U.S. patent application number 10/730962 was filed with the patent office on 2005-06-09 for catalysts comprising ultrafine particles.
Invention is credited to Banerjee, Chandra Kumar, Cash, Sheila Lynnette, Cole, Stephen Keith, Sears, Stephen Benson.
Application Number | 20050121044 10/730962 |
Document ID | / |
Family ID | 34634275 |
Filed Date | 2005-06-09 |
United States Patent
Application |
20050121044 |
Kind Code |
A1 |
Banerjee, Chandra Kumar ; et
al. |
June 9, 2005 |
Catalysts comprising ultrafine particles
Abstract
The present invention provides catalyst compositions, articles
of manufacture incorporating the catalyst compositions and methods
for producing catalyst compositions. The catalyst compositions
comprise a substrate and ultrafine particles. Disclosed articles of
manufacture include filter apparatus, such as those utilized in gas
masks or smoking articles. Also disclosed are smoking articles
comprising the catalyst compositions of the present invention.
Inventors: |
Banerjee, Chandra Kumar;
(Clemmons, NC) ; Sears, Stephen Benson; (Siler
City, NC) ; Cole, Stephen Keith; (Winston-Salem,
NC) ; Cash, Sheila Lynnette; (Greensboro,
NC) |
Correspondence
Address: |
Charles W. Calkins, Esq.
Kilpatrick Stockton LLP
1001 West Fourth Street
Winston-Salem
NC
27101-2400
US
|
Family ID: |
34634275 |
Appl. No.: |
10/730962 |
Filed: |
December 9, 2003 |
Current U.S.
Class: |
131/334 ;
131/207 |
Current CPC
Class: |
B01J 23/52 20130101;
A24D 3/16 20130101; B01J 35/0013 20130101; A24B 15/165 20130101;
A24B 15/28 20130101; B82Y 30/00 20130101; B01J 23/38 20130101; A24B
15/287 20130101; A24D 1/02 20130101; A24B 15/288 20130101 |
Class at
Publication: |
131/334 ;
131/207 |
International
Class: |
A24F 001/20 |
Claims
What is claimed is:
1. A catalyst composition comprising: a substrate and ultrafine
particles.
2. The catalyst composition of claim 1 wherein the substrate
comprises a metal oxide; a ceramic; a metal; an alloy; a zeolite; a
polymer; a carbon-containing material or mixtures thereof.
3. The catalyst composition of claim 1 wherein the ultrafine
particles comprise gold, copper, silver, platinum, palladium,
rhodium, nickel, and other transition metals; iron; alloys of noble
metals; metal oxides; and mixtures thereof.
4. A smoking article, comprising: a rod of aerosol generating
material a filter element coupled to a first end of the rod; and at
least one catalyst composition comprising ultrafine particles the
at least one catalyst composition being operative to convert carbon
monoxide to carbon dioxide at temperatures below 150 C.
5. The smoking article of claim 4 wherein the catalyst composition
is located within the filter element.
6. The smoking article of claim 5 wherein the filter element
comprises carbon.
7. The smoking article of claim 6 wherein the filter element
further comprises an adsorbent.
8. The smoking article of claim 4 wherein the catalyst composition
is located within the rod of aerosol generating material.
9. The smoking article of claim 4 further comprising a heat
source.
10. The smoking article of claim 9 wherein the catalyst composition
is located adjacent the heat source.
11. The smoking article of claim 9 wherein the catalyst composition
is located in the filter element.
12. The smoking article of claim 4, wherein the catalyst
composition comprises a plurality of ultrafine particles positioned
on at least one substrate.
13. The smoking article of claim 12, wherein the at least one
substrate comprises at least one of cerium oxide (CeO.sub.2),
titanium dioxide (TiO.sub.2), alumina (Al.sub.2O.sub.3), or
mixtures thereof.
14. The smoking article of claim 13, wherein the at least one
substrate comprises alumina (Al.sub.2O.sub.3).
15. The smoking article of claim 13 wherein the ultrafine particles
comprise a noble metal.
16. The smoking article of claim 15, wherein the noble metal has an
average particle size up to about 100 nanometers.
17. The smoking article of claim 16, wherein the noble metal has an
average particle size up to about 10 nanometers.
18. The smoking article of claim 17, wherein the noble metal has an
average particle size between about 2 and about 4 nanometers.
19. A method for facilitating the conversion of carbon monoxide to
carbon dioxide in a smoking article, comprising incorporating at
least one catalyst composition in a filter element of the smoking
article, the at least one catalyst composition comprising: at least
one substrate; and a plurality of ultrafine particles positioned on
the at least one substrate.
20. The method of claim 19, wherein the at least one substrate
comprises at least one of cerium oxide (CeO.sub.2), titanium
dioxide (TiO.sub.2), alumina (Al.sub.2O.sub.3), or mixtures
thereof.
21. The method of claim 19, wherein the at least one substrate
comprises alumina (Al.sub.2O.sub.3).
22. The method of claim 21, wherein the ultrafine particles
comprise gold.
23. An article of manufacture comprising a catalyst composition of
claim 1.
24. A filter element comprising a catalyst composition of claim 1.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to catalyst
compositions, and more particularly to catalyst compositions
comprising ultrafine particles. Embodiments of the present
invention are useful in catalyzing reactions in aerosol/gaseous
media. In an embodiment, the catalyst compositions may be utilized
in a smoking article to reduce the amount of gas phase components,
for example carbon monoxide, in the cigarette smoke.
BACKGROUND OF THE INVENTION
[0002] The terminology "catalyst" is generally used to define a
substance, usually used in small amounts relative to the reactants,
that increases the rate of a reaction without being consumed in the
process. Catalysts are widely utilized in process chemistry and
have been used to catalyze reactions occurring in a gaseous stream
or aerosol. Catalyst compositions have been used in smoking
articles to catalyze reactions in the aerosol/gaseous stream
flowing through the smoking article.
[0003] Cigarettes are popular smoking articles that use tobacco in
various forms. Descriptions of cigarettes and the various
components thereof are set forth in Tobacco Production, Chemistry
and Technology, Davis et al. (Eds.) (1999).
[0004] Cigarettes generally include a substantially cylindrical
rod-shaped structure and include a charge, roll or column of
smokeable material such as shredded tobacco (e.g., in cut filler
form) surrounded by a paper wrapper thereby forming a so-called
"tobacco rod." Normally, a cigarette has a cylindrical filter
element aligned in an end-to-end relationship with the tobacco rod.
Typically, a filter element includes cellulose acetate tow
circumscribed by plug wrap, and is attached to the tobacco rod
using a circumscribing tipping material. It also has become
desirable to perforate the tipping material and plug wrap, in order
to provide dilution of drawn mainstream smoke with ambient air.
[0005] Cigarettes and cigarette-like tobacco articles are employed
by the smoker by lighting one end thereof and burning the tobacco
rod, or igniting the heat source and aerosolizing components in the
aerosol-generating rod. The smoker then receives mainstream smoke
into his/her mouth by drawing on the opposite end (i.e., the filter
end) of the cigarette.
[0006] Numerous cigarettes and cigarette-type smoking articles that
employ carbonaceous components have been proposed. Examples of such
smoking articles are set forth in U.S. patent application Ser. No.
10/382,244, entitled "Smoking Articles Comprising Ultrafine
Particles" and filed on Mar. 5, 2003, which is hereby incorporated
by reference. Cigarettes having carbonaceous combustible material
components have been marketed by R. J. Reynolds Tobacco Company
under the tradenames Premier and Eclipse. It has also been
suggested to incorporate catalytic materials into the carbonaceous
combustible material components of certain types of smoking
articles. See, for example, U.S. Pat. No. 5,040,551 to Schlatter et
al.; U.S. Pat. No. 5,211,684 to Shannon et al.; U.S. Pat. No.
5,240,014 to Deevi et al.; and U.S. Pat. No. 5,258,340 to Augustine
et al. The disclosure of each of these patents is incorporated
herein by reference.
[0007] Catalysts have been utilized in cigarettes to alter the
chemistry of the cigarette smoke. The use of catalysts in
cigarettes is described in U.S. Pat. Nos. 4,182,348 to Seehofer et
al.; and U.S. Pat. No. 6,286,516 to Bowen et al. (treatment of
sidestream smoke). The disclosure of each of these patents is
incorporated herein by reference.
[0008] There have also been other attempts to modify the chemistry
of cigarette smoke. U.S. patent Publication 2003/0188758 to
Hajaligol et al., the disclosure of which is hereby incorporated
herein by reference, discloses the use of an oxyhydroxide compound
in a cigarette.
[0009] Certain cigarettes have filter elements which incorporate
materials such as carbon. Exemplary cigarettes and filters are
described in U.S. Pat. No. 2,881,770 to Tovey; U.S. Pat. No.
3,353,543 to Sproull et al.; U.S. Pat. No. 3,101,723 to Seligman et
al.; and U.S. Pat. No. 4,481,958 to Ranier et al. and European
Patent Application Nos. 532,329 and 608,047. Certain commercially
available filters have particles or granules of carbon (e.g., an
activated carbon material or an activated charcoal material)
dispersed within cellulose acetate tow; other commercially
available filters have carbon threads dispersed therein; while
still other commercially available filters have so-called "cavity
filter" or "triple filter" designs. Exemplary commercially
available filters are available as SCS IV Dual Solid Charcoal
Filter from American Filtrona Corp.; Triple Solid Charcoal Filter
from FIL International, Ltd.; Triple Cavity Filter from Baumgartner
Papiers Holding SA; and ACT from FIL International, Ltd. See also,
Clarke et al., World Tobacco, p. 55 (November 1992). Detailed
discussion of the properties and composition of cigarettes and
filters is found in U.S. Pat. No. 5,360,023 to Blakley et al.; U.S.
Pat. No. 5,404,890 to Gentry et al.; U.S. Pat. No. 5,568,819 to
Gentry et al.; and U.S. Pat. No. 6,537,186 to Veluz, which are
hereby incorporated by reference.
[0010] Various annular configurations of filters having
carbon-bearing annular filter regions are disclosed in the prior
art. For example, European Patent Application No. 579,410 shows a
number of cigarette embodiments having an annular carbon-bearing
region surrounding either porous filtration material or an empty
tubular cavity formed by a vapor-phase-porous membrane. Similarly,
U.S. Pat. No. 3,894,545 to Crellin et al. shows various
configurations of annular carbon-bearing regions surrounding a
vapor-phase-porous membrane or a rod of carbon-bearing material
surrounded by a vapor phase porous membrane.
[0011] Cigarette filter elements which incorporate carbon have the
ability to change the character of mainstream smoke which passes
therethrough. For example, such filter elements have the propensity
to reduce the levels of certain gas phase components present in the
mainstream smoke, resulting in a change in the organoleptic
properties of that smoke. However, such filter elements often
incorporate relatively high levels of carbon (e.g., in particulate
form),. and/or are longitudinally segmented in format and
configuration. As such, filter elements incorporating carbon
require numerous and labor intensive processing steps; and
cigarettes incorporating such filter elements often can be
characterized as having slightly metallic, drying and powdery
flavor characteristics.
[0012] U.S. patent Publication No. 2002/0014453, to Lilly et al.,
the disclosure of which is hereby incorporated herein by reference,
proposes the removal of unsaturated hydrocarbons from mainstream
smoke using nano-clusters, which selectively remove gaseous
components such as 1,3 butadiene, isoprene, and toluene from the
mainstream smoke. While the nano-clusters described in this
publication purportedly remove certain classes of gaseous
components, such nano-clusters may not be effective catalysts for
other components, for example the conversion of carbon monoxide to
carbon dioxide in a cigarette filter.
[0013] U.S. patent Publication No. 2003/0131859 to Li et al., the
disclosure of which is hereby incorporated herein by reference,
proposes the use of nanoparticle additives capable of acting as an
oxidant for the conversion of carbon monoxide to carbon dioxide
and/or as a catalyst for the conversion of carbon monoxide to
carbon dioxide and/or catalyst for the conversion of hydrocarbons,
aldehydes, or phenolic compounds to carbon dioxide and water. The
nanoparticle additives described in this publication act as
catalysts/oxidants at temperatures of 150 C or higher and are
described as being effective in the combustion and pyrolysis
regions of the cigarette.
[0014] U.S. patent Publication No. 2003/0075193 to Li et al., the
disclosure of which is hereby incorporated herein by reference,
proposes the use of nanoparticle additives capable of acting as an
oxidant for the conversion of carbon monoxide to carbon dioxide
and/or as a catalyst for the conversion of carbon monoxide to
carbon dioxide. The nanoparticle additives described in this
publication act as catalysts/oxidants at temperatures of 150 C or
higher and are described as being effective in the combustion and
pyrolysis regions of the cigarette. The nanoparticle additives are
incorporated into the cut filler used in the tobacco rod.
[0015] Despite the developments to date, there remains a need for
improved and more efficient methods and compositions for altering
the gas phase components in the mainstream smoke of a smoking
article. It would be desirable for such methods and compositions to
catalyze or oxidize carbon monoxide to carbon dioxide in mainstream
cigarette smoke at temperatures which do not require excess heat to
drive the conversion process.
SUMMARY OF THE INVENTION
[0016] The present invention provides catalyst compositions;
articles of manufacture, including, but not limited to: smoking
articles, catalyst apparatus, and filter apparatus comprising
catalyst compositions; and methods for producing catalyst
compositions. The catalyst compositions are useful in a variety of
applications, particularly in applications involving catalysis of
reactions in a gaseous or aerosol medium. Embodiments of the
catalyst compositions of the present invention are advantageous for
use in smoking articles; and may be particularly advantageous for
use in the filter elements of smoking articles. Embodiments of the
catalyst compositions of the present invention are also
advantageous for use in other filter apparatus.
[0017] In an aspect, the present invention provides a catalyst
composition comprising a substrate and ultrafine particles. The
choice of substrate and/or ultrafine particles, including the sizes
and physical structures of each, may be made based on the chemical
reaction to be catalyzed and the environment in which the reaction
will take place.
[0018] In another aspect, the present invention provides articles
of manufacture comprising catalyst compositions. An embodiment of
the present invention is a smoking article comprising catalyst
compositions. In certain embodiments, a filter element of the
smoking article comprise catalyst compositions. In other
embodiments, other component parts of the smoking article comprise
catalyst compositions. Another embodiment of an article of
manufacture of the present invention is a filter apparatus
comprising catalyst compositions. A further embodiment of an
article of manufacture of the present invention is a catalyst
apparatus comprising catalyst compositions.
[0019] In a further aspect, the present invention provides methods
for producing catalyst compositions. The methods of the present
invention may be utilized to produce catalyst compositions of the
present invention, and/or may be utilized to produce other useful
catalyst compositions.
[0020] Further details relating to the present invention, and its
advantages, are set forth in the following sections.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 provides a perspective view of an embodiment of a
filter element of the present invention.
[0022] FIG. 2 provides a perspective view of another embodiment of
a filter element of the present invention.
[0023] FIG. 3 provides a perspective view of an additional
embodiment of a filter element of the present invention.
[0024] FIG. 4 provides a perspective view of a further embodiment
of a filter element of the present invention.
[0025] FIG. 5 provides a perspective view of a still further
embodiment of a filter element of the present invention.
[0026] FIG. 6 provides a perspective view of an embodiment of a
smoking article of the present invention.
[0027] FIG. 7 provides a perspective view of another embodiment of
a smoking article of the present invention.
[0028] FIG. 8 provides a perspective view of a further embodiment
of a smoking article of the present invention.
[0029] FIG. 9 provides a graphical plot illustrating efficiency of
a catalyst composition of the present invention in converting
carbon monoxide to carbon dioxide.
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS
[0030] The present invention provides catalyst compositions
comprising ultrafine particles. The present invention also provides
articles of manufacture comprising catalyst compositions of the
present invention. Included among the articles of manufacture are
filter apparatus and catalyst apparatus. Also included are smoking
articles. In an embodiment, the present invention provides catalyst
compositions that catalyze reactions in and/or among gas phase
components in mainstream smoke from a smoking article, for example,
the conversion of carbon monoxide to carbon dioxide. Further, the
present invention provides methods for producing catalyst
compositions comprising ultrafine particles.
[0031] Reference is made below to specific embodiments of the
present invention. Each embodiment is provided by way of
explanation of the invention, not as a limitation of the invention.
In fact, it will be apparent to those skilled in the art that
various modifications and variations can be made in the present
invention without departing from the scope or spirit of the
invention. For instance, features illustrated or described as part
of one embodiment may be incorporated into another embodiment to
yield a further embodiment. Thus, it is intended that the present
invention cover such modifications and variations as come within
the scope of the appended claims and their equivalents.
[0032] For the purposes of this specification, unless otherwise
indicated, all numbers expressing quantities of ingredients,
reaction conditions, and so forth used in the specification are to
be understood as being modified in all instances by the term
"about." Accordingly, unless indicated to the contrary, the
numerical parameters set forth in the following specification are
approximations that can vary, depending upon the desired properties
sought to be obtained by the present invention. At the very least,
and not as an attempt to limit the application of the doctrine of
equivalents to the scope of the claims, each numerical parameter
should at least be construed in light of the number of reported
significant digits and by applying ordinary rounding
techniques.
[0033] Notwithstanding that the numerical ranges and parameters
setting forth the broad scope of the invention are approximations,
the numerical values set forth in the specific examples are
reported as precisely as possible. Any numerical value, however,
inherently contains certain errors necessarily resulting from the
standard deviation found in their respective testing measurements.
Moreover, all ranges disclosed herein are to be understood to
encompass any and all subranges subsumed therein, and every number
between the end points. For example, a stated range of "1 to 10"
should be considered to include any and all subranges between (and
inclusive of) the minimum value of I and the maximum value of 10;
that is, all subranges beginning with a minimum value of 1 or more,
e.g., 1 to 6.1, and ending with a maximum value of 10 or less,
e.g., 5.5 to 10, as well as all ranges beginning and ending within
the end points, e.g., 2 to 9, 3 to 8, 3 to 9, 4 to 7, and finally
to each number 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 contained within
the range. Additionally, any reference referred to as being
"incorporated herein" is to be understood as being incorporated in
its entirety.
[0034] It is further noted that, as used in this specification, the
singular forms "a," "an," and "the" include plural referents unless
expressly and unequivocally limited to one referent.
[0035] An aspect of the present invention is catalyst compositions
comprising a substrate component and ultrafine particles. The
ratio, by weight, of ultrafine particles to substrate may be varied
based on the reaction to be catalyzed. Typically a catalyst
composition of the present invention will comprise 51-99%, by
weight substrate and 1-49%, by weight ultrafine particles. In
certain embodiments a catalyst compostion of the present invention
will generally comprise greater than 50%, by weight, substrate,
often greater than 80%, by weight, substrate, or greater than 90%,
by weight, substrate, or even greater than 95%, by weight substrate
with the remainder, or a substantial portion of the remainder
comprising ultrafine particles.
[0036] The substrate component of the catalyst composition of the
present invention may comprise a metal oxide; a ceramic; a metal;
an alloy; a zeolite; a polymer; a carbon-containing material and/or
other materials. The substrate may be inert with respect to the
reaction being catalyzed, or in certain embodiments, play an active
role in the catalysis. A purpose of the substrate in particular
embodiments of the present invention is to provide a location to
physically immobilize ultrafine particles. The substrate may also
assist in catalysis by providing dissociative oxygen for an
oxidation reaction.
[0037] The substrate component of the catalyst composition of the
present invention may take many forms with porous or non-porous
surfaces including, but not limited to, substantially spherical;
ovoid, polygonal (eg. cubical), and/or undefined amorphous
granules; particles; planar forms/sheets; webs; screens/mesh forms
and/or fiber forms. and the like. It is generally advantageous to
use physical shapes or forms that increase the contact surface area
between the ultrafine particle component of the catalyst
composition and a gaseous stream.
[0038] Substrates with large surface areas, BET surface areas of
0.1 to 3000 m.sup.2/g are generally preferred. Methods of
determining BET surface area are well known and described, for
example, in U.S. Pat. No. 4,947,874, to Brooks et. al., the
disclosure of which is incorporated herein by reference. As used
herein the surface area refers to a nominal surface area as
determined by known analytical techniques.
[0039] In embodiments utilizing granular substrates, the substrate
may have an average particle diameter of 0.05 mm to 2 mm,
preferably 0.2 mm to 1.5 mm, more preferably 0.5mm to 1 mm. It is
generally advantageous for a substrate to have sufficient surface
area to promote contact between an ultrafine particle located on
the substrate and mainstream smoke. As set forth above, in
embodiments of the present invention, the nominal surface area of
the substrate may range from 0.1 to 3000 m.sup.2/g, preferably 50
to 1000 m.sup.2/g as determined by ASTM Test Procedure
C1274-00.
[0040] The physical form of the substrate may be selected based on
the intended use of the catalyst composition. For certain
applications, it is advantageous to maximize the surface area of
the substrate and distribute ultrafine particles over the largest
portion of the surface area possible. In an embodiment, a catalyst
composition of the present invention comprises a thin layer coating
of substantially uniformly spaced ultrafine particles on the
surface of a substrate.
[0041] A number of suitable substrates may be used in embodiments
of the present invention. In selecting a substrate, various
geometric and thermodynamic considerations may be taken into
account, to insure that oxidation and/or catalysis will occur
efficiently. For example, substrates useful in embodiments of the
present invention may be able to bond with ultrafine particles,
such as gold, and may be available in sizes that allow the
substrate to be packed fairly tightly in a filter element without
resulting in excess performance-detracting pressure drops.
[0042] Metal oxides are particularly well-suited for use as
substrates in embodiments of the present invention. Examples of
suitable metal oxides for use as substrates in embodiments of the
present invention include, without limitation, alumina
(Al.sub.2O.sub.3), cerium oxide (CeO.sub.2), iron oxide
(Fe.sub.2O.sub.3), titania (TiO2), and a number of other transition
metal oxides, including mixtures and alloys thereof. In general, it
has been found advantageous for use in filter apparatus for the
substrate to comprise at least one of cerium oxide (CeO.sub.2),
titanium dioxide (TiO.sub.2), iron oxide (Fe.sub.2O.sub.3), alumina
(Al.sub.2O.sub.3), and mixtures thereof.
[0043] In one non-limiting embodiment, the substrate comprises
alumina. Alumina may be particularly useful as a substrate in
embodiments of the present invention, as alumina will permit oxygen
to dissociatively adsorb. In general, any phase of alumina is
suitable for use in embodiments of the present invention. For
certain embodiments, alpha alumina is preferable to gamma alumina
in the present invention. The preparation of alumina for use as a
substrate in embodiments of the present invention will be discussed
in greater detail below. An example of alumina suitable for use in
embodiments of the present invention is activated gamma alumina
(8-14 mesh), commercially available from Fisher Scientific
International as item #A505-212. For additional information
regarding the use of alumina in smoking articles, see U.S. Pat. No.
4,771,795 to White et al.; U.S. Pat. No. 4,917,128 to Clearman et
al.; U.S. Pat. No 4,967,774 to White; and U.S. Pat. No. 5,016,654
to Bernasek et al.; which are hereby incorporated by reference.
[0044] As used herein, the terminology ultrafine particle refers to
particles having dimensions less than 10,000 nanometers, including
nanoparticles and slightly larger particles. The term nanoparticle
is generally used to indicate particles with dimensions less than
100 nanometers (one nanometer is one billionth of a meter).
Ultrafine particles manifest advantageous and unique properties
which can be exploited in embodiments of the present invention for
a variety of purposes relating to the catalysis of chemical
reactions.
[0045] The size of the ultrafine particle utilized in a catalyst
composition of the present invention may vary depending on the
reaction being catalyzed. For example, in a certain embodiment of
the present invention, the ultrafine particle may comprise a
nanoparticle having a particle size of 10 nanometers or less.
[0046] The composition of ultrafine particles suitable for use in
the present invention includes, but is not limited to, ultrafine
particles capable of catalyzing chemical reactions, including, but
not limited to, noble metals, alloys, metal oxides and the like.
The ultrafine particles may be doped or coated. Suitable ultrafine
particles for use in the present invention include, but are not
limited to, those comprising a noble metal; metals such as gold,
copper, silver, platinum, palladium, rhodium, nickel, zinc,
zirconium, other transition metals; iron; alloys of noble metals;
metal oxides; and mixtures thereof.
[0047] For catalyzing the conversion of carbon monoxide to carbon
dioxide, noble metals, such as gold, which are capable of
catalyzing the conversion at temperatures found in smoking articles
or a smoking article filter, are advantageous. Other ultrafine
particles having similar properties to gold may also work as
catalysts in embodiments of the present invention.
[0048] In embodiments of the present invention utilizing gold
ultrafine particles, the gold ultrafine particles may have an
average particle size up to about 100 nanometers. In other
embodiments, the gold ultrafine particles may have an average
particle size up to about ten nanometers. In still other
embodiments, the gold ultrafine particles may have an average
particle size up to about five nanometers.
[0049] The catalytic properties of gold depend largely on its
particle size. Gold ultrafine particles may be particularly
effective at converting carbon monoxide to carbon dioxide when the
average particle size is between about two and about four
nanometers. Thus, further embodiments of the present invention
comprise gold ultrafine particles having an average particle size
between about two and about four nanometers.
[0050] The preparation of gold ultrafine particles for use in
embodiments of the present invention will be discussed in greater
detail below. An example of a suitable starting material for
obtaining gold ultrafine particles is hydrogen tetrachloroaurate
III, which is commercially available from Alfa Aesar as item
#12325.
[0051] While gold ultrafine particles are particularly effective at
particle sizes between about two nanometers and four nanometers,
such small particle sizes can be difficult to implement in a filter
apparatus, such as the filter element of a gas mask or smoking
article. When positioned in the filter, such small particles pack
so tightly that an unusually high pressure drop results.
[0052] As used herein, the term "pressure drop" refers to the
difference between atmospheric pressure and the pressure at the
extreme mouthend point of a cigarette, as measured at a given flow
rate through the cigarette. Typical pressure drop values for
cigarettes of the present invention are greater than about 30 mm of
H.sub.2O, more frequently greater than about 50 mm of H.sub.2O, at
17.5 cc/sec. of air flow rate.
[0053] One other potential issue with the use of gold ultrafine
particles in a filter (e.g., gas mask filter or smoking-article
filter) is that the active catalyst sites of the gold ultrafine
particles may be deactivated by the aerosol passing through the
filter. The aerosol may comprise an aerosol composed of a complex
mixture of water and many other complex chemicals, some of which
can rapidly deactivate the active sites of the catalyst.
[0054] The choice of substrate composition and/or ultrafine
particle composition may be made based on the chemical reaction to
be catalyzed and the environment in which the reaction will take
place. A feature of the present invention is that certain
embodiments of the present invention will act as catalysts at
temperatures below 300 Celsius (C), in effect temperatures below
the operating range of other catalysts. For example, certain
embodiments of the present invention will catalyze reactions in a
gaseous stream at temperatures between 10 C and 300 C. Other
embodiments of the present invention act as catalysts between 80 C
and 200 C, or between 130C and 180 C.
[0055] In embodiments of the present invention, the substrate
advantageously provides a larger structure, which results in a
looser packing of the filter element. Accordingly ultrafine
particles of a desirable size can be applied to a substrate, which,
when incorporated in a filter apparatus, reduces or eliminates high
pressure drops. Ultrafine particles supported on a substrate may
also facilitate contact between aerosol components (e.g., CO) and
the catalyst.
[0056] Catalyst compositions of the present invention may be
produced by a variety of methods, including chemical deposition,
precipitation deposition, impregnation, combustion synthesis, vapor
deposition, solution chemistry and/or other methods that will be
recognized by those of ordinary skill in the art. Representative
methods are described herein and also described in "The Preparation
of Highly Dispersed Au/Al2O3 by Aqueous Impregnation" by Xu et al.,
Catalyst Letters Vol. 85, No. 3-4, February 2003, p. 229 et seq.,
the disclosure of which is incorporated herein by reference.
[0057] In a further aspect, the present invention provides methods
for producing catalyst compositions comprising ultrafine particles.
The methods of the present invention may be utilized to produce
catalyst compositions of the present invention. The methods of the
present invention, however may be used to produce other catalyst
compositions, e.g. platinum (Pt), palladium (Pd), copper (Cu),
rhodium (Rh), gold (Au), silver (Ag), iron (Fe), nickel (Ni), Zinc
(Zn) and zirconium (Zr) compositions, and the catalyst compositions
of the present invention may be produced by other methods.
[0058] Catalyst compositions of the present invention may be
prepared by a method of the present invention and/or other methods.
One method of producing a catalyst composition comprising gold
ultrafine particles comprises: dissolving hydrogen
tetrachloroaurate III (HAuCl.sub.4) in water, acidifying the
solution of tetrachloroaurate III in water with hydrochloric acid,
coating the substrate with the acidified solution, washing the
coated substrate and calcining the washed and coated substrate to
form the catalyst composition. Other embodiments may further
comprise removing chloride ions and/or drying the coated
substrate.
[0059] An embodiment of a method of the present invention
comprises:
[0060] applying a solution comprising an ultrafine particle
precursor and an acid to a particulate substrate;
[0061] drying the substrate;
[0062] suspending the substrate in water;
[0063] admixing a basic solution to the suspension to form a
particle precursor solution;
[0064] separating the thus created substrate and ultrafine particle
complex; and
[0065] treating the complex to produce a catalyst composition
comprising the substrate and ultrafine particles.
[0066] Optionally, the composition may be heat treated in the
presence of hydrogen gas to assist in activation. The ultrafine
particle complex may be treated by calcining, drying or similar
methods depending on the particular end use of the catalyst
composition. The method may be used to deposit an ultrafine
catalyst particle on monoliths of various geometries and
compositions as well as onto granules of various geometry and
composition.
[0067] Suitable ultrafine particle precursors include salts
comprising the catalyst composition of interest. Additional
ultrafine particle precursors are described in more detail below
and in the patents relating to ultrafine particles referenced
herein. Suitable acids include organic and/or inorganic acids such
as hydrochloric acid (HCl), sulfuric acid (H.sub.2SO.sub.4),
hydrofluoric acid (HF), nitric acid (HNO.sub.3) and the like.
[0068] The solution comprising an ultrafine particle precursor and
acid may be applied to the substrate using conventional production
techniques for contacting a physical substrate with a solution. For
example, the substrate may be submerged in the solution. It is
generally preferred to ensure that the desired catalytically active
portion of the substrate is substantially completely coated with
the solution. Alternatively, the solution can be added dropwise or
sprayed onto the substrate, or deposited thereon by other methods,
so as to generate a substantially uniform coverage.
[0069] Drying of the substrate after application of the solution
may be accomplished by conventional techniques. Drying may be
conducted at a temperature, generally at least above ambient
temperature, for a period of time sufficient to drive off a
substantial portion of the moisture from the substrate. As shown in
the description and examples below, it has been found that drying
the substrate at 50 C to 150 C, typically 80 C to 120 C, for 1 to 3
hours, typically 1.5 to 2.5 hours is appropriate for certain
substrate/ultrafine particle precursor solutions.
[0070] The particle precursor solution may comprise water
(H.sub.2O) or other solvents. The step of suspending the dried
substrate in the aqueous solution may be performed by conventional
techniques, including admixing the aqueous solution and the dried
substrate with slow stirring to form a suspension of the
substrate.
[0071] Suitable basic solutions include sodium hydroxide; sodium
bicarbonate; sodium carbonate; potassium hydroxide; calcium
hydroxide; ammonium hydroxide; and the like. Generally the basic
solution will have a pH greater than 8.
[0072] Admixing of the basic solution into the suspension may be
performed using conventional techniques including mixing while
stirring. After admixing is completed, the particles of the
substrate/ultrafine particle complex are separated from the
mixture. The separation may be achieved through physical separation
means including sieving, filtering, and the like.
[0073] The recovered particles may be calcined using conventional
techniques. Generally the particles will be held at a temperature
greater than ambient temperature for a period of time sufficient to
drive substantially all residual moisture from the particles. In
certain embodiments of a method of the present invention, for
example, the particles are calcined at a temperature of 100 C to
500 C for 2 to 10 hours, typically at a temperature of 300 C to 400
C for 5 to 7 hours
[0074] Suitable substrates include those listed above and below in
the descriptions of the catalyst compositions of the present
invention. To produce granular substrates, a granular
high-surface-area substrate starting material may be ground and
sieved to a preferred particle size, for example between 0.1
millimeters and 2 millimeters, generally 0.3 millimeters to 1.7
millimeters, or for certain embodiments between 0.5 and 1.1
millimeters.
[0075] Particulate catalyst compositions produced by a method of
the present invention possess several practical advantages. In
particular, they may be free flowing and substantially free from
agglomeration. They may also be substantially free of dust.
[0076] In addition to methods of the present invention described
above, gold ultrafine particles may be positioned on alpha alumina
using combustion synthesis as set forth in "Combustion synthesis of
nanometal particles supported on .alpha.-Al.sub.20O.sub.3: CO
oxidation and NO reduction catalysts", Bera et al., Journal of
Material Chemistry, Vol. 9, pp. 1801-1805 (1999), which is hereby
incorporated by reference.
[0077] In another aspect, the present invention provides articles
of manufacture comprising the catalyst compositions of the present
invention. The articles of manufacture may comprise catalytic
apparatus, for example particles, screens, panels and the like
suitable for use in chemical process reactions. In another aspect,
the articles of manufacture of the present invention are filter
apparatus comprising the catalyst compositions of the present
invention. The filter apparatus may further comprise a particulate
screening medium, a filler and/or other inert or active
ingredients. A particulate screening medium may comprise a fibrous,
granular or other material that acts to remove particulate and/or
gaseous matter that could poison the catalyst. Examples of filter
apparatus include, but are not limited to: gas mask filters; smoke
purification filters; and filters utilized in smoking articles.
[0078] In a further aspect, the present invention provides smoking
articles. It is desirable that the smoking articles of the present
invention deliver good flavor, pleasure and satisfaction.
[0079] In an embodiment, the present invention provides smoking
articles comprising a combustible material to provide an aerosol
and/or to heat an aerosol-forming material, the smoking articles
comprising a catalyst composition of the present invention. For
example, aerosol may be formed by burning to produce smoke or by
heating aerosol-forming material on a suitable substrate. The
location and position of the catalyst composition may be selected
such that specific performance properties of the smoking article
are modified. For example, in an embodiment of the present
invention wherein it is desired to modify the composition of the
aerosol, for example mainstream smoke, the catalyst composition(s)
are located/positioned within the smoking article such that there
is contact between the catalyst composition and the mainstream
smoke. An example of such an embodiment includes modification of
smoke to reduce levels of carbon monoxide in the smoke.
[0080] In an embodiment of the present invention, the filter
component of a smoking article comprises catalyst compositions of
the present invention. The catalyst compositions may be present in
an amount sufficient to alter the chemistry of an aerosol, e.g.
cigarette smoke, drawn through the filter. In an embodiment, the
catalyst compositions may act to catalyze reactions occurring
within the aerosol, e.g. cigarette smoke. The catalyzed reactions
may result from contact between the aerosol and the catalyst
composition, the aerosol and the substrate component of the
catalyst composition, or both.
[0081] In alternate embodiments of the present invention, catalyst
compositions of the present invention may be incorporated into
other components of a smoking article, for example as a part of,
and/or surrounding, the aerosol-generating component and/or
tobacco, in addition to, or instead of, incorporation in the filter
component.
[0082] In embodiments of the present invention using particulate
catalyst compositions in smoking articles, the particle size of the
composition may range from 0.1 millimeter (mm) to 1.5 mm. For
certain embodiments, the particle size may range from 0.5 mm to 1.0
mm, and more particularly for certain embodiments a particle size
of 0.75 mm to 0.85 mm is preferred. Particle size may be determined
by ASTM Test Procedure B761-02 and E1617-97 (2002).
[0083] The substrate and ultrafine particle materials of a catalyst
composition of the present invention for use in a smoking article
may comprise any of the materials set forth above. In general, for
the conversion of carbon monoxide to carbon dioxide in an aerosol,
the catalyst composition may serve as a substrate for the enhanced
oxidation of carbon monoxide to carbon dioxide.
[0084] Embodiments of the present invention include, but are not
limited to embodiments utilizing the catalyst compositions of the
present invention to modify components of the smoke, for example by
lowering levels of carbon monoxide. The catalyst compositions may
be incorporated into the smoking article, or component parts of the
smoking article, by a variety of methods including those set forth
in detail below and/or other methods understood in the art. The
catalytic process may occur over a range of temperatures including
room temperature or below.
[0085] Smoking articles of the present invention may further
include additional materials that enhance the performance of the
catalyst composition and/or the smoking article. For example, a
filter of a smoking article comprising catalyst compositions of the
present invention may further comprise particulate matter to filter
components of mainstream smoke that would otherwise impair the
catalytic function of the catalyst composition.
[0086] Catalyst compositions for use in smoking-article embodiments
of the present invention may comprise a plurality of ultrafine
particles positioned on at least one substrate. The location and
position of the catalyst compositions may be selected such that
specific performance properties of the smoking article are
modified. For example, in an embodiment of the present invention
wherein it is desired to modify the composition of mainstream
smoke, the catalyst compositions comprising ultrafine particles are
located/positioned within the filter element such that there is
contact between the ultrafine particles and the mainstream smoke.
In such an embodiment, the catalyst compositions reduce the levels
of carbon monoxide in the smoke. The ultrafine particles can
advantageously act as catalysts for the conversion of carbon
monoxide to carbon dioxide in mainstream smoke.
[0087] Mainstream smoke refers to the aerosol of gases and
particles created when the smoker draws through the tobacco rod.
The mainstream smoke includes smoke that has been drawn through the
lighted region of the cigarette, the tobacco rod, and the filter
(if the smoking article is so equipped).
[0088] In an embodiment of the present invention, a catalyst
composition of a smoking article may comprise 0.01% to 10%, by
weight, preferably 0.1% to 5%, by weight ultrafine particles. The
theoretical loading, which corresponds to the percentage weight of
ultrafine particles may be calculated. The percent loading will
equal the amount of ultrafine particle salt in grams multiplied by
the fraction of ultrafine particle in the ultrafine particle salt,
divided by the total amount of ultrafine particle salt plus the
amount of substrate, the quotient multiplied by 100.
[0089] The temperature of the mainstream smoke is lower as the
smoke passes through the filter element than it is when the smoke
passes through the tobacco rod. In the filter element, the
temperature ranges from near ambient to about 150 C. By way of
comparison, temperatures in the tobacco rod, including temperatures
in the so-called combustion and pyrolysis regions, range from 200 C
to 900 C. Thus, as the catalyst compositions may be positioned in
the filter element in accordance with embodiments of the present
invention, the catalyst compositions are effective as catalysts for
the conversion of carbon monoxide to carbon dioxide at temperatures
below 150 C.
[0090] In one embodiment of the present invention, the ultrafine
particles comprise gold. Although gold may not be an active
catalyst in its bulk form, gold ultrafine particles exhibit
excellent catalytic properties, particularly in the conversion of
carbon monoxide to carbon dioxide. Further, gold ultrafine
particles can advantageously catalyze the conversion of carbon
monoxide to carbon dioxide at room temperature.
[0091] Catalyst compositions for use in filter elements of smoking
articles in accordance with embodiments of the present invention
may comprise a plurality of ultrafine particles deposited on at
least one substrate. A filter element may comprise a plurality of
catalyst compositions. In a further embodiment, the plurality of
catalyst compositions may be positioned in at least one cavity in
the filter element. The plurality of catalyst compositions, in an
embodiment, may be positioned in a cavity between two filter
plugs.
[0092] In one embodiment of the present invention, catalyst
compositions comprise a plurality of gold ultrafine particles
positioned on at least one alumina particle. In further
embodiments, the gold ultrafine particles comprise gold
nanoparticles. In further embodiments, the gold nanoparticles have
a particle size up to about ten nanometers. In another embodiment,
the gold nanoparticles have a particle size up to about five
nanometers. In another embodiment, the gold nanoparticles have a
particle size between about two nanometers and about four
nanometers.
[0093] The size and geometry of the alumina substrate prior to gold
deposition, in embodiments of the present invention, may be
selected such that the catalyst composition may be packed into a
component part of a smoking article in a manner that maximizes
contact between the catalyst composition and the aerosol without
exceeding acceptable pressure-drop limits. In one embodiment, the
alumina substrate has a particle size of between about 12 and about
35 U.S. mesh (between about 0.5 and about 1.4 millimeters). In
another embodiment, the alumina substrate, prior to gold
deposition, has a particle size between about eighteen and about
thirty U.S. mesh (between about 0.6 millimeters and about 1
millimeter).
[0094] The catalyst compositions in another embodiment of the
present invention comprise a plurality of gold ultrafine particles
having particle sizes between about two nanometers and about four
nanometers positioned on at least one alumina substrate having a
particle size between about 0.6 millimeter and about 1.0
millimeter.
[0095] In an embodiment the untreated gamma alumina substrate for
use in a catalyst composition of the present invention has a
surface area, as measured by gas adsorption, of approximately 340
m.sup.2/g. After addition of gold, the ultrafine alumina-gold
composite has a surface area of approximately 270 m.sup.2/g.
[0096] As will be appreciated by those of ordinary skill in the
art, the relationship between the pore size of the substrate, as
reflected in the substrate's surface-area measurement, and the
particle size of the ultrafine particle, may be optimized to
achieve desired performance properties in a catalyst composition of
the present invention.
[0097] Further details relating to embodiments of catalyst
compositions of the present invention and articles of the present
invention comprising the catalyst compositions will become apparent
to those of ordinary skill in the art from the following
descriptions of specific embodiments of an article of manufacture
of the present invention comprising an embodiment of a catalyst of
the present invention.
[0098] Embodiments of the present invention, comprising a plurality
of catalyst composition, are illustrated in the appended
figures.
[0099] FIGS. 1-5 depict cross-sectional views of embodiments of
filter elements, 10A, 10B, 10C, 10D and 10E of the present
invention, incorporating catalyst compositions of the present
invention. The filter elements may be used as a filter element of a
smoking article, wherein the filter element will generally have a
substantially circular shape. Designs similar to the filter
elements may be used in other applications. For use in the
description below FIGS. 1-5 include an arrow indicating the
direction of flow of an aerosol through filter element.
Like-numbered elements are generally described with reference to
the first Figure in which they appear.
[0100] With reference to FIG. 1, filter element 10A includes filter
material 11, in filter-element sections 12 and 16. Suitable filter
material includes cellulose acetate tow and other materials
described in detail below.
[0101] A cavity, 14, is located between sections 12 and 16. In an
embodiment of the present invention, catalyst compositions of the
present invention, 13, are distributed throughout cavity 14. Cavity
14 further includes air dilution holes 18 that allow air to be
drawn into the cavity. The air dilution holes will extend through
any outer wrapping material surrounding filter element 10 when the
filter element is positioned in a smoking article.
[0102] Catalyst compositions of the present invention may be
positioned in the cavity 14 using techniques known to those of
skill in the art for positioning particulate matter (e.g., carbon)
in a filter element. Examples of such techniques are set forth in
U.S. Pat. No. 6,537,186 and in U.S. patent Publication No.
2002/0020420, which are hereby incorporated by reference.
[0103] FIG. 2 illustrates an alternate embodiment of a filter
element 10B, of the present invention. In an embodiment of the
present invention, cavity 14 includes an admixture of catalyst
compositions of the present invention 13, and particulate carbon
15. The admixture may comprise 1 to 80%, by weight, catalyst
compositions of the present invention and 1 to 80% by weight,
particulate carbon. The admixture may be positioned in cavity 14
using techniques known to those of skill in the art for positioning
particulate matter in a filter element.
[0104] FIG. 3 illustrates another alternative embodiment of a
filter element 10C, of the present invention. In the embodiment
depicted in FIG. 3, cavity 14 is subdivided into cavities 14A and
14B. Catalyst compositions of the present invention 13, are
positioned in cavity 14A, the downstream cavity. Particulate
carbon, 15, is positioned upstream of cavity 14A in cavity 14B. The
relative positions of the catalyst compositions and the particulate
carbon in the cavity may be reversed.
[0105] In FIGS. 1-3, the relative lengths of sections 12 and 16,
and cavity 14, or 14A and 14B is not drawn to scale. In general, in
embodiments of the present invention similar to filter elements 10A
and 10B the percentage length of each section and the cavity,
12/14/16 will be 30 to 45/10 to 40/30 to 45. For a filter element
of 27 millimeters length, this translates to section 12 being 8.1
to 12.2 millimeters in length; cavity 14 being 2.7 to 10.8
millimeters in length; and section 16 being 8.1 to 12.2 millimeters
in length. For filter element 10C the relative percentage lengths
of 12/14A/14B/16 will be 30 to 45/5 to 20/5 to 20/30 to 45. For a
filter element of 27.2 millimeters length, this translates to 12
being 8.1 to 12.2 millimeters in length; cavity 14A being 1.4 to
5.4 millimeters in length; cavity 14B being 1.4 to 5.4 millimeters
in length and section 16 being 8.1 to 12.2 millimeters in
length.
[0106] FIG. 4 illustrates another embodiment of a filter element of
the present invention. Filter element 10D includes a cavity 21
encircled by a high density filter material 23. Suitable high
density filter materials include, but are not limited to, steam
bonded cellulose acetate filters available from Filtrona. These
steam bonded filters have a filtration efficiency of more than 75%.
The ends of the cavity may be bounded by regions of a filter
material 11, which may have a lower filtration efficiency than
filter material 23 to facilitate the passage of an aerosol/gaseous
mixture through filter element 10D. The filter element includes air
dilution holes 18 to allow passage of air between cavity 21 and the
outside environment.
[0107] The relative dimensions of the cavity may vary depending on
the application. In an embodiment, the cavity will have a diameter
between 10 and 50 percent of the diameter of the filter element,
and a length between 10 and 80 percent of the length of the filter
element.
[0108] Cavity 21 includes catalyst compositions of the present
invention, 13. Alternatively, cavity 21 may be filled with an
admixture of catalyst compositions 13 and particulate carbon.
[0109] As noted in the prior descriptions, the embodiments of the
present invention depicted in FIGS. 1-4 include a portion of a
filter element comprising catalyst compositions of the present
invention. The packing density of the catalyst compositions, or the
catalyst compositions and other particulate matter (e.g.
particulate carbon), in the filter element will generally range
from 0.5 to 2.0 grams per cubic centimeter. Higher or lower packing
densities may be desirable for particular embodiments in order to
maintain an acceptable pressure drop across the filter.
[0110] FIG. 5 illustrates another possible embodiment of a filter
element of the present invention. As shown in FIG. 5, filter
element 10E includes a filter material, 11, and a cellulose acetate
filter segment 12. The filter element 11 comprises a filter
material in communication with catalyst compositions of the present
invention, 13, that are distributed throughout the filter element.
The filter material 11 may be pretreated with the catalyst
composition prior to incorporation into the filter element.
[0111] Filter elements 10A-10E depicted in FIGS. 1-5 are depicted
and described with reference to a particular inline filtering
application, such as found in a smoking article. It should be
appreciated that the geometry of the filter elements may be adapted
for other applications, for example use in a gas mask filter
without departing from the present invention.
[0112] Further details regarding the use of filter elements 10A-10E
in a smoking article are provided below with reference to the
remaining Figures. The invention is described in more detail with
reference to a particular smoking article, namely a cigarette
utilizing a catalyst composition comprising ultrafine particles in
the filter element. As will be understood by those of ordinary
skill in the art, however, the principals/principles of the present
invention apply to other tobacco articles and other filter
applications.
[0113] FIG. 6 illustrates an embodiment of a smoking article of the
present invention. As shown in FIG. 6, cigarette 30, includes a
generally cylindrical rod 35 of a charge or roll of smokable filler
material 40 contained in a circumscribing wrapping material 45. The
rod 35 is typically referred to as a "smokable rod" or a "tobacco
rod". The ends of the tobacco rod are open to expose the smokable
filler material.
[0114] In an embodiment of the present invention, cigarette 30
includes a filter element comprising catalyst compositions such as
filter element 10A depicted in FIG. 1. Although filter element 10A
is depicted in FIG. 6, any of filter elements 10A, 10B, 10C, 10D,
10E, or any other design incorporating catalyst compositions of the
present invention may be utilized in an embodiment of a smoking
article of the present invention.
[0115] The filter element 10A is positioned adjacent one end of the
tobacco rod 35 such that the filter element and tobacco rod are
axially aligned in an end-to-end relationship, preferably abutting
one another. Filter element 10A has a generally cylindrical shape,
and the diameter thereof is essentially equal to the diameter of
the tobacco rod. The ends of the filter element are open to permit
the passage of air and smoke therethrough. The filter element 10A
includes filter material 11 which is overwrapped along the
longitudinally extending surface thereof with circumscribing plug
wrap material 60. The filter element can have two or more filter
segments, and/or flavor additives incorporated therein.
[0116] The filter element 10A may be attached to the tobacco rod 35
by tipping material 65 which circumscribes both the entire length
of the filter element and an adjacent region of the tobacco rod.
The inner surface of the tipping material 65 may be fixedly secured
to the outer surface of the plug wrap 60 and the outer surface of
the wrapping material 45 of the tobacco rod, using a suitable
adhesive. A ventilated or air diluted smoking article is provided
with an air dilution means, such as a series of perforations 18,
each of which extend through the tipping material and plug wrap.
The wrapping material 45 has a width which is equal to the
circumference of the cigarette plus the lap zone of the glue line
which ultimately results during cigarette manufacture.
[0117] Catalyst compositions, 13, are positioned in a cavity within
filter element 10A. The wrapping material surrounding the catalyst
composition may include dilution holes 18 that extend through the
tipping material.
[0118] FIG. 7 illustrates an embodiment of a smoking article
comprising a filter element with a plurality of catalyst
compositions positioned therein. Such a smoking article can be
prepared using the techniques described in U.S. Pat. No.
6,537,186.
[0119] As illustrated in FIG. 7, the cigarette 102 includes a
combustible material component 110 circumscribed within a retaining
jacket of insulating material 112. Situated longitudinally behind
the combustible material component 110 is an aerosol-generating
means, 116. The aerosol generating means comprises one or more
aerosol forming materials (such as glycerin), a form of tobacco
(such as tobacco powder, extract or dust), and flavor components,
which are volatilized by heat generated by the burning of the
combustible material component. Preferably, the aerosol-generating
means comprises a substrate advantageously made from a
reconstituted tobacco cast-sheet cut-filler material. Such
substrates are described in U.S. patent application Ser. No.
07/800,679, filed 27 Nov., 1991, which is incorporated herein by
reference. The combustible material component 110 may include
ultrafine particles as described in the commonly assigned,
co-pending patent application entitled "Smoking Article Comprising
Ultrafine Particles", by Crooks et al., U.S. patent application
Ser. No. 10/382,244, the disclosure of which is incorporated herein
by reference.
[0120] The cigarette may further comprise a filter element 10A or
other suitable mouthpiece positioned adjacent one end of the
aerosol generating means 116 such that the filter element and
tobacco rod are axially aligned in an end-to-end relationship,
preferably abutting one another. Filter element 10A has a generally
cylindrical shape, and the diameter thereof is essentially equal to
the diameter of the tobacco rod. The ends of the filter element are
open to permit the passage of air and smoke therethrough. The
filter element 10A may include a filter material, 11 which is
overwrapped along the longitudinally extending surface thereof with
circumscribing plug wrap material. The filter element includes
catalyst compositions of the present invention 13 comprising
ultrafine particles. As will be realized from the description
below, the actual size of a typical ultrafine particle may be less
than 100 nm. The portion of the filter element comprising the
catalyst compositions will include air dilution holes, 18 in the
wrapper material(s) adjacent to the filter portion comprising the
ultrafine particles.
[0121] Referring again to the embodiment of the cigarette shown in
FIG. 7, the filter element 10A comprises a cavity positioned
between two filter plugs, 11. The two filter plugs may be
conventional filter materials, such as cellulose acetate filter
material. The cavity is filled with a plurality of catalyst
compositions 13 of the present invention. The cavity may further
include other components such as those described above (e.g.,
particulate carbon).
[0122] The particular embodiment of a smoking article of the
present invention described with reference to FIGS. 6 and 7
incorporates catalyst compositions in the filter element of the
smoking article. The same embodiment, or alternative embodiments,
of the present invention may comprise catalyst compositions of the
present invention located in other component parts of the smoking
article. For example, catalyst compositions may be incorporated
into, or positioned near or within, the aerosol generating
material; including incorporation into the smokable material; the
wrapping material; the fuel element and/or other components.
[0123] FIG. 8 depicts an embodiment of a smoking article of the
present invention wherein catalyst compositions 13 are positioned
adjacent fuel element 110 in a smoking article similar to the one
described with reference to FIG. 7 and U.S. Pat. No. 6,537,186. As
shown in FIG. 8, air dilution holes, 18, are provided in the
portion of the smoking article comprising the catalyst
compositions. Filter element 130 in FIG. 8 represents a
conventional cigarette filter, however a filter element of the
present invention may also be utilized.
[0124] As will be realized by those of ordinary skill in the art,
the description in the following paragraphs applies generally to
embodiments of smoking articles of the present invention, including
the smoking articles depicted in FIGS. 6 and 7.
[0125] Smoking articles are typically circumscribed by a wrapping
material. The wrapping material has a width which is equal to the
circumference of the smoking article plus the lap zone of the glue
line which ultimately results during manufacture. Suitable wrapping
materials are generally known to those of ordinary skill in the art
and described in the patent application referenced above and the
following U.S. Patents, each of which is incorporated herein by
reference, U.S. Pat. No. 4,452,259 to Norman; U.S. Pat. No.
5,878,754 to Peterson et al.; U.S. Pat. No. 5,103,844 to Hayden et
al.; U.S. Pat. No. 5,060,675 to Milford et al.; U.S. Pat. No.
4,998,541 to Perfetti et al.; U.S. Pat. No. 4,805,644 to Hampl, Jr.
et al.; U.S. Pat. No. 4,461,311 to Matthews et al.; U.S. Pat. No.
4,450,847 to Owens; U.S. Pat. No. 4,420,002 to Cline; and U.S. Pat.
No. 4,231,377 to Cline et al.
[0126] Paper wrapping materials suitable for use in carrying out
the present invention are commercially available. Representative
cigarette-paper wrapping materials have been available as Ref. Nos.
419, 454, 456, 460 and 473 from Ecusta Corp.; Ref. Nos. Velin 413,
Velin 430, VE 825 C20, VE 825 C30, VE 825 C45, VE 826 C24, VE 826
C30 and 856 DL from Miquel; Terig LK18, Tercig LK24, Tercig LK38,
Tercig LK46 and Tercig LK60 from Tervakoski; and Velin Beige 34,
Velin Beige 46, Velin Beige 60, and Ref. Nos. 454 DL, 454 LV, 553
and 556 from Wattens. Exemplary flax-containing cigarette-paper
wrapping materials have been available as Grade Names 105, 114,
116, 119, 170, 178, 514, 523, 536, 520, 550, 557, 584, 595, 603,
609, 615 and 668 from Schweitzer-Mauduit International. Exemplary
wood-pulp-containing cigarette-paper wrapping materials have been
available as Grade Names 404, 416, 422, 453, 454, 456, 465, 466 and
468 from Schweitzer-Mauduit International.
[0127] In certain embodiments of the present invention a wrapping
material for the smoking article may comprise ultrafine particles
as described in the commonly assigned, co-pending patent
application entitled "Smoking Article Wrapping Materials Comprising
Ultrafine Particles", by Crooks et al., U.S. patent application
Ser. No. 10/342,618, the disclosure of which is incorporated herein
by reference.
[0128] The filter element may be attached to the
tobacco-rod/aerosol-gener- ating rod by a tipping material which
circumscribes both the entire length of the filter element and an
adjacent region of the tobacco rod. The inner surface of the
tipping material is fixedly secured to the outer surface of the
plug wrap and the outer surface of the wrapping material of the
tobacco rod, using a suitable adhesive. A ventilated or air-diluted
smoking article is provided with an air-dilution means, such as a
series of perforations, each of which extends through the tipping
material and plug wrap.
[0129] A conventional automated cigarette rod-making machine useful
for manufacturing smoking articles of the present invention is of
the type commercially available from Molins PLC or Hauni-Werke
Korber & Co. KG. For example, cigarette rod-making machines of
the type known as Mark 8 (commercially available from Molin PLC) or
PROTOS (commercially available from Hauni-Werke Korber & Co.
KG) can be employed, and can be suitably modified if desired. A
description of a PROTOS cigarette-making machine is provided in
U.S. Pat. No. 4,474,190, at col. 5, line 48 through col. 8, line 3,
which is incorporated herein by reference. Types of equipment
suitable for the manufacture of cigarettes also are set forth in
U.S. Pat. No. 4,844,100 to Holznagel; U.S. Pat. No. 5,156,169 to
Holmes et al. and U.S. Pat. No. 5,191,906 to Myracle, Jr. et al.;
and PCT WO 02/19848. Designs of various components of
cigarette-making machines, and the various materials used to
manufacture those components, will be readily apparent to those
skilled in the art of cigarette making.
[0130] The smoking article typically has a length which ranges from
about 50 mm to about 100 mm, and a circumference of about 16 mm to
about 28 mm. The aerosol-generating means and the resulting smoking
articles can be manufactured in any known configuration using known
cigarette making techniques and equipment. The wrapping material is
formed into a circular shape such that the ends of the sides
thereof abut one another. The ends of wrapping material can abut
one another, nearly abut one another, or slightly overlap one
another. A cigarette rod having such a configuration can be
provided by supplying a paper wrapper from a bobbin on a suitably
equipped cigarette-making machine, passing the wrapping material
through the garniture region of the cigarette-making machine, and
forming the tobacco rod.
[0131] The tobacco materials used for the manufacture of smoking
articles of the present invention can vary. Descriptions of various
types of tobaccos, growing practices, harvesting practices and
curing practices are set forth in Tobacco Production, Chemistry and
Technology, Davis et al. (Eds.) (1999). The tobacco normally is
used in cut filler form (e.g., shreds or strands of tobacco filler
cut into widths of about {fraction (1/10)} inch to about {fraction
(1/60)} inch, preferably about {fraction (1/20)} inch to about
{fraction (1/35)} inch, and in lengths of about 1/4 inch to about 3
inches). The amount of tobacco filler normally used within a
cigarette ranges from about 0.6 g to about 1 g. The tobacco filler
normally is employed so as to fill the tobacco rod at a packing
density of about 100 mg/cm.sup.3 to about 300 mg/cm.sup.3, and
often about 150 mg/cm.sup.3 to about 275 mg/cm.sup.3. As used
herein, "packing density" means the weight of the filler material
which occupies a unit volume within the smokable rod.
[0132] Tobaccos can have a processed form, such as processed
tobacco stems (e.g., cut-rolled or cut-puffed stems), volume
expanded tobacco (e.g., puffed tobacco, propane-expanded tobacco
and dry-ice-expanded-tobacco (DIET)), or reconstituted tobacco
(e.g., reconstituted tobaccos manufactured using paper-making-type
or cast-sheet-type processes).
[0133] Typically, tobacco materials for cigarette manufacture are
used in a so-called "blended" form. For example, certain popular
tobacco blends, commonly referred to as "American blends," comprise
mixtures of flue-cured tobacco, burley tobacco and Oriental
tobacco, and in many cases, certain processed tobaccos, such as
reconstituted tobacco and processed tobacco stems. The precise
amount of each type of tobacco within a tobacco blend used for the
manufacture of a particular cigarette brand varies from brand to
brand. See, for example, Tobacco Encyclopedia, Voges (Ed.) p. 44-45
(1984), Browne, The Design of Cigarettes, 3.sub.rd Ed., p.43 (1990)
and Tobacco Production, Chemistry and Technology, Davis et al.
(Eds.) p. 346 (1999). Other representative tobacco blends also are
set forth in U.S. Pat. No. 4,924,888 to Perfetti et al.; U.S. Pat.
No. 5,056,537 to Brown et al.; and U.S. Pat. No. 5,220,930 to
Gentry; and Bombick et al., Fund. Appl. Toxicol., 39, p. 11-17
(1997). See, also, U.S. patent Publication No. 2003/0131860 to
Ascraft et al. the disclosures of which are hereby incorpated by
reference.
[0134] If desired, in addition to the aforementioned tobacco
materials, the tobacco blend of the present invention, or
aerosol-generating materials may further comprise catalyst
compositions of the present invention. The catalyst compositions
may be distributed substantially uniformly throughout the tobacco
or aerosol-generating materials, or may be located as a separate
component part in the smoking article. By way of example, catalyst
compositions may be incorporated in processed tobacco which is
utilized in a smoking article. Details relating to processed
tobacco are disclosed in U.S. patent application Ser. No.
10/463,211 filed Jun. 17, 2003, the disclosure of which is hereby
incorporated herein by reference.
[0135] The tobacco and/or aerosol generating material can further
include other components. Other components include casing materials
(e.g., sugars, glycerin, cocoa and licorice) and top dressing
materials (e.g., flavoring materials, such as menthol). The
selection of particular casing and top dressing components is
dependent upon factors such as the sensory characteristics that are
desired, and the selection of those components will be readily
apparent to those skilled in the art of cigarette design and
manufacture. See, Gutcho, Tobacco Flavoring Substances and Methods,
Noyes Data Corp. (1972) and Leffingwell et al., Tobacco Flavoring
for Smoking Products (1972).
[0136] Smoking articles also can incorporate at least one flavor
component within the side-seam adhesive applied to the wrapping
material during the manufacture of the tobacco rods. That is, for
example, various flavoring agents can be incorporated in a
side-seam adhesive, such as CS-2201A available from National
Starch, and applied to the seam line of the wrapping material.
Those flavoring agents are employed in order to mask or ameliorate
any off-taste or malodor provided to the smoke generated by smoking
articles. Exemplary flavors include methyl cyclopentenolone,
vanillin, ethyl vanillin, 4-parahydroxyphenyl-2-butanone,
gamma-undecalactone, 2-methoxy-4-vinylphenol,
2-methoxy-4-methylphenol,
5-ethyl-3-hydroxy-4-methyl-2(5H)-furanone, methyl salicylate, clary
sage oil and sandalwood oil. Typically, such types of flavor
components are employed in amounts of about 0.2 percent to about
6.0 percent, based on the total weight of the adhesive and flavor
components.
[0137] Typically, the tipping material circumscribes the filter
element and an adjacent region of the tobacco rod such that the
tipping material extends about 3 mm to about 6 mm along the length
of the tobacco rod. Typically, the tipping material is a
conventional paper-tipping material. The tipping material can have
a porosity which can vary. For example, the tipping material can be
essentially air-impermeable, air-permeable, or may be treated
(e.g., by mechanical or laser-perforation techniques) so as to have
a region of perforations, openings or vents thereby providing a
means for air dilution to the cigarette. The total surface area of
the perforations and the positioning of the perforations along the
periphery of the cigarette can be varied in order to control the
performance characteristics of the cigarette.
[0138] Embodiments of the present invention include embodiments
wherein catalyst compositions comprising ultrafine particles are
incorporated into the filter element of a smoking article.
Typically, the filter element has a length which ranges from about
5 mm to about 40 mm, preferably about 10 mm to about 35 mm; and a
circumference of about 17 mm to about 27 mm, preferably about 22 mm
to about 25 mm. The catalyst compositions of the present invention
may be positioned within the filter element in a position that
maximizes their catalytic activity while maintaining the desired
performance characteristics of the smoking article. In an
embodiment, the catalyst compositions of the present invention are
located between 10-15 mm from the mouth end of the filter.
[0139] The filter element can have a wide range of filtration
efficiencies. The filter element can have one segment of filter
material, two or more longitudinally positioned segments, or other
configurations. The filter may also include an axially located hole
to form a hollow filter element.
[0140] The filter material can be any suitable material such as
cellulose acetate, polypropylene, tobacco material, or the like.
The filter material may further comprise carbon, for example carbon
particles. Examples of suitable filter materials are cellulose
acetate tow items having (i) about 3 denier per filament and about
35,000 total denier, and (ii) about 3.5 denier per filament and
about 35,000 total denier. Such tow items conveniently provide
filter elements exhibiting a removal efficiency of particulate
matter from mainstream smoke of greater than about 40 weight
percent. The plug wrap typically is a conventional paper plug wrap,
and can be either air-permeable or essentially air-impermeable.
However, if desired, a nonwrapped cellulose acetate filter element
can be employed. Filter elements having two or more segments, and
which are provided using known plug-tube-combining techniques, also
can be employed. The various filter elements suitable for use in
this invention can be manufactured using known cigarette
filter-making techniques and equipment.
[0141] Certain filter elements can provide minimal mainstream-smoke
removal efficiencies while maintaining the desirable draw
characteristics of the cigarette. Such minimal smoke-removal
efficiencies are provided by the so-called "low-efficiency"
filters. Low-efficiency filters have a minimal ability to remove
mainstream-smoke particulates. Generally, low-efficiency filters
provide about 40 weight percent mainstream-smoke
particulate-removal efficiency or less. The low-efficiency filter
can be used because the relatively low "tar" yield is obtained
primarily as a result of a relatively high level of filter
ventilation or air dilution. Such cigarette configurations provide
a means for reducing the yields of mainstream gaseous components.
An example of a suitable material for providing a low-efficiency
filter element is a cellulose acetate tow item having about 8
denier per filament and about 40,000 total denier.
[0142] Filter elements can be manufactured with cavities to be
filled with particulate matter such as carbonaceous materials. For
example, filter elements can be manufactured to have a cavity
between two filter plugs, such as those traditionally used in
making cellulose acetate filters. An apparatus and process for
manufacturing such filter elements is described in U.S. Pat. No.
6,537,186, which is hereby incorporated by reference. As will be
set forth below, the catalyst compositions of the present invention
can be positioned in the cavity of such a filter element. The
cavity may also comprise other suitable active or inactive
components, including sepiolite, silica gel, and activated or
non-activated carbon.
[0143] Embodiments of catalyst compositions for use in smoking
articles of the present invention will now be illustrated in the
following specific, non-limiting examples.
EXAMPLE 1
Catalyst Preparation
[0144] A catalyst composition of the present invention is prepared
in the following manner.
[0145] Approximately 0.5128 g of hydrogen tetrachloroaurate III
(49.5% gold metal, Alfa Aesar) is dissolved in 10 ml of deionized
water and the solution is acidified with 0.0671 g of 6N
hydrochloric acid. About 20.0233 g of alumina (18-30 US mesh) is
evenly coated with this acidified gold solution. The gold-coated
alumina particles (which had a yellow tint) were dried at 95 C for
sixteen hours. The dried gold-coated alumina is added to 750 ml of
deionized water containing 35 ml of 5.0 N ammonium hydroxide. The
suspension is vigorously stirred overnight. Next, the gold-coated
alumina is allowed to settle and the liquid decanted. About 750 ml
of deionized water is added and the mixture stirred for an
additional twenty minutes. The gold-coated alumina is allowed to
settle for approximately thirty minutes and the supernatant is
tested for the presence of chloride ions with an aqueous silver
nitrate solution. The gold-coated alumina is washed several times
with deionized water. Washing is complete when no chloride ions
were present in the supernatant. The gold-coated alumina is dried
overnight at 95 C. The dried gold-coated alumina is heated to 375 C
for about 8 hours. The final catalyst particles were free flowing
granules, deep purple in color, and had a theoretical gold loading
of about 1.2% (weight of ultrafine particles to weight of catalyst
composition (W/W)). The catalyst is stored in sealed container.
EXAMPLE 2
Catalyst Preparation
[0146] An alternate embodiment of a catalyst composition of the
present invention is prepared as follows:
[0147] Granular high surface area, activated alumina (8-14 U.S.
mesh) is obtained as item number A505-212 from Fisher Scientific
International. The alumina is ground in a pestle mortar to reduce
the particle size of the alumina. A set of sieves were used to
collect 18-30 U.S. mesh-fraction ground alumina, which corresponds
to particle sizes between about 0.6 millimeters and about one
millimeter. The collected alumina is dried at 95 C for two
hours.
[0148] Gold is obtained in the form of hydrogen tetrachloroaurate
III (49.5% gold metal) as item number 12325 from Alfa Aesar.
Approximately 0.5022 grams of hydrogen tetrachloroaurate III is
dissolved in ten milliliters of deionized water and the solution is
acidified with 0.050 grams of six normal (6N) hydrochloric acid.
About 20.35 grams of the dried alumina (from above) is evenly
coated with this acidified gold solution. The gold-coated alumina
particles, which have a yellow tint, were dried at 95 C for two
hours. The dried gold-coated alumina is poured in 700 milliliters
of deionized water containing 35 milliliters of five normal (SN)
ammonium hydroxide. The suspension is vigorously stirred overnight.
The following day, the gold-coated alumina is allowed to settle and
the liquid decanted. About 750 milliliters of deionized water is
added and the mixture stirred for an additional five minutes. The
gold-coated alumina is allowed to settle and the supernatant tested
for the presence of chloride ions with an aqueous silver nitrate
solution. The gold-coated alumina is washed several times with
deionized water. When no more chloride ions were detected in the
supernatant using the aqueous silver nitrate solution, washing is
considered complete. The gold-treated alumina is dried overnight at
95 C. The dried gold-coated alumina is then heated to 375 C for
sixteen hours. The final catalyst particles were free-flowing
granules, deep purple in color and had a theoretical gold loading
of 1.2% (W/W). When not in use, the catalyst compositions were
stored in a sealed container.
EXAMPLE 3
Catalyst Performance Properties
[0149] The efficacy of the catalyst compositions of the present
invention produced in Examples 1 and 2 is demonstrated in a gas
mixture containing 95% air and 5% carbon monoxide and in mainstream
whole smoke generated by smoking ECLIPSE.RTM. prototype cigarettes
and conventional burn down cigarettes.
[0150] For the following tests, a carbon monoxide/carbon dioxide
NDIR (nondispersive infrared analyzer) is attached at one end of a
Filamatic Smoking Machine, Model DAB-5, produced by National
Instruments Co., of Baltimore, Md. The CO/CO.sub.2 NDIR analyzer
used in the following examples is commercially available from
Rosemount Analytical Inc.
[0151] Reduction of Amount Carbon Monoxide in Carbon Monoxide-Air
Mixture
[0152] A gas mixture consisting of 5% carbon monoxide (CO) and 95%
air, by weight, is drawn through a glass tube containing a packed
bed of catalyst composition. The tube is twelve centimeters long
and 1.25 centimeters in diameter. The catalyst composition used is
the catalyst composition prepared in Example 1.
[0153] Approximately five grams of catalyst composition is packed
approximately to the dimensions of the tube and is held in place
with glass wool. A packed bed of this dimension had a pressure drop
of about 70 millimeters of water measured at a flow rate of 17.5
cubic centimeters per second. The gas stream is passed through the
packed bed at a flow rate of 50 cubic centimeters per two seconds,
in a puff cycle of 30 second intervals (i.e., 50/30/2 smoking
conditions).
[0154] The gas exiting the bed is passed through the CO/CO.sub.2
NDIR analyzer. The control (glass tube with no catalyst
composition) did not result in the conversion of any carbon
monoxide to carbon dioxide. The catalyst composition, however, is
effective in oxidizing carbon monoxide to carbon dioxide. In the
first puff of fifty milliliters, about 85% of the carbon monoxide
is converted to carbon dioxide. Several puffs of the same gas
composition were passed through the bed. The bed of catalyst
composition maintained the efficiency of conversion even after
passing 750 milliliters of gas through it. Average efficiency of
conversion is about 74.4% for fifteen puffs of fifty milliliters
each. There is no deactivation of the catalyst even after heavy
exposure to the test gas mixture.
[0155] Reduction in Carbon Monoxide in Mainstream ECLIPSE.RTM.-type
Cigarette Smoke
[0156] A glass tube containing the catalyst composition of Example
1 is prepared as described above. An experimental prototype of an
ECLIPSE.RTM.-type cigarette is used for this example. The prototype
is similar to the current market product. Whole smoke from the
mouth end of the cigarette is directly passed through the bed of
catalyst composition. Fifty milliliters of smoke were passed
through the bed for a duration of two seconds every thirty seconds.
Smoke exiting the bed is passed through a Cambridge pad to trap the
particulate phase of the smoke. The resulting particulate-free gas
phase of the smoke is passed through the NDIR analyzer for
CO/CO.sub.2 analysis. Subsequently two additional prototype
cigarettes were smoked under the same smoking conditions and the
smoke passed through the same bed of catalyst compositions. In all,
smoke from three cigarettes is passed through the catalyst bed.
[0157] A prototype cigarette is smoked with no catalyst composition
in the glass tube to establish the amount of carbon monoxide in the
prototype cigarette. The prototype cigarette yielded 33.5 units of
carbon monoxide in fifteen puffs of fifty milliliters each. Smoking
the first test cigarette smoked through the catalyst bed resulted
in a reduction in carbon monoxide from 33.5 units/cigarette in the
control to 13.9 units /cigarette, a 58.55% reduction in carbon
monoxide. Smoking a second prototype cigarette smoked through the
same packed bed resulted in 22.9 units of carbon monoxide per
cigarette, a 31.6% reduction in carbon monoxide. Smoking a third
prototype cigarette through the same packed bed resulted in 25.6
units of carbon monoxide per cigarette, a 23.5% reduction in carbon
monoxide.
[0158] The deactivation seen in the catalyst composition with the
smoking of the second and third prototype cigarettes is not
observed when the catalyst composition is subjected to the mixture
of air and carbon monoxide only. Thus, the deactivation observed
may be due to a specific component, or components, other than
carbon monoxide in the smoke.
EXAMPLE 4
Measurement of Catalytic Activity
[0159] This example illustrates the catalytic activity of the
ultrafine particle catalyst composition produced in Example 2
above.
[0160] Catalytic activity is expressed herein in terms of
"Turn-Over Frequency " or TOF. For this application TOF is measured
by placing a known amount of the test catalyst composition in a 12
cm long glass tube of 1.25 cm diameter. The catalyst composition is
sandwiched between two fiberglass mats. A gas mixture comprising 5%
carbon monoxide and 95% air at room temperature is passed through
the bed of catalyst at a rate of 50 cubic centimeters per 2 seconds
in a puff cycle of 30 second intervals. This results in an
effective flow rate of 1.5 liter/minute. The exit gas is passed
through a non-dispersive infrared analyzer where concentrations of
CO and CO.sub.2 are recorded. To measure the TOF, fifteen 50
milliliter puffs of the test gas (5% CO, 95% air) are passed
through the bed containing the catalyst composition. The
concentrations of CO and CO.sub.2 exiting the bed are recorded in
the final 50 milliliter puff of the exit gas. TOF is expressed as %
CO converted per gram of catalyst per second. Thus
TOF=(CO.sub.Input-CO.sub.Output).times.100/(CO.sub.Input.times.Weight
of Catalyst.times.2)
[0161] Table 1 provides the TOF of the catalyst composition
produced by the procedures described herein.
1TABLE 1 TOF of Gold Catalyst Compositions Catalyst Example No.
Composition, g Input CO, mg Output CO, mg TOF 1 5 3.4 0.81 7.6 2 2
3.2 0.5 21.1
[0162] The catalyst composition from Example 2 showed about 2.8
times the catalytic activity of the catalyst composition from
Example 1.
EXAMPLE 5
Reduction in Carbon Monoxide in Mainstream Smoke of a Conventional
Cigarette
[0163] A conventional cigarette equipped with a cavity filter
containing activated carbon is used to measure the efficacy of the
catalyst preparations in reducing the amount of CO in cigarette
smoke for this study. Smoke exiting from the cigarette is passed
through a bed of the catalyst composition produced in Example 2
contained in a glass tube (12 cm in length by 1.25 cm in diameter).
The smoke exiting from the catalyst bed is filtered through a
Cambridge pad. The filtered smoke is fed to the NDIR analyzer.
[0164] This arrangement subjects the catalyst composition to the
whole (i.e., both particulate and gas-phase) smoke. Wet Total
Particulate Matter ("WTPM") is determined as gain in weight of the
Cambridge pad, and CO is determined by NDIR.
[0165] As a control, 25 cigarettes were smoked under FTC 35/60/2
smoking conditions. Results for the control cigarettes are
presented in Table 2. The data represents the average of 25
cigarettes.
2TABLE 2 Results for Control PUFFS/CIG 7.7 WTPM mg/cig 11.7 NIC
mg/cig 0.84 H.sub.2O mg/cig 1.2 TAR mg/cig 9.7 mg CO 9.3 mg
CO.sub.2 28.5
[0166] Table 2 presents the FTC smoking yields from the Control
cigarette. The cigarette produced 11.7 mg WTPM, 9.7 mg of Tar and
9.3 mg CO when smoked under standard FTC conditions.
[0167] For this example, cigarettes were smoked for eight puffs at
50/30/2 smoking conditions. The Control cigarette produced 31 mg
WTPM and 11.0 mg CO. The same cigarette when smoked in the presence
of the catalyst produced 27 mg WTPM and 7.6 mg CO. These results
are presented in FIG. 9. The catalyst bed removed 3.4 mg CO and 4
mg WTPM. Thus CO is reduced by about 31%.
[0168] One potential issue with the use of a catalyst composition
in a filter element of a cigarette is that the active sites of the
catalyst may be deactivated by cigarette smoke. Several methods to
reduce the deactivating effects of smoke on the catalyst
composition were tested. Removal efficiency of the catalyst
composition "doubled" when 1 gram activated carbon (Pica G277, 20 X
50 US mesh) is mixed with 1 gram of the catalyst composition from
Example 1 and the test described herein is repeated. The mixture
containing only half the amount of catalyst removed the same amount
of CO from the smoke as 2 g of the catalyst composition from
Example 1. Removal efficiency of the mixture is significantly
reduced when activated carbon is replaced with the same amount of
high-surface-area alumina (Fisher Scientific). Thus, the activated
carbon is potentially more effective than alumina in removing smoke
components which pollute the catalyst.
[0169] While the invention has been described with reference to
preferred embodiments, it 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.
* * * * *