SOLVENT EXTRACTION PROCESS

Abstract: A process for extracting a compound or composition of matter from a raw material containing that compound or composition as a constituent part is described. The process comprises the steps of (1) contacting the raw material with an extraction solvent comprising a pentafluoropropane so as to extract the compound or composition from the raw material into the solvent, and (2) separating the solvent containing the extracted compound or composition from the raw material. The process is particularly adapted for extracting flavours and fragrances from materials of plant origin.

Description: WO 00/64555 PCTtGBOO/01554 1 SOLVENT EXTRACTION PROCESS The present invention relates to a solvent extraction process in which a raw material containing a particular compound or composition is treated with an extraction solvent so as to remove at least a proportion of that compound or composition from the raw material. Processes for extracting a desired compound or composition from a raw or bulk material which contains that compound or composition as a constituent part using an extraction solvent are known in the art. In these known processes, the raw material is contacted with the extraction solvent, often under vigorous mixing conditions so as to facilitate the dissolution of the desired compound or composition into the extraction solvent, and the resulting solvent liquor containing the desired compound or composition is then separated from the raw material for subsequent processing, e.g. distillation to remove the extraction solvent. Multiple extractions may suitably be carried out on the same raw material sample so as to maximise the amount of the desired compound or composition which is extracted from that sample. Typical examples of extraction solvents which have been used in the prior art extraction processes include hexane, methyl acetate, ethyl acetate, acetone and methanol. Although solvent extraction processes are used on a commercial scale, the extraction solvents which are currently used in these processes are not wholly satisfactory. Thus, when solvents such as hexane are used to extract flavoured or aromatic oils, such as are used in the food and cosmetic industries, from plant matter containing those oils, unwanted materials contained in the plant, e.g. high molecular weight waxes, tend to be eluted along with the desired oil. This problem necessitates subjecting the resultant hexane liquor to further processing in which the unwanted waxes are removed by extraction, e.g. using ethanol. Furthermore, the extraction solvents which are currently in use have fairly high boiling points, and the elevated temperatures which are employed in the distillation process to remove these high boiling solvents from the extracted material can cause problems. For example, the flavoured or aromatic oils contained in certain plants are complex substances containing a large number of individual compounds some of which are relatively volatile or relatively thermally unstable. Consequently, high distillation temperatures can tend to result in a loss of product either through co- evaporation of the more volatile compounds with the extraction solvent or thermal degradation of the more thermally unstable compounds. The use of hydrofluorocarbons such as 1,1,1,2-tetrafluoroethane (R-134a) for extracting products such as flavours and fragrances from materials of natural origin is also known from EP-A-616821. The present invention provides a new solvent extraction process which can be used to extract a wide variety of compounds or compositions from raw or bulk materials of which they form a constituent part. In one particular embodiment, the present invention provides a solvent extraction process which is capable of extracting the flavoured or aromatic oils contained in certain plant materials. According to the present invention there is provided a process for extracting a compound or composition of matter from a raw material containing that compound or composition as a constituent part, which process comprises the steps of (1) contacting the raw material with an extraction solvent comprising a pentafluoropropane, e.g. 1,1,1,3,3- pentafluoropropane (R-245fa), so as to extract the compound or composition from the raw material into the solvent and (2) separating the solvent containing the extracted compound or composition from the raw material. It will be appreciated that the process of the present invention will not necessarily extract all of the desired compound or composition that is contained in the raw material. In one particular embodiment, the extraction process of the present invention can be used to extract a natural product, such as a flavoured or aromatic oil, from a plant material containing that product. Accordingly, the present invention provides a process for extracting a natural product from a plant material containing that product as a constituent part, which process comprises the steps of (1) contacting the plant material with an extraction solvent comprising a pentafluoropropane so as to extract the natural product from the plant material into the solvent, and (2) separating the solvent containing the extracted natural product from the plant material. When used in this specification, the expression "plant material" not only includes materials which are essentially unprocessed and as such are clearly recognisable as being of plant origin, for example bark, leaves, flowers and seeds, but also materials, which although originating from plants, have been subjected to various processes and as such have a form which is somewhat different than the plants from which they originated, for example ground cumin and ground ginger . The process of the present invention is particularly suitable for extracting flavoured/aromatic oils from star anise, coriander and cloves. In a further embodiment, the extraction process of the present invention can be used to extract a biologically active compound, such as a pesticide or a pharmaceutically active substance, or a precursor to such a compound from a raw material containing that compound or precursor, such as a plant material, a cell culture or a fermentation broth. Accordingly, the present invention provides a process for extracting a composition comprising a biologically active compound or a precursor thereof from a raw material containing that composition as a constituent part, which process comprises the steps of (1) contacting the raw material with an extraction solvent comprising a pentafluoropropane so as to extract the composition from the raw material into the solvent, and (2) separating the solvent containing the extracted composition from the raw material. Suitable pesticides which may be extracted using the extraction process of the present invention include insecticides such as the pyrethroids. Suitable pharmaceutically active substances which may be extracted using the extraction process of the present invention include the penicillins, the alkaloids, paclitaxel, monensin and cytochalasin. Precursors to these compounds may also be extracted using the extraction process of the present invention. Any pentafluoropropane may be usefully employed in the process of the present invention including 1,1,1,3,3-pentafluoropropane (R-245fa), 1,1,2,2,3-pentafluoropropane (R-245ca), 1,1,1,2,3-pentafluoropropane (R-245eb) and 1,1,2,3,3-pentafluoropropane (R-245ea) as well as mixtures thereof. The preferred pentafluoropropane is 1,1,1,3,3-pentafluoropropane (R-245fa). The extraction solvent which is used in the process of the present invention may also comprise a co-solvent in addition to the pentafluoropropane . Suitable co-solvents include the fluorinated hydrocarbons, by which we mean compounds containing only carbon, hydrogen and fluorine atoms, such as the hydrofluoromethanes, the hydrofluoroethanes and the hydrofluoropropanes other than pentafluoropropanes. Examples of hydrofluoromethanes, hydrofluoroethanes and hydrofluoropropanes which may be used as co-solvents include, inter alia, trifluoromethane (R-23), fluoromethane (R-41), difluoromethane (R-32), pentafluoroethane (R- 125), 1,1,1-trifluoroethane (R-143a), 1,1,2,2-tetrafluoroethane (R-134), 1,1,1,2-tetrafluoroethane (R-134a), 1,1-difluoroethane (R-152a), 1,1,1 ,2,3 ,3-hexafluoropropane (R-236ea), 1,1,1 ,2,2,3-hexafluoropropane (R-236cb) and 1 , 1 , 1 ,3 ,3 ,3-hexafluoropropane (R-236fa) . Preferably, if a co-solvent is used in combination with the pentafluoropropane, it will be a fluorine free material and more particularly a halogen free material. Suitable halogen free co-solvents will typically have a boiling point of 60°C or below, for example in the range of from -85 to 60°C. The preferred co-solvents have a boiling point of 20°C or below, for example in the range of from -85 to 20°C, preferably 10°C or below, for example in the range of from -70 to 10°C, and more preferably 0°C or below, for example in the range of from -60 to 0°C. Mixtures of two or more co-solvents may be used if desired. Preferred solvents may be selected from the C 2 ^, particularly the C 2-4 hydrocarbon compounds by which we mean compounds containing only carbon and hydrogen atoms. Suitable hydrocarbons may be aliphatic or alicyclic. Preferred hydrocarbons are the alkanes and cycloalkanes, with alkanes such as ethane, n-propane, i-propane, n-butane and i-butane being especially preferred. Other preferred co-solvents include the hydrocarbon ethers, by which we mean compounds having the formula R J -0-R 2 in which R 1 and R 2 are independently hydrocarbyl groups containing only carbon and hydrogen atoms, such as C^ and preferably C,. 3 alkyl groups. Preferred dialkyl ethers include dimethyl ether, methyl ethyl ether and diethyl ether. Dimethyl ether and butane are particularly preferred co-solvents and of these dimethyl ether is especially preferred. The extraction solvent typically comprises from 50.0 to 100 % by weight, e.g. from 50.0 to 99.5 % by weight, of a pentafluoropropane and from 0 to 50 % by weight, e.g. from 0.5 to 50 % by weight, of a co-solvent. Preferred extraction solvents comprise from 70.0 to 100.0 % by weight, e.g. from 70.0 to 99.0 % by weight, of the pentafluoropropane and from 0 to 30 % by weight, e.g. from 1 to 30 % by weight, of the co-solvent. Particularly preferred extraction solvents comprise from 80.0 to 100.0 % by weight, e.g. from 80.0 to 98.0 % by weight, of the pentafluoropropane and from 0 to 20.0 % by weight, e.g. from 2.0 to 20.0 % by weight, of the co-solvent. If the co-solvent is a flammable material, which will be the case with the hydrocarbon and hydrocarbon ethers identified above, then the extraction solvent will preferably comprise sufficient of the pentafluoropropane to render it non-flammable overall. Where the extraction solvent is a blend of one or more compounds, the resulting blend may be zeotropic, azeotropic or azeotrope-like. The extraction solvent which is used in the process of the present invention may be in liquid, gaseous or vaporous form, but is preferably in liquid form. Where the extraction solvent has a boiling point below room temperature, maintaining the solvent in liquid form will involve the application of cooling and/or super-atmospheric pressures. The preferred extraction solvents comprise only low boiling materials so that removal of the solvent from the solvent liquor containing the extract tends to be relatively facile allowing the distillation to be carried out at relatively low temperatures, e.g. room temperature and below. This, in turn, reduces the risk of loosing desired product either through co- evaporation of the more volatile compounds with the extraction solvent or thermal degradation of the more thermally unstable compounds. The raw material which is subjected to the present extraction process may be a liquid, e.g. a solution, suspension or emulsion, or a solid. If the raw material is a solid, then the efficiency of the extraction process may be significantly improved by reducing the solid to a finely divided form, such as a powder. The extraction process of the present invention may be conducted at the supercritical temperature of the extraction solvent, in which case elevated temperatures will need to be employed. Preferably, however, the extraction process is conducted at a temperature in the range of from -60 to 150°C, more preferably in the range of from -40 to 60°C and particularly in the range of from -30 to 40°C. The extraction process of the present invention may be conducted at atmospheric or super-atmospheric pressures. The precise operating pressure will depend, inter alia, on the extraction solvent which is used, particularly its boiling point, and whether the extraction process is to be conducted with that solvent in liquid or gaseous form. Preferred operating pressures are in the range of from 0.1 to 200 bar, more preferably in the range of from 0.5 to 30 bar and particularly in the range of from 1 to 15 bar. The contacting of the extraction solvent with the raw material to be processed may be carried out under vigorous mixing conditions so as to facilitate the dissolution of the material to be extracted into the extraction solvent. The vigorous mixing may be achieved by mechanically shaking the extraction vessel containing the raw material/extraction solvent mixture or by stirring that mixture. After the extraction process of the present invention has been completed, the solvent liquor containing the extract can be distilled to remove the extraction solvent from the extract. The resulting extract may then be used as it is or, alternatively, it may be subjected to one or more further processes, for example to purify the extract or to isolate a given compound or compounds contained in the extract. The extraction process of the present invention may be operated continuously with the same extraction solvent being used repeatedly. A suitable installation for carrying out a continuous extraction process typically comprises an extraction vessel, a distillation unit, a compressor, a condenser and a suitable arrangement of connecting pipe work. The extraction solvent is first charged to the extraction vessel where it is contacted with the raw material to be processed, possibly under vigorous mixing conditions so as to facilitate the dissolution of the compound or composition to be extracted into the extraction solvent. The resulting solvent liquor containing the extract is then separated from the raw material, e.g. by allowing the liquor to drain through a filter arranged at the bottom of the extraction vessel, and passed to the distillation unit where the extraction solvent is removed by evaporation to leave the extract. The vapour generated in the distillation unit is compressed, e.g. using a diaphragm compressor, and is then delivered to a condenser which returns the extraction solvent to liquid form for recharging to the extraction vessel. With a continuous extraction process of this kind, it is possible to maximise the amount of the extract obtained without subjecting the same raw material sample to a succession of individual extractions. Once the raw material sample is exhausted, it is then removed from the extraction vessel and replaced with a fresh raw material sample. The present invention is now illustrated but not limited by the following examples. General Procedure 1: The natural product to be extracted is crushed and a weighed amount of the crushed product is placed in a cylinder. A fitting having an entry pipe for charging a solvent to the cylinder and an on/off valve for opening and closing this pipe to the passage of fluid is then attached to the open end of the cylinder. A weighed amount of the extraction solvent is then filled into the cylinder via the entry pipe. After the required amount of extraction solvent has been charged, the on-off valve is closed, the cylinder is shaken to mix the contents and then allowed to stand to allow the crushed natural product to become soaked with the extraction solvent. The cylinder is then placed in a fridge together with a Goertz tube of known weight and once the cylinder and tube have cooled, the cylinder is inverted, the on/off valve opened and the extraction solvent containing the extract poured from the cylinder into the Goertz tube via the entry pipe. The Goertz tube is then capped with stoppers which provide for the escape of the evaporating solvent while preventing moisture from entering the tube and the solvent allowed to steadily evaporate while gently warming the tube. Finally, nitrogen gas is flushed through the tube in order to assist the evaporation of the final traces of solvent and leave the extract behind. The Goertz tube is then weighed and the amount of extract in the tube determined. A sample of this extract is then dissolved in ethanol and subjected to analysis by Gas Chromatography (GC)/Mass Spectrometry (MS) using the following method and conditions. Columns: CPsil5 and CPsill9 capillary columns (each 320 m x 25 m) connected in series. The combination of columns gives good peak separation. Both columns are available from Chrompack Ltd. Method: The temperature of the oven was controlled as follows: Initial Temperature: 150°C Initial Time: 2 minutes Rate: 3°C/minute Final Temperature: 225°C Final Time: 30 minutes General Procedure 2: The natural product is prepared and weighed into a cellulose thimble. The cellulose thimble containing the natural product is then placed in a soxhlet extractor and a pre-weighed receiver flask is attached in position on the extractor. The glassware is lowered into an autoclave, fitted with a suitable condenser and heating coil, which is then sealed and evacuated. The required amount of solvent is then transferred into the evacuated autoclave via a ball valve which is then resealed. The transfer of solvent into the autoclave raises the pressure in the autoclave and the solvent condenses into the glassware. The condenser and heating coil temperatures are then set at about 0°C and 40°C respectively and the extraction allowed to proceed for the required time period. On completion of the extraction, the solvent is reclaimed by opening the ball valve and condensing the solvent into a cooled Whitey Bomb. The autoclave is then opened and the glassware retrieved. The receiver flask is detached and re-weighed to determine the yield. A sample of the extract is then analysed by GC/MS using the following column and oven conditions: Column type: DB 5, 30m x 0.32mm Temperature: 200 °C, isothermal Examples 1 and 2 In these examples, General Procedure 1 described above was used to extract and collect the oil contained in samples of ground cloves and star anise. The extraction solvent used was R-245fa. In Example 1, about 5 g of ground cloves and about 91 g of the R-245fa extraction solvent were used. About 0.8 g of pale yellow clove oil was extracted from the ground cloves to give a yield of 16 % oil based on the weight of biomass which was subjected to the extraction. The oil was analysed by GC/MS in accordance with General Procedure 1. The composition of the oil based on the area % of the GC/MS trace was found to be: Eugenol 58.8 % Caryophyllene 10.8 % Eugenyl acetate 30.4 % The other components amounted in total to less than 0.5 % of the total peak area. In Example 2, about 5 g of ground star anise and about 41 g of the R- 245fa extraction solvent were used. About 0.23 g of star anise oil was extracted from the ground star anise to give a yield of 4.6 % oil based on the weight of biomass which was subjected to the extraction. The oil was analysed by GC/MS in accordance with General Procedure 1. The composition of the oil based on the area % of the GC/MS trace was found to be: trans-annethole 87.2 % p-anisaldehyde 9.1 % Limonene 2.4 % Anisketone 1.3 % The other components amounted in total to less than 1.0 % of the total peak area. Example 3 In this example, the General Procedure 2 described above was used to extract ginger. The ginger was ground to a particle size of approximately 1 to 3 mm and then extracted in accordance with General Procedure 2 using R-245fa as the extraction solvent. The amounts of ginger and solvent used in the extraction are given in Table 1 together with the yield of the extract. The final extract was a yellow/orange translucent liquid. The liquid was analysed by GC/MS in accordance with General Procedure 2. The composition of the liquid based on the area % of the GC/MS trace was found to be: Camphene 1.82 % Sabiene 3.36 % Cedrene 9.22 % Farnesene 17.69 % Zingibrene 58.81 % Bisabolene 6.74 % The other components amounted in total to less than 1.0 % of the total peak area. Example 4 In this example, the General Procedure 2 described above was used to extract vanilla. The vanilla was chopped into approximately 3 mm pieces and then extracted in accordance with General Procedure 2 using R-245fa as the extraction solvent. The amounts of vanilla and solvent used in the extraction are given in Table 1 together with the yield of the extract. The final extract was a yellow solid. The solid was dissolved in ethanol and analysed by GC/MS in accordance with General Procedure 2. The vanilla extract was found to be mainly composed of vanillin by GC/MS. Example 5 In this example, the General Procedure 2 described above was used to extract jasmine. Jasmine concrete was melted and loaded onto a veπniculite support and then extracted in accordance with General Procedure 2 using R-245fa as the solvent. The amounts of jasmine and solvent used in the extraction are given in Table 1 together with the yield of the extract. The final extract was a golden orange oil. The oil was analysed by GC/MS in accordance with General Procedure 2. The composition of the oil based on the area % of the GC/MS trace was found to be: Linalool 26.03 % Benzyl Acetate 51.18 % Indole 3.24 % Eugenol 9.99 % Jasmone 5.34 % Farnesene 2.03 % Benzoic Acid 2.19 % The other components amounted in total to less than 1.0 % of the total peak area. Table 1

Claims: Claims: 1. A process for extracting a compound or composition of matter from a raw material containing that compound or composition as a constituent part, which process comprises the steps of (1) contacting the raw material with an extraction solvent comprising a pentafluoropropane so as to extract the compound or composition from the raw material into the solvent, and (2) separating the solvent containing the extracted compound or composition from the raw material. 2. A process as claimed in claim 1, wherein the raw material is of plant origin and the composition to be extracted is a flavour or a fragrance. 3. A process as claimed in claim 2, wherein the flavour or fragrance is comprised in an oil. 4. A process as claimed in claim 1, wherein the compound or composition to be extracted from the raw material comprises a biologically active compound or a precursor thereof. 5. A process as claimed in claim 4, wherein the biologically active compound is a pesticide or a precursor thereof. 6. A process as claimed in claim 4, wherein the biologically active compound is a pharmaceutically active substance or a precursor thereof. 7. A process as claimed in any one of the preceding claims, wherein the extraction solvent comprises at least one pentafluoropropane selected from the group consisting of 1,1,1,3,3-pentafluoropropane (R-245fa), 1,1,2,2,3-pentafluoropropane (R-245ca), 1,1,1,2,3-pentafluoropropane (R-245eb) and 1,1,2,3,3-pentafluoropropane (R-245ea). 8. A process as claimed in claim 7, wherein the extraction solvent comprises 1,1,1,3,3-pentafluoropropane (R-245fa). 9. A process as claimed in any one of the preceding claims, wherein the extraction solvent comprises a co-solvent in addition to the pentafluoropropane. 10. A process as claimed in claim 9, wherein the co-solvent comprises at least one C 2 ^ hydrocarbon. 11. A process as claimed in claim 10, wherein the C 2-6 hydrocarbon is selected from the alkanes and cycloalkanes. 12. A process as claimed in claim 11, wherein the co-solvent comprises at least one compound selected from ethane, n-propane, i-propane, n- butane and i-butane. 13. A process as claimed in claim 12, wherein the co-solvent comprises n-butane. 14. A process as claimed in claim 9, wherein the co-solvent comprises at least one hydrocarbon ether having the formula R J -0-R 2 in which R 1 and R 2 are independently C,^ alkyl groups. 15. A process as claimed in claim 14, wherein the co-solvent comprises at least one ether selected from dimethyl ether, methyl ethyl ether and diethyl ether. 16. A process as claimed in claim 15, wherein the co-solvent comprises dimethyl ether. 17. A process as claimed in any one of the preceding claims, wherein the extraction solvent is in liquid form. 18. A process as claimed in any one of the preceding claims which is conducted at a temperature in the range of from -60 to 150°C.

Inventors: CORR STUART, DOWDLE PAUL ALAN, HILL CLAIRE ELIZABETH, CORR, STUART, DOWDLE, PAUL, ALAN, HILL, CLAIRE, ELIZABETH
Applicants: CORR STUART, DOWDLE PAUL ALAN, HILL CLAIRE ELIZABETH, ICI PLC, CORR, STUART, DOWDLE, PAUL, ALAN, HILL, CLAIRE, ELIZABETH, IMPERIAL CHEMICAL INDUSTRIES PLC
Application year: 2000
Main classification: B01D11
IPC codes: A01N65, A61K8, A61Q13, B01D11, C07B63, C07C7, C07C9, C07C13, C07C29, C07C33, C07C41, C07C43, C07C45, C07C47, C07C49, C07C51, C07C63, C07C67, C07C69, C11B9