US3338246A - Smoking tobacco preparation - Google Patents

Description

United States Patent 3,338,246 SMOKENG TGBACCO 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. 364,758 1 Claim. (Cl. 131-17) 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 an adsorbent and a catalytically active metal having vapor pressure below 1 atmosphere at 1000" C. The metal is supported by the adsorbent in quantity sufficient to constitute between about 0.05% and 15% by weight of the catalyst composition. That is, a physical and/or chemical bond exists between the metal and the adsorbent. 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 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 preoaration is not desirable as this would eliminate much of its pleasing taste.

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 an adsorbent and a catalytically active metal having vapor pressure below 3,338,246 Patented Aug. 29, 1967 ice 1 atmosphere at 1000 C. being supported by the adsorbent. 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 seems 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 the 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 partially remove 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.

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 catalytical active metal in the burning zone. Certain of the reaction products are more readily adsorbed than the reactants, so that the catalyst serves to increase the effectiveness of the adsorbent 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 component, the metal catalyzing conversion of the organic vapors in the immediate vicinity of the adsorbent surfaces which then retain the reaction products. The adsorbent in turn holds the organic compounds for a longer period of contact with the catalyst. These enhancing effects would not be present if the adsorbent and catalytically active metal were physically separated.

When the burning zone advances into the previously preheated zone containing the adsorbent and the organic irritant adsorbate, the latter is desorbed 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 previously 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 adsorption, desorption, and reaction before final withdrawal from the inner end of the cigarette into the mouth of the smoker. 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 may 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 insuflicient 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 sufficient duration to be converted into less irritating forms.

Any non-toxic 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 groups. The preferred metals are copper, iron, silver, nickel, and chromium because they are especially active in promoting conversion of organic compounds.

Metals having vapor pressures above about 1 atmosphere at 1000 C. are not suitable because the burning zone reaches this temperature level and the volatile metal would be distilled off the adsorbent-catalyst support surface during smoking. Moreover, such metal vapors would eventually enter the mouth in the smoke and may well irritate the human body. Accordingly, zinc, cadmium, and mercury are not suitable.

Any material having substantial iadsorptive capacity for organic compounds may be used in this preparation. Suitable adsorbent-catalyst supports include silicas, aluminas, aluminosilicates, charcoal, cellulose, and silicon carbide. The adsorbent-catalyst support may be amorphous or crystalline, and naturally occurring or synthetically prepared. A particularly suitable class of materials are the crystalline zeolitic aluminosilicates known as molecular sieves. These compounds are characterized by interlocking silica and alumina tetrahedra with very small but uniformly sized pores or channels extending from the outer surface into a very large inner adsorption region. Typical molecular sieves that may be used are zeolite A described in U.S.P. 2,882,243 and zeolite X described in U.S.P. 2,882,244, both issued Apr. 14, 1959 in the name of R. M. Milton. The use of molecular sieves as the adsorbentcatalyst support of my tobacco smoking prepanation is described in more detail and specifically claimed in my copending application Ser. No. 364,801 filed simultaneously with this application, and now US. Patent No. 3,292,636, granted Dec. 20, 1966.

The catalytically active metal may be deposited on the adsorbent-catalyst support in any convenient manner, as will be understood by those skilled in the catalyst art. For example, the metal may be impregnated in the adsorbent using an aqueous solution of a suitable metal compound followed by drying and thermal or chemical decomposition of the metal compound. Suitable compounds of the preferred metals include copper chloride, iron nitrate, silver nitrate, nickel acetate and chromium chloride. As a specific illustration, if platinum is to be impregnated onto the adsorbent-catalyst support, water soluble compounds such as ammonium chloroplatinate or platinum chloride may be used as a source of the catalyst. The resulting composition is then dried and heated to a temperature sufficient to thoroughly remove the water leaving the metal of the compound in a uniform deposit, e.g. 300 C. Further heating may in some instances be required to convert the metal to its catalytically active state, such as heating in hydrogen or other reducing atmospheres.

A further method of synthesizing the catalytically active metal-adsorbent catalyst base composition is by contacting the latter in an inert atmosphere with a decomposable fluid compound of the desired metal whereby the compound is adsorbed on the base. The adsorbed decomposable compound is then reduced to the elemental metal which is retained in the adsonbed state. The metals which can be introduced in this manner incude copper, silver, platinum, aluminum, iron, nickel, and titanium. These reducible compounds of these elements which are particularly suitable include the halides, metal alkyls, and other metal-organic compounds such as cyclopentadienyl metal compounds and ethylenic complex compounds of the noble metals. This pr ocess is described more completely in U.S.P. 3,013,987 to Castor et al.

In the aforedescribed methods, there is no characteristically chemical interaction between the catalytically active metal and the adsorbent catalyst support. If the latter contains exchangeable cations, the metal may be introduced using an aqueous solution of a suitable cationic metal salt followed by chemical reduction of the metal cations. Alternatively, cation exchange may be employed with 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, These ion exchange methods ditfer in that the first relates to the use of metal salts such as the chlorides and nitrates of the iron gnoup metals wherein the metal itself is the cation. The second ion exchange method relates to the use of compounds of metals, such as the platinum and palladium group metals, in which the metal is contained in the cationic portion of the compound in coordination complex form.

The catalyst composition should be well dispersed through the tobacco so that it will be uniformly efective during the entire smoke. For this reason it is employed as a fine powder of a 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 has 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 the adsorbent is colloidal alumina in a powder compose-d of minute fiber-like crystals of the boehmite structure having a surface area of 256 square meters per gram. Two hundred grams of this colloidal alumina is added to 5 liters of distilled water While vigorously stirring at a temperature of 50 C. To the resulting aqueous suspension of alumina is added one liter of an aqueous solution containing 60 grams of Cu(C H O -H O With continued stirring. The mixture is then evaporated to dryness and the solids transferred to a crucible and heated to 400 C. in a stream of hydrogen gas. A product yield of grams is obtained containing 10 Weight percent copper. The alumina in this product retains its high surface area although it has been crystallographically altered to gamma alumina. The adsorbent alumina-copper catalyst rafter mill grinding and screening to a uniform flowable powder is added to smoking tobacco in the shredding process stage at a rate of about 20 grams for each 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.

What is claimed is:

A smoking preparation comprising tobacco and a catalyst composition consisting essentially of an adsorbent selected from the group consisting of silica, alumina, alu'minosili'cate, charcoal and silicon carbide, and a catalytically active elemental metal, the said metal being a member selected from the groups consisting of copper, iron, silver, nickel and chromium having vapor pressure below 1 atmosphere at 1000 C., said metal being impregnated into said adsorbent in quantity 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 in quantity such that said catalyst composition comprises from about 0.5% to about 25% by weight of said smoking preparation.

References Cited UNITED STATES PATENTS 1,519,470 12/1924 Wilson et al. 2,759,859 8/1956 Lahr 131-17 3,039,475 6/1962 Neukomm et al. 131140 3,229,697 1/1966 Maebashi 131-140 3,251,365 5/1966 Keith et al. 13110 FOREIGN PATENTS 28,470 2/ 1903 Great Britain.

834,854 5/1960 Great Britain.

841,074 7/ 1960 Great Britain.

SAMUEL KOREN, Primary Examiner.

MELVIN D. REIN, Examiner.

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