US3292636A - Smoking tobacco preparation - Google Patents

Description

United States Patent 3,292,636 SMOKING TOBACCO PREPARATION Rolland L. Mays, Williamsville, N.Y., assignor to Union Carbide Corporation, a corporation of New York No Drawing. Filed May 4, 1964, Ser. No. 364,801 13 Claims. (Cl. 13117) This invention relates to a smoking tobacco preparation and more specifically to preparations for use as cigarettes, cigars and for pipe smoking.

Smoking tobacco preparations contain materials which are vaporized and at least partially oxidized to carbon dioxide and water during use. It is well-known that some of these vaporized and at least partially oxidized materials are irritants to parts of the human body such as the throat. They at least produce disagreeable physiological effects.

An object of this invention is to provide a smoking tobacco preparation which on burning produces less irritation in the human body and yet retains its otherwise pleasant taste.

Other objects will be apparent from the ensuing disclosure and appended claims.

According to this invention, a novel smoking preparation is provided which comprises tobacco and a catalyst composition consisting essentially of a crystalline zeolitic molecular sieve adsorbent having pores sufficiently large to receive benzene, and a catalytically active metal having vapor pressure below 1 atmosphere at 1000 C. The metal is contained in finely divided form in the inner adsorption region of the molecular sieve in quantity sufficient to constitute between about 0.5% and 15% by weight of the catalyst composition. That is, a physical and/or chemical void exists between the metal and the molecular sieve. At least 0.05 weight percent metal is required to obtain some catalytic conversion of the vaporized organics and more than 15% metal does not appreciably improve the effectiveness of this conversion. A range of from about 1% to about by weight catalytically active elemental metal is a preferred balance of these characteristics. The catalyst composition is uniformly dispersed in the tobacco as particles smaller than about 350 mesh and in quantity such that the catalyst composition comprises from about 0.5% to about 25% by weight of the smoking preparation. At least 0.5 weight percent catalyst composition is needed to effect some degree of adsorption and catalytic conversion of the vaporized organics and more than 25% does not significantly reduce the quantity of irritants reaching the smokers mouth. A range of from about 1% to about by weight catalyst composition in the smoking tobacco preparation represents a preferred balance of these requirements.

In general, a preheating zone is established ahead of the burning zone in a smoking tobacco preparation and the preheating zone progressively advances in front of the burning zone. The preparation contains numerous organic materials such as acids, aldehydes and ketones, and depending on their volatility and vapor pressure, at least some are vaporized in the preheating zone and drawn by the smoker through the remaining unheated portion of the tobacco preparation into his mouth. Thus, vaporizable organics may be inhaled either in their originally occurring state, or alternatively may be at least partially oxidized. Certain of these materials are of course completely oxidized to carbon dioxide and water. However, complete oxidation of the entire tobacco preparation is not desirable as this would eliminate much of its pleasing taste. 7

I have discovered that the aforedescribed mechanism may be advantageously modified by incorporating a catalyst composition in the tobacco preparation. This catalyst composition consists essentially of a highly selective molecular sieve adsorbent and a catalytically active metal contained in the finely divided form in the inner adsorption region of the molecular sieve. The catalyst composition is uniformly dispersed in the tobacco so that it is present in the zones of burning, preheating and the region of substantially ambient temperature. The catalyst serves to change the character of the reactions by reducing the activation energy required for pyrolysis and/or oxidation and improves the kinetics of such reactions. For example, cracking of the heavier organic components to lighter compounds and the isomerization of other organics is believed to reduce the irritant effect of the smoke. The presence of a high surface area support also serves to change the character of certain of the products by bringing reactive species into intimate contact on the support surface.

The catalyst support is also an adsorbent, and performs a unique function in the preheating-oxidation mechanism of the instant smoking tobacco preparation. In conventional preparations the vaporized and at least partly oxidized organics flow through the preheated'and non-preheated sections for eventual inhalation as smoke. Of course filters may partiallyremove these materials in cigarettes but some of the irritating constituents are not separated and enter the human body. Also, filtering devices are not particularly effective in cigars or pipe tobacco. a

In my tobacco preparation, the vaporized and at least partially oxidized organic compounds are adsorbed in the preheated and ambient temperature sections of the preparation after contact with the oatalytically active metal in the burning zone. Certain of the reaction products are more readily absorbed than the reactants, so that the catalyst serves to increase the eifect-ivness of the absorbent in separating the irritating constituents of the smoke being inhaled. The physical and/or chemical bond between the catalytically active metal and the adsorbent greatly increases the effectiveness of each com ponent, the metal catalyzing conversion of the organic vapors in the immediate vicinity of the molecular sieve absorbent surfaces which then retain the reaction products. The molecular sieve in turn holds the organic compound for a longer period of contact with the catalyst. These enhancing effects would not be present if the adsorbent and catalytically active metal were phys-' ically separated.

When the burning zone advances into the previously preheated zone containing the molecular sieve adsorbent and the organic irritant adsorbate, the latter is d'esorbed by the heat generated (e.g. about 884 C.). However, the organic desorbate is then exposed to additional catalytically active metal and is further oxidized to less irritating materials before passage into the mouth. The relatively high temperature in the burning zone also serves to desorb water from the adsorbent, thereby keeping the catalytic surface available to irritating components of the smoke.

Although I believe this tobacco preparation functions during smoking under the general mechanism as previ-' ously described, I do not wish to be bound by this particular theory. Also it should be appreciated that the specific adsorption-desorption-reaction mechanism of any particular molecule varies considerably depending on the origin of the molecule. For example, if the molecule originates as vapor from the first burned section of a cigarette, it probably experiences more than one cycle of adsorption-desorption-reaction before final Withdrawal from the inner end of the cigarette into the smokers month. Also the sequence of these steps may vary considerably. For example, the molecule may react in the adsorbed state by virtue of intimate contact with the catalytically active metal if the temperature is sufficiently high for conversion. Then the resulting reaction products would be desorbed from the adsorbent, either because their adsorptivities are lower than the original unreacted molecule or because the burning zone has engulfed the adsorbate, or due to a combination of these factors. On the other hand, if the molecule originates as vapor near the mouth, there may be insufiicient catalyst composition surface area in the short remaining length of the cigarette for the vapor to be adsorbed, reacted and desorbed. Accordingly, such vapor may be drawn into the mouth without significant treatment. However, most of the organic vapor formed during smoking of the instant tobacco preparation is believed contacted with enough of the catalyst composition surface for sufiicient duration to be converted into less irritating forms.

The structure of crystalline zeolitic molecular sieves may be described as an open three-dimensional framework of SiO.; and A tetrahedra. The tetrahedra are cross-linked by the sharing of oxygen atoms, so that the ratio of oxygen atoms to the total of the aluminum and silicon atoms is equal to two, or O/(Al+Si)=2. The negative electrovalence of tetrahedra containing aluminum is balanced by the inclusion within the crystal of cations, for example, alkali metal, and alkaline earth metal ions such as sodium, potassium, calcium and magnesium ions. One cation may be exchanged for another by ion-exchange techniques.

The zeolites may be activated by driving off substantially all of the water of hydration. The space remaining in the crystals after activation is available for adsorption of adsorbate molecules having a size, shape, and energy which permits entry of the adsorbate molecules into the pores of the molecular sieves. These pores are very small but of substantially identical size, as contrasted with other adsorbents which may possess a relatively small number of pores having widely varying sizes.

For use in the present invention, the molecular sieve must have pores sufiiciently large to receive benzene. This is because the organic vapors formed during the smoking of tobacco preparations vary in critical dimension from relatively small to as large as the benzene molecule. If a relatively small pored molecular sieve were employed, the large molecules of organic vapors would be blocked by the pores and could not pass into the inner adsorption region of the molecular sieve.. Since the surface area of this inner region is about one hundred times the external surface area, the molecular sieve would be largely ineffective for both adsorption and contact between organic vapors and the catalytically active metal.

Among the large-pored molecular sieves suitable for use in this invention are the synthetic types L, X and Y, the synthetic mordenite material described in Belgian Patent No. 626,790 and the naturally occurring faujasite.

Zeolite X is a synthetic crystalline zeolitic molecular sieve which may be represented by the formula:

wherein M represents a metal, particularly alkali and alkaline earth metals, n is the valence of M, and y may have any value up to about 8 depending on the identity of M and the degree of hydration of the crystalline Zeolite. Sodium zeolite X has an apparent pore size of about 10 angstrom units. Zeolite X, its X-ray diffraction pattern, its properties, and method for its preparation are described in detail in U.S. Patent No. 2,882,244, issued April 14, 1959.

Zeolite Y may be represented by the formula:

0.9i0.2Na O:A1 O :xSiO :yH O wherein x is a value greater than 3 up to about 6 and y may be a value up to about 9. Zeolite Y has pores of about 10 angstroms size, and is completely described in U.S. Patent No. 3,130,007, issued April 21, 1964.

Zeolite L is described and claimed in U.S. Patent application Serial No. 214,479, filed August 3, 1962 in the names of D. W. Breck and N. A. Acara. Its pores are about 10 angstroms size.

Any metal or metal oxide which (1) possesses catalytic activity for organic conversion, and (2) has a vapor pressure below 1 atmosphere at 1000 C. may be used in my smoking preparation. As used herein organic conversion refers to those processes by which organic compounds are altered either in molecular configuration or in molecular weight. Hence, among those processes included in the term organic conversion are oxidation, isomerization, reforming, cracking, polymerization, alkylation, and dealkylation. Among the metals and their oxides which are useful in the present invention are copper, silver, gold, titanium, tin, lead, vanadium, antimony, bismuth, chromium, molybdenum, tungsten, manganese, rhenium, iron, cobalt, nickel, and the noble metals of the palladium and platinum group. The preferred metals are copper, iron, silver, nickel, and chromium be cause their activity in promoting conversion of organic compounds is especially high.

Metals having vapor pressures above about 1 atmosphere at 1000 C. are not suitable because the burning zone reduces this level and the metal could be distilled out of the molecular sieve inner adsorption region during smoking. Moreover, such metal vapors may eventually enter the mouth in the smoke and may Well irritate the human body. Accordingly, zinc, cadmium, and mercury are not suitable. Y

As previously indicated, the metallic organic conversion catalyst is contained in a finely divided state in the inner adsorption region of the molecular sieve. This is because such compositions demonstate far greater conversion'activity than materials in which the metal is simply deposited o'rimpregnated into the outer surface of the catalyst base. The primary reason for this striking difference is that the internal surface area of molecular sieves is about one hundred times as large as the external area, as previously indicated, and the metal isconsequently deposited over a far greater area if inside. Consequently the organic vapors passing through the pores into the inner adsorption region achieve far more intimate and sustained contact with the catalytically active metal and the effectiveness of the catalyst composition is greatly enhanced.

Among the methods suitable for introducing the catalytically active metal are (1) adsorption of a fluid decomposable compound of the metal followed 'by thermal or chemical decomposition of the metal compound; (2) cation exchange using an aqueous solution of a suitable metal salt followed by chemical reduction of the cations; (3) cation exchange using an aqueous solution of a suitable metal compound in which the metal is in the cationic state with coordination complexing agents, followed by thermal or chemical decomposition of the cationic complex. Method (2) is more completely described in U.S.P. 3,013,982 to D. W. Breck and R. M. Milton. The .ion exchange techniques of methods (2) and (3) are particularly advantageous since their products exhibit the highest catalytic activities.

In method (1) the molecular sieve is first activated to remove any adsorbed water and then contacted with a fluid decomposable compound of the metal thereby adsorbing the compound into the sieve. Typical of such compounds are the halides, metal alkyls and other metalorganic compounds such as cyclopentodienyl metal compounds and ethylenic complex compounds of the noble metals. The internally adsorbed compound is then reduced to its elemental metal thus leaving an active metal uniformly dispersed throughout the internal adsorption region of the molecular sieve. Metals which can be introduced in this manner include copper, silver, platinum, aluminum, iron,-and titanium. This method is described more completely in U.S.P. 3,013,987 to Castor et al.

The previously mentioned ion exchange methods (2) and (3) difier in that (2) relates to the use of metal salts such as the chlorides and nitrates of the ion group metals wherein the metal itself is the cation. Method (3) relates to the use of compounds of metals, such 'as the platinum and palladium group metals, in which the metal is contained in coordination complex form.

Suitable compounds include the amine complexes, e.g. Pt(NH Cl and the ethylene diamine complexes, e.g. Pd(en) Cl and Co(en) Cl The ion exchange methods may be practiced by first dissolving the metal compound in an excess of water in an amount calculated to obtain the desired amount of metal in the catalyst composition. This solution is preferably then added to the zeolitic molecular sieve with stirring and after a sufi'icient time has elapsed to allow the ion-exchange to take place, the exchanged zeolite is separated by filtration. The ion-exchange of the active metal-containing cations into the zeolite is substantially quantitative and the completeness of the exchange process can be detected by chemical tests for the metal in a sample of liquid from the exchanging solution. The filtered zeolite may then be washed to the extent necessary to remove any residual occluded salts followed by drying to produce a powder. Decomposition of the active metal-containing cation is eflected by heating to above 300 C., and preferably above 400 C. When the metal employed is of the iron-group, it is preferred to conduct this operation in a reducing atmosphere such as provided by hydrogen, methane or carbon monoxide while in the case of the noble metals air may be employed.

The catalyst composition should be well dispersed through the tobacco so that it will be uniformly eifective during the entire smoke. For this reason, it is employed as a fine powder of particle size smaller than about 350 mesh. Also, the fine powder form eliminates the need for a tobacco-catalyst composition binder which would be needed if the latter were introduced as relatively large particles. The powder may be added to the tobacco at any of several points in the tobacco processing operation. For instance, it may be dusted into the tobacco leaves entering the shredding machine or it may be added after the tobacco leaves have been shredded and clarified of stem pieces and other debris. Alternatively, the catalyst composition may be introduced along with other additives such as humectant or flavoring which are also added in a manner to assure uniform dispersion in the mixture.

The smoking preparation may be further processed and formed into any desired shape, e.g., cigars and cigarettes, in a manner well-known to those skilled in the tobacco art.

The invention will be more clearly understood from the following example in which a slurry was prepared consisting of 200 grams of calcium cation-exchanged zeolite X and 0.5 liter of distilled water. To this slurry was added 0.5 liter of aqueous solution containing 30 grams of AgNO and stirring was continued for 1 hour after which the solids were recovered by filtration and thorough washing with distilled water. The filter cake was dried by heating at 400 C. in a stream of air. The temperature was then adjusted to 300 C. and after the air was displaced of nitrogen, a stream of hydrogen was passed over the zeolite thereby reducing the contained silver cation to the elemental state. The product was cooled and allowed to rehydrate in normally humid air for 16 hours, yielding approximately 210 grams of zeolite X loaded with 9 weight percent silver. This was easily pulverized and screened to a fine, flow-able powder which is added to smoking tobacco in the shredding process state at a rate of about 20 grams per pound of tobacco.

Although preferred embodiments have been described in detail, it should be appreciated that modifications are contemplated all within the scope of this invention. For example, the molecular sieve itself possesses some catalytic activity for certain organic reactions. This activity may in some cases be enhanced by substitution of polyvalent metal cations for at least about 40% of the structural monovalent cations, usually sodium, in the as-synthesized or purified molecular sieves. Substitution is effected by simple cation exchange in an aqueous solution containing a soluble polyvalent metal cationic salt. The catalytic activity of the molecular sieve may also be enhanced by removal of at least 10% of the cationic sites in the molecular sieve structure, i.e., decationization. This may be accomplished by ion-exchanging the as-synthesized or purified molecular seive with decomposable cations, e. g., ammonium or hydrogen. The :resulting cation exchanged molecular sieve is then heated to 350 C.-600 C. for removal of the decomposable cations. Decationization is described more completely in U.S.P. 3,103,006 issued April 21, 1964 to J. A. Rabo et al.

What is claimed is: Y

1. A smoking preparation comprising tobacco and a catalyst composition consisting essentially of a crystalline zeolitic molecular sieve adsorbent having pores sufiicient- 1y large to receive benzene, and a catalytically active metal having vapor pressure below 1 atmosphere at 1000 C. and contained in finely divided form in the inner adsorption region of said molecular sieve in quantity suflicient to constitute between about 0.05% and 15% by weight of said catalyst composition, the latter being uniformly dispersed in the tobacco as particles smaller than about 350 mesh and in quantity such that said catalyst composition comprises from about 0.5% to about 25% by weight of said smoking preparation.

2. A smoking preparation comprising tobacco and a catalyst composition consisting essentially of a crystalline zeolitic molecular sieve adsorbent having pores sufficiently large to receive benzene, and a catalytically active elemental metal having vapor pressure below 1 atmosphere at 1000 C. and contained in finely divided form in the inner adsorption region of said molecular sieve in quantity sufiicient to constitute between about 0.05% and 15% by weight of said catalyst composition, the latter being uniformly dispersed in the tobacco as particles smaller than about 350 mesh and in quantity such that said catalyst composition comprises from about 0.5% to about 25% by weight of said smoking preparation.

3. A smoking preparation according to claim 2 in which said catalytically active elemental metal comprises from about 1% to about 10% by weight of said catalyst composition.

4. A smoking preparation according to claim 2 in which said catalyst composition comprises from about 1% to about 15% by weight of said smoking preparation.

5. A smoking preparation according to claim 2 in which said catalytically active elemental metal comprises from about 1% to about 10% by weight of said catalyst composition, and such composition comprises from about 1% to about 15 by weight of said smoking reparation.

6. A smoking preparation according to claim 2 in which said catalytically active elemental metal is a member selected from the group consisting of copper, iron, silver, nickel, and chromium.

7. A smoking preparation according to claim 1 in which the molecular sieve is at least 10% decationized.

8. A smoking preparation according to claim 1 which the molecular sieve has at least 40% polyvalent cations.

9. A smoking preparation according to claim 1 in which zeolite X is said molecular sieve.

10. A smoking preparation according to claim 1 in which zeolite Y is said molecular sieve.

11. A cigarette comprising tobacco and a catalyst composition consisting essentially of a crystalline zeolitic molecular sieve adsorbent having pores sufficiently large to receive benzene, and a catalytically active metal having vapor pressure below 1 atmosphere at 1000 C. and contained in finely divided form in the inner adsorption region of said molecular sieve in quantity sufiicient to constitute between about 1% and 10% by Weight of said catalyst composition, the latter being uniformly dispersed in the tobacco as particles smaller than about 350 mesh and in quantity such that said catalyst composition comprises'from about 1% to about 15% by weight of said cigarette.

12. A cigar comprising tobacco and a catalyst composition consisting essentially of a crystalline zeolitic molecular sieve adsorbent having pores sufliciently large to receive benzene, and a catalytically active metal having vapor pressure below 1 atmosphere at 1000 C. and contained in finely divided form in the inner adsorption region of said molecular sieve in quantity suflicient to constitute between about 1% and 10% by weight of said catalyst composition, the latter being uniformly dispersed in the tobacco as particles smaller than about 350 mesh and in quantity such that said catalyst composition comprises from about 1% to about 15% by weight of said cigar.

13. A pipe smoking preparation comprising tobacco and a catalyst composition consisting essentially of a crystalline zeolitic molecular sieve adsorbent having pores sufiiciently large to receive benzene, and a catalytically active metal having vapor pressure below 1 atmosphere at 1000 C. and contained in finely divided form in the inner adsorption region of said molecular sieve in quantity suflicient to constitute between about 1% and 10% by weight of said catalyst composition, the latter being uniformly dispersed in the tobacco as particles smaller than about 350 mesh and in quantity such that said catalyst composition comprises from about 1% to about 15% by weight of said pipe smoking preparation.

References Cited by the Examiner UNITED STATES PATENTS 1,519,470 12/ 1924 Wilson 131-208 2,755,207 7/1956 Frankenburg 131-15 2,759,859 8/1956 Lahr 131-17 FOREIGN PATENTS 841,074 7/1960 Great Britain.

ALDRICH F. MEDBERY, Acting Primary Examiner. MELVIN D. REIN, Examiner.

Claims (1)

1. A SMOKING PREPARATION COMPRISING TABACCO AND A CATALYST COMPOSITION CONSISTING ESSENTIALLY OF A CRYSTALLINE ZEOLITIC MOLECULAR SIEVE ADSORBENT HAVING PORES SUFFICIENTLY LARGE TO RECEIVE BENZENE, AND A CATALYTICALLY ACTIVE METAL HAVING VAPOR PRESSURE BELOW 1 ATMOSPHERE AT 1000* C. AND CONTAINED IN FINELY DIVIDED FORM IN THE INNER ADSORPTION REGION OF SAID MOLECULAR SIEVE IN QUANITY SUFFICIENT TO CONSTITUTE BETWEEN ABOUT 0.05% AND 15% BY WEIGHT OF SAID CATALYST COMPOSITION, THE LATTER BEING UNIFORMLY DISPERSED IN THE TOBACCO AS PARTICLES SMALLER THAN ABOUT 350 MESH AND QUANTITY SUCH THAT SAID CATALYST COMPOSITION COMPRISES FROM ABOUT 0.5% TO ABOUT 25% BY WEIGHT OF SAID SMOKING PREPARATION.