this region, the catalyst can convert carbon monoxide to carbon dioxide via both catalysis and oxidation mechanisms. The combustion zone is highly exothermic and the heat generated is carried to the pyrolysis/distillation zone.
30 The pyrolysis zone is the region behind the combustion zone, where the
temperatures range from about 2000 C to about 6000 C. The pyrolysis zone is where
most of the carbon monoxide is produced. The major reaction is the pyrolysis (i.e.,
thermal degradation) of the tobacco that produces carbon monoxide, carbon dioxide,
smoke components, charcoal and/or carbon using the heat generated in the
combustion zone. There is some oxygen present in this region, and thus the catalyst
may act as an oxidation catalyst for the oxidation of carbon monoxide to carbon
dioxide. The catalytic reaction begins at 150Q C and reaches maximum activity
around 300D C.
31 In the condensation/filtration zone the temperature ranges from ambient to
about 1500 C. The major process in this zone is the condensation/filtration of the
smoke components. Some amount of carbon monoxide and carbon dioxide diffuse
out of the cigarette and some oxygen diffuses into the cigarette. The partial pressure
of oxygen in the condensation/filtration zone does not generally recover to the
atmospheric level.
32 The catalyst comprises metal and/or metal oxide nanoscale particles
supported on high surface area support particles. The high surface area support
particles can comprise porous granules and beads, which may or may not comprise
interconnected passages that extend from one surface of the support to another, hi
addition, the high surface area support particles can comprise nanoscale particles.
The high surface area support preferably comprises particles having a surface area
greater than about 20, preferably greater than about 50 m2/g. The support may be a
catalytically active support.
33 Nanoscale particles are a class of materials whose distinguishing feature is
that their average diameter, particle or other structural domain size is below about
100 nanometers. The nanoscale particles can have an average particle size less than
about 100 nm, preferably less than about 50 nm, more preferably less than about 10
run, and most preferably less than about 7 nm. Nanoscale particles have very high
surface area to volume ratios, which malces them attractive for catalytic applications.
34 The synergistic combination of catalytically active nanoscale particles with
a catalytically active high surface area support can produce a more efficient catalyst.
Thus, nanoscale particles disposed on a high surface area support advantageously
allow for the use of small quantities of material to catalyze, for example, the
oxidation of CO to CC>2.
35 The catalyst comprises metal and/or metal oxide particles and a high
surface area support. The support can comprise inorganic oxide particles such as
silica gel beads, molecular sieves, magnesia, alumina, silica, titania, zirconia, iron
oxide, cobalt oxide, nickel oxide, copper oxide, yttria optionally doped with
zirconium, manganese oxide optionally doped with palladium, ceria and mixtures
thereof. Also, the support can comprise activated carbon particles, such as PICA
carbon (PICA carbon, Levallois, France). The supports are preferably characterized
by a BET surface area greater than about 50 m2/g, e.g., 100 m"Vg to 2,500 m2/g, with
pores having a pore size greater than about 3 Angstroms, e.g., 10 Angstroms to 10
microns.
36 An example of a non-porous, high surface area support is nanoscale
iron oxide particles. For instance, MACH I, Inc., King of Prussia, PA sells Fe2O3
nanoscale particles under the trade names NANOCATD Superfine Iron Oxide
(SFIO) and NANOCATO Magnetic Iron Oxide. The NANOCATD Superfine Iron
Oxide (SFIO) is amorphous ferric oxide in the form of a free flowing powder, with a
particle size of about 3 nm, a specific surface area of about 250 m2/g, and a bulk
density of about 0.05 g/ml. The NANOCATQ Superfine Iron Oxide (SFIO) is
synthesized by a vapor-phase process, which renders it free of impurities that may be
present in conventional catalysts, and is suitable for use in food, drugs, and
cosmetics. The NANOCATQ Magnetic Iron Oxide is a free flowing powder with a
particle size of about 25 nm and a surface area of about 40 m2/g. According to a
preferred embodiment, narioscale metal particles, e.g., noble metal particles such as gold, can be supported on high surface area iron oxide particles.
37 An example of a porous, high surface area support is silica gel beads.
Fuji-Silysia (Nakamura-ka, Japan) sells silica gel beads that range in size from
about 5 to 30 microns and have a imge of average pore diameters of from about 2.5
nm to 100 nm. The surface area of the silica gel beads ranges from about 30-800
rn2/g.
38 Exemplary classes of porous ceramic materials that can be used as a
high surface area support include molecular sieves such as zeolites, microporous
aluminum phosphates, silicoaluminum phosphates, silicoferrates, silicoborates,
silicotitanates, magnesiumaluminate spinels and zinc aluminates.
39 According to a preferred method, both nanoscale particles and a high
surface area support can be formed in situ upon heating a mixture of suitable metal
precursor compounds. For example, a metal precursor such as gold hydroxide,
silver pentane dionate, copper (U) pentane dionate, copper oxalate-zinc oxalate, or
iron pentane dionate can be dissolved in a suitable solvent such as alcohol and
mixed with a second metal precursor such as titanium pentane dionate. The metal
precursor mixture can be heated to a relatively low temperature, for example about
200-400EC, wherein thermal decomposition of the metal precursors results in the
formation of nanoscale metal or metal oxide particles deposited on porous titania
support particles that can range in size from about 100 nm to 500 nm.
0040 Alternatively, nanoscale particles can be formed in situ upon heating a mixture of a suitable metal precursor compound and high surface area support. By way of example, metal precursor compounds such as gold hydroxide, silver pentane dionate, copper (II) pentane dionate, copper oxalate-zinc oxalate, or iron pentane dionate can be dissolved in a suitable solvent such as alcohol and mixed with a dispersion of a support material such as colloidal silica, which can be gelled in the presence of an acid or base and allowed to dry such as by drying in air. Acids and bases that can be used to gel the colloidal mixture include hydrochloric acid, acetic acid, formic acid, ammonium hydroxide and the like. When an acid containing chlorine is used to gel the colloidal mixture, preferably the gel is washed in de-ionized water in order to reduce the concentration of chloride ions in the gel. The colloidal support material can be any suitable concentration such as, for example, 10 to 60 wt.%, e.g., a 15 wt.% dispersion or a 40 wt.% dispersion. During or after gelation, the metal precursor-colloidal silica mixture can be heated to a relatively low temperature, for example 200-400EC, wherein thermal decomposition of the metal precursor results in the formation of nanoscale metal or metal oxide particles deposited on silica support particles. In place of colloidal silica, colloidal titania or a colloidal silica-titania mixture can be used as a support. Colloidal support particles can range in size from about 10 to 500 nm.
0041 Silica hydrogel, also known as silica aquagel, is a silica gel formed in water. The pores of a silica hydrogel are filled with water. An xerogel is a hydrogel
with the water removed. An aerogel is a type of xerogel from which the liquid has been removed in such a way as to minimize collapse or change in the structure as the water is removed.
42 Silica gel can be prepared by conventional means such as by mixing
an aqueous solution of an alkali metal silicate (e.g., sodium silicate) with a strong
acid such as nitric or sulfuric acid, the mixing being done under suitable conditions
of agitation to form a clear silica sol which sets into a hydrogel. The resulting gel
can be washed. The concentration of the SiOa in the hydrogel is usually in the range
of between about 10 to 60 weight percent, and the pH of the gel can be from about 1
to 9.
43 Washing can be accomplished simply by immersing the newly
formed hydrogel in a continuously moving stream of water which leaches out the
undesirable salts, leaving essentially pure silica (SiC^). The pH, temperature, and
duration of the wash water can influence the physical properties of the silica
particles, such as surface area and pore volume.
44 Molecular organic decomposition (MOD) can be used to prepare
nanoscale particles. The MOD process starts with a metal precursor containing the
desired metallic element dissolved in a suitable solvent. For example, the process
can involve a single metal precursor bearing one or more metallic atoms or the
process can involve multiple single metallic precursors that are combined in solution
to form a solution mixture. As described above, MOD can be used to prepare
nanoscale metal particles and/or nanoscale metal oxide particles, including the support particles.
0045 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 such that the ligands are vaporized or otherwise separated from the metal.
Preferably all of the ligand(s) decompose. However, nanoscale particles may also
contain carbon obtained from partial decomposition of the organic or inorganic components present in the metal precursor and/or solvent. Preferably the nanoscale particles are substantially carbon free.
46 The metal precursors used in MOD processing preferably are high
purity, non-toxic, and easy to handle and store (with long shelf lives). Desirable
physical properties include solubility in solvent systems, compatibility with other
precursors for multi-component synthesis, and volatility for low temperature
processing.
47 Nanoscale particles can be obtained from mixtures of metal
precursors or from single-source metal precursor molecules in which one or more
metallic elements are chemically associated. The desired stoichiometry of the
resultant particles can match the stoichiometry of the metal precursor solution.
48 An aspect of the MOD method for making a catalyst is that a
commercially desirable stoichiometry can be obtained. For example, the desired
atomic ratio in the catalyst can be achieved by selecting a metal precursor or mixture of metal precursors having a ratio of first metal atoms to second metal atoms that is equal to the desired atomic ratio.
49 The metal precursor compounds are preferably metal organic
compounds, which have a central main group, transition, lanthanide, or actinide
metal atom or atoms bonded to a bridging atom (e.g., N, O, P or S) that is in turn
bonded to an organic radical. Examples of the main group metal atom include, but
are not limited to B, Mg, Al, Si, Ti, Fe, Co, Ni, Cu, Zn, Ge, Zr, Nb, Mo, Ru, Rh, Pd,
Ag, Sn, Ce, Hf, Ta, W, Re, Os, Ir, Pt and Au. Such compounds may include metal
alkoxides, p-diketonates, carboxylates, oxalates, citrates, metal hydrides, thiolates,
amides, nitrates, carbonates, cyanates, sulfates, bromides, chlorides, and hydrates
thereof. The metal precursor can also be a so-called organometailic compound,
wherein a central metal atom is bonded to one or more carbon atoms of an organic
group. Aspects of processing with these metal precursors are discussed below.
50 Precursors for the synthesis of nanoscale oxides are molecules having
pre-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), p-diketonates
M(p-diketonate)n (p-diketonate - RCOCHCOR') and metal carboxylates M(O2CR)n.
Metal alkoxides have both good solubility and volatility and are readily applicable to MOD processing. Generally, however, these compounds are highly hygroscopic and require storage under inert atmosphere. In contrast to silicon alkoxides, which

arc liquids and monomeric, the alkoxides based on most metals are solids. On the other hand, the high reactivity of the metal-alkoxide bond can make these metal precursor materials useful as starting compounds for a variety of heteroleptic species (/. e., species with different types of ligands) such as M(OR)n.xZx (Z = p-diketonate or O2CR).
51 Metal alkoxides M(OR)n react easily with the protons of a large variety of
molecules. This allows easy chemical modification and thus control of
stoichiometry by using, for example, organic hydroxy compounds such as alcohols,
silanols (RiSiOH), glycols OH(CH2)nOH, carboxylic and hydroxycarboxylic acids,
hydroxyl surfactants, etc.
52 Fluorinated alkoxides M(ORF)n (Rp = CH(CF3)2, C6F5;)...) are readily
soluble in organic solvents and less susceptible to hydrolysis than classical
alkoxides. These materials can be used as precursors for fluorides, oxides or
fluoride-doped oxides such as F-doped tin oxide, which can be used as metal oxide
nanoscale particles and/or as a high surface area support.
53 Modification of metal alkoxides reduces the number of M-OR bonds
available for hydrolysis and thus hydrolytic susceptibility. Thus, it is possible to
control the solution chemistry in situ by using, for example, p-diketonates (e.g.
acetylacetone) or carboxylic acids (e.g. acetic acid) as modifiers for, or in lieu of, the
alkoxide.
54 Metal (i-diketonates [M(RCOCUCOR')nJm are attractive precursors for
MOD processing because of their volatility and high solubility. Their volatility is
governed largely by the bulk of the R and R' groups as well as the nature of the
metal, which will determine the degree of association, m, represented in the formula
above. Acetylacetonates (R-R'^CHb) are advantageous because they can provide
good yields.
55 Metal p-diketonates are prone to a chelating behavior that can lead to a
decrease in the nuclearity of these precursors. These ligands can act as surface
capping reagents and polymerization inhibitors. Thus, small particles can be
obtained after hydrolysis of M(OR)n.x(p-diketonate)x. Acetylacetone can, for
instance, stabilize nanoscale colloids. Thus, metal p-diketonate precursors are
preferred for preparing nanoscale particles.
56 Metal carboxylates such as acetates (M(02CMe)n) are commercially
available as hydrates, which can be rendered anhydrous by heating with acetic
anhydride or with 2-methoxyethanol. Many metal carboxylates generally have poor
solubility in organic solvents and, because carboxylate ligands act mostly as
bridging-chelating ligands, readily form oligomers or polymers. However,
2-ethylhexanoates (M(O2CCHEtnlki)n), which are the carboxylates with the smallest
number of carbon atoms, are generally soluble in most organic solvents. A large
number of carboxylate derivatives are available for aluminum. Nanoscale aluminum-
oxygen macromolecules and clusters (alumoxanes) can be used as catalyst materials. For
example, formate A1(P2CH)3(H2O) and carboxylate-alumoxanes [AlOx(OH)y(O2CR)7Jm can be prepared from the inexpensive minerals gibsite or boehmite.
57 Multicomponent materials can be prepared from mixed metal (hetero-
metallic) precursors or, alternatively, from a mixture of single metal (homo-metallic)
precursors.
58 The use of multiple single-metal precursors has the advantage of
flexibility in designing precursor rheology as well as product stoichiometry.
Hetero-metallic precursors, on the other hand, may offer access to metal systems
whose single metal precursors have undesirable solubility, volatility or
compatibility.
59 Mixed-metal species can be obtained via Lewis acid-base reactions or
substitution reactions by mixing alkoxides and/or other metal precursors such as
acetates, p-diketonates or nitrates. Because the combination reactions are controlled
by thermodynamics, however, the stoichiometry of the hetero-compound once
isolated may not reflect the composition ratios in the mixture from which it was
prepared. On the other hand, most metal alkoxides can be combined to produce
hetero-metallic species that are often more soluble than the starting materials.
60 The solvent(s) used in MOD processing are selected based on a
number of criteria including high solubility for the metal precursor compounds;
chemical inertness to the metal precursor compounds; rheological compatibility with
the deposition technique being used (e.g. the desired viscosity, wettubility and/or compatibility with other rheology adjusters); boiling point; vapor pressure and rate of vaporization; and economic factors (e.g. cost, recoverability, toxicity, etc.).
61 Solvents that may be used in MOD processing include pentanes,
hexanes, cyclohexanes, xylenes, ethyl acetates, toluene, benzenes, tetrahydrofuran,
acetone, carbon disulfide, dichlorobenzenes, nitrobenzenes, pyridine, methyl
alcohol, ethyl alcohol, butyl alcohol, chloroform and mineral spirits.
62 According to a preferred embodiment, nanoscale particles of metals
or metal oxides can be formed on a high surface area iron oxide support. Suitable
precursor compounds for the metal, metal oxide or iron oxide are those that
thermally decompose at relatively low temperatures, such as discussed above.
According to an embodiment, a metal precursor solution can be combined with a
dispersion of iron oxide particles. The support can be commercially available
particles, such as NANOCA'fD iron oxide particles, or the support can be prepared
from a colloidal solution or metal precursor solution as described above.
63 Nanoscale metal particles may be incorporated into the support by
various methods, such as ion exchange, impregnation, or physical admixture. For
example, the metal precursor may be dissolved or suspended in a liquid, and the high
surface area support may be mixed with the liquid having the dispersed or suspended
metal precursor. The dissolved or suspended metal precursor can be adsorbed onto a
surface of the support or absorbed into the support. The metal precursor may also be
deposited onto a surface of the support by removing the liquid, such as by evaporation so that the metal precursor remains on the support. The liquid may be substantially removed from the support during or prior to thermally treating the metal precursor, such as by heating the support at a temperature higher than the boiling point of the liquid or by reducing the pressure of the atmosphere surrounding the support.
64 Addition of the metal to molecular sieves, for example, can be
accomplished through mixing the molecular sieves with a solution, preferably
aqueous, of an appropriate metal precursor. The mixing can be performed at about
ambient temperature or at elevated temperatures, e.g., through reflux. After
incorporation of the metal precursor, but before heating, the metal precursor
solution-molecular sieve mixture can optionally be filtered and washed with water.
65 Thermal treatment causes decomposition of the metal precursor to
dissociate the constituent metal atoms, whereby the metal atoms may combine to
form a nanoscale metal or metal oxide particle having an atomic ratio approximately
equal to the stoichiometric ratio of the metal(s) in the metal precursor solution.
66 The thermal treatment can be carried out in various atmospheres. For
instance, the support can be contacted with a metal precursor solution and the
contacted support can be heated in an inert or reducing atmosphere to form activated
nanoscale metal particles. Alternatively, the support can be contacted with a metal
precursor solution and the contacted support can be heated in the presence of an
oxidi/.ing atmosphere and then heated in the substantial absence of an oxidizing atmosphere to form activated nanoscale metal oxide particles.
67 The metal precursor-contacted support 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 particular ligands
used as well as on the degradation temperature of the metal(s) and any other desired
groups which are to remain. However, the preferred temperature is from about
200EC to 400RC, for example 300EC or 350EC. The heating of the metal
precursor-contacted support can occur in an oxidizing and/or reducing atmosphere.
68 As an example, iron oxide particles smaller than 100 nm can be used
as a support for nanoscale gold particles. The Au-FeiOs catalyst can be produced
from gold hydroxide that is dissolved in alcohol and mixed with the iron oxide
particles. Decomposition of the hydroxide into nanoscale gold particles, which can
be intimately coated/mixed with the iron oxide particles, can be caused by heating
the mixture to about 300 or 400EC. TEM images of nanometer scale gold particles
supported on nanometer scale iron oxide particles are shown in Figures 1-4.
0069 As a further example, nanoscale copper particles can be deposited on
a high surface area substrate such as silica gel beads, activated carbon, molecular
sieves, magnesia, alumina, silica, titania, zirconia, iron oxide, cobalt oxide, nickel
oxide, copper oxide, yttria optionally doped with zirconium, manganese oxide
optionally doped with palladium, ceria and mixtures thereof. For example, copper
pentane dionate, copper oxalate, or other copper compounds that undergo low temperature decomposition can be combined with the substrate material, such as PICA carbon or silica gel beads, and heated to above the decomposition temperature of the precursor to deposit nanoscale copper particles on the substrate material.
0070 Table 1 illustrates various examples. As shown in Table 1, metal precursor compounds, mixtures of metal precursor compounds and/or mixtures of nanoscale particles and metal precursor compounds were used to prepare nanoscale metal and/or metal oxide particles on high surface area supports. In each of the examples, a dispersion of the substrate material was combined with a solution containing the metal precursor compounds and/or nanoscale particles. In Examples ] -4, both silica gel and MCA carbon substrates were used. Example 5 was prepared on a porous silica gel substrate only. The mixtures were heated under flowing argon to a temperature of about 300-400EC. The product was nanoscale metal and/or metal oxide particles, typically ranging in size from about 300 to 500 nm, supported on the high surface area support particles. The cobalt oxide-iron oxide nanoscale particles of Example 4 were found to be magnetic.
Table Removed
0071 In general, a metal precursor and a support can be combined in any
suitable ratio to give a desired loading of metal particles on the support. Gold
hydroxide and iron oxide can be combined, for example, to produce from about 0.1
to 25% wt,%, e.g., 2 wt.%, 5 wt.%, or 15 wt.% gold on iron oxide.
72 The support may include substantially any material which, when
heated to a temperature at which a metal precursor is converted to a metal on the
surface thereof, does not melt, vaporize completely, or otherwise become incapable
of supporting nanoscale particles.
73 During the conversion of CO to CO2, the nanoscale particles and/or
the high surface area support may become reduced. For example, FeaOs, which may
comprise the support or particles disposed on a support, may be reduced to FesO^
FeO or Fe during the reaction of CO to CO2.
74 Iron oxide is a preferred constituent in the catalyst because is has a
dual function as a CO or NOX catalyst in the presence of oxygen and as a CO oxidant
for the direct oxidation of CO in the absence of oxygen. A catalyst that can also be
used as an oxidant is especially useful for certain applications, such as within a
burning cigarette where the partial pressure of oxygen can be very low.
75 A catalyst is capable of affecting the rate of a chemical reaction, e.g.,
increasing the rate of oxidation of carbon monoxide to carbon dioxide without
participating as a reactant or product of the reaction. An oxidant is capable of
oxidizing a reactant, e.g., by donating oxygen to the reactant, such that the oxidant
itself is reduced.
76 In selecting a catalyst various thermodynamic considerations may be
taken into account to ensure that catalysis will occur efficiently, as will be apparent
to the skilled artisan. For example, Figure 5 shows a thermodynamic analysis of the
Gibbs Free Energy and Enthalpy temperature dependence for the oxidation of carbon
monoxide to carbon dioxide. Figure 6 shows the temperature dependence of the
percentage of carbon dioxide conversion with carbon to form carbon monoxide.
77 Figure 7 shows a comparison between the catalytic activity of FeaOs
nanoscale particles (MANOCATD Superfine Iron Oxide (SFIO) from MACH I, Inc.,
King of Prussia, PA) having an average particle size of about 3 nm, versus FeaOs
powder (from Aldrich Chemical Company) having an average particle size of about
Sum. The Fe?O3 nanoscale particles show a much higher percentage of conversion
of carbon monoxide to carbon dioxide than the larger Fe2C>3 particles.
78 As mentioned above, F^Ch nanoscale particles are capable of acting
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. The FeaOs
nanoscale particles can act as a catalyst for the conversion of carbon monoxide to
carbon dioxide in the pyrolysis zone, and as an oxidant for the conversion of carbon monoxide to carbon dioxide in the combustion region.
79 To illustrate the effectiveness of nanoscale metal oxide, Figure 8
illustrates a comparison between the temperature dependence of conversion rate for
CuO (curve A) and FeaOs (curve B) nanoscale particles using 50 mg CuO particles
and 50 mg Fe^Oa nanoscale particles as a catalyst in a quartz tube reactor. The gas
(3.4% CO, 21 % O2, balance He) flow rate was 1000 ml/min. and the heating rate
was 12.4 K/min. Although the CuO nanoscale particles have higher conversion rates
at lower temperatures, at higher temperatures the CuO and FeaOs have comparable
conversion rates.
80 Table 2 shows a comparison between the ratio of carbon monoxide to
carbon dioxide, and the percentage of oxygen depletion when using CuO and Fe2O3
nanoscale particles.
Table 2. comparison between CuO and Fe2O3 nanoscale particles
(Table Removed)
0081 In the absence of nanoscale particles, the ratio of carbon monoxide to carbon dioxide is about 0.51 and the oxygen depletion is about 48%. The data in
Table 2 illustrates the improvement obtained by using nanoscale particles. The ratio of carbon monoxide to carbon dioxide drops to 0.29 and 0.23 for CuO and Fe2O3 nanoscale particles, respectively. The oxygen depletion increases to 67% and 100% for CuO and I^Ch nanoscale particles, respectively.
82 The catalysts will preferably be distributed throughout the tobacco
rod portion of a cigarette. By providing the catalysts throughout the tobacco rod, it
is possible to reduce the amount of carbon monoxide drawn through the cigarette,
and particularly in both the combustion region and in the pyrolysis zone.
83 The catalysts, as described above, may be provided along the length
of a tobacco rod by distributing the catalyst on the tobacco or incorporating them
into the cut filler tobacco using any suitable method. The catalysts may be provided
in the form of a powder or in a solution in the form of a dispersion. Catalysts in the
form of a diy powder can be dusted on the cut filler tobacco and/or cigarette filter
material or the catalyst material can be added to the paper stock of a cigarette paper
making machine. The catalysts may also be present in the form of a dispersion and
sprayed on the cut filler tobacco, cigarette paper and/or cigarette filter material.
Alternatively, the tobacco and/or cigarette filter material may be coated with a
dispersion containing the catalysts. The catalyst may also be added to the cut filler
tobacco stock supplied to the cigarette making machine or added to a tobacco
column prior to wrapping cigarette paper around the tobacco column. The step of
heating a mixture comprising a metal precursor solution to a temperature sufficient
to thermally decompose the metal precursor into nanoscale particles is preferably performed prior to adding the catalyst to the cigarette.
84 The amount of the catalyst can be selected such that the amount of
carbon monoxide in mainstream smoke is reduced during smoking of a cigarette.
Preferably, the amount of the catalyst will be a catalytically effective amount, e.g.,
from about a few milligrams, for example, about 5 nig/cigarette, to about 200
mg/cigarette. More preferably, the amount of catalyst will be from about 10
mg/cigarette to about 100 mg/cigarette.
85 One embodiment provides a cut filler composition comprising
tobacco and at least one catalyst that is capable of converting carbon monoxide to
carbon dioxide, where the catalyst is in the form of a nanoscale metal particles
and/or nanoscale metal oxide particles supported on a high surface area support.
86 Any suitable tobacco mixture may be used for the cut filler.
Examples of suitable types of tobacco materials include flue-cured, Burley,
Maryland or Oriental tobaccos, the rare or specialty tobaccos, and blends thereof.
The tobacco material can be provided in the form of tobacco lamina, processed
tobacco materials such as volume expanded or puffed tobacco, processed tobacco
stems such as cut-rolled or cut-puffed stems, reconstituted tobacco materials, or
blends thereof The tobacco can also include tobacco substitutes.
87 In cigarette manufacture, the tobacco is normally employed in the
form of cut filler, i.e. in the form of shreds or strands cut into widths ranging from
about 1/10 inch to about 1/20 inch or even 1/40 inch. The lengths of the strands range from between about 0.25 inches to about 3.0 inches. The cigarettes may further comprise one or more flavorants or other additives (e.g. bum additives, combustion modifying agents, coloring agents, binders, etc.) known in the art.
0088 Another embodiment provides a cigarette comprising a tobacco rod,
wherein the tobacco rod comprises tobacco cut filler having at least one catalyst, as
described above, which is capable of converting carbon monoxide to carbon dioxide.
A further embodiment provides a method of making a cigarette, comprising (i) adding a catalyst to a tobacco cut filler; (ii) providing the cut filler to a cigarette making machine to form a tobacco column; and (iii) placing a paper wrapper around the tobacco column to form the cigarette.
0089 Techniques for cigarette manufacture are known in the art. Any
conventional or modified cigarette making technique may be used to incorporate the
catalysts. The resulting cigarettes can be manufactured to any known specifications
using standard or modified cigarette making techniques and equipment. Typically,
the cut filler composition is optionally combined with other cigarette additives, and
provided to a cigarette making machine to produce a tobacco rod, which is then
wrapped in cigarette paper, and optionally tipped with filters.
0090 Cigarettes may range from about 50 mm to about 120 mm in length. Generally, a regular cigarette is about 70 mm long, a "King Size" is about 85 mm long, a "Super King Size" is about 100 mm long, and a "Long" is usually about 120
mm in length. The circumference is from about 15 mm to about 30 mm in circumference, and preferably around 25 mm. The tobacco packing density is typically between the range of about 100 mg/cm3 to about 300 mg/cm3, and preferably 150 mg/cm3 to about 275 mg/cm3.
91 Yet another embodiment provides a method of smoking the cigarette
described above, which involves lighting the cigarette to form smoke and drawing
the smoke through the cigarette, wherein during the smoking of the cigarette, the
catalyst acts as a catalyst for the conversion of carbon monoxide to carbon dioxide.
92 While the invention has been described with reference to preferred
embodiments, ii is to be understood that variations and modifications may be
resorted to as will be apparent to those skilled in the art. Such variations and
modifications are to be considered within the purview and scope of the invention as
defined by the claims appended hereto.








We Claim:
1. A cigarette in which carbon monoxide is converted to carbon dioxide, the cigarette comprising tobacco and a catalyst capable of converting carbon monoxide to carbon dioxide, characterized in that the catalyst comprises nanoscale metal particles and/or nanoscale metal oxide particles supported on high surface area support particles and wherein the nanoscale metal particles and/or nanoscale metal oxide particles comprise Cu, Zn, Co and/or Fe and the high surface area support particles comprise silica gel beads and/or activated carbon having a surface area greater than 20 m2/g.
2. The cigarette as claimed in claim 1 comprising a cut filler composition, wherein the tobacco and the catalyst are present in the cut filler composition.
3. The cigarette as claimed in claim 1 or 2, further comprising a filter and cigarette paper, wherein the catalyst is present in the filter and/or cigarette paper.
4. The cigarette as claimed in any of claims 1 to 3, wherein the nanoscale metal particles and/or nanoscale metal oxide particles comprise B, Mg, Al, Si, Ti, Fe, Co, Ni, Cu, Zn, Ge, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Sn, Ce, Hf, Ta, W, Re, Os, Ir, Pt, Au and mixtures thereof.
5. The cigarette as claimed in any of claims 1 to 4, wherein the high surface area support particles comprise silica gel beads, activated carbon, molecular sieves, magnesia, alumina, silica, titania, zirconia, iron oxide, cobalt oxide, nickel oxide, copper oxide, yttria optionally doped with zirconium, manganese oxide optionally doped with palladium, ceria and mixtures thereof.
6. The cigarette as claimed in any of claims 1 to 5, wherein the catalyst comprises from 0.1 to 25 wt.% nanoscale particles supported on high surface area support particles.
7. The cigarette as claimed in any of claims 1 to 6, wherein the high surface area support particles are derived from a colloidal solution.
8. The cigarette as claimed in any of claims 1 to 7, wherein the nanoscale metal particles and/or nanoscale metal oxide particles have an average particle size less than about 50 nm.
9. The cigarette as claimed in any of claims 1 to 8, wherein the nanoscale metal particles and/or nanoscale metal oxide particles have an average particle size less than about 10 nm.
10. The cigarette as claimed in any of claims 1 to 9, wherein the surface area of the high
surface area support particles is from about 20 to 2500 m2/g.
11. The cigarette as claimed in any of claims 1 to 10, wherein the high surface area
support particles comprise millimeter, micron, submicron and/or nanoscale particles.
12. The cigarette as claimed in claims 1 to 11, wherein the nanoscale metal particles
and/or nanoscale metal oxide particles comprise carbon from partial decomposition of the metal
precursor and/or solvent.
13. The cigarette as claimed in any of claims 1 to 12, wherein the nanoscale metal
particles and/or nanoscale metal oxide particles are substantially carbon free.
14. The cigarette as claimed in any of claims 1 to 13, wherein the nanoscale metal
particles and/or nanoscale metal oxide particles comprise magnetic particles.
15. A method of making a cigarette as claimed in any of claims 1 to 14, comprising:
(i) adding a catalyst to tobacco cut filler, cigarette paper and/or a cigarette filter,
characterized in that the catalyst comprises nanoscale metal particles and/or nanoscale metal oxide particles supported on high surface area support particles and wherein the nanoscale metal particles and/or nanoscale metal oxide particles comprise Cu, Zn, Co and/or Fe and the high surface area support particles comprise silica gel beads and/or activated carbon having a surface area greater than 20 m2/g;
(ii) providing the cut filler to a cigarette making machine to form a tobacco column;
(iii) placing a paper wrapper around the tobacco column to form a tobacco rod; and
(iv) attaching the filter to the tobacco rod to form the cigarette.
16. The method as claimed in claim 15, wherein from 0.1 to 25 wt.% nanoscale particles supported on high surface area support particles are added to the tobacco cut filler.

Documents:

250-DELNP-2006-Abstract (12-01-2010).pdf

250-delnp-2006-Abstract-(21-07-2011).pdf

250-delnp-2006-abstract.pdf

250-DELNP-2006-Claims (12-01-2010).pdf

250-DELNP-2006-Claims-(17-02-2010).pdf

250-DELNP-2006-Claims-(21-06-2011).pdf

250-delnp-2006-Claims-(21-07-2011).pdf

250-delnp-2006-claims.pdf

250-delnp-2006-Correspondence Others-(16-06-2011).pdf

250-DELNP-2006-Correspondence Others-(21-06-2011).pdf

250-delnp-2006-Correspondence Others-(21-07-2011).pdf

250-DELNP-2006-Correspondence-Others (12-01-2010).pdf

250-DELNP-2006-Correspondence-Others (17-02-2010).pdf

250-DELNP-2006-Correspondence-Others-(25-02-2011).pdf

250-delnp-2006-Correspondence-Others-(26-05-2010).pdf

250-DELNP-2006-Correspondence-Others.pdf

250-DELNP-2006-Corresponence-Others-(14-07-2009).pdf

250-DELNP-2006-Description (Complete) (12-01-2010).pdf

250-delnp-2006-description (complete).pdf

250-delnp-2006-drawings.pdf

250-DELNP-2006-Form-1 (12-01-2010).pdf

250-delnp-2006-Form-1-(21-07-2011).pdf

250-delnp-2006-form-1.pdf

250-DELNP-2006-Form-18.pdf

250-DELNP-2006-Form-2 (12-01-2010).pdf

250-delnp-2006-Form-2-(21-07-2011).pdf

250-delnp-2006-form-2.pdf

250-DELNP-2006-Form-26 (12-01-2010).pdf

250-delnp-2006-form-26.pdf

250-DELNP-2006-Form-3-(14-07-2009).pdf

250-DELNP-2006-Form-3-(21-06-2011).pdf

250-delnp-2006-form-3.pdf

250-delnp-2006-form-5.pdf

250-DELNP-2006-Others-Documents-(14-07-2009).pdf

250-delnp-2006-pct-101.pdf

250-delnp-2006-pct-210.pdf

250-delnp-2006-pct-220.pdf

250-delnp-2006-pct-237.pdf

250-delnp-2006-pct-304.pdf


Patent Number 249962
Indian Patent Application Number 250/DELNP/2006
PG Journal Number 47/2011
Publication Date 25-Nov-2011
Grant Date 24-Nov-2011
Date of Filing 13-Jan-2006
Name of Patentee PHILIP MORRIS PRODUCTS S.A.
Applicant Address QUAI JEANRENAUD 3, CH-2000 NEUCHATEL, SWITZERLAND.
Inventors:
# Inventor's Name Inventor's Address
1 DEEVI, SAROJINI 8519 WHIRLAWAY DRIVE, MIDLOTHIAN, VA 23112 (US)
2 KOLLER, KENT, B 8401 KINTAIL DRIVE, CHESTERFIELD, VA 23838 (US)
PCT International Classification Number A24B 15/18
PCT International Application Number PCT/IB2004/002180
PCT International Filing date 2004-06-10
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10/460,631 2003-06-13 U.S.A.