CA1161037A - Carbon-caffeine separation - Google Patents
Carbon-caffeine separationInfo
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- CA1161037A CA1161037A CA000378286A CA378286A CA1161037A CA 1161037 A CA1161037 A CA 1161037A CA 000378286 A CA000378286 A CA 000378286A CA 378286 A CA378286 A CA 378286A CA 1161037 A CA1161037 A CA 1161037A
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- caffeine
- solvent
- carbon
- process according
- acetic acid
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Abstract
CARBON-CAFFEINE SEPARATION ABSTRACT The object of the invention is to provide an improved process for recovering caffeine adsorbed on activated carbon. Caffeine removed from the commercial decaffeination of vegetable materials and extracts can be effectively removed from the extraction solvent, or can be purified, by the use of activated carbon. Unfortunately, the caffeine is tenaciously held by the carbon and none of the techniques currently available for removing the caffeine is wholly satisfactory. The recovery of caffeine from activated carbon is accomplished according to the present invention by employing a liquid food-grade caffeine solvent which comprises an organic acid or alcohol, and which is capable of competing for the active sites on the carbon occupied by the caffeine to displace at least a portion of the caffeine which is then dissolved in the solvent. After the desired period of contact, the caffeine is separated from the solvent. The solvent will preferably comprise glacial acetic acid or an acetic acid azeotrope, and contact will preferably be at a temperature above 100 C.
Description
~ DESCRIPTION
C~RBON-CAFFEINE SEP~RATION
Technical Field The present invention relates to decaffeination, 05 and particularly to an improved process ~or recovering caffeine from an activated carbon adsorbent.
The decaffeination of vegetable materials and vegetable material extracts is of major commercial importance. Also significant is the recovery and sale of the caffeine removed from ~egetable sources such as coffee and tea. It is known that activated carbon is a good adsorbent in caffeine recovery and purification procedures, but the carbon tends to hold the caffeine so tenaciously that, often, significank quantities of caffeine are lost or reduced in commercial value. None of the techniques currently available to the art for separa~ing the caffeine from the carbon has been wholly satisfactory ; in terms of both degree and quality of caffeine recovery.
~.~
C~RBON-CAFFEINE SEP~RATION
Technical Field The present invention relates to decaffeination, 05 and particularly to an improved process ~or recovering caffeine from an activated carbon adsorbent.
The decaffeination of vegetable materials and vegetable material extracts is of major commercial importance. Also significant is the recovery and sale of the caffeine removed from ~egetable sources such as coffee and tea. It is known that activated carbon is a good adsorbent in caffeine recovery and purification procedures, but the carbon tends to hold the caffeine so tenaciously that, often, significank quantities of caffeine are lost or reduced in commercial value. None of the techniques currently available to the art for separa~ing the caffeine from the carbon has been wholly satisfactory ; in terms of both degree and quality of caffeine recovery.
~.~
- 2 - ~ ~61~7 Back~ound Art The recovery of caffeine from decaffeinating solvents has been an active area of concern for many years. For example, in U.S. 2,508,545, Shuman Q5 discloses that activated carbon and other adsorbents had been used to remove impurities from solutions of caffeine extracted from coffee. Shuman indicates that until the time of his invention caffeine losses due to adsorption onto the carbon ran as high as 10 to 14%. To rectify this, Shuman disclosed alternate use of organic and agueous extractions with the final aqueous extraction being done at a pH of at least 7. While activated carbon is employed to remove impurities from the aqueous extract, the ~5 amounts employed are apparently small and no mention of separating caffeine from the carbon is made.
Similarly, in U.S. 2,472,881, Bender employs activated carbon to remove impurities from an agueous caffeine solution but does not discuss the steps taken to recover the caffeine adsor~ed on the carbon.
Recently, an improved decaf~eination method was disclosed in U.S. 3,879,569 wherein ~uantitative extraction of caffeine -from raw coffee beans is achieved with moist supercritical carbon dioxide.
This process produces an extract from which essentially all of the caffeine can be removed by activated carbon. Unfortunately, the prior art techniques do not economically provide good levels of recovery of caffeine or they reguire the use of chlorinated hydrocarbon solvents which are o~herwise avoided by the use o~ carbon dio~ide as an extracta~t.
Disclosu_e of Invention The present invention now enables improved recovery of caffein~ from an activated carbon adsorbent, by an improved process which comprises: contacting activated ~.~.6~
carbon having caffeine adsorbed thereon with a li~uid, food-grade caffeine solvent which comprises an organic acid or an alcohol, and which is capable of displacing at least a portion of the caffeine 05 from active sites on the carbon; maintaining the contact for a period of time and at a temperature effective for th~ solvent to displace at least a portion of the caffeine from the carbon and dissolve the displaced caffeine; and separating the caffeine 10 from the solvent.
The present invention takes ad~antage of the discovery that ~ome liguid, food-grade caffeine solvents which have the ability to effect desorption both by -~heir strong solvent ability and their ability to displace the adsorbed material from active sites on the adsorbent, are extremely effective in separating caffeine from carbon adsorbents. The strong solvent effect causes a partitioning between the activated carbon and the solvent. The site displacement effect is achieved by the solvent molecules themselves competing for the active adsorbent sites. Once a caffeine molecule is displaced, it is then taken into solution by ~h~ solvent which is a strong solvent for caffeine.
The solvents employed according to the present invention are employed in their liquid state and preferably at temperatures in excess of 100 C to obtain the greatest rates of recovery. Temperature has a strong effect on desorption and should therefore be as high as possible, consistent with maintaining the solvent as a liquid. Where temperatures higher than the boiling point of the solvent are desired, it will be necessary to employ pressures in excess of atmospheric. It is preferred, however, to maintain ~ 3 the pressure at no gxeater than ahout atmospheric.
Therefore, the higher boiling solvents are pre~erred.
Because the caffeine is valuable for food and pharmaceutical use, the soIvents must be food-grade.
05 By this, it is meant that the materials are on the Generally Recognized As Safe (GRAS) list maintained by the Food and Drug Administration to this type of use. This is important because where any measurable quantity of a non GRAS material works its way into either the product caffeine or the product tea or coffee, the value of the product will be seriously diminished, if not wholly lost.
The organic acids and alcohols which are food-grade, liquid at the proposed processing temperature and preferably at room temperature, excellent solvents ~or caffeine, and capable of displacing caffeine from the ac~ive sites on the carbon, are effective ; solvents for use accordiny to the invention. Preferably, the solvent will comprise a member selected from the group consisting of acetic acid, propionic acid, butyric acid, ethanol, isopropanol, benzyl alcohol, butanol, amyl alcohol, and azeotropes comprising at least one of these. Among the co-solvents which can be employed in forming the azeotropes are water, n-hexane, n-heptane, n-octane, toluene, benzyl acetate, me~hylene chloride, ethyl acetate and other food-~rade solve~ts. The pre~erred solvents are those which have boiling points over 100 C, and of these glacial acetic acid and acetic acid azeotropes are the most preferred. The azeotropes of acetic acid with butyl alcohol, iso-amyl alcohol, toluene, and n-octane all have boiling points above 100 C as can be see~l from the following table:
, - 5 - ~6~L~3~
Acetic _cld Azeotropes Boilin~ Point ( C~
Acetic Acid 43% wt.
Butyl Alcohol 57% wt. 120.3 Acetic Acid 16% wt.
05 Iso-Amyl Alcohol 84% wt. 133.0 Acetlc Acid 65% wt.
Toluene 35% wt. 105.4 Acetic Acid 53% wt.
n-Octane 47% ~t. 105.0 10 Other azeotropes suitable for use in the process of the invention, but re~iring the use of superatmospheric pressures when temperatures of 100 C or more are employed, are:
Acetic Acld Azeotropes Boilinq Point ~ C~
15 Acetic Acid 6% wt.
n-Hexane 94% wt. 68 Acetic Acid 33% wt.
n-~eptane 67% wt. 95 Other Azeotropes . , 20 Ethanol g6% wt.
Water 4% wt. 78.2 Isopropanol 88% wt.
Water 12% wt. 80.1 " : :
.
,, ~:~6~ ~3>~
Benzyl Alcohol 9~ wt.
Water 91% wt 99-9 Non-Azeotropes Ethyl Acetate 10-50% wt.
Acetic Acid 50-90% wt. Non-Azeotropic Methylene Chloride 10-50% wt.
Acetic Acid 50-90% wt. Non-Azeotropic Benzyl Acetate 10-30% wt.
Acetic Acid 70-90% wt. Non-Azeotropic Based on economy, effect on final product quality and effectiveness, glacial acetic acid is the most efficient of all the solvents. It will be appreciated, however, that care must be taken when using glacial acetic acid due to its low flashpoint in the order of 104F - 110F. (open cut test~ and burn causing properties well known in the literature for example in The Con-densed Chemical Dictionary-Rose-Reinhold Publishing Corporation -1966.
The solvent is maintained in contact with the carbon having caffeine adsorbed thereon for a period of time and at a temperature effective for the solvent to displace at least a por-tion of the caffeine from the carbon and dissolve the displacedcafEeine. As noted above, preferred temperatures will be above 100C., but the specific temperature for any particular process will be selected on its own set oE economic considerations and may be below this. Practical contact times will be determined on the basis of the desired degree of recovery and the desorption rate for a particular system. Preferably, the contact time should be sufficient to permit displacernent of at least 75% by weight of the caffeine from the carbon and into solution with the solvent.
Because the caffeine is valuable as a product, and if not removed from the carbon, decreases the adsorbent capacity of the carbon, still higher ra-tes of dis-; placement, on the order of 90% by weight or more, are desired.
05 As the activa~ed carbon adsorbent can be any of those types commercially available which are effective caffeine adsorbents and capable of withstanding the riyors of recycling permitted by the invention.
Preferred activated carbons are those prepared from coconut, coal and lignite, particularly those available commer~ially from Calgon Corporation, ICI, Carborund~m and Union Carbide Corporation.
After contact for the requi~ite period of time, the activated carbon is preferably separated from the solvent prior to separation of the caffeine from the solvent. The simplest and most effective manner or removing the carbon from the solvent is by filtration.
The caffeine can be separated from the solvent in any suitable manner such as steam distillation or simply evaporating the solvent. In a preferred form o~ recovery, steam is passed through the caffeine-containing solvent in a vented vessel until the solvent concentration is reduced to about zero, most preferably about Cl ppm, leaving an a~ueous caffeine solution. The caffeine is then precipitated from the a~ueous solution by cooling to form pure white needle-shaped crystals.
Best Mode for Carrying Out the_Invention The following examples are for the purpose of illustraiing and explaining the best mode for carrying out the irivention, but are not meant to be limiting in any regard. Unless otherwise indicated, all parts and percenta~es are by weightO
Similarly, in U.S. 2,472,881, Bender employs activated carbon to remove impurities from an agueous caffeine solution but does not discuss the steps taken to recover the caffeine adsor~ed on the carbon.
Recently, an improved decaf~eination method was disclosed in U.S. 3,879,569 wherein ~uantitative extraction of caffeine -from raw coffee beans is achieved with moist supercritical carbon dioxide.
This process produces an extract from which essentially all of the caffeine can be removed by activated carbon. Unfortunately, the prior art techniques do not economically provide good levels of recovery of caffeine or they reguire the use of chlorinated hydrocarbon solvents which are o~herwise avoided by the use o~ carbon dio~ide as an extracta~t.
Disclosu_e of Invention The present invention now enables improved recovery of caffein~ from an activated carbon adsorbent, by an improved process which comprises: contacting activated ~.~.6~
carbon having caffeine adsorbed thereon with a li~uid, food-grade caffeine solvent which comprises an organic acid or an alcohol, and which is capable of displacing at least a portion of the caffeine 05 from active sites on the carbon; maintaining the contact for a period of time and at a temperature effective for th~ solvent to displace at least a portion of the caffeine from the carbon and dissolve the displaced caffeine; and separating the caffeine 10 from the solvent.
The present invention takes ad~antage of the discovery that ~ome liguid, food-grade caffeine solvents which have the ability to effect desorption both by -~heir strong solvent ability and their ability to displace the adsorbed material from active sites on the adsorbent, are extremely effective in separating caffeine from carbon adsorbents. The strong solvent effect causes a partitioning between the activated carbon and the solvent. The site displacement effect is achieved by the solvent molecules themselves competing for the active adsorbent sites. Once a caffeine molecule is displaced, it is then taken into solution by ~h~ solvent which is a strong solvent for caffeine.
The solvents employed according to the present invention are employed in their liquid state and preferably at temperatures in excess of 100 C to obtain the greatest rates of recovery. Temperature has a strong effect on desorption and should therefore be as high as possible, consistent with maintaining the solvent as a liquid. Where temperatures higher than the boiling point of the solvent are desired, it will be necessary to employ pressures in excess of atmospheric. It is preferred, however, to maintain ~ 3 the pressure at no gxeater than ahout atmospheric.
Therefore, the higher boiling solvents are pre~erred.
Because the caffeine is valuable for food and pharmaceutical use, the soIvents must be food-grade.
05 By this, it is meant that the materials are on the Generally Recognized As Safe (GRAS) list maintained by the Food and Drug Administration to this type of use. This is important because where any measurable quantity of a non GRAS material works its way into either the product caffeine or the product tea or coffee, the value of the product will be seriously diminished, if not wholly lost.
The organic acids and alcohols which are food-grade, liquid at the proposed processing temperature and preferably at room temperature, excellent solvents ~or caffeine, and capable of displacing caffeine from the ac~ive sites on the carbon, are effective ; solvents for use accordiny to the invention. Preferably, the solvent will comprise a member selected from the group consisting of acetic acid, propionic acid, butyric acid, ethanol, isopropanol, benzyl alcohol, butanol, amyl alcohol, and azeotropes comprising at least one of these. Among the co-solvents which can be employed in forming the azeotropes are water, n-hexane, n-heptane, n-octane, toluene, benzyl acetate, me~hylene chloride, ethyl acetate and other food-~rade solve~ts. The pre~erred solvents are those which have boiling points over 100 C, and of these glacial acetic acid and acetic acid azeotropes are the most preferred. The azeotropes of acetic acid with butyl alcohol, iso-amyl alcohol, toluene, and n-octane all have boiling points above 100 C as can be see~l from the following table:
, - 5 - ~6~L~3~
Acetic _cld Azeotropes Boilin~ Point ( C~
Acetic Acid 43% wt.
Butyl Alcohol 57% wt. 120.3 Acetic Acid 16% wt.
05 Iso-Amyl Alcohol 84% wt. 133.0 Acetlc Acid 65% wt.
Toluene 35% wt. 105.4 Acetic Acid 53% wt.
n-Octane 47% ~t. 105.0 10 Other azeotropes suitable for use in the process of the invention, but re~iring the use of superatmospheric pressures when temperatures of 100 C or more are employed, are:
Acetic Acld Azeotropes Boilinq Point ~ C~
15 Acetic Acid 6% wt.
n-Hexane 94% wt. 68 Acetic Acid 33% wt.
n-~eptane 67% wt. 95 Other Azeotropes . , 20 Ethanol g6% wt.
Water 4% wt. 78.2 Isopropanol 88% wt.
Water 12% wt. 80.1 " : :
.
,, ~:~6~ ~3>~
Benzyl Alcohol 9~ wt.
Water 91% wt 99-9 Non-Azeotropes Ethyl Acetate 10-50% wt.
Acetic Acid 50-90% wt. Non-Azeotropic Methylene Chloride 10-50% wt.
Acetic Acid 50-90% wt. Non-Azeotropic Benzyl Acetate 10-30% wt.
Acetic Acid 70-90% wt. Non-Azeotropic Based on economy, effect on final product quality and effectiveness, glacial acetic acid is the most efficient of all the solvents. It will be appreciated, however, that care must be taken when using glacial acetic acid due to its low flashpoint in the order of 104F - 110F. (open cut test~ and burn causing properties well known in the literature for example in The Con-densed Chemical Dictionary-Rose-Reinhold Publishing Corporation -1966.
The solvent is maintained in contact with the carbon having caffeine adsorbed thereon for a period of time and at a temperature effective for the solvent to displace at least a por-tion of the caffeine from the carbon and dissolve the displacedcafEeine. As noted above, preferred temperatures will be above 100C., but the specific temperature for any particular process will be selected on its own set oE economic considerations and may be below this. Practical contact times will be determined on the basis of the desired degree of recovery and the desorption rate for a particular system. Preferably, the contact time should be sufficient to permit displacernent of at least 75% by weight of the caffeine from the carbon and into solution with the solvent.
Because the caffeine is valuable as a product, and if not removed from the carbon, decreases the adsorbent capacity of the carbon, still higher ra-tes of dis-; placement, on the order of 90% by weight or more, are desired.
05 As the activa~ed carbon adsorbent can be any of those types commercially available which are effective caffeine adsorbents and capable of withstanding the riyors of recycling permitted by the invention.
Preferred activated carbons are those prepared from coconut, coal and lignite, particularly those available commer~ially from Calgon Corporation, ICI, Carborund~m and Union Carbide Corporation.
After contact for the requi~ite period of time, the activated carbon is preferably separated from the solvent prior to separation of the caffeine from the solvent. The simplest and most effective manner or removing the carbon from the solvent is by filtration.
The caffeine can be separated from the solvent in any suitable manner such as steam distillation or simply evaporating the solvent. In a preferred form o~ recovery, steam is passed through the caffeine-containing solvent in a vented vessel until the solvent concentration is reduced to about zero, most preferably about Cl ppm, leaving an a~ueous caffeine solution. The caffeine is then precipitated from the a~ueous solution by cooling to form pure white needle-shaped crystals.
Best Mode for Carrying Out the_Invention The following examples are for the purpose of illustraiing and explaining the best mode for carrying out the irivention, but are not meant to be limiting in any regard. Unless otherwise indicated, all parts and percenta~es are by weightO
3~
Example 1 One hundred parts of glacial acetic acld and 10 parts of ~ctivated carbon pellets co~taining 10% by weight caffeine, obtained from the process of 05 U.S. 3,879,569, were admixed and then raflu~ed in a vessel at atmospheric pressure and 117 C for two ~ hours. The acetic acid was decanted from the carbon and found to contain 0 . 801% caffeine. The carbon had 9.5 parts of acetic acid remaining on it. The caffeine was recovered from the solukion by evaporation.
The total amount of caffeine in the acetic acid was 0.725 parts, nearly 73% recovery in a single stage.
Example 2 The procedure of Example 1 was repeated but this time the components were introduced into a Soxhlet extraction tube and refluxed at 117 C for four hours. Total recovery of caffeine based on the 10% initial caf~eine was 99%.
Example 3 The procedure of Example 2 was repeated, but this time employing a solvent containing 57 parts of n-butyl alcohol and 43 parts of glacial acetic acid.
After four hours contact a~ 120 C, 82% o~ the caffeine was recovered. On evaporation, white crystals of caffeine precipit~ted from the solution.
Exam~le 4 In this example, green coffee beans are contacted with methylene chloride solvent to obtain a caffeine extract as described in U.S~ 3,671,263. The solvent is removed from the extract by evaporation, leaving a brown, crude~ caffeine sludge containing lar~e amounts of impurities in addition to caffeine. The sludge is preliminarily dissolved in water. Then the caffeine e~tract is contacted with DARCO powdered - 35 activated carbon which adsorbs mos~ of the impurities g from the extract to prepare it for crystallization into pure, white caffeine crystals. The carbon picks up about 10% caffeine in addition to the impurities. The caffeine is removed from the carbon 05 by contacting the charcoal with glacial acetic acid for 4 hours at 100 C in a vessel. The carbon is separated from the acetic acid solution by filtration --- and the acid is evaporated to leave rela~ively pure cxystals of caffein~. The acetic acid is condensed and recycled. The carbon is regenerated for recycle by thermal reactivation.
The above description has been for the purpose of teaching a person skilled in the art how to practice the invention. It is not intended to describe in detail each and every modification and variation of the invention which will become apparent to those skilled in the art upon study. It is applicant's intention, however, that all such modifications and variations be included within the scope of the invention as defined by the following claims.
-10~ 33~
SUPPLEMENTARY DISCLOSURE
' - -he preceding disclosure relates to a process of recovering caffeine from activated carbon by contacting the carbon having caffeine adsorbed thereon with a liquid, food-grade caffeine solvent which comprises an organic acid or an alcohol and azeotropes thereof and which is capable of displacing at least a portion of the caffeine from actlve sites on the car-bon, while maintaining -the contact for a period of time and at a temperature effective for the solvent to displace at least a por-tion of the caffeine from the carbon and dissolve the displaced caffeine, and separating caffeine from the solvent.
Acetic acid and acetic acid azeotropes are preferred solvents but when glacial acetic acid (which is the most efficient of the solvents) is employed it will be appreciated that care must be taken because of the low (104F) flashpoint of glacial acetic acid and its skin burning effect.
It has been determined that acetic acid water mixtures, preferably having a concentration of between about 50% and 80%, 20 by weight, may be employed to elute either batchwise or contin-uously in a countercurrent manner the caffeine and other solids frorn the spent activated carbon. Although acetic acid-water mix-tures are usually less efficient than pure glacial acetic acid they offer the advantage of being totally non-fIammable with no flashpoint. Glacial acetic acid is flammable with a flashpoint of 104F. requiring the use of equipment providing operational safety and this increases the capital costs for the process.
By adding water to glacial acetic acid or using acetic acid-water mixtures this re~uirement is eliminated and thereby dram-atically reduces capital ccsts. Most preterably, acetic acid cr :
70% concentration which is commercially available is used.
The aqueous acetic acid solution is liquid at the pro-posed processing temperature a~d at room temperature, is an ex-cellent solvent for caffeine, is capable of displacing caffeine from the active sites on the carbon and is an especially effect-ive solvent for use according to the invention. As indicated, the acetic acid solution preferably has a concentration of about 50 to 80~, and most preferably 70%, by weight.
The recovery of caffeine is of commercial importance, and the carbon itself is of commercial value for upon regenera-tion it may again be employed in caffeine recovery and purifi-cation processes.
One hundred parts of 70% acetic acid solution and 10 parts of activated carbon pellets containing 9.1% by weight caf-feine, obtained from the process of U.S. 3,879,569, of Vitzthum et al. were introduced into a Soxhlet extraction tube and then refluxed at atmospheric pressure and 110C. for 16 hours. The caffeine was recovered from the solution by evaporation. The total amount of caffeine recovered was ~.91 parts, 100% recovery.
Example 1 One hundred parts of glacial acetic acld and 10 parts of ~ctivated carbon pellets co~taining 10% by weight caffeine, obtained from the process of 05 U.S. 3,879,569, were admixed and then raflu~ed in a vessel at atmospheric pressure and 117 C for two ~ hours. The acetic acid was decanted from the carbon and found to contain 0 . 801% caffeine. The carbon had 9.5 parts of acetic acid remaining on it. The caffeine was recovered from the solukion by evaporation.
The total amount of caffeine in the acetic acid was 0.725 parts, nearly 73% recovery in a single stage.
Example 2 The procedure of Example 1 was repeated but this time the components were introduced into a Soxhlet extraction tube and refluxed at 117 C for four hours. Total recovery of caffeine based on the 10% initial caf~eine was 99%.
Example 3 The procedure of Example 2 was repeated, but this time employing a solvent containing 57 parts of n-butyl alcohol and 43 parts of glacial acetic acid.
After four hours contact a~ 120 C, 82% o~ the caffeine was recovered. On evaporation, white crystals of caffeine precipit~ted from the solution.
Exam~le 4 In this example, green coffee beans are contacted with methylene chloride solvent to obtain a caffeine extract as described in U.S~ 3,671,263. The solvent is removed from the extract by evaporation, leaving a brown, crude~ caffeine sludge containing lar~e amounts of impurities in addition to caffeine. The sludge is preliminarily dissolved in water. Then the caffeine e~tract is contacted with DARCO powdered - 35 activated carbon which adsorbs mos~ of the impurities g from the extract to prepare it for crystallization into pure, white caffeine crystals. The carbon picks up about 10% caffeine in addition to the impurities. The caffeine is removed from the carbon 05 by contacting the charcoal with glacial acetic acid for 4 hours at 100 C in a vessel. The carbon is separated from the acetic acid solution by filtration --- and the acid is evaporated to leave rela~ively pure cxystals of caffein~. The acetic acid is condensed and recycled. The carbon is regenerated for recycle by thermal reactivation.
The above description has been for the purpose of teaching a person skilled in the art how to practice the invention. It is not intended to describe in detail each and every modification and variation of the invention which will become apparent to those skilled in the art upon study. It is applicant's intention, however, that all such modifications and variations be included within the scope of the invention as defined by the following claims.
-10~ 33~
SUPPLEMENTARY DISCLOSURE
' - -he preceding disclosure relates to a process of recovering caffeine from activated carbon by contacting the carbon having caffeine adsorbed thereon with a liquid, food-grade caffeine solvent which comprises an organic acid or an alcohol and azeotropes thereof and which is capable of displacing at least a portion of the caffeine from actlve sites on the car-bon, while maintaining -the contact for a period of time and at a temperature effective for the solvent to displace at least a por-tion of the caffeine from the carbon and dissolve the displaced caffeine, and separating caffeine from the solvent.
Acetic acid and acetic acid azeotropes are preferred solvents but when glacial acetic acid (which is the most efficient of the solvents) is employed it will be appreciated that care must be taken because of the low (104F) flashpoint of glacial acetic acid and its skin burning effect.
It has been determined that acetic acid water mixtures, preferably having a concentration of between about 50% and 80%, 20 by weight, may be employed to elute either batchwise or contin-uously in a countercurrent manner the caffeine and other solids frorn the spent activated carbon. Although acetic acid-water mix-tures are usually less efficient than pure glacial acetic acid they offer the advantage of being totally non-fIammable with no flashpoint. Glacial acetic acid is flammable with a flashpoint of 104F. requiring the use of equipment providing operational safety and this increases the capital costs for the process.
By adding water to glacial acetic acid or using acetic acid-water mixtures this re~uirement is eliminated and thereby dram-atically reduces capital ccsts. Most preterably, acetic acid cr :
70% concentration which is commercially available is used.
The aqueous acetic acid solution is liquid at the pro-posed processing temperature a~d at room temperature, is an ex-cellent solvent for caffeine, is capable of displacing caffeine from the active sites on the carbon and is an especially effect-ive solvent for use according to the invention. As indicated, the acetic acid solution preferably has a concentration of about 50 to 80~, and most preferably 70%, by weight.
The recovery of caffeine is of commercial importance, and the carbon itself is of commercial value for upon regenera-tion it may again be employed in caffeine recovery and purifi-cation processes.
One hundred parts of 70% acetic acid solution and 10 parts of activated carbon pellets containing 9.1% by weight caf-feine, obtained from the process of U.S. 3,879,569, of Vitzthum et al. were introduced into a Soxhlet extraction tube and then refluxed at atmospheric pressure and 110C. for 16 hours. The caffeine was recovered from the solution by evaporation. The total amount of caffeine recovered was ~.91 parts, 100% recovery.
Claims (21)
1. A process for recovering caffeine from activated carbon comprising:
contacting activated carbon having caffeine adsorbed thereon with a liquid, food-grade caffeine solvent which comprises an organic acid or an alcohol, and which is capable of displacing at least a portion of the caffeine from active sites on the carbon;
maintaining the contact for a period of time and at a temperature effective for the solvent to displace at least a portion of the caffeine from the carbon and dissolve the displaced caffeine; and separating caffeine from the solvent.
contacting activated carbon having caffeine adsorbed thereon with a liquid, food-grade caffeine solvent which comprises an organic acid or an alcohol, and which is capable of displacing at least a portion of the caffeine from active sites on the carbon;
maintaining the contact for a period of time and at a temperature effective for the solvent to displace at least a portion of the caffeine from the carbon and dissolve the displaced caffeine; and separating caffeine from the solvent.
2. A process according to claim 1 wherein the solvent comprises a member selected from the group consisting of acetic acid, propionic acid, butyric acid, ethanol, isopropanol, benzyl alcohol, butanol, amyl alcohol, and azeotropes comprising at least one of these.
3. A process according to claim 2 wherein the contact is maintained at a temperature of at least 100°C.
4. A process according to claim 3 wherein the contact is maintained at a pressure in excess of atmospheric.
5. A process according to claim 3 wherein the the contact is maintained at a pressure of no greater than about atmospheric.
6. A process according to claim 2 wherein the solvent is glacial acetic acid or an acetic acid azeotrope containing a co-solvent selected from the group consisting of butyl alcohol, iso-amyl alcohol, toluene, n-hexane, n-heptane, and n-octane.
7. A process according to either of claims 2 or 6 wherein the solvent is glacial acetic acid or an acetic acid azeotrope containing a co-solvent selected from the group consisting of butyl alcohol, iso-amyl alcohol, toluene, and n-octane.
8. A process according to either of claims 1 or 6 wherein the solvent is glacial acetic acid.
9. A process according to claim 1 wherein contact is maintained for a period of time sufficient to permit displacement of at least 75% by weight of the caffeine from the carbon and into solution with the solvent.
10. A process according to claim 9 wherein the solvent is separated from the carbon by filtration prior to separating the caffeine from the solvent.
11. A process according to claim 10 wherein the caffeine is separated from the solvent by steam distillation.
12. A process according to claim 10 wherein the caffeine is separated from the solvent by evaporating the solvent.
CLAIMS SUPPORTED BY SUPPLEMENTARY DISCLOSURE
CLAIMS SUPPORTED BY SUPPLEMENTARY DISCLOSURE
13. A process for recovering caffeine from activated carbon comprising:
contacting activated carbon having caffeine adsorbed thereon with an aqueous acetic acid solution and which is capable of displacing at least a portion of the caffeine from active sites on the carbon;
maintaining the contact for a period of time and at a temperature effective for the solution to displace at least a portion of the caffeine from the carbon and dissolve the displaced caffeine; and separating the carbon from the solution.
contacting activated carbon having caffeine adsorbed thereon with an aqueous acetic acid solution and which is capable of displacing at least a portion of the caffeine from active sites on the carbon;
maintaining the contact for a period of time and at a temperature effective for the solution to displace at least a portion of the caffeine from the carbon and dissolve the displaced caffeine; and separating the carbon from the solution.
14. A process according to claim 13, wherein the con-centration of said acetic acid solution is between about 50% and 80%, by weight.
15. A process according to claim 14, wherein the con-tact is maintained at a temperature of at least 100°C.
16. A process according to claim 15, wherein the con-tact is maintained at a pressure in excess of atmospheric.
17. A process according to claim 13, wherein contact is maintained for a period of time sufficient to permit displacement of at least 80% by weight of the caffeine from the carbon and into solution with the acetic acid solution.
18. A process according to claim 17, wherein the carbon is separated from the solution by decantation prior to separating the caffeine from the solution.
19. A process according to claim 18, wherein the caffeine is separated from the solution by steam distillation.
20. A process according to claim 18, wherein the caffeine is separated from the solution by evaporating the solution.
21. A process according to claim 19, or claim 20, wherein the caffeine is further purified and refined and the carbon is regenerated and/or reactivated.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/159,724 US4298736A (en) | 1980-06-16 | 1980-06-16 | Carbon-caffeine separation |
| US159,724 | 1980-06-16 | ||
| US30627681A | 1981-09-28 | 1981-09-28 | |
| US306,276 | 1981-09-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1161037A true CA1161037A (en) | 1984-01-24 |
Family
ID=26856215
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000378286A Expired CA1161037A (en) | 1980-06-16 | 1981-05-26 | Carbon-caffeine separation |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1161037A (en) |
-
1981
- 1981-05-26 CA CA000378286A patent/CA1161037A/en not_active Expired
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| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry | ||
| MKEX | Expiry |
Effective date: 20010124 |