WO2015151002A1

WO2015151002A1 - Activated carbon for smoking articles

Info

Publication number: WO2015151002A1
Application number: PCT/IB2015/052275
Authority: WO
Inventors: Maria Angeles LILLO-RODENAS; Angel LINARES-SOLANO; Gaetan COUDERC
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2014-03-31
Filing date: 2015-03-27
Publication date: 2015-10-08
Anticipated expiration: 2016-09-30
Also published as: RU2016138543A3; RU2678898C2; KR20160138952A; KR102537198B1; JP2017510266A; RU2016138543A

Abstract

A smoking article includes a smokable material and an activated carbon material downstream of the smokable material. The activated carbon material has a ratio of narrow micropore volume to total micropore volume of about 0.9 or less. The activated carbon material may be activated carbon in a carbon on tow configuration, plug-space- plug configuration, or any other suitable configuration. The activated carbon material may have a ratio of total micropore volume to total pore volume of about 0.9 or greater. The activated carbon material may contain surface oxygen at a concentration of about 5000 micromole per gram or less. The activated carbon material may have a BET surface area of about 1100 m²/g or greater.

Description

ACTIVATED CARBON FOR SMOKING ARTICLES

This disclosure relates to activated carbon suitable for smoking articles, to filters containing such activated carbon, and related smoking articles.

Combustible smoking articles, such as cigarettes, typically have shredded tobacco (usually in cut filler form) surrounded by a paper wrapper forming a tobacco rod. A cigarette is employed by a smoker by lighting one end of the cigarette and burning the tobacco rod. The smoker then receives mainstream smoke by drawing on the opposite end or mouth end of the cigarette, which typically contains a filter. The filter is positioned to entrap some constituents of mainstream smoke before the mainstream smoke is delivered to a smoker and may contain activated carbon for adsorbing smoke constituents.

Pores of activated carbon for use in smoking articles have been characterized as microporous (2 nm or less) or mesoporous (2 nm to 50 nm), with reports suggesting that increasing the ratio of mesopores to micropores can be advantageous for adsorption of smoke constituents. More recently, a subset of micropores, called narrow micropores has been described. Narrow micropores have a size of 0.7 nm or less. Some have suggested that to optimize the adsorption capacity of activated carbon for volatile organic pollutants in gaseous stream of industrial processes at low concentrations, the volume of narrow micropores needs to be maximized.

One object of the present invention is to employ activated carbon in filters of smoking articles, where the activated carbon is more effective at removing at least selected smoke constituents than existing activated carbon that has been used or suggested for use in smoking articles. Other objects of the present invention will be evident to those of skill in the art upon reading and understanding the present disclosure, which includes the claims that follow and accompanying drawings.

In aspects of the present invention, a smoking article includes a smokable material and an activated carbon material downstream of the smokable material. The activated carbon material has a ratio of narrow micropore volume to total micropore volume of about 0.9 or less and has a surface oxygen at a concentration of about 5000 micromole per gram or less as determined by temperature-programmed desorption. ln aspects of the present invention, a method includes (i) providing activated carbon material having a ratio of narrow micropore volume to total micropore volume of about 0.9 or and having a surface oxygen at a concentration of about 5000 micromole per gram or less as determined by temperature-programmed desorption; (ii) providing filter material for use in a smoking article; and (iii) combining the activated carbon material and the filter material to form a filter for a smoking article.

Various aspects of the filters and smoking articles of the present invention may have one or more advantages relative to currently available filter and smoking articles. For example, improved efficiency of activated carbon for removing at least selected smoke constituents may allow for less activated carbon material to be used, thereby reducing manufacturing cost. Use of less activated carbon material may also result in less particle breakthrough. By way of further example, selective adsorption of smoke constituents may result in a better smoking experience. For example, enhanced flavour may result due to removal of selective constituents rather than all constituents, including flavour constituents. Additional advantages of one or more aspects of filters and smoking articles described herein will be evident to those of skill in the art upon reading and understanding the present disclosure.

Activated carbon is a generic term used to describe a family of carbonaceous adsorbents with an extensively developed internal pore structure. Activated carbon can be produced from a carbonaceous source material such as wood, lignite, coal, coconut husk or shells, peat, pitch, polymers, cellulose fibers, polymer fibers, or the like.

Activated carbon may be produced by any suitable process such as physical activation or chemical activation. In physical activation, the source material is developed into activated carbon using hot gases by carbonization, activation/oxidization or

carbonization and activation/oxidization. The process of carbonization includes pyrolyzing source material at high temperatures, typically in the range of about 600°C to about 900°C, in the absence of oxygen. Activation/oxidization includes exposing carbonized material to oxidizing atmospheres, such as steam, carbon dioxide or oxygen, at temperatures above 250°C. Temperatures for activation/oxidization typically range from about 600°C to about 1200°C.

Chemical activation includes impregnating raw source material with certain chemicals, such as an acid, base or salt, such as phosphoric acid, potassium hydroxide, sodium hydroxide, calcium chloride, or zinc chloride. The raw materials are then carbonized at temperatures that are typically lower than physical activation

carbonization. For example, temperatures for chemical activation carbonization may be in the range of from about 450°C to about 900^eC. Carbonization and activation may occur simultaneously.

For purposes of the present disclosure, carbonaceous source material may be activated via any suitable process. For example, the activation process can comprise chemical activation, which may include shorter activation times and lower temperatures relative to physical activation. Alternatively, physical activation may be employed.

Pore size and surface characteristics may be varied according to well-known techniques, which can affect the efficiency with which activated carbon can remove selected smoke constituents, such as 1,2-propadiene, 1 ,3-butadiene, isoprene, benzene, 1 ,2-pentadiene, 1 ,3-cyclopentadiene, 2,4-hexadiene, 1,3-cyclohexadiene, methyl-1 ,3-cyclopentadiene, benzene, toluene, p-xylene, m-xylene, o-xylene, styrene (vinylbenzene), 1-methylpyrrole, formaldehyde, acetaldehyde, acrolein,

propionaldehyde, isobutyraldehyde, 2-methyl isovaleraldehyde, acetone, methyl vinyl ketone, diacetyl, methyl ethyl ketone, methyl propyl ketone, methyl 2-furyl ketone, hydrogen cyanide and acrylonitrile. The activated carbon for use in filters and smoking articles of the present invention preferably efficiently removes benzene, acrolein, or both benzene and acrolein, but may also efficiently remove one or more other smoke constituents.

The activated carbon for use in filters or smoking articles of the present invention preferably has a mesopore volume to total pore volume of about 10% or less.

Mesopores are pores having a size of 2 nanometers to 50 nanometers. More preferably, the mesopore volume to total pore volume is about 5% or less.

The activated carbon for use in filters or smoking articles of the present invention preferably has a ratio of micropore volume to total pore volume of about 90% or more. Micropores are pores having a size of 2 nanometers or less. More preferably, the micropore volume to total pore volume is about 95% or more. Even more preferably, the micropore volume to total pore volume is about 96% or more or about 98% or more.

The activated carbon for use in filters or smoking articles of the present invention preferably has a narrow micropore to total micropore ratio of about 0.9 or less. Narrow micropores are pores having a size of 0.7 nanometers or less. More preferably, the narrow micropore to total micropore ratio is about 0.85 or less. Even more preferably, the narrow micropore to total micropore ratio is about 0.8 or less. Yet more preferably, the narrow micropore to total micropore ratio is about 0.75 or less.

The activated carbon for use in filters or smoking articles of the present invention preferably contains a surface oxygen concentration of about 5000 micromole per gram or less. More preferably, the surface oxygen concentration is about 4000 micromole per gram or less. Even more preferably, the surface oxygen concentration is about 3000 micromole per gram or less. Yet even more preferably, the surface oxygen

concentration is about 2000 micromole per gram or less.

The activated carbon for used in filters or smoking articles of the present invention preferably has a specific surface area (BET) of about 1100 m²/g or greater. Generally, the activated carbon will have a BET of about 2500 m²/g or less. Preferably, the activated carbon has a BET of about 1600 m²/g.

In some preferred embodiments, activated carbon for used in filters or smoking articles of the present invention has a ratio of narrow micropore volume to total micropore volume ratio of about 0.75 or less and has a total micropore volume to total pore volume ratio of about 0.9 or greater. In such embodiments, the activated carbon can have any suitable BET, which may often be less than about 2500 m²/g. Preferably, the BET is about 1100 m²/g or greater. Preferably, the BET is about 1600 m²/g.

In some preferred embodiments, activated carbon for used in filters or smoking articles of the present invention has a surface oxygen concentration of about 2000 micromole per gram or less and has a ratio of total micropore volume to total pore volume of about 0.95 or greater. In such embodiments, the activated carbon can have any suitable BET, which may often be less than about 2500 m²/g. Preferably, the BET is about 1100 m²/g or greater. Preferably, the BET is about 1600 m²/g.

In some preferred embodiments, activated carbon for used in filters or smoking articles of the present invention has a ratio of narrow micropore volume to total micropore volume ratio of about 0.75 or less; has a surface oxygen concentration of about 2000 micromole per gram or less; and has a ratio of total micropore volume to total pore volume of about 0.95 or greater. In such embodiments, the activated carbon can have any suitable BET, which may often be less than about 2500 m²/g. Preferably, the BET is about 1100 m²/g or greater. Preferably, the BET is about 1600 m²/g.

As discussed above, the ability to control pore size distribution and surface characteristics, such as surface oxygen concentration, of activated carbon are well known in the art. See, for example, (i) WO 2010/103323 A1 , entitled METHODS FOR INCREASING MESOPORES INTO MICROPOROUS CARBON; (ii) Lillo-Rodenas et al. (2005), Behaviour of activated carbons with different pore size distributions and surface oxygen groups for benzene and toluene adsorption at low concentrations, Carbon 43: 1758-1767; and (iii) Romero-Anaya, et al. (2010), Spherical activated carbon for low concentration toluene adsorption, Carbon 48:2625-2633. In general, the pore size distribution and surface characteristics can be readily modified by adjusting the activating atmosphere (e.g., 0₂, C0₂ or steam) and the activation time and temperature. Further treatment, e.g. in an inert atmosphere, may be performed to modify surface oxygen content without modifying porosity. One of skill in the art may readily adjust activation parameters to achieve activated carbon for use in filters and smoking articles of the present invention. For a point of reference, activated carbon may be prepared as described in the Examples presented below or modified from the procedures presented in the Examples as desired to achieve suitable activated carbon material.

Pore size distribution may be determined in any suitable manner. For example, micropore volume may be calculated from N₂ adsorption isotherms at -196°C using the Dubinin-Radushkevich equation as taught by, for example, Gregg SJ, Sing KSW;

Adsorption, Surface Science and Porosity; Academic Press, New York, 1982. Narrow micropore volume may be calculated from C0₂ adsorption at 0°C as described in (i) Cazorla-Amoros et al, Lanqmuir 1996: 12:2820-24; (ii) Cazorla-Amoros et al, Lanqmuir 1998; 14:4589-96; and (iii) Cazorla-Amoros et al, Usefulness of C02 adsorpotion at 273K for the characterization of porous carbons. Carbon 2004; 42:1233-42. Total pore volume can be determined by, for example, N₂ isotherm at -196°C, calculating the adsorbed volume of nitrogen at P/P0 = 0.95 following the method of Gregg SJ, Sing KSW. Adsorption, Surface Science and Porosity. Academic Press, New York, 1982. As a point of reference, total pore volume, micropore volume and narrow micropore volume may be determined as described below in the Examples. Once the total pore volume, micropore volume and narrow micropore volume are determined, the ratio of narrow micropore volume to total micropore volume, the ratio of total micropore volume to total pore volume, and the like may be readily calculated.

Surface oxygen concentration may be determined in any suitable manner. By way of example, surface oxygen concentration may be determined by temperature- programmed desorption (TPD) experiments using, for example, a differential scanning calomiter (DSC) - thermo-gravimetric analyzer (TGA) coupled to a mass

spectrophotometer, as described in, for example, (i) Roman-Martinez et al. (1993), TPD and TPR characterization of carbonaceous supports and Pt C catalysts, Carbon 31 :894- 902; (ii) Otake Y. and Jenkins R.G. (1993), Characterization of oxygen-containing surface complexes created on microporious carbon by air and nitric acid treatment, Carbon 31 :109-21 ; and (iii) Zielge et al. (1996), Surface oxidized carbon fibers: I.

Surface structure and chemistry, Carbon 34:983-98. In such TPD experiments, a 10 milligram sample of activated carbon may be heated up to 950°C at a heating rate of 20°C/minute under a helium flow rate of 100 milliliters/minute.

Activated carbon may be placed in a filter for a smoking article in any suitable manner. For example, activated carbon can be intermingled with fibrous filter material, placed in a void space in the filter, or in a combination, i.e., intermingled with fibrous filter material and in a void space in the filter.

In embodiments, activated carbon is provided in a filter in a plug-space-plug configuration, where the activated carbon is present in a void space between two sections of filter plug material. Preferably, the plugs of filter sections in a plug-space- plug filter configuration are plugs of cellulose acetate tow. In embodiments, activated carbon is provided in a carbon on tow configuration. Preferably, the tow is cellulose acetate tow. Regardless of the filter configuration, it may be desirable to include a white cellulose acetate tow section at the mouth end of the filter for purposes of aesthetics or to meet consumer expectations.

In aspects of the present invention, a filter of a smoking article or a filter for a smoking article includes activated carbon described herein. The filter may include filter material, such as cellulose acetate tow. In some preferred embodiments, the activated carbon is incorporated in or on the cellulose acetate tow. In some preferred

embodiments, the filter includes first and second cellulose acetate tow elements and activated carbon material is disposed between the first and second cellulose acetate tow elements in a plug-space-plug configuration. In some plug-space plug

configurations, activated carbon may be incorporated into or on one or both of the first and second cellulose acetate tow elements.

Any suitable smoking article may include a filter having activated carbon as described in this disclosure, where the filter is disposed downstream of a smokable material. The term "downstream" refers to relative positions of elements of the smoking article described in relation to the direction of mainstream smoke as it is drawn from a smokable material and into a user's mouth.

The term "smoking article" includes cigarettes, cigars, cigarillos and other articles in which a smokable material, such as a tobacco, is lit and combusted to produce smoke. The term "smoking article" also includes articles in which smokable material is not combusted, such as but not limited to smoking articles that heat a smoking composition directly or indirectly, or smoking articles that use air flow or a chemical reaction, with or without a heat source, to deliver nicotine or other materials from the smokable material.

As used herein, the term "smoke" is used to describe an aerosol produced by a smoking article. An aerosol produced by a smoking article may be, for example, smoke produced by combustible smoking articles, such as cigarettes, or aerosols produced by non-combustible smoking articles, such as heated smoking articles or non-heated smoking articles.

The activated carbon for use in filters and smoking articles of the present invention preferably removes one or more constituent from smoke when a smoking article is smoked by a user. The activated carbon may remove one or more

constituents from smoke by any suitable mechanism, such as binding, adsorption, adsorption, or the like. Preferably, activated carbon for use in filters and smoking articles of the present invention removes benzene, acrolein, or both benzene and acrolein.

All scientific and technical terms used herein have meanings commonly used in the art unless otherwise specified. The definitions provided herein are to facilitate understanding of certain terms used frequently herein. As used herein, the singular forms "a", "an", and "the" encompass embodiments having plural referents, unless the content clearly dictates otherwise.

As used herein, "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise. The term "and/or" means one or all of the listed elements or a combination of any two or more of the listed elements.

As used herein, "have", "having", "include", "including", "comprise", "comprising" or the like are used in their open ended sense, and generally mean "including, but not limited to". It will be understood that "consisting essentially of, "consisting of, and the like are subsumed in "comprising," and the like.

The words "preferred" and "preferably" refer to embodiments of the invention that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the disclosure, including the claims.

FIGS. 1-2 are schematic perspective views of embodiments of partially unrolled smoking articles. The smoking articles depicted in FIGS. 1-2 illustrate embodiments of smoking articles or components of smoking articles described above. The schematic drawings are not necessarily to scale and are presented for purposes of illustration and not limitation. The drawings depict one or more aspects described in this disclosure. However, it will be understood that other aspects not depicted in the drawings fall within the scope and spirit of this disclosure.

Referring now to FIG. 1, a smoking article 10, in this case a cigarette, is depicted. The smoking article 10 includes a rod 20, such as a tobacco rod, and a mouth end filter 30. The filter 30 includes a mouth end segment 32, such as a white cellulose acetate tow segment, and an upstream carbon on tow segment 34. Filter segments 32 and 34 are shown as being separated for purposes of illustration, but may be abutting.

Similarly, filter segment 34 and rod 20 are shown as being separated for purposes of illustration, but may be abutting. The depicted smoking article 10 includes plug wrap 60, cigarette paper 40, and tipping paper 50. In the depicted embodiment, the plug wrap 60 circumscribes at least a portion of the filter 30. The cigarette paper 40 circumscribes at least a portion of the rod 20. Tipping paper 50 or other suitable wrapper circumscribes the plug wrap 60 and a portion of the cigarette paper 40 as is generally known in the art.

FIG. 2 illustrates an embodiment where filter 30 is in a plug 32-space 37-plug 35 configuration. Activated carbon (not shown) may occupy the void space 37 between filter plugs 32 and 35. In FIG. 2, filter segment 35 and rod 20 are shown as being separated for purposes of illustration, but may be abutting. In FIG. 2 components labelled with the same number as components depicted in FIG.1 are the same as, or similar to, those components as discussed with regard to FIG. 1 above. For those components not specifically discussed with regard to FIG. 2, reference is made to the discussion above with regard to FIG. 1.

Non-limiting examples illustrating activated carbon as described above and filters and smoking articles having such activated carbon are described below.

Examples

In the following examples, characterization of activated carbon produced from a variety of sources and the function of some of the activated carbon in filters of smoking articles is described.

Activated carbon was prepared as follows. A commercial spherical activated carbon serving as precursor (obtained from polymer) provided by Gun-Ei, was selected as starting material. With the aim of further developing its porosity, activated carbons were prepared by physical activation with C0₂ using the experimental procedure described in Romero-Anaya, et al. (2010), Carbon 48 :2625-2633. For physical activation with C0₂, a horizontal quartz furnace tube 2 m long and 0.7 m diameter was used, and the precursor was placed in a crucible. A flow of 80 ml/min of C0_2> heating at 10°C/min from room temperature to 880°C and times of activation of 3, 5, 10, 15 and 20 hours were used for preparing samples 2 to 6. The nomenclature of these samples has been selected according to the activation degree. A spherical commercial activated carbon provided by Gun-Ei, sample 7, has also been selected and studied.

A commercial granular activated carbon from eadWestvaco (WVA1100) sample 11 has been selected as a granular material. Several heat treatments in inert atmosphere have been performed over this sample with the aim of modifying its surface chemistry and studying in more depth the effect of this parameter on the performance of these samples towards smoking article application, since surface chemistry has proved to have an important effect on the adsorption of many organic compounds. The heat treatments have been performed in nitrogen atmosphere using a 100 ml/min flow rate up to three different maximum temperatures, 300, 600 and 900°C, which were held for one hour. The cooling step was performed in the same nitrogen flow.

To be sure that these treatments have not substantially modified porosity, both the textural properties and surface chemistry of the heat-treated activated carbons have been characterized. The original WVA1100 will be referred to as sample 11, whereas the heat-treated samples are referred to as sample 12 to 14, where the number refers to the maximum heat-treatment temperature in inert atmosphere.

The characteristics of activated carbon can be analysed by routine methods for determining the total pore volume, total micropore volume, and narrow micropore volume. The samples were characterized as follows. The characterization of all samples was performed using nitrogen (N₂) adsorption at -196 °C and C0₂ adsorption at 0 °C in a volumetric Autosorb-6B apparatus from Quantachrome. Before the analysis, the samples were outgassed at 250°C for 4 hours. The BET equation was applied to the nitrogen adsorption data to get the apparent BET surface area (SBET) (Linares-Solano et al., Tanso 1998; 185:316-325). The Dubinin-Radushkevich equation was applied to the nitrogen adsorption data to determine the total micropore volume (pores with size < 2 nm) V-DR-N2, and the total pore volume (V N2 at P/P0 = 0.95). The Dubinin- Radushkevich equation was applied to the carbon dioxide adsorption isotherms to determine narrow micropore volumes V-DR-C02 (pores with size < 0.7 nm).

Surface oxygen content on the surface of the activated carbon can be determined by temperature-programmed desorption (TPD) under standard conditions. The surface oxygen content of the samples was determined as follows. TPD experiments were done in an equipment for differential scanning calorimetry (DSC) and thermo- gravimetric analysis (TGA) (TA Instruments, SDT 2960 Simultaneous) coupled to a mass spectrometer (Balzers, OmniStar) to characterize the oxygen surface chemistry of all the samples, comprising measurement of water, carbon monoxide, carbon dioxide content under an inert atmosphere. See, for example, (i) Roman-Martinez et al. (1993), TPD and TPR characterization of carbonaceous supports and Pt/C catalysts, Carbon 31:894-902; (ii) Otake Y. and Jenkins R.G. (1993), Characterization of oxygen- containing surface complexes created on microporous carbon by air and nitric acid treatment, Carbon 31:109-21; and (iii) Zielge et al. (1996), Surface oxidized carbon fibers: I. Surface structure and chemistry, Carbon 34:983-98. In these experiments, 10 mg of sample were heated up to 950 °C (heating rate 20 °C/min) under a helium flow rate of 100 ml/min.

Bed density of the activated carbons (also called bulk, tap or apparent density) can be defined as the weight of porous solid per volume. This volume includes the volume of pores, both opened and closed, and the space volume between the solid particles. This magnitude was measured using an experimental procedure similar to that described by the D2854-89 ASTM method (Romero-Anaya et al., Carbon 2010;

48:2625-2633). In our case, the density measurement was performed with 0.5 g of sample using a 10 ml measuring cylinder.

Mock-up cigarettes were prepared as follows:

A filter in plug-space-plug configuration with 11 mm cellulose acetate plugs and a 5 mm cavity was adjusted to 54 mm length tobacco rod with a constant tobacco weight (about 600 mg) and attached by a tipping paper. The cavity was filled respectively by 165 mg, 127 mg, 100 mg, 70 mg, 55 mg, 40 mg and 30 mg of sample 1 to 7 and an adequate quantity of a non-porous material such as cellulose beads in order to obtain a complete cavity filling. The BET surface available for adsorption in each filter was maintained around 67 m2 from sample 2 to sample 7. The cigarettes were designed to maintain a constant pressure drop for non-ventilated cigarettes at about 140 mmWG.

In table 2, we added 60 mg of samples 11 , 12 and 13 and 75 mg of sample 14 to get about 108 m2.

Filters of reference cigarettes were containing only the non-porous material in the cavity.

Cigarette were smoked following the methodology described in WHO TobLabNet Official Method SOP01 :° Standard operating procedure for intense smoking of cigarette". The method was adapted to smoke 10 sticks per samples.

Benzene and acrolein were measured from cigarettes smoke analysis and % reduction were calculated from cigarettes not containing activated carbons. For the smoking article employing sample 14, 75 mg of activated carbon was used to compensate for the smaller BET surface and smaller pore volumes (see Table 2). Table 1 below provides characterization results for samples 1-8, and Table 2 below provides characterization results for samples 11-14.

Table 1 : Characterization of samples 1-8

Table 2: Characterization of samples 11-14

FIG. 3 is a graph of the N₂ isotherms at -196°C of samples 1-7.

FIG. 4 is a graph of the percent reduction of benzene (relative to a cigarette with no activated carbon) for cigarettes containing activated carbon of each of samples 1-7.

FIG. 5 is a graph of the percent reduction of acrolein (relative to a cigarette with no activated carbon) for cigarettes containing activated carbon of each of samples 1-7.

FIG. 6 is a graph of the percent reduction of benzene (relative to a cigarette with no activated carbon) for cigarettes containing activated carbon of each of samples 11-14.

FIG. 7 is a graph of the percent reduction of acrolein (relative to a cigarette with no activated carbon) for cigarettes containing activated carbon of each of samples 11-14.

In general, the results, among other things, indicate that (i) a decreased ratio of narrow micropore volume to total micropore volume increases adsorption of benzene and acrolein; (ii) an increased ratio of total micropore volume to total pore volume increases adsorption of benzene and acrolein; and (iii) decreased surface oxygen concentration results in increased adsorption of benzene and acrolein.

For example and with reference to FIGS. 4-5 and Table 1, the percent reduction in benzene and the percent reduction in acrolein increases from sample 3 to 4 as the narrow micropore portion increases. Note that in FIG. 5, the percent reduction of acrolein for sample 7 is less than from sample 6 despite having a higher BET. Without intending to be bound by theory, it is believed that the lower ratio of micropore volume to total pore volume for sample 7 relative to sample 6 (0.93 versus 0.96) may be a factor in the decreased reduction of acrolein with sample 7.

Referring now to FIGS. 6-7 and Table 2, increased percent reduction of benzene and acrolein were observed as the oxygen surface content decreased (from sample 11 to sample 14).

Claims

CLAIMS:

1. A smoking article comprising:

a smokable material; and

an activated carbon material downstream of the smokable material, the activated carbon material having a ratio of narrow micropore volume to total micropore volume of about 0.9 or less, wherein the activated carbon material contains surface oxygen at a concentration of about 5000 micromole per gram or less as determined by temperature-programmed desorption.

2. A smoking article according to claim 1, wherein the activated carbon material has a ratio of narrow micropore volume to total micropore volume of about 0.8 or less.

3. A smoking article according to claim 1 or claim 2, wherein the activated carbon material has a BET surface area of about 1100 m²/g or greater.

4. A smoking article according to claim 1 or claim 2, wherein the activated carbon material has a BET surface area of about 1600 m²/g.

5. A smoking article according to any one of the preceding claims, wherein the activated carbon material has a ratio of total micropore volume to total pore volume of about 0.9 or greater.

6. A smoking article according to any one of the preceding claims, wherein the activated carbon material has a ratio of total micropore volume to total pore volume of about 0.95 or greater.

7. A smoking article according to any one of the preceding claims, wherein the activated carbon material contains surface oxygen at a concentration of about 3000 micromole per gram or less as determined by temperature-programmed desorption.

8. A smoking article according to any one of the preceding claims, wherein the surface oxygen concentration is determined by heating the activated carbon up to 950°C at a rate of 20°C/minute under a helium flow rate of 100

milliliters/minute.

9. A smoking article according to any one of the preceding claims, wherein the activated carbon material is present in a filter of the smoking article.

10. A smoking article according to claim 9, wherein the filter comprises cellulose acetate tow.

11. A smoking article according to claim 10, wherein the activated carbon is

incorporated in or on the cellulose acetate tow.

12. A smoking article according to claim 10, wherein the filter comprises first and second cellulose acetate tow elements, and wherein the activated carbon material is disposed between the first and second cellulose acetate tow elements.

13. A method comprising:

providing activated carbon material having a ratio of narrow micropores volume to total micropore volume of about 0.9 or less and having a surface oxygen at a concentration of about 5000 micromole per gram or less as determined by temperature-programmed desorption;

providing filter material for use in a smoking article; and

combining the activated carbon material and the filter material to form a filter for a smoking article. A method according to claim 13, further comprising incorporating the filter into smoking article.