Process of extracting nicotine from tobacco
United States Patent 2128043

This invention relates to improvements in the x extraction of tobacco for the preparation of nicotine, nicotine extracts, tobacco wax or resins and other products, while leaving the tobacco itself in condition for commercial use. A particular object of the invention is to prepare a denicotinized...

Garner, James B.
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This invention relates to improvements in the x extraction of tobacco for the preparation of nicotine, nicotine extracts, tobacco wax or resins and other products, while leaving the tobacco itself in condition for commercial use.

A particular object of the invention is to prepare a denicotinized tobacco suitable for making mild smoking tobacco and similar products.

A further object of the invention is to prepare a solution of nicotine in a volatile hydrocarbon, which can be used as such under its own vapor pressure for insecticidal or germicidal purposes, or the like.

Another object of the invention is to prepare nicotine concentrates adapted for use in compounding with solvents and other ingredients for the manufacture of insecticides and germicides.

These and other objects of the invention which will be apparent as the description proceeds, are obtained by treating the tobacco with a material adapted to liberate nicotine from its salts. This material is preferably anhydrous liquid ammonia, though other alkali forming substances may be used. The tobacco is then extracted with a liquefied normally gaseous hydrocarbon, especially liquid normal butane.

Nicotine is now manufactured on a rather extensive scale from inferior grades of tobacco, tobacco stems and trimmings. The nicotine thus made finds a ready market as an insecticide and germicide. The tobacco residue, however, in the usual commercial manufacture of nicotine has little or no value.

It is known that nicotine, which is a liquid di-acid base, may be liberated from its salts, such as those of citric, malic, and oxalic acids, in which it occurs in tobacco, by treatment with anhydrous liquid ammonia. This reagent does not discolor the tobacco if properly applied. Ac10 cording to the present invention, the released nicotine is then extracted with a liquefied normally gaseous hydrocarbon. This may be liquid propane, liquid normal butane, isobutane, butylene, isobutylene or mixtures of these hydrocarbons, or any other liquefied normally gaseous hydrocarbons or mixtures thereof which will dissolve nicotine. Small amounts of the more volatile and less volatile hydrocarbons such as ethane and pentane, may be present without interfering with the process. Liquid normal butane, however, is the preferred solvent in most cases. It can also be obtained most economically in large quantities at a reasonable price.

In the following description and claims the term "butane" is intended to include any of the lormally gaseous hydrocarbons just mentioned »r their admixtures, where the context so pernits.

In the accompanying drawing, the single figure s a diagrammatic view of one form of extraction. apparatus. The process will be described in connection with the recovery of nicotine from tobacco leaves or tobacco residues.

In carrying out the invention, tobacco containing approximately 10-25% by weight of water, as commonly encountered in commercial practice, is treated with anhydrous liquid ammonia to liberate all the nicotine from its salts, and then extracted with as many consecutive amounts of liquid butane as is indicated to reduce the nicotine content to the desired amount. It is generally desirable to place the tobacco, loosely but with slight pressure into a bag I, insert this bag into an extractor 2, and immerse the bag in the liquid butane at substantially room temperature (40-90° F., corresponding to 3-30 pounds pressure per square inch). The butane is run into the extractor through a line 3 in which there is a valve 3a. Liquid anhydrous ammonia is then introduced gradually so that no appreciable rise in pressure ensues, through a line 4 in which there is a valve 4a. The ammonia reacts at it enters the mixture, usually until four to eight times the amount calculated to correspond to the nicotine present has been added. From this point on there is a continuous rise in pressure which does not recede with elapsing time, and the inflow of ammonia is stopped.

The mixture is then left to react by circulation of the liquid for several hours until a sufficient concentration of the extractives Is obtained in the liquid. The circulation takes place by means of a pump 5, a bottom draw-off line 6 having a valve 1, and a top supply line 8 having a valve 9, both the valves being open. A storage tank 10 is connected with the pump by means of a line I having a valve 12.

After a test of the liquid, run off through the valved sample line 13, shows a substantially completed reaction (the desired point varying with several operating conditions and the purposes in mind), the liquid is drawn off as completely as possible and replaced by successive fresh amounts ofbutane. Each batch of butane is circulated for a time and the extraction is continued until the nicotine content of the leaves has been reduced to the desired amount. The various batches of butane are accumulated in the tank 10, from which they are run by line I , pump 5, and line 14 (valves I and 9 being closed and valves 12 and. 15 open) into a still 16. A vapor line IT, having a valve 18 leads from the top of extractor 2, connecting with the vapor line from still 16. If desired, the separate charges of butane may be distilled by drawing them off individually through the sample line 13 to a suitable still. The combined or successive amounts of butane are distilled to recover the components, namely, butane, ammonia, and extractives. The extraction may be carried out continuously without affecting the purpose of the invention.

The extractives are drawn off, usually as a liquid containing some residual butane, and the nicotine is separated subsequently from the waxes, etc. if a pure grade of nicotine is desired. The vapor line from the still is designated 19 and in it there is a valve 20. The mixture of butane and ammonia withdrawn passes first to a compressor 21 and thence through line 22 to a condenser 23. A valved vent line 24 is provided on line IT and a valved vent line 25 on line 23. From the condenser the butane and ammonia pass through line 26 into a receiver 27, from which they are returned to tank 10 through line 28. The nicotine extractives are removed from the still 6I in which they have been freed from butane and ammonia, into an accumulator 16a and thence to a place of disposal through line 16b. The still is shown as heated by means of a hot water circulating systern including a heater 2S and circulating pipes 30 and 31.

In order to clear the extractor of residual solvents, dry air, nitrogen, carbon dioxid, or other inert gas may be passed under pressure through a 3S line 32, sample line iS and draw-off line 6 into extractor 2. This is a convenient way of accomplishing the result but other methods, such as vacuum evaporation, may be adopted.

In order to retain the leaves in their natural condition to the maximum extent, it is desirable to control rather carefully the content of moisture during the extraction and solvent removal periods.

In the extracting period the water content of the tobacco should be between 10 and 25% by weight. If the tobacco leaves are too dry they are too brittle for handling and the extraction proceeds too slowly. A higher moisture content than 25% has been found unnecessary and it tends to discolor the leaves. In the period for removal of residual ammonia and solvent, if a gas is used, its moisture content should be approximately between 55 and 65% of saturation at the prevailing tempera-. ture.

The preferred way of conducting the extraction is to pile the leaves in a filter cloth bag in a pressure vessel. The treating liquids are then circulated continually through the mass of leaves.

Any small fragments of tobacco are thus retained inside of the bag and hence do not in any way collect in or stop flow of liquids through piping and pump. The invention, however, is not limited to any special form of extraction equipment or arrangement therein.

The nicotine content of tobacco may vary from about 2.5% to 2.8% by weight of the dry leaves, under usual conditions. The ammonia used in this process should range in concentration from about 4-8 times the calculated amount necessary to set the nicotine free from its combination with organic or other acids. Less than four equivalents is inadequate to effect practically complete removal of nicotine, more than eight equivalents Is wasteful and uneconomical. As high as 17 equivalents have been used but with no better results than when eight equivalents are used, Ammonium hydroxid solution will also liberate the nicotine but tends to impair the color of the leaves; hence, when denicotinized tobacco is to be manufactured, anhydrous ammonia must be used. When the production of nicotine alone is the end in view, butane plus aqueous ammonia or other alkali adapted to liberate nicotine may be used and in this case any suitable source of nicotine may be used. The butane should be present in convenient excess so as to insure the rapid extraction of substantially all the nicotine. The concentration in the residual tobacco can be reduced in this way to about 0.10% or less.

It will be understood that some of the tobacco wax and resins are dissolved along with the nicotine and are to be separated from it at a later stage, as by solution and precipitation, if the pure product is desired.

The butane solution of nicotine and tobacco waxes and resins is treated for the separation of the extracted materials, preferably as described, by distilling off the butane at relatively low temperature, not necessarily higher than 100° F., although vacuum evaporation, with or without fractional precipitation of the solutes, may be used. The distillation may be stopped at a point where the solution contains a suitable insecticidal or germicidal concentration of nicotine and the product used as such. It can be conveniently applied from devices of the kind which eject a material carried by a liquefied normally gaseous substance. The nicotine is deposited in this way on the plant, or other object to be sprayed, in a very finely divided form and entirely undiluted, since the normally gaseous substance evaporates at once.

If all the butane is evaporated off, there is left a mass of nicotine and tobacco wax which together may amount to as much as 6-8% by weight of the tobacco used. A lesser quantity of wax may be obtained if desired. Tobacco wax or resin is dark brown in color, burns with the production of acrid fumes, and has a strong odor resembling that of an "old" pipe. The wax has been found to be composed of a weak acid (about 0.94% by weight), a stronger acid (about 1.27%), and a neutral substance (about 97.79%).

The extract may be treated in various ways for the recovery of the nicotine and wax, for example, by dissolving the mass in ether or other suitable solvent and adding an excess of dilute hydrochloric acid to remove the nicotine as the hydrochloride. Then a 2% solution of sodium bicarbonate is added to remove the stronger wax acid. Next 2% sodium hydroxid solution is applied to separate the weaker wax acid. The remaining solution is evaporated to recover the neutral portion of the extract.

These products may be used for various purposes. The nicotine may be used as such or together with the tobacco waxes as insecticides and germicides. The waxes or portions thereof may be returned to the residual tobacco leaves and also to untreated tobacco leaves to impart thereto desirable flavors. The value of inferior grades of tobacco may thus be enhanced.

As noted, the tobacco leaves are not impaired and can be used with special advantage for making mild smoking tobacco, cigarettes, or other tobacco products. The tobacco retains a desirable flavor but since the nicotine has been almost completely removed, the tobacco has little or no harmful physiological effect.

It is also evident: (1) That the same process or processes may be carried out as specified with any solvent, other than hydrocarbon solvents. providing it has an appreciable solvent action on nicotine and does not react with the ammonia or other alkali used; (2) that other alkalies, such as the aliphatic gaseous amines, may be used in place of ammonia; (3) that aqueous solutions of alkalies, such as sodium, potassium, calcium, strontium, barium, magnesium hydroxids, their carbonates, or the ethanolamines, may be used to liberate nicotine when their effect upon the tobacco is no disadvantage.

Various other changes and alternative procedures may be adopted within the scope of the appended claims in which it is my intention to claim all novelty inherent in the invention as broadly as the prior art permits.

I claim: 1. Process of extracting nicotine, comprising freeing the nicotinefrom its salts by means of an acid neutralizing reagent, and dissolving it in a liquefied, normally gaseous hydrocarbon.

2. Process of extracting nicotine from tobacco, comprising freeing the nicotine from its salts by means of an acid neutralizing reagent, and dissolving the liberated nicotine in liquid butane.

3. Process according to claim 2 in which liquid normal butane is used.

4. Process according to claim 2 in which an alkali is used to liberate the nicotine.

5. Process according to claim 2 in which liquid anhydrous ammonia is used to liberate the nicotine from its salts.

6. Ptocess of extracting nicotine from tobacco, comprising treating the tobacco with liquid anhydrous ammonia to liberate the nicotine from its salts and with liquid butane to extract the liberated nicotine.

7. Process of extracting nicotine from tobacco, comprising freeing the nicotine from its salts by means of reaction with an aliphatic gaseous amine, and extracting the liberated nicotine with a liquefied, normally gaseous hydrocarbon.

8. Process of extracting nicotine from tobacco by liberating the nicotine from its salts by neutralization with an alkaline reacting substance selected from the class of aqueous solutions of alkalies of sodium, potassium, calcium, strontium, barium and magnesium and the ethanolamines, and extracting the liberated nicotine with a liquefled, normally gaseous hydrocarbon.

9. Method of preparing nicotine and tobacco waxes comprising extracting these materials from tobacco by liberating the nicotine from its salts by means of an acid neutralizing reagent and dissolving in liquid butane, removing the liquid butane containing the nicotine and tobacco waxes from tobacco, separating the liquid butane from the nicotine and tobacco waxes, treating the residue with a suitable solvent to dissolve the nicotine and tobacco waxes, and then separating the nicotine from the resulting solution.

10. Method according to claim 9, comprising selectively separating the acidic components of the tobacco wax from the solution in a suitable solvent after removal of the nicotine by treatment with alkalies of progressively increasing strength.