US3139435A - Process for selective extraction of alkaloid - Google Patents

Description

June 30, 1964 J. STALEY ETAL 3 Sheets-Sheet 1 Filed March 7, 1963 June 30, 1964 J. STALEY ETAL 3,139,435

PROCESS FOR SELECTIVE EXTRACTION E ALKALOID Filed March 7, 1963 3 Sheets-Sheet 2 o. I 5 E 0.1 2 u, E S 2 005 Z 0 IO 5o 60 Mg. H O per Ml. MEK.

N I m 0 IO 20 30 40 5o Mg. H O/ MLMEK.

June 30, 1964 STALEY ETAL 3,139,435

PROCESS FOR SELECTIVE EXTRACTION OF ALKALOID Filed March 7, 1963 3 Sheets-Sheet 3 DECANTER AN HYDROUS SOLVENT WATITIR SOLVENT STORAGE BRINE STORAGE NOLLOVHLXB HCI REFRIGERATION UNIT United States atent 3,139,435 PRUCESS FQR SELECTIVE EXTRAQTKGN F ALKALGID John Staley, Richmond, and Allan liellerby Clarke, Midlothian, Va, assignors to Philip Morris incorporated,

New York, N.Y., a corporation of Virginia Filed Mar. 7, 1963, Ser. No. 263,637 8 Claims. (Cl. ass-2st This invention relates to extraction of nicotine and other alkaloid fractions from tobacco. More particularly it relates to extraction of such fractions without materially affecting the non-alkaloid constituents of the tobacco and accordingly provides tobacco which is substantially unaffected in composition, save for the removal of nicotine and other alkaloids therefrom. The invention also provides substantially pure nicotine and other alkaloid fractions essentially free from contamination by fats, waxes, sugars and other related tobacco constituents.

Nicotine and other alkaloids occur in tobacco in both the free and combined states and are readily extractable in common organic solvents, as are a number of other tobacco constituents. It is to be understood that references in this specification to nicotine and alkaloids include nicotine and alkaloids in their salt form.

Solvent extraction of tobacco to remove nicotine has long been practiced. Such methods have been characterized, however, by a number of attendant disadvantages, principally that solvent-soluble tobacco constituents other than nicotine are removed thereby, yielding nicotine in admixture with substantial amounts of undesirable impurities and providing tobacco of markedly inferior character as a result of the removal of desirable tobacco con stituents.

In United States Patent 3,046,997 to John D. Hind a process for selective extraction of alkaloid fractions from tobacco is set forth, which process overcomes many of the disadvantages inherent in prior processing for removal of nicotine from tobacco. Briefly, that process entails extraction of tobacco with organic solvent which is saturated with non-alkaloid tobacco constituents, contacting the resultant alkaloid-laden solvent with aqueous brine having an acid pH to transfer the alkaloid selectively from the solvent to the brine, and recycling the alkaloidrelieved solvent to the same or other tobacco. Alkaloid is recovered from the brine by rendering the brine alkaline, extracting with solvent, and distilling oil the solvent from the extract. The present invention constitutes an improvement over the process of the patent.

A particular advantage of the present invention in one aspect is the provision of a markedly simpler and less expensive means for removing nicotine from the brine following contact with the alkaloid-laden solvent. Nicotine is removed from the brine to permit recycling of the brine and its repeated use to remove nicotine from alkaloidladen solvent. The nicotine so recovered is, in addition, a valuable item of commerce.

Our method of nicotine removal is based on the discovery that a phase relationship develops between nicotime and salt brine as a function of temperature. We have further found that the capacity of the brine for nicotine increases as temperature of the brine-solvent system is lowered. We prefer a temperature substantially below room temperature, preferably below about 10 C., for transfer of nicotine from solvent to brine. The lower operative limit of temperature is that at which freezing or separation of contained solids occurs. The economic cost of refrigeration may constitute a limiting factor on the temperature which is employed; a suitable low temperature may readily be selected by one skilled in the art in accordance with the teachings herein contained.

Efiiciency of alkaloid transfer from the solvent to the brine also improves markedly as the pH is lowered. In FIG. 1 there is shown the equilibrium relationship between nicotine concentration in a methyl ethyl ketone (MEK) saturated aqueous NaCl brine system at 25 C., and it will be observed that reduction of pH markedly increases efficiency of transfer of alkaloid from solvent to brine. At pH 7, roughly equal concentrations of alkaloid are found in the solvent and the brine at equilibrium; acidification to pH increases substantially the proportion of alkaloid in the brine. Below pH 5, and particularly below pH 4, virtually all the alkaloid is transferred to the brine. Since the solvent, following contact with brine, is to be recycled and should desirably have a nearly neutral pH during extraction of tobacco, however, it is economically disadvantageous to bring the pH of the solvent-brine system to very low limits since the pH of the solvent must again be raised prior to extracting further tobacco. We accordingly prefer a pH below about 6.5, a pH below 4 being more preferred.

In accordance with the present invention in one embodiment, the pH of the alkaloid-laden solvent, which is desirably nearly neutral following extraction of tobacco, is reduced and the solvent is chilled to a tern erature substantially below room temperature before contacting the solvent with the brine. Since we prefer to employ a counter-current extraction column for contacting the alkaloid-laden solvent with the brine, and since the volume of solvent passing through the column is as a matter of operating efficiency preferably substantially greater than the volume of brine passing through the column, the alkaloid-laden brine emerges from the extraction column at a low temperature and an acid pH after contact with the solvent. An effluent brine pH of about 4.5 and a temperature of about 10 C. are illustrative of the operating conditions in one embodiment of this invention. Alternatively, refrigeration means may be provided in the vessel or column in which the solvent and brine are contacted. The important feature is the lower temperature of the brine-solvent system; the manner of obtaining such lower temperature is largely a matter of choice.

Under these transfer conditions of low temperature and acidic pH, efficient transfer of alkaloid from solvent to brine is obtained, and the alkaloid, together with any trace amounts of tobacco solubles, exists as a single phase with the brine. Upon warming the resultant alkaloidladen brine, the nicotine separates into a distinct phase or layer floating atop the brine and may readily be separated therefrom by simple decantation or equivalent physical means.

The invention in this aspect accordingly provides an improvement in a continuous process of tobacco extraction and alkaloid recovery and includes the steps of contacting the alkaloid-laden solvent with brine at a temperature substantially below that at which alkaloid is ultimately recovered from the brine and at a pH below about 6.5. The resultant alkaloid-enriched brine is thereafter warmed to a temperature at which an alkaloid phase separates from the brine and the alkaloid phase is physically removed from the brine, as by decantation.

The alkaloid-relieved brine, i.e., warmed brine from which the alkaloid phase has been separated contains only a minor amount of alkaloid; although saturated, the alkaloid concentration is very low, e.g., less than 1 mg./ml. of brine. When its temperature is lowered, as by contact with cooled alkaloid-laden solvent, however, the capacity of the alkaloid-relieved brine for alkaloid increases. At this lower temperature (below that at which alkaloid is ultimately recovered from the brine) the increased capacity of brine for alkaloid permits transfer of alkaloid from solvent to brine. The acidic pH of the solvent (which is preferably lower than the pH of the entering brine) causes a decrease in brine pH, and the acidic environment enhances transfer of alkaloid from solvent to brine. An acidic environment may, of course, be provided by acidifying the brine rather than the solvent, or acidification may be accomplished by adding acid or acidic material directly to the vessel or column in which the solvent and brine are contacted. The particular means of providing an acidic environment are not of especial importance.

We prefer to raise the pH of the alkaloid-enriched brine to a nearly neutral level, suitably 5.5-8, prior to decanting the alkaloid, but the step of neutralizing the brine is optional and may in addition take place either before or after the cold alkaloid-enriched brine is warmed. Somewhat greater amounts of alkaloid are recovered from the brine at a higher pH.

It will readily be appreciated that our improved process, which in this aspect permits simple physical separation of nicotine from brine without the need for more cumbersome processes such as solvent extraction and the like, offers a distinct advantage over prior processes.

We have also found that the efficiency of the process disclosed in the Hind patent is improved by maintaining the pH of the extracting solvent nearly neutral and preferable slightly on the acid side. A suitable range of pH is about 5.5 to about 8, with a preferred range being from about 6.0 to 7.0. Extraction efiiciency is also improved by use of warm or hot solvent, but care should be taken to avoid extraction temperatures which can cause damage to the tobacco leaf. We prefer an extraction temperature of about 85 C. or less. For solvents boiling below this temperature we prefer an extraction temperature slightly below the boiling point of the solvent extraction medium (e.g., about 75 C. for MEK, which has a boiling point of about 79.6 C.). Use of a pressurized system of course permits employment of a temperature above the solvent boiling point.

The data in the following table demonstrate that at a constant temperature, efiiciency is improved by a less acid pH and that at constant pH, efiiciency is improved by increased temperature (data for MEK and bright leaf tobacco).

Minimum gallemperlons solvent to atnre, pH extract 90% of C. the nicotine from 18 lbs. tobacco We have further found that efficiency of alkaloid extraction is related to the moisture content of the extracting solvent. Surprisingly, virtually no alkaloid is removed from tobacco upon extraction of dry tobacco with anhydrous solvent. The amount of alkaloid removed by solvent extraction increases with increasing the moisture content up to a certain point and then, again unexpectedly, decreases.

FIG. 2 is a graph setting forth the relationship between the moisture content of the system and the amount of nicotine extracted. The graph is based upon equilibrium data obtained by extracting 25 g. bright leaf tobacco found by analysis to contain 1.48% of alkaloid with 1250 ml. MEK. As shown in FIG. 2, efiiciency of nicotine extraction increases with increasing moisture content in the system up to a point, and then drops off rapidly to a significantly lower level.

The relationship between moisture content of the extracting solvent and amount of nicotine extracted, such as that shown in FIG. 2, exists for all common organic solvents. While FIG. 2 is based upon MEK extraction, other solvents may be employed, as set forth in the Hind patent, and the optimum moisture content for a given .l solvent under particular extraction conditions can readily be ascertained by one skilled in the art.

The moisture content of the extracting solvent is influenced by the moisture content of the tobacco being extracted, and also by the concentration and composition of the brine. Adjustment of solvent moisture level is most conveniently effected by addition of water or anhydrous solvent to the extraction solvent. While, as shown in FIG. 2, optimum moisture content may be expressed in terms of mg. H O per m1. of solvent, the numerical value of this measure for various solvents can be quite different.

We have found, however, that the moisture content of the tobacco, with which the solvent is in equilibrium, is about the same for optimum moisture contents of a wide variety of solvents. Thus we prefer a solvent moisture content corresponding to at least about 10% moisture in the tobacco being extracted. Levels below about 10% are preferably to be avoided due to low extraction efiiciency, while levels above about 25% are preferably to be avoided because of less than optimum efiiciency and because bleeding (i.e., loss of water-soluble tobacco con stituents) or other injury to the tobacco becomes objectionable at moisture levels significantly above 25%.

In FIG. 3 there is shown the equilibrium relationship between moisture in tobacco and moisture in extracting solvent at 23 C. (data obtained with 1250 ml. MEK and 25 g. bright leaf tobacco). By comparison of FIG. 2 and FIG. 3 it will be seen that a tobacco moisture content between about 10%-25% provides a solvent moisture content in the optimum range for extraction of nicotine.

An illustrative embodiment of the invention is shown in FIG. 4, which is a schematic flow sheet showing an arrangement of apparatus suitable for practicing the invention. It is to be understood that various changes may be made in the system illustrated and that the flow sheet is not to be taken in a limiting sense.

There are provided a plurality of suitable receptacles 1, which may be hogsheads, to contain tobacco from which alkaloid is to be extracted. Preferably, these are equipped with warming means, such as steam heated coils within the containers. In FIG. 4 there is illustratively shown steam admitting means 2 and condensate returning means 3, and there may also be provided means such as a temperature sensing device 4 located in an efiluent solvent line in operative connection with an automatic valve 5 located in the steam admitting line to afford regulation of temperature by controlling the amount of steam admitted responsively to the temperature of effiuent solvent. A tobacco density as great as about 15-20 lbs./ cu. ft. is suitable and advantageous, reducing size and cost of the equipment and decreasing solvent hold-up, as well as increasing extraction efficiency and facilitating heat transfer. System materials which adversely affect tobacco, e.g., copper, should be avoided; glass, stainless steel, porcelain and other preferably inert materials are desirably employed.

Alkaloid-relieved solvent, which is saturated with nonalkaloid solvent-soluble tobacco fractions from previous extraction of the same or other tobacco is drawn from solvent storage tank 6 and pumped to receptacles 1. Alternatively, fresh or make-up solvent may be employed, i.e., solvent which has not previously been employed for extraction, in which event it will become saturated with solvent-soluble tobacco fractions as it passes through the successive receptacles 1 of tobacco. Pump means such as that indicated illustratively at 28 between receptacles D and E may be included in the system as desired. Advantageously, the solvent may pass through the tobacco containers serially, but provision may be made for feeding solvent from tank 6 directly to more than one of the tobacco containers, and provision may also be made for cycling solvent from one or more tobacco containers directly to the subsequent process operations without passing such solvent through additional batches of tobacco.

The latter arrangement is particularly useful when employing a solvent which has not previously been used for extraction of tobacco and which accordingly is not saturated with non-alkaloid tobacco fractions.

It is also desirable to contact the solvent with the several batches of tobacco in countercurrent flow. Preferably, in a continuous process, a fresh hogshead of tobacco will replace the receptacle designated A in FIG. 4, displacing the receptacle of longest residence in the system (F in FIG. 4), which may then be processed for recovery of residual solvent (not shown).

The solvent drawn from the storage tank may have a nearly neutral pH, suitably about 6.5. As many varieties of tobacco contain organic acids and other acidic constituents, it may be desirable to provide means for adjusting the pH of the extracting solvent, should it become more acidic during extraction, to maintain a generally constant level of pH. To this end, a tank 7 of alkali, such as KOH or other acid-neutralizing material, may be provided, communicating through appropriate valve means with a line of solvent which is to be used for further extraction. Preferably, such arrangement may be in combination with pH sensing means 8 located in a solvent efliuent line downstream from and in operative connection with automatic valve 9 to admit controlled amounts of alkali to the stream of solvent for maintaining pH at a desired level or within a desired range.

The moisture content of the extracting solvent may, as heretofore described, be ascertained by measurement of the moisture content of the tobacco being extracted. Adjustment of solvent moisture may be accomplished by addition of controlled amounts of water from tank 26 or of anhydrous solvent from tank 25, as may be appropriate; less conveniently, adjustment may be etfectuated by altering the concentration or composition of the brine.

Alkaloid-laden solvent passes from the extraction zone through a heat exchanger 10, which it leaves at a temperature lower than that at which it entered. In one embodiment of the invention the warm solvent may enter the heat exchanger at about 70 C. and leave at about 45 C. The pH of the solvent stream is then decreased by addition of acid such as HCl. Preferably, pH sensing means 13 downstream from the point of addition may be employed to control the admission of acid through valve 12, with which such sensing means is in operative connection. A pH below about 6.5 is preferred, and a pH of about 4 or below is more preferred.

The solvent is then passed through a chilling unit 14, cooled by refrigeration unit 15. Acidification may take place after chilling, but in such event allowance should be made for increase in temperature upon addition of acid. In any event care should be taken to avoid separation of any part of the solvent solution by reason of too low a temperature. An efiiuent temperature of 5-10 C. is suitable.

The chilled and acidified alkaloid-laden solvent then passes through a liquid-liquid extraction column 16 against brine, preferably in countercurrent flow. Suitable brines are set forth in the Hind patent. In an efficient system, a very much greater volume of solvent than of brine will pass through the column, and the efiluent brine will therefore have a temperature and pH only slightly higher than has the entering solvent. Efl luent solvent from the extraction column is cycled to the heat exchanger, whence it may have a temperature of about 35 C. and a pH of about 4.0. Before reaching solvent storage tank 6, the pH of the solvent may be adjusted to the level desired for extraction, as by addition of alkali from tank 7. pH sensing means 23 and automatic valve 24 may be em- 6 ployed for adjustment in a manner such as that previously described.

Effiuent alkaloid-laden brine from column 16 comprising water, salt, alkaloid and perhaps a minor amount of non-alkaloid tobacco solubles, all as a single phase, is then passed through heat exchanger 17 and warmed at least to a temperature at which the nicotine fraction of the brine separates into a distinct and separate phase. Generally, a greater amount of nicotine will separate as the temperature is increased, but no particular advantage is obtained by increasing the temperature much above the ambient, i.e., about 25 C. The pH of the warmed brine is then increased to a nearly neutral level, suitably about 6.5, a tank 19 of alkali and pH sensing means 18 in operative connection with automatic valve 20 being desirable. Adjustment of pH may precede the warming step, if desired. The nicotine floating atop the brine is then tapped off in decanter 21 and collected in pool 22. Alkaloid-relieved brine is recycled to column 16.

It will be evident that changes may be made in the foregoing description without departing from the invention. In particular, optional features and controls may be omitted, and other features may be added.

We claim:

1. In a continuous process for selective removal and recovery of alkaloid from tobacco which includes the steps of extraction of tobacco with organic solvent, contacting the resultant alkaloid-laden solvent extract with brine to remove alkaloid selectively from said extract, recycling the alkaloid-relieved solvent to tobacco, recovering alkaloid from the brine and recycling the alkaloidrelieved brine for contacting with further alkaloid-laden solvent, the improvement which comprises contacting the alkaloid-laden solvent with the brine at a temperature substantially below that at which alkaloid ultimately is recovered from the brine and at a pH below about 6.5, thereafter warming the resultant alkaloid-enriched brine to a temperature at which an alkaloid phase separates from the brine, and effecting physical removal of the alkaloid phase from the brine.

2. A process according to claim 1 wherein the temperature at which the solvent and brine are contacted is below about 10 C.

3. A process according to claim 2 wherein the pH at which the solvent and brine are contacted is below about 4.0.

4. A process according to claim 1 wherein the pH of the alkaloid-enriched brine is increased to between about 5.5 and about 8 prior to recovery of alkaloid therefrom.

5. A process according to claim 1 wherein the tobacco is extracted with organic solvent at a pH between about 5.5 and about 8.

6. A process according to claim 1 wherein the solvent employed for extraction of tobacco contains moisture in an amount effective to enhance the extraction of alkaloid from said tobacco.

7. A process according to claim 6 wherein the moisture content of the tobacco is at least about 10%.

8. A process according to claim 7 wherein the moisture content of the tobacco is between about 10% and about 25%.

References Cited in the file of this patent UNITED STATES PATENTS 802,487 Wimmer Oct. 24, 1905 1,196,184 Villiers-Stuart Aug. 29, 1916 1,577,768 Smith Mar. 23, 1926 2,525,785 Feinstein et al. Oct. 17, 1950 3,046,997 Hind July 31, 1962

Claims (1)

1. IN A CONTINUOUS PROCESS FOR SELECTIVE REMOVAL AND RECOVERY OF ALKALOID FROM TOBACCO WHICH INCLUDES THE STEPS OF EXTRACTION OF TOBACCO WITH ORGANIC SOLVENT, CONTACTING THE RESULTANT ALKALOID-LADEN SOLVENT EXTRACT WITH BRINE TO REMOVE ALKALOID SELECTIVELY FROM SAID EXTRACT, RECYCLING THE ALKALOID-RELIEVED SOLVENT TO TOBACCO, RECOVERING ALKALOID FROM THE BRINE AND RECYCLING THE ALKALOIDRELIEVED BRINE FOR CONTACTING WITH FURTHER ALKALOID-LADEN SOLVENT, THE IMPROVEMENT WHICH COMPRISES CONTACTING THE ALKALOID-LADEN SOLVENT WITH THE BRINE AT A TEMPERATURE SUBSTANTIALLY BELOW THAT AT WHICH ALKALOID ULTIMATELY IS RECOVERED FROM THE BRINE AND AT A PH BELOW ABOUT 6.5, THEREAFTER WARMING THE RESULTANT ALKALOID-ENRICHED BRINE TO A TEMPERATURE AT WHICH AN ALKALOID PHASE SEPARATES FROM THE BRINE, AND EFFECTING PHYSICAL REMOVAL OF THE ALKALOID PHASE FROM THE BRINE.

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