Patent Grant
7832412
Porous sorbent materials such as adsorbent carbon, activated carbon, silica gel, alumina, polyester resins, zeolites or zeolite-like materials, and mixtures thereof can be effective in removing a wide spectrum of gas phase constituents from mainstream cigarette smoke when incorporated in cigarette filters. However, their lack of selectivity between smoke constituents may cause reduced shelf life and poor smoke subjectives. To improve filtration performance in cigarette filters, activated carbon, silica gel, and other porous substrates can be modified with chemical reagents that can target specific smoke constituents.
According to a preferred embodiment, a surface-modified adsorbent comprises a reagent incorporated in a porous carrier, the reagent comprising 2-HMP or an analogue thereof. The porous carrier is preferably an adsorbent carbon, activated carbon, silica gel, alumina, polyester resin, zeolite or zeolite-like material, or mixture thereof, and more preferably activated carbon comprising at least about 80% micropores and having an average particle size from about 6 mesh to about 300 mesh or an average particle size from about 0.2 mm to about 1 mm. In a preferred embodiment, the reagent can comprise 1 to 80% or 3 to 10% by weight of the adsorbent.
The reagent preferably comprises 2-hydroxymethylpiperidine (2-HMP) or a 2-HMP analogue such as 2-(2-piperidine)ethanol (2-PE), N-piperidineethanol (N-PE), 2-(4-piperidine)ethanol (4-PE), 3-hydroxypiperidine hydrochloride (3-HPH), 4-hydroxypiperidine (4-HP), 3-N-piperidinyl-1,2-propanediol (3-PDP), 2-amino-1-phenylethanol (2-APE), 2-(N-anilino)ethanol (2-AE) or S-(−)2-phenylglycinol (2-PG).
The surface-modified adsorbent (e.g., adsorbent beads) can be incorporated into a cigarette (e.g., a cigarette filter) in an amount effective to reduce the concentration of mainstream tobacco smoke constituents such as carbon dioxide, hydrogen cyanide, ethane, 1,3-butadiene, isoprene, cyclohexadiene, 1,3-cyclohexadiene, methyl cyclopentadiene, formaldehyde, acetaldehyde, acrolein, acetone, diacetyl, methyl ethyl ketone, cyclopentanone, benzene, toluene, acrylonitrile, methyl furan, 2,5 dimethyl furan, hydrogen sulfide, methyl mecaptan, propene, propadiene, carbonyl sulfide, propionaldehyde, butyraldehyde, methanol, and 1-methylpyrrole. For example, the reagent can be incorporated in a cigarette in an amount effective to reduce the concentration in mainstream smoke of hydrogen cyanide, 1,3-butadiene, formaldehyde, acetaldehyde, acrolein, diacetyl, acrylonitrile, and hydrogen sulfide by at least 90%. A preferred filter comprises a plug-space-plug configuration having the surface-modified adsorbent incorporated in the space between the plugs.
Porous sorbent materials such as adsorbent carbon, activated carbon, silica gel, alumina, polyester resins, zeolites or zeolite-like materials, and mixtures thereof can be used to adsorb a wide spectrum of gas phase constituents from mainstream cigarette smoke when incorporated in cigarette filters. However, the lack of selectivity of these materials for specific smoke constituents may cause reduced shelf life and poor smoke subjectives. To improve filtration performance in cigarette filters, activated carbon can be modified with chemical reagents that can specifically react with targeted smoke constituents.
In an embodiment, a porous substrate such as carbon (e.g., activated carbon) or silica gel is treated with a reagent such as 2-HMP or one or more analogues thereof to form a surface modified adsorbent. Analogues of 2-HMP such as 3-N-piperidinyl-1,2-propanediol (3-PDP) and S-(−)-2-phenylglycinol (2-PG) comprise the functional groups —NH— and —O, which can react with carbonyl (═C═O) or nitrile (—CN) groups of targeted tobacco smoke constituents. Additional 2-HMP analogues include 2-(2-piperidine)ethanol (2-PE), N-piperidineethanol (N-PE), 2-(4-piperidine)ethanol (4-PE), 3-hydroxypiperidine hydrochloride (3-HPH), 4-hydroxypiperidine (4-HP), 2-amino-1-phenylethanol (2-APE), and 2-(N-anilino)ethanol (2-AE).
The filtration efficiency of chemically modified porous substrates can depend on the loading level of the reagent. For a porous carbon substrate, it has been found that for higher levels of reagent loading, e.g., 25% or more of 2-HMP by weight, adsorbent selectivity for targeted tobacco smoke constituents (i.e., chemisorption) can be achieved. At higher levels of loading, the pores on the surface of the porous substrate can be flooded by an excess of reagent, and the physical adsorption (physisorption) of non-reactive constituents such as 1,3-butadiene can be mostly blocked. Reactive smoke constituents include hydrogen cyanide, formaldehyde, acrolein and diacetyl.
For lower levels of loading, e.g., 5-10% of 2-HMP by weight, modified carbons with improved activity for removing a broad range of constituents can be obtained. Surface modified carbon comprising lower levels of chemical loading can adsorb both chemically reactive and non-chemically reactive constituents. A hypothesis for this observation is the formation of an intermediate impregnation stage where the physical adsorption surface area of carbon can be increased after the impregnation. Similar effects in filtration performance were also observed in carbons treated with 2-HMP analogues such as 3-N-piperidinyl-1,2-propanediol (3-PDP) and S-(−)-2-phenylglycinol (2-PG), the formulas of which are:
Surface modified adsorbents having different loading levels of reagent can be prepared and incorporated into a test cigarette.
Porous carriers such as carbon, activated carbon, silica gel, alumina, polyester resins, zeolites, zeolite-like materials such as mesoporous silica and the like can be treated with 2-HMP reagent or an analogue thereof to improve tobacco smoke filtration performance. For example, granules of the carrier material can be mixed with a liquid containing the reagent, and the infiltrated granules can be dried under a flowing gas such as air or nitrogen to obtain an impregnated carrier having a desired loading of reagent.
Commercially-available PICA-G277 carbon granules or commercially-available Grace Davison silica gel particles were used as the porous carrier (i.e., substrate) to form surface modified adsorbent particles. The particle sizes for both the carbon and silica gel ranged from about 35×60 mesh to 20×50 mesh.
In a typical synthesis, 2 g of the porous substrate was mixed thoroughly with an aqueous solution containing 0.1 g of 2-HMP solids (or 2-HMP analogue) and about 2 g of water. The mixture was then dried overnight at room temperature in a venting oven, resulting in about 3.6 g of surface modified adsorbent.
Table 1 sets forth examples of various reagents loaded on G-277 carbon wherein the reagents are identified as follows: 2-hydroxymethylpiperidine (2-HMP), 2-(2-piperidine)ethanol (2-PE), N-piperidineethanol (N-PE), 2-(4-piperidine)ethanol (4-PE), 3-hydroxypiperidine hydrochloride (3-HPH), 4-hydroxypiperidine (4-HP), 3-N-piperidinyl-1,2-propanediol (3-PDP), 2-amino-1-phenylethanol (2-APE), 2-(N-anilino)ethanol (2-AE), and S-(−)2-phenylglycinol (2-PG). Table 4 shows that the preparation of modified carbon can be an efficient process with nearly 100% recovery. The relatively low yield of 89% (for 2-APE) is believed to be due to loss of sample during handling.
Table 2 sets forth examples of various reagents loaded on silica gel. Table 2 shows that the preparation of modified silica gel can be an efficient process with nearly 100% recovery.
The multiplex puff-by-puff GC/MS method, which is described by Thomas et al., “Puff-by-puff Mainstream Smoke Analysis by Multiplex Gas Chromatography/Mass Spectrometry,” CORESTA, 2000, was used to evaluate the filtration performance of the surface modified adsorbent particles in 1R4F cigarettes. Results from the testing are shown in Table 3 wherein the % reduction of the various smoke constituents are shown for impregnated carbon (1 wt. %, 5 wt. % and 25 wt. % 2-HMP) and non-impregnated carbon (0 wt. %). In Table 3, the absence of data corresponds to filtration activity (i.e., reduction in constituent concentration) of less than 30%.
As seen in Table 3, improved filtration can be achieved by treating carbon with a desired level of 2-HMP (e.g., greater than 1 wt. %).
In general, the filtration performance of porous adsorbent materials (i.e., via physisorption and/or chemisorption) can be improved by incorporating therein an effective amount of reagent. Physisorption is a process whereby a molecule adheres to a surface without the formation of a chemical bond, usually by van der Waals forces or electrostatic attraction. The formation of a chemical bond leads to chemisorption.
The improvement achieved using 2-HMP impregnated carbon can be seen in the puff-by-puff gas delivery data shown in
From the foregoing, it can be seen that relatively low levels of impregnation (3-10%) provide retained or improved reactivity for a broad range of smoke constituents. On the other hand, high loadings (25% and above) can provide targeted selectivity for constituents such as formaldehyde, acrolein, diacetyl and hydrogen cyanide.
The degree of modification depends on the chemical treatment levels. Under a high level of chemical loading, e.g., at least 25% of 2-HMP by weight, it is believed that the pores of the substrate can be filled with the chemical reagents whereby adsorbent materials with very exclusive high selectivity to hydrogen cyanide, formaldehyde, acrolein, diacetyl can be obtained. Under a lower level of chemical loading, e.g., 5-10% of 2-HMP by weight, materials with improved overall activity to a broad range of smoke constituents may be obtained. For instance, for a 1R4F cigarette comprising 100 mg of modified carbon incorporated in the filter region (e.g., 5-10 wt. % 2-HMP), the concentration of 1,3-butadiene and acrolein in mainstream smoke can be reduce by more than 90%. Replacing the non-impregnated carbon in a test cigarette with 10 wt. % 2-HMP (or analogue thereof) results in undetectable acrolein delivery (<0.08 microgram/cigarette) and no change in dienes delivery (2.4 micrograms/cigarette). Similar results may be obtained with reagents such as 3-pipiridinal 1,2-propanediol (3-PDP) and S-(−)-2-phenylglycinol (2-PG).
The adsorption results for test cigarettes having a filter comprising silica gel or 2-HMP modified silica gel are shown in Table 4. Corresponding data for surface modified carbon are shown in Table 5. Included in Tables 4-5 are the resistance to draw (RTD) (measured in millimeters of mercury) and direct dilution index (DDI) (measure in percent) data of each test cigarette, as well as the composition (measured in milligrams) of the porous carrier or modified porous carrier that was incorporated into the test cigarette. Also shown in Tables 4-5 is the amount of cellulose acetate (CA) that was replaced by way of the addition of adsorbent material. S1 and S2 stand for repeat tests using commercially-available silica gel (Grace Davison), and C1 and C2 stand for repeat tests using commercially available carbon (PICA). The absence of data corresponds to filtration activity (i.e., reduction in concentration) of less than 30%.
In Table 4, for equivalent resistance to draw, untreated silica gel (S1 and S2) showed strong adsorption activity for polar components such as formaldehyde and cyclopentanone, and less activity for acrylonitrile and 1-methyl pyrrole. After treatment with 2-HMP, the modified silica gel were increasingly selective for hydrogen cyanide, formaldehyde and diacetyl. As shown in Tables 4-5, the addition of the modified adsorbent particles to the filter of the test cigarette did not substantially change the resistance to draw or the direct dilution index of the test cigarette.
Table 6 shows the effect of incorporating 200 mg of adsorbent material (untreated G-277 carbon or G-277 carbon loaded with 10 wt. % 2-HMP) in the space of a plug-space-plug filter. The data show the average amount (in micrograms) of each smoke constituent along with the standard deviation for 3 replicas, 10 samples per replica. The data is presented as “average±standard deviation.” In Table 6, TPM stands for total particulate matter. As seen in Table 6, the 10 wt. % 2-HMP carbon achieved a high reduction in acrolein and, of the 13 constituents measured, all but three were reduced compared to untreated carbon.
Table 7 sets forth adsorption measurements for acetaldehyde (AA), hydrogen cyanide (HCN), methanol (MEOH), and isoprene (ISOP). Total particulate matter is abbreviated (TPM), puff count is abbreviated (PUFF), burn time (in minutes) is abbreviated (BT), direct dilution index is abbreviated (DDI) stance to draw (in millimeters of mercury) is abbreviated (RTD). The test cigarettes used to obtain the data in Table 7 are illustrated in
All of the above-mentioned references are herein incorporated by reference in their entirety to the same extent as if each individual reference was specifically and individually indicated to be incorporated herein by reference in its entirety.
While various embodiments have been described, 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 claims appended hereto.
This application claims priority under 35 U.S.C. §119(e) to U.S. provisional Application No. 60/621,544 filed on Oct. 25, 2004, the entire content of which is incorporated herein by reference.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3664352 | Norman et al. | May 1972 | A |
| 3875949 | Harendza-Harinxma et al. | Apr 1975 | A |
| 3889691 | Urbanic | Jun 1975 | A |
| 4182743 | Rainer et al. | Jan 1980 | A |
| 4195649 | Noguchi et al. | Apr 1980 | A |
| 4204980 | Pasha et al. | May 1980 | A |
| 4483833 | Stogryn et al. | Nov 1984 | A |
| 5060672 | Irimi et al. | Oct 1991 | A |
| 5076294 | Kramer | Dec 1991 | A |
| 5206204 | Tsutsumi et al. | Apr 1993 | A |
| 5360023 | Blakley et al. | Nov 1994 | A |
| 5462908 | Liang et al. | Oct 1995 | A |
| 5549125 | White | Aug 1996 | A |
| 5568819 | Gentry et al. | Oct 1996 | A |
| 5904908 | Suzuki et al. | May 1999 | A |
| 6080457 | Charlton et al. | Jun 2000 | A |
| 6209547 | Koller et al. | Apr 2001 | B1 |
| 6257242 | Stavridis | Jul 2001 | B1 |
| 20050092176 | Ding et al. | May 2005 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20060086366 A1 | Apr 2006 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60621544 | Oct 2004 | US |
