GB2360470A

GB2360470A - Solvent mixture.

Info

Publication number: GB2360470A
Application number: GB0119284A
Authority: GB
Inventors: Mazin Nicola
Original assignee: Advanced Phytonics Ltd
Current assignee: Advanced Phytonics Ltd
Priority date: 1997-04-08
Filing date: 1998-04-08
Publication date: 2001-09-26
Anticipated expiration: 2018-04-08
Also published as: GB0119284D0; GB2360470B

Abstract

A co-solvent mixture for use in a process for extraction of polar compounds from materials comprises at least 70 wt% of a tetrafluoroethane and a co-solvent having a dielectric constant (at 20{C) of at least 6.

Description

SOLVENT EXTRACTION This invention relates to solvent extraction and particularly, although not exclusively, provides a solvent extraction process and a novel solvent mixture for use in solvent extraction.

Applicant's co-pending European Patent Application No. 94 301199.9 describes an improved method for the extraction, concentration and preservation of fragrances and flavours using an extraction solvent comprising a non- chlorinated hydrocarbon solvent in the liquid phase. The method is found to selectively extract oils from natural raw materials, for example rose oil from roses.

PCT Patent Publication No. WO 95/26794 (Imperial Chemical Industries Plc) describes a process for extracting a composition comprising a biologically active compound or a precursor thereof from a raw material using an extraction solvent comprising a C,-4 (hydro)fluorocarbon together with a co-solvent selected from dimethyl ether and butane.

Whilst the processes described in the aforementioned documents are advantageous in some circumstances, there is a limit to the types of materials that can be extracted. For example, relatively polar materials cannot be extracted from raw materials.

It is an object of the present invention to address problems associated with the aforementioned processes. According to a first aspect of the present invention, there is provided a process for the extraction of at least one relatively polar component from a material comprising the steps of: (a) contacting the material with a solvent mixture comprising a CI to C4 fluorinated hydrocarbon and a co- solvent having a dielectric constant (at 20 C) of at least 5; and (b) separating the charged solvent mixture from said material.

Unless otherwise stated herein, an alkyl group may have up to10, preferably up to 8, more preferably up to 6, especially up to 4 carbon atoms, with methyl and ethyl groups being preferred. Any alkyl group referred to herein may be optionally substituted with one or more substituents which may be selected from halogen atoms, and optionally substituted alkyl, acyl, acetal, hemiacetal, acetalalkyloxy, hemiacetalalkyloxy, nitro, cyano, alkoxy, hydroxy, amino, alkylamino, sulphinyl, alkylsulphinyl, sulphonyl, alkylsulphonyl, sulphonate, amido, alkylamido, alkylcarbonyl, alkoxycarbonyl, halocarbonyl and haloalkyl groups. Preferably, alkyl groups referred to are un- substituted.

The CI to C4 fluorinated hydrocarbon may be non- chlorinated. Preferably, it comprises one or more carbon, fluorine and hydrogen atoms only. Preferably, said fluorinated hydrocarbon is a C, to C3, more preferably, a C1 to C2 fluorinated hydrocarbon. Especially preferred is a C2 fluorinated hydrocarbon.

Said fluorinated hydrocarbon may include up to 10, preferably up to 8, more preferably up to 6, especially up to 4, fluorine atoms. Said fluorinated hydrocarbon is preferably aliphatic. It is preferably saturated.

Said fluorinated hydrocarbon may have a boiling point at atmospheric pressure of less than 20 C, preferably less than 10 C, more preferably less than 0 C, especially less than -10 C. The boiling point may be greater than -90 C, preferably greater than -70 C, more preferably greater than -500C.

A preferred fluorinated hydrocarbon solvent is tetrafluoroethane with 1,1,1,2-tetrafluoroethane being especially preferred.

The dielectric constant of said co-solvent may be at least 6, is preferably at least 15 and is especially at least 20. The dielectric constant may be less than 120, preferably less than 110, more preferably less than 100, especially less than 90.

The boiling point of said co-solvent may be greater than 0 C, preferably greater than 25 C, more preferably greater than 40 C, especially greater than 50 C. Said boiling point may be less than 250 C, preferably less than 215 C, more preferably less than 175 C, especially less than 150 C.

Said solvent mixture may include at least 0.25 wt%, preferably at least 0.5 wt%, more preferably at least 1 wt%, especially at least 2 wt% of said co-solvent. Said solvent mixture may include less than 20 wt%, preferably less than 15 wt%, more preferably less than 10 wt%, of said co-solvent. Said solvent mixture may include at least 60 wt-*,, preferably at least 70 wt%, more preferably at least 80 wt%, especially at least 90 wt% of said fluorinated hydrocarbon.

Said solvent mixture preferably comprises a substantially saturated solution of said co-solvent in said fluorinated hydrocarbon.

Said co-solvent may be selected from amides, especially N,N'-dialkylamides and alkylamides, with dimethylformamide and formamide being preferred; sulphoxides, especially dialkyl sulphoxides, with dimethylsulphoxide being preferred; alcohols, especially aliphatic alcohols for example alkanols, with methanol, ethanol, 1-propanol and 2-propanol being preferred; ketones, especially aliphatic ketones, for example dialkyl ketones, with acetone being especially preferred; organic acids, especially carboxylic acids with formic acid and acetic acid being preferred; carboxylic acid derivatives, for example anhydrides, with acetic anhydride being preferred; cyanide derivatives, for example hydrogen cyanide and alkyl cyanides, with methyl cyanide and liquefied anhydrous hydrogen cyanide being preferred; ammonia; sulphur containing molecules including sulphur dioxide, hydrogen sulphide and carbon disulphide; inorganic acids for example hydrogen halides with liquefied anhydrous hydrogen fluoride, chloride, bromide and iodide being preferred; nitro derivatives, for example nitroalkanes and nitroaryl compounds, with nitromethane and nitrobenzene being especially preferred.

Preferably, said co-solvent is selected from carboxylic acids, carboxylic acid derivatives, especially amides, ketones and alcohols. Said co-solvent may have - 5 less than 10, preferably less than 8, more preferably less than 6, especially less than 4 carbon atoms. Said co- solvent is preferably an aliphatic compound.

Said co-solvent is preferably substantially unable to react with said component and/or with said material under the conditions of said process.

Said co-solvent and said C1-4 fluorinated hydrocarbon preferably form a constant boiling mixture or azeotrope. Said solvent mixture may include a first and second co-solvent each of which may independently have any of the properties or features of said co-solvent referred to hereinabove.

In the method, the charged solvent may be collected by decantation. Alternatively, the charged solvent may be collected by sedimentation. Alternatively, the charged solvent may be collected by filtration.

The method preferably includes the step of removing said solvent mixture from the remainder of said material, after step (b). Removal of said solvent material may be achieved by providing conditions for the evaporation of said solvent. For example, the temperature may be raised, suitably less than 50 C, preferably less than 40 C, more preferably less than 30 C, and/or the pressure may be reduced to less than atmospheric pressure.

As an alternative to evaporating the solvent or in addition thereto, the solvent mixture (including the extract(s)) may be washed with copious amounts of water which may be suitable when the co-solvent(s) have some solubility in water and/or is/are less volatile than the fluorinated hydrocarbon. Thus, in this case, the co- solvent(s) may be removed by dissolution in water and, subsequently, the C1_4 fluorinated hydrocarbon may be removed by evaporation as aforesaid. Where washing with water in the manner described does not produce a satisfactory result, for example due to the formation of an emulsion or where the extract itself is also removed in high qualities by dissolution in the water, a salt, for example sodium sulphate or sodium chloride, may be added to the water to suppress the ionisation and solubility of the extracted components.

The process may include additional steps before or after the steps described above. In one embodiment, said material containing said component may be contacted with an alternative solvent or solvent mixture, suitably prior to steps (a) above. Said alternative solvent or solvent mixture preferably is arranged to extract relatively non- polar components and preferably comprises a C1_4 fluorinated hydrocarbon, optionally in combination with one or more co-solvents having a dielectric constant at 20 C of less than 5. Said Cl,, fluorinated hydrocarbon of said alternative solvent or solvent mixture may be as described in any statement herein. Said co-solvent(s) may be as described in WO 95/26794, the contents of which are incorporated herein by reference.

Said material containing said component may be naturally occurring or a synthetic mixture, for example a reaction mixture. Said component may be a pharmaceutical product or an intermediate produced from the fermentation of mycelial or fungal culture or a product from a synthetic chemical reaction. Said component is preferably an active ingredient, for example it may be a pharmaceutical or pesticide, or a precursor thereof. Said material containing said component is preferably an organic material which is preferably naturally occurring (or at least a precursor thereof is naturally occurring) and/or is of natural origin. Said material is preferably a biomass.

According to a second aspect of the present invention, there is provided a solvent mixture comprising a C1 to C4 fluorinated hydrocarbon and a co-solvent having a dielectric constant (at 20 C) of at least 5.

The invention extends to the use of a solvent mixture as described herein in a solvent extraction process.

Any feature of any aspect of any invention or embodiment described herein may be combined with any feature of any other aspect of any invention or embodiment described herein.

The invention will now be described, by way of example.

Example -1 Two PET 210ml extraction bottles were each charged with a known weight of dried and finely ground ginger root. Each bottle was then assembled with a gas tight lid incorporating an aerosol valve and a filter element. 1,1,1,2-tetrafluorethane (1,1,1,2-TFE) (100g) was charged to a first bottle and to the other was charged a pre . prepared solution of 1,1,1,2-tetrafluoroethane/10% v/v acetone (100g). Both bottles were treated in an identical manner as follows: agitated for 5 minutes; solvent extract released into an evaporator flask and evaporated under slight vacuum and gentle heating; and when constant weight was attained, the remaining oil was isolated and weighed. Results Both samples produced were found to be largely composed of the sesquiterpene "zingiberene", the major functional component of ginger flavour.

Example 2 A known weight of dried and ground marigold flowers was charged into each of two PET bottles as described in example 1. 1,1,1,2-TFE (100g) was charged to one bottle and to the other was charged 100g of a solution of 1,1,1,2-TFE containing 10% acetic acid. The two bottles were treated in an identical manner as follows : agitated vigorously for 5 minutes the allowed to stand for a further 5 minutes; the extract solution was discharged into a pre-weighed evaporation flask and the solvents were evaporated, us;ipg slight vacuum and moderate heat; and when constant weight was attained, the resulting oil was isolated and weighed.

Results GC analysis on the resulting oils showed that the extract obtained using the mixture of 1,1,1,2-TFE and acetone was richer in carotenoids than the TFE only extract.

1,1,1,2-TFE 1,1,1,2-TFE + 10% acetic acid Weight marigold (g) 36.05 35.54 Weight solvent (g) 100 100 Weight product (g) 0.63 1.05 Yield (% w/w) 1.75 2.95 Example 3 A known weight of dried and ground sage leaves was charged into each of two PET bottles as described in the above examples. To one bottle was charged 100g of 1,1,1,2-TFE and to the other was charged a solution of 1,1,1,2-TFE containing 10% methanol. Both bottles were treated in an identical manner as described in Examples 1 and 2.

Results The mixture of 1,1,1,2-TFE and methanol was markedly greener in colour than the sample of 1,1,1,2-TFE alone indicating a higher rosmarinic acid content in the solvent mixture. Rosmarinic acid is a major constituent of sage oil.

1,1,1,2-TFE 1,1,1,2-TFE + l0% methanol Weight sage (g) 14.05 13.92 Weight solvent (g) 100 100 Weight product (g) 0.06 0.35 Yield (% w/w) 0.43 2.49 Example 4 A known weight of dried and ground thyme leaves was charged into each of two PET bottles as described in the above examples. To one bottle was charged 100g of 1,1,1,2-TFE and to the other a solution of 1,1,1,2-TFE containing 5% acetic acid. Both bottles were treated in an identical manner as described in the previous examples. Results Similar products were obtained from both experiments with both oils exhibiting typical characteristics of thyme oil.

1,1,1,2-TFE 1,1,1,2-TFE + 5% acetic acid Weight thyme (g) 12.76 12.85 Weight solvent (g) 100 100 Weight product (g) 0.33 0.42 Yield (% w/w) 2.59 3.27 Example 5 The apparatus used for this experiment consisted of a 191t extraction vessel, an evaporator vessel, a gas compressor and a heat exchanger. The whole apparatus was assembled in such a way that would allow a continuous recycling of the extractant solvent through the packed biomass bed.

2.OKg of dried and ground rosemary (Rosemarinus Officinalis L) were packed into the extraction vessel. The apparatus was then sealed and evacuated to 1Ombar pressure and extraction was achieved by passing a total of 5Kg of 1,1,1,2-TFE through the packed biomass bed. The resulting extract was evaporated to a constant weight and the oil produced was isolated and weighed. A fresh charge of rosemary was treated in an identical manner but using a solution of 1,1,1,2-TFE containing 10% acetone.

Results Both products exhibited similar characteristics typical of conventionally produced rosemary .oih with rosmarinic acid being the dominant constituent.

1,1,1,2-TFE 1,1,1,2-TFE + 10% acetone Weight rosemary (Kg) 2.00 2,00 Weight solvent (Kg) 5.00 5.00 Weight product (g) 17.79 106.04 Yield (%) 0.89 5.30 The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of a11 such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or a11 of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment (s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

CLAIMS 1. A solvent mixture comprising at least 70 wt% of a tetrafluoroethane and a co-solvent having a dielectric constant (at 20 C) of at least 6. 2. A mixture according to claim 1, wherein said tetrafluoroethane is 1,1,1,2-tetrafluoroethane. 3. A mixture according to claim 1 or claim 2, wherein said dielectric constant of said co-solvent is at least 15. 4. A mixture according to any preceding claim, wherein said dielectric constant of said co-solvent is at least 20. 5. A mixture according to any preceding claim, wherein said dielectric constant of said co-solvent is less than 120. 6. A mixture according to any preceding claim, wherein the boiling point of said co-solvent is greater than 25 C. 7. A mixture according to any preceding claim, wherein the boiling point of said co-solvent is greater than 40 C. 8. A mixture according to any preceding claim, wherein the boiling point of said co-solvent is less than 250 C. 9. A mixture according to any preceding claim, wherein said mixture includes at least 0.25 wt% of said co-solvent. 10. A mixture according to any preceding claim, wherein said mixture includes at least 0.5wt% of said co-solvent. 11. A mixture according to any preceding claim, wherein said mixture includes at least lwt% of said co-solvent. 12. A mixture according to any preceding claims, wherein said mixture includes at least 2wt% of said co-solvent. 13. A mixture according to any preceding claim, wherein said mixture includes less than 20 wt% of said co-solvent. 14. A mixture according to any preceding claim, wherein said mixture includes less than 1Swt% of said co-solvent. 1S. A mixture according to any preceding claim, wherein said mixture includes less than lOwt% of said co-solvent. 16. A mixture according to any preceding claim, wherein said solvent mixture includes at least 80wt% of tetrafluoroethane. 17. A mixture according to any preceding claim, wherein said solvent mixture includes at least 90wt% of tetrafluoroethane. 18. A mixture according to any preceding claim, wherein said co-solvent is selected from amides, sulphoxides, alcohols, ketones, organic acids, carboxylic acid derivatives, cyanide derivatives, ammonia, sulphur containing molecules, inorganic acids and nitro derivatives. 19. A mixture according to any preceding claim, wherein said co-solvent is selected from carboxylic acids, carboxylic acid derivatives, ketones and alcohols. 20. A mixture according to any preceding claim, wherein said co-solvent has less than 10 carbon atoms. 21. A mixture according to any preceding claim, wherein said co-solvent has less than 4 carbon atoms. 22. A mixture according to any preceding claim, wherein said co-solvent is an aliphatic compound. 23. A mixture according to any preceding claim, which includes a first co-solvent having a dielectric constant (at 20 C) of at least 6 and a second co-solvent. 24. A mixture according to claim 23, wherein said second co-solvent has a dielectric constant (at 20 C) of at least 5. 25. A mixture according to claim 23 or claim 24, wherein the boiling point of said second co-solvent is greater than 25 C. 26. A mixture according to any of claims 23 to 25, wherein the boiling point of said second co-solvent is less than 250 C. 27. A mixture according to any of claims 23 to 26, wherein said mixture includes at least 0.25 wto of said second co- solvent. 28. A mixture according to any of claims 23 to 27, wherein said mixture includes less than 20 wta of said second co- solvent. 29. A mixture according to any of claims 23 to 28, wherein said co-solvent is selected from amides, sulphoxides, alcohols, ketones, organic acids, carboxylic acid derivatives, cyanide derivatives, ammonia, sulphur containing molecules, inorganic acids and nitro derivatives. 30. A mixture according to any of claims 23 to 29, wherein said second co-solvent is selected from carboxylic acids, carboxylic acid derivatives, ketones and alcohols. 31. A mixture according to any of claims 23 to 30, wherein said second co-solvent has less than 10 carbon atOoms. 32. A mixture according to any of claims 23 to 31, wherein said second co-solvent has less than 4 carbon atoms. 33. A mixture according to any of claims 23 to 32, wherein said second co-solvent is an aliphatic compound. 34. A solvent mixture substantially as heredescribed with reference to the examples.