EXTRACTION PROCESS AND PURIFICATION PROCESS

The present invention relates to a process for extracting a particular compound or composition from a raw or crude material containing that compound or composition as a constituent part and to a process for purifying a crude material using a particular type of solvent for conducting the extraction or purification.

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. More recently, hydrofluorocarbons such as 1,1,1,2- tetrafluoroethane (R- 134a) have also been used for extracting products such as flavours and fragrances from materials of natural origin as disclosed in EP-A- 616821.

Although solvent extraction processes are used on a commercial scale, many of the extraction solvents that 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 or product concentrate to further processing in which the unwanted components are removed by extraction, e.g. using ethanol. Furthermore, many of 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. Hydrofluorocarbon solvents, such as R- 134a, can exhibit certain advantages over traditionally used solvents, being both selective and low boiling so that they can be more easily removed from the extracted material. However, the global warming potential (GWP) of hydrofluorocarbons is higher than is desirable.

Solvent based purification processes, such as liquid chromatography and high performance liquid chromatography (HPLC), are also known. In these known processes, the crude material to be purified is contacted with a solid adsorbent known as the stationary phase and the resulting solid is then eluted with a suitable solvent known as the mobile phase to progressively and selectively remove various compounds held on the adsorbent. The particular compound or compounds of interest can be collected in essentially pure form by monitoring the solvent eluate as it is recovered from the adsorbent.

In many liquid chromatography processes, the crude material to be purified is charged to the top of a chromatography column packed with a finely divided adsorbent solid as the stationary phase and is effectively washed through the column at a controlled rate by means of a flow of solvent. As the solvent flows through the column, it carries the crude material along with it, but the various components of the crude material are carried along at differing rates owing to the differing affinities that those components have for the adsorbent/solvent pair.

Thus, as the crude material passes through the column it is gradually separated into its component parts, and by appropriate selection of the packing material and

solvent medium the desired compound or compounds can be collected off the column in essentially pure form as a solution in the solvent medium.

High performance liquid chromatography (HPLC) is a particularly efficient form of liquid chromatography in which very finely divided solids, e.g. solids having mean particle diameters in the range of from 5 to 10 microns (μm), are used to pack the column and high pressures, e.g. up to 8000 psi, are employed to drive the solvent through the column so as to achieve a realistic solvent flow rate. The first commercial use of HPLC was as an analytical tool in which only very small quantities of complex organic mixtures were separated in the column. However, more recent developments have enabled HPLC to be used for the isolation/purification of development and even production quantities of a desired compound such as a pharmaceutical product.

The use of hydrofluorocarbons such as R- 134a as the eluting solvent in a liquid chromatography process is taught in US-5, 824,225.

It is also known to reduce the terpene content of essential oils using a liquid solvent extraction technique in which the crude essential oil is first contacted with a solid adsorbent and the adsorbent/essential oil mixture then eluted with a suitable solvent or solvent system.

Essential oils are typically extracted or expressed from plant materials and are used for flavouring, fragrance and medicinal purposes. These oils typically contain quantities of undesirable compounds, particularly the terpenes, and the desired organoleptic compounds, which can be structurally related to the terpenes, but carry heteroatom functionality, e.g. oxygen containing functional groups such as hydroxyl, carbonyl or ether groups. One particular class of organoleptic compounds contained in essential oils is the terpenoids.

The terpenoid content of essential oils often contributes significantly to the desired organoleptic properties of the essential oil. For example, the aroma and

flavour of citrus peel oils is largely determined by the presence of citral (an aldehyde), nerol and geraniol (alcohols) and their ethyl esters.

However, the terpenes are often present in large quantities in essential oils and tend to dilute or mask the desirable properties of the organoleptic compounds. For example, citrus peel oils typically contain between 90% and 98% terpenes, primarily α-limonene, and α- and β-pinene. Rosemary oil also typically contains between 85% and 90% terpenes and celery seed oil between 80% and 85%.

It is for this reason that crude essential oils are often treated to reduce the level of terpenes in the oils to provide an oil that is enriched in the desired organoleptic compounds, such as the terpenoids. These enriched oils are known in the art as "terpeneless", although the term is a misnomer in reality, because the majority of terpeneless oils still contain substantial quantities of terpenes. However, the important characteristic of terpeneless oils is that they contain higher quantities of the compounds, such as the terpenoids, which contribute to the desired organoleptic properties of the essential oil. For example, typical terpeneless citrus oils contain between 5 and 20 times the concentration of the desirable terpenoid compounds as compared to the essential oil starting material. This concentration enhancement is referred to as "folding", and an oil having a 5-times enhancement is referred to as a "5-fold oil".

Terpeneless oils, including citrus peel oils (orange, lemon, lime, grapefruit, bergamot) amongst others, have been available commercially for some time and are valuable materials in the flavours and fragrance areas.

The use of hydrofluorocarbons such as R- 134a in the production of essential oils having a reduced terpene content is taught in EP-A-1332201.

In one aspect, 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 solvent extraction process can be used to extract the flavoured,

functional or aromatic oils or components contained in certain plant or culture materials.

Accordingly, the present invention provides 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 at least one fluorocarbon selected from the pentafluoropropenes and fluorinated cyclopropanes, 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 extraction process of the present invention will not necessarily extract all of the desired compound or composition that is contained in the raw material.

After the solvent containing the extracted compound or composition has been separated from the raw material, the solvent is usually removed, e.g. by distillation or flash evaporation, to leave the extract which can be used as it is or sent for further processing, e.g. purification.

In one particular embodiment, the extraction process of the present invention can be used to extract a natural product 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 at least one fluorocarbon selected from the pentafluoropropenes and fluorinated cyclopropanes 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, roots 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, dried roots or seeds, such as ground cumin and ground ginger, and expressed oils.

In a preferred embodiment, the process of the present invention is used to obtain an extract, such as an essential oil, a concrete or an oleoresin, especially an essential oil, comprising one or more flavour and/or fragrance compounds (hereinafter referred to collectively as organoleptic compounds) from a plant material.

By the term "essential oil" we include oils which contain, inter alia, one or more terpenes and one or more desired organoleptic compounds, such as the oxygen containing terpenoids. Suitable essential oils which may be extracted in accordance with the process of the present invention include citrus peel oils, such as orange, lemon, lime and grapefruit, peppermint, lavandin, rosemary oil and celery seed oil.

After the solvent containing the extracted natural product has been separated from the plant material, the solvent is usually removed, e.g. by distillation or flash evaporation, to leave the natural product which can be used as it is or sent for further processing, e.g. purification.

In a further embodiment, the extraction process of the present invention can be used to extract a biologically active compound, such as a pesticide, a neutraceutical or a pharmaceutical, or a precursor to such a biologically active 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 at least one fluorocarbon selected from the (hydro)fluoropropenes and fluorinated cyclopropanes 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 pharmaceuticals which may be extracted using the extraction process of the present invention include antibiotics, antimicrobials, antifungals and antivirals, for example the penicillins, the alkaloids, paclitaxel, monensin, cytochalasin and artemisinin. Precursors to these compounds may also be extracted using the extraction process of the present invention.

Suitable neutraceuticals that may be extracted include dietary supplements such as antioxidants and vitamins.

After the solvent containing the extracted biologically active compound or precursor thereof has been separated from the raw material, the solvent can be removed, e.g. by distillation or flash evaporation, to leave an extract which can be used as it is or sent for further processing, e.g. purification.

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, by stirring that mixture, by passing the liquid solvent through a stationary packed bed of solid biomass or by the application of ultrasonic excitation.

In a further aspect, the present invention provides a purification process for reducing the concentration of one or more undesired compounds in a composition containing those compounds and one or more desired compounds.

According to this aspect of the present invention there is provided a process for treating a crude composition comprising one or more undesired compounds and one or more desired compounds so as to produce a purified composition comprising an increased concentration of the one or more desired compounds and a reduced concentration of the one or more undesired compounds, which process comprises the steps of (1) contacting the crude composition with a solid adsorbent, (2) eluting the solid adsorbent with which the crude composition has been contacted with a solvent comprising at least one fluorocarbon selected from the (hydro)fluoropropenes and fluorinated cyclopropanes, and (3) collecting a solvent eluate containing the purified composition from the solid adsorbent.

By the term "purified composition" we include compositions from which all or substantially all of the one or more undesired compounds have been removed so that they consist essentially of the one or more desired compounds and only small amounts of the undesired compounds if any at all. We also include compositions that still comprise appreciable amounts of the one or more undesired compounds but which comprise an increased concentration of the one or more desired compounds and a reduced concentration of the one or more undesired compounds as compared to the original crude composition that was subjected to the process of the invention.

The desired compounds in the above process are often polar, e.g. by virtue of carrying oxygen containing functional groups, while the undesired compounds are often non-polar. This is true, for example, of many essential oils in which the unwanted terpenes are non-polar, while the desired organoleptic compounds, such as the oxygen containing terpenoids, are polar. As a result, by using a polar adsorbent it is possible to adsorb the desired compounds more strongly or even preferentially as a result of their polar character. In fact, a proportion of the

undesired non-polar compounds may not even adsorb onto the adsorbent and instead will occupy the voids or interstices between the adsorbent particles.

This stronger or preferential adsorption of the polar compounds will allow the undesired non-polar compounds to be more readily removed from the polar adsorbent with a solvent. The solvent which is used to remove at least a proportion of the undesired non-polar compounds from the adsorbent may be a fluorocarbon solvent of the type which is used to elute the adsorbent to recover a purified composition containing a reduced concentration of those undesired compounds. Alternatively, however, the adsorbent could firstly be eluted with a non-polar or substantially non-polar solvent, such as hexane, petroleum ether or a mixture of one or both of these compounds with a small quantity (typically less than 10 weight %) of a polar compound, prior to being eluted with the fluorocarbon solvent, in order to remove at least a proportion of the undesired non-polar compounds. Suitable polar compounds include the amides, sulphoxides, alcohols, ketones, carboxylic acids, carboxylic acid derivatives, inorganic acids and nitro compounds mentioned below. The prior treatment with a non-polar solvent is particularly advantageous when the mixture of the adsorbent and the composition to be treated contains undesired compounds held in the voids between the adsorbent particles.

Where a non-polar or substantially non-polar solvent is used to remove the interstitial oil, it will preferably be used in an amount of up to 10 % of the volume of the adsorbent bed.

In a preferred embodiment, the crude composition which is treated to reduce the concentration of undesired compounds is a flavour and/or fragrance composition comprising one or more undesired compounds and one or more desired flavour and/or fragrance compounds having desired organoleptic properties. More particularly, the crude composition to be treated is a terpene containing flavour and/or fragrance composition, such as an essential oil, an oleoresin or a concrete, especially an essential oil, that contains one or more desired flavour and/or fragrance compounds, such as the oxygen containing terpenoids, in addition to the

terpenes and the objective of the process is to reduce the terpene content of that composition.

Accordingly, in one preferred embodiment the present invention provides a process for treating a crude composition containing one or more terpenes and one or more desired compounds as constituent parts so as to produce a purified composition containing an increased concentration of the one or more desired compounds and a reduced terpene concentration, which process comprises the steps of (1) contacting the crude composition with a polar, solid adsorbent, (2) eluting the polar, solid adsorbent with which the crude composition has been contacted with a solvent comprising at least one fluorocarbon selected from the (hydro)fluoropropenes and fluorinated cyclopropanes, and (3) collecting a solvent eluate containing the purified composition from the polar, solid adsorbent.

Thus, in one preferred aspect, the purification process of the present invention can provide essential oils that are enriched with the more desirable flavour and/or fragrance compounds, such as the oxygen containing terpenoids. In another preferred aspect, the purification process of the present invention can provide essential oils of low colour. Preferably, the deterpenated essential oil has a terpenoid and other oxygenates enrichment of greater than 5-fold, preferably greater than 10 fold. The process of the invention may allow up to 50 fold oils, e.g. up to 90 fold oils to be obtained depending on the initial terpene content of the raw material.

Essential oils that can be treated in accordance with the purification process of the present invention include oils that have been extracted or expressed from plant materials, e.g. by distillation, solvent extraction or cold pressing. Suitable essential oils include citrus peel oils, such as orange, lemon, lime, grapefruit and bergamot, peppermint oil, lavandin oil, rosemary oil, ginger oil and celery seed • oil.

When the process of the present invention is applied to an essential oil, that oil may be an unrefined oil obtained directly from a plant material containing that oil.

Alternatively, the essential oil obtained from a plant may be subjected to one or more pre-treatment or refining steps before being subjected to the process of the present invention.

In another preferred embodiment, the crude composition which is treated to reduce the concentration of undesired compounds is a neutraceutical or pharmaceutical containing composition comprising one or more undesired compounds and one or more compounds having desired neutraceutical or pharmacological properties.

Thus, in one preferred aspect, the purification process of the present invention can provide compositions that are enriched in the more desirable neutraceutically- or pharmaceutically-active compounds. These compositions are preferably of low colour.

The crude composition to be treated in the purification process of the present invention may be dissolved or dispersed in a solvent before it is brought into contact with the adsorbent in order to facilitate the adsorption. For example, if the composition is a viscous essential oil, adsorption of that oil on the adsorbent can be facilitated by dissolving the oil in a suitable non-polar solvent. If desired, the composition to be treated can be charged to the adsorbent as a solution or dispersion in the fluorocarbon containing solvent which is to be used to elute the adsorbent.

The solid adsorbent is usually a polar material, is preferably in particulate form and is normally packed in a column to form a bed to which the crude composition to be treated, e.g. an essential oil, optionally dissolved in a suitable solvent, and then the fluorocarbon containing eluting solvent are conveyed. The solvent entrains or dissolves the composition to be treated and transports it through the column, specifically through the adsorbent material packing the column. As the fluorocarbon solvent is passed through the adsorbent, the different affinities that the desired compounds have for the adsorbent and solvent compared to the undesired compounds, e.g. as a result of different polarities, allows for at least

partial separation of these compounds. As a result, a fraction can be collected from the column which contains a purified composition, such as a terpeneless essential oil, that is enriched in the desired compounds.

Although the solvent may be allowed to pass passively through the packed column under the action of gravity, it is preferred to forcibly drive the solvent through the column using a pump or some other means to create a positive (super- atmospheric) pressure at the inlet end of the column. The flow of solvent through the column is continued at least until the desired product has been eluted from the column.

In an alternative embodiment, the crude composition to be treated, optionally dissolved in a suitable solvent, is charged to a chromatography column containing an adsorbent bed and the bed then eluted with a non-polar or substantially non- polar solvent, such as hexane, petroleum ether or a mixture of one or both of these compounds with a small quantity (typically less than 10 weight %) of a polar compound in order to remove at least a proportion of the undesired non-polar compounds from the adsorbent. The prior treatment with a non-polar solvent is particularly advantageous when the adsorbent bed contains undesired compounds held in the voids between the adsorbent particles. When this treatment has been completed, the adsorbent can either be retained in the column and the bed treated with the fluorocarbon solvent, or it can be removed from the column and then treated with the fluorocarbon solvent.

When the purification process is conducted on a column, as is preferred, and the composition to be treated is an essential oil, the step of charging the oil to the column is preferably followed by passing air or an inert gas such as nitrogen through the adsorbent bed in order to reduce the quantity of interstitial oil, i.e. oil which is held in the gaps between the particles of adsorbent making up the adsorbent bed, but which is not adsorbed by the adsorbent. As stated above, the removal of at least some of the interstitial oil can also be effected by washing the adsorbent bed with a non-polar or substantially non-polar solvent. If desired, the

gas and solvent treatments can both be used to remove interstitial oil, e.g. the solvent treatment could be conducted prior to the gas treatment.

Suitable polar adsorbents for use in the purification process include, inter alia, activated alumina, aluminium hydroxide, silica gel, silicic acid, cellulose and polymeric ion-exchange resins, such as strongly-acidic, strongly-basic, weakly- acidic and weakly-basic modified cross-linked polystyrene resins. The preferred adsorbent will depend, inter alia, on the nature of the composition which is being processed. Suitable adsorbents can be determined readily by the skilled person. However, silica gels and silicic acid and basic or weakly acidic activated aluminas have been found to be particularly effective adsorbents when treating essential oils. In order to minimise the possibility of undesirable isomerisation and hydrolytic processes, the activated and partially-deactivated silica gel and silicic acid adsorbents are particularly useful.

According to a particular aspect of the purification process of the present invention, there is provided a process for purifying a crude material containing one or more desired compounds and one or more impurities so as to at least substantially separate the one or more desired compounds from the remainder of the crude material. The process comprises the steps of (1) contacting the crude material with a particulate adsorbent solid packing a chromatography column, (2) passing a solvent comprising at least one fluorocarbon selected from the (hydro)fluoropropenes and fluorinated cyclopropanes through the column so as to elute the adsorbent solid with which the crude material has been contacted and transport at least the one or more desired compounds through the adsorbent solid and (3) collecting a solvent eluate comprising the one or more desired compounds as it emerges from the column.

In stating that the one or more desired compounds are at least substantially separated from the remainder of the crude material, we include a level of purification where at least 50 % by weight, preferably at least 70 % by weight and more preferably at least 90 % by weight of the total weight of the one or more desired compounds that are contained in the crude material are recovered from

that material to yield a purified composition that comprises at least 80 % by weight, preferably at least 90 % by weight and more preferably at least 98 % by weight of the one or more desired compounds based on the total weight of that composition.

In this particular aspect of the purification process, the crude material to be separated, optionally dissolved or dispersed in a suitable solvent, is charged to the inlet end of the packed chromatography column and a supply of the fluoro carbon solvent or eluent is then fed to the same end of the packed column. The solvent entrains or dissolves at least the one or more desired compounds and often unwanted impurities and transports these materials with it through the column, specifically through the adsorbent solid material packing the column. However, because the different materials have different affinities for the adsorbent material and the solvent, they are transported through the column at different rates. Hence, it is possible to effect a substantial separation of the one or more desired compounds from the impurities contained in the crude material.

Where the crude material is dissolved or dispersed in a solvent before it is brought into contact with the adsorbent, suitable solvents include the fluorocarbon containing solvent which is to be used subsequently to elute the adsorbent.

Although the solvent may be allowed to pass passively through the column under the action of gravity, it is much preferred to use a HPLC technique in which the solvent is forcibly driven through the packed column using a pump or some other means to create a positive pressure at the inlet end of the column. The flow of solvent through the column is continued at least until the one or more desired compounds have been eluted from the column.

The chromatography process of the present invention may be used in any of the usual applications for liquid chromatography including enantiomer separation using a chiral column. Columns designed for reverse phase or standard phase HPLC may also be employed.

The particulate adsorbent solid which is used to pack the chromatography column may be any of the materials which are routinely used for this purpose including coated materials of the type which are used in reverse phase HPLC. Particularly suitable materials include silica and alumina (which may be coated) both of which are available in chromatography grades, including HPLC grades. In the case of HPLC ₅ the particulate adsorbent solid used to pack the column will typically have a mean particle diameter in the range of from 0.5 to 20.0 μm, more typically in the range of from 1.0 to 10.0 μm. The column packing may be wetted with the solvent prior to charging the crude material to the head of the column.

The weight ratio of the composition to be treated to the adsorbent is typically in the range of from 20:1 to 1:2, preferably in the range of from 10:1 to 1 :1 and particularly in the range of from 4:1 to 1:1. The optimum ratio depends, inter alia, on the nature of the composition to be treated. For a terpene containing flavour or fragrance composition, the optimum ratio depends particularly on the terpene content.

The solvent eluate that is recovered from the purification process of the present invention is usually treated to remove the solvent, e.g. by distillation or flash evaporation, to leave the purified material behind which can be used as it is or, alternatively, subjected to one or more further processes including further purification processes. For example, the purified material may once again be subjected to the purification process of the present invention in order to reduce further the concentration of the unwanted impurities and increase the concentration of the desired compounds.

The eluate may also be subjected to a filtration step before the solvent is removed in order to separate it from any adsorbent which becomes entrained in the solvent.

The solvent that is employed in the extraction and purification processes of the present invention must comprise at least one (hydro)fluoropropene, which may be a pentafluoropropene, or at least one fluorinated cyclopropane. Mixtures comprising two or more (hydro)fluoropropenes and mixtures comprising two or

more fluorinated cyclopropanes can also be employed as can mixtures comprising one or more (hydro)fluoropropenes and one or more fluorinated cyclopropanes.

By the term (hydro)fluoropropene we include perfluoropropene as well as the various hydrofluoropropenes. Hydrofluoropropenes, by which we mean compounds that contain just carbon, hydrogen and fluorine atoms, are preferred over perfluoropropene. Suitable hydrofluoropropenes include compounds having the formula:

R ₂ C=CR-CR ¹ _S

where each R and each R ¹ are independently either hydrogen or fluorine providing that at least one R substituent is hydrogen. Preferably each R ¹ substituent is fluorine and at least one of the R substituents is also fluorine. Preferred hydrofluoropropenes include the tetrafluoropropenes, such as 1,1,1,3- tetrafluoropropene (R-1234ze) and 1,1,1,2-tetrafluoropropene (R-1234yf), and the pentafluoropropenes, such as 1,1,1, 2,3 -pentafluoropropene (R-1225ye). It will be appreciated that 1,1,1,3-tetrafluoropropene and 1,1,1,2,3-pentafluoropropene can exist in cis- and trans- isomeric forms and any references herein to 1 ,1,1,3- tetrafluoropropene and 1,1,1,2,3-pentafluoropropene include the cis- and trans- isomers as well as mixtures of those isomers in any proportion.

Where the solvent is a pentafluoropropene, it is preferably 1,1,1,2,3- pentafluoropropene (R-1225ye).

Suitable fluorinated cyclopropanes may be selected from the group consisting of monofluorocyclopropane, 1 , 1 -difluorocyclopropane, 1 ,2-difluorocyclopropane, 1 , 1 ,2-trifluorocyclopropane, 1 ,2,3-trifluorocyclopropane, 1 , 1 ,2,3- tetrafluorocyclopropane, 1,1,2,2-tetrafluorocyclopropane and pentafluorocyclopropane.

The solvent which is used in the extraction and purification processes of the present invention may also comprise one or more co-solvents in addition to the at

least one fluorocarbon selected from the (hydro)fluoropropenes and fluorinated cyclopropanes.

Suitable co-solvents will typically have a boiling point of 80°C or below, for example in the range of from -85 to 80°C. The preferred co-solvents have a boiling point of 60°C or below, for example in the range of from -85 to 60°C, preferably 20°C or below, for example in the range of from -70 to 20 ⁰ C, and more preferably 10°C or below, for example in the range of from -60 to 10°C. Mixtures of two or more co-solvents may be used if desired.

The co-solvent may be another fluorocarbon, by which we mean a compound that includes fluorine and carbon atoms and optionally other substituent atoms. Suitable substituent atoms include halogen atoms other than fluorine and hydrogen.

Suitable fluorocarbons include perfluoroalkanes, such as perfluoroethane (R- 116) and perfluoropropane (R-218), and hydrofluoroalkanes, such as the hydrofluoromethanes, hydrofluoroethanes and hydrofluoropropanes. Suitable hydrofluoroalkanes include 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), 1,1,1,3,3-pentafluoropropane (R-245fa), 1,1,2,2,3- pentafluoropropane (R-245ca), 1,1,1, 2,3 -pentafluoropropane (R-245eb), 1,1,2,3,3- pentafluoropropane (R-245ea), 1,1, 1,2,3, 3-hexafluoropropane (R-236ea), 1,1,1, 2,2,3 -hexafluoropropane (R-236cb), 1,1,1,3,3,3-hexafluoropropane (R- 236fa), 1,1,1,2,3,3,3-heptafluoroproρane (R-227ea) and 1,1,1,2,2,3,3- heptafluoropropane (R-227ca). Particularly preferred hydrofluoroalkanes include R- 134a, R-245fa, R-236ea and R-227ea, especially R- 134a.

Anther suitable fluorocarbon is trifluoroiodomethane (CF ₃ I).

Other suitable co-solvents include fluorine-free and more particularly halogen- free materials.

Suitable halogen-free co-solvents may be selected from the C ₂ . ₆ , 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 halogen free co-solvents include the hydrocarbon ethers, by which we mean compounds having the formula R'-O-R ² in which R ¹ and R ² are independently hydrocarbyl groups containing only carbon and hydrogen atoms, such as C _1-6 and preferably C _1-3 alkyl groups. Preferred dialkyl ethers include dimethyl ether, methyl ethyl ether and diethyl ether.

Still further suitable co-solvents may be selected from the amides, sulphoxides, alcohols, ketones, carboxylic acids, carboxylic acid derivatives, inorganic acids and nitro compounds.

Preferred amide co-solvents include the N,N'-dialkylamides and alkylamides,' especially dimethylformamide and formamide.

Preferred sulphoxide co-solvents include the dialkylsulphoxides, especially dimethylsulphoxide.

Preferred alcohol co-solvents include the aliphatic alcohols, particularly the alkanols. Preferred alkanols are selected from the C _1-6 , particularly the C _1-3 alkanols, with methanol, ethanol, 1-propanol and 2-propanol being especially preferred.

Preferred ketone co-solvents include the aliphatic ketones, particularly the dialkyl ketones. A particularly preferred dialkyl ketone is acetone.

Preferred carboxylic acid co-solvents include formic acid and acetic acid.

Preferred carboxylic acid derivatives for use as co-solvents include the anhydrides, especially acetic anhydride, and the C,_ ₆ , particularly the C _1-3 alkyl esters Of C _1-6 , particularly C _1-3 alkanoic acids, especially ethyl acetate.

Preferred nitro compounds for use as co-solvents include the nitroalkanes and nitroaryl compounds, with nitromethane and nitrobenzene being especially preferred.

Where a co-solvent is used, it typically comprises from 0.5 to 60.0 % by weight, of the total weight of the solvent with the one or more (hydro)fluoropropenes and/or fluorinated cyclopropanes constituting the remainder. Preferably, the co- solvent comprises from 0.5 to 50 % by weight, more preferably from 1 to 30 % by weight and particularly preferably from 2.0 to 20.0 % by weight of the total weight of the solvent.

Preferred solvents are non-flammable. Where the solvent is a blend of one or more compounds, the resulting blend may be zeotropic, azeotropic or azeotrope- like.

The solvent which is used in the processes of the present invention may be a liquid or a supercritical fluid, but is preferably in liquid form. Where the 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. For example, the required liquid form may be attained by cooling the solvent to a suitably low temperature at some point before it is conveyed to the process or by over-pressurizing the container in which the solvent is contained, e.g. by means of an inert gas such as helium.

The preferred solvents comprise only low boiling compounds so that removal of the solvent from the solvent liquor containing the desired material tends to be relatively facile and can be accomplished by flash evaporation or distillation at relatively low temperatures, e.g. room temperature and below. This, in turn, reduces the risk of losing desired product either through co-evaporation of the

more volatile compounds with the solvent or thermal degradation of the more thermally unstable compounds.

In the purification process of the present invention, the composition of the solvent can be varied during the course of a run to enhance the resolution of the separation, as is common with conventional chromatography practice.

The raw or crude material which is subjected to the present extraction or purification process may be a liquid, including a solution, suspension or emulsion, or a solid. If the raw material used in the extraction process is a solid, then the efficiency of the extraction may be improved significantly by reducing the solid to a finely divided form, such as a powder.

The extraction and purification processes of the present invention may be conducted at the supercritical temperature of the solvent, in which case elevated temperatures will need to be employed. Preferably, however, the solvent used is in the liquid state and both processes are conducted at a temperature in the range of from -60 to 150 ⁰ C.

The extraction process is preferably conducted at a temperature in the range of from -40 to 60°C and particularly in the range of from -30 to 40°C.

The purification process is preferably conducted at a temperature in the range of from -10 to 80°C. This includes the initial contacting step, in which the composition to be treated is charged to the adsorbent, as well as the elution step with the fluorocarbon containing solvent. Operating temperatures at or below ambient, e.g. in the range of from -10 to 30°C, are particularly preferred.

The processes of the present invention may be conducted at atmospheric, sub- atmospheric or super-atmospheric pressures. Atmospheric and super-atmospheric pressures are preferred. The precise operating pressure will depend, inter alia, on the solvent which is used, particularly its boiling point.

Preferred operating pressures for processes other than HPLC 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. When the purification process of the invention utilizes an adsorbent which is packed into a column, the process is preferably operated at elevated pressures to drive the solvent through the column.

Preferred operating pressures for HPLC are in the range of from 10 to 850 bar, more preferably in the range of from 40 to 200 bar.

The apparatus which is used to carry out the process of the present invention may employ a solvent recovery system which removes the solvent from the recovered solvent liquor by evaporation and then condenses the resulting solvent vapour for reuse.

A suitable recovery system for low boiling point solvents, by which we mean solvents having a boiling point of 25°C or below, e.g. O ⁰ C or below, comprises an evaporator into which the eluate emerging from the process is passed, a compressor for compressing the vapour generated in the evaporator and a condenser for cooling the compressed vapour emerging from the compressor. The solvent is removed from the eluate in the evaporator by flash evaporation induced by suction from the compressor and the solvent vapour so generated then passes to the compressor, which may be a diaphragm compressor, where it is compressed. From the compressor, the solvent vapour passes to the condenser where it is cooled and returned to liquid form for recharging to the process or possibly to a solvent reservoir supplying solvent to the process. The condenser, which may take the form of a coiled tube, can be arranged inside the evaporator so that the latent heat of condensation provides at least some of the energy required to evaporate the solvent, the remainder being supplied by the work done by the compressor.

A further suitable recovery system for low boiling point solvents comprises a solvent recycling circuit comprising an evaporator into which the eluate emerging from the process is passed and in which the solvent is evaporated and a condenser

in which the vapour emerging from the evaporator is cooled and returned to liquid form for recharging to the process or possibly to a solvent reservoir supplying solvent to the process. Heating of the evaporator and cooling of the condenser may be carried out independently, but in a preferred embodiment an external heat pump system is used to both heat the evaporator and to cool the condenser. The external heat pump system comprises an evaporator, a compressor, a condenser and an expansion valve which are sequentially arranged in a circuit through which a heat transfer fluid is caused to flow. The evaporator of the external heat pump system, which may take the form of a coiled tube, is arranged inside or around the outside of the condenser of the solvent recycling circuit so that evaporation of the heat transfer fluid in the evaporator cools the condenser and provides for the condensation of the solvent vapour passing through the solvent recycling circuit. The vapour generated in the evaporator of the external heat pump system is then compressed and passes to the condenser where it condenses and gives off heat. The condenser of the external heat pump system, which may also take the form of a coiled tube, is arranged inside or around the outside of the evaporator of the solvent recycling circuit so that the latent heat of condensation associated with the condensation of the heat transfer fluid provides the heat required to evaporate the solvent passing through the solvent recycling circuit. The condensed heat transfer fluid is then returned through an expansion valve to the evaporator so completing the cycle in the external heat pump system.

As an alternative to an external heat pump system, an external circulating heat- transfer fluid may be used to transfer the heat of solvent condensation to the evaporator vessel to provide heat for solvent evaporation.

The processes of the present invention may be operated in a batch, batch continuous or continuous fashion.

The present invention is now illustrated but not limited by the following examples.

General Procedure A:

The extraction apparatus comprised a glass aerosol tube that was closed at one end and open at its other end. The open end was provided with a thread for fitting a screw-on metal cap. The top of the metal cap was provided with a centrally disposed, integral connecting member on its outside and a fluid transfer conduit extended through the top of the cap and through the integral connecting member.

A three-way valve was attached to the connecting member to provide for the introduction of an extraction solvent into the aerosol tube and for the egress of the solvent/extract mixture formed by the extraction into a receiver assembly.

The receiver assembly comprised a receiver flask connected to one arm of a three- way branch connector. The other two arms of the branch connector were provided respectively with a vent pipe for venting solvent evaporated in the receiver flask and an in-line connector for connecting the three-way branch connector to the three-way valve discussed previously. The fully assembled extraction apparatus is depicted in Figure 1.

In use, the plant biomass to be extracted was ground in a blender and the required amount of biomass placed in the glass aerosol tube. The metal cap and attached three-way valve were then secured in position over the open end of the glass aerosol tube and the tube evacuated using a vacuum pump connected to the three- way valve. The vacuum pump was then disconnected, leaving the glass tube under vacuum, and a pressurised container containing the solvent to be tested connected to the three-way valve via a quick-fit connector and the required amount of liquefied solvent transferred to the aerosol tube from the container. The aerosol tube was then shaken and allowed to stand for about 30 minutes.

After 30 minutes, the receiver assembly was connected to the three-way valve via the in-line connector and the aerosol tube inverted and clamped in this position by means of a clamp stand. The receiver flask was then immersed in a warm water bath to assist with the evaporation of the solvent and the valve opened to allow a liquid solvent eluate containing the extracted material to pass from the aerosol

tube to the receiver flask. When all the liquid had drained from the aerosol tube, the valve was closed. The extraction solvent evaporated in the receiver flask and escaped into the confines of a fume cupboard in which the extraction apparatus was assembled via the vent pipe.

The extract was weighed and analysed by either GCMS or HPLC.

The GCMS analysis was conducted using a Varian Saturn GCMS fitted with a CIP-SIL 8 CB column of 30 m length and 0.25 mm internal diameter. The temperature program that was run for the GCMS was as follows:

( 1 ) Starting Temperature 60°C

(2) Ramping to 24O ⁰ C at 3°C/minute

(3) Ramping to 250°C at 20°C/minute (4) Hold at 25O ⁰ C for 6 minutes

For the HPLC analysis, the extract was dissolved in 5 ml of methanol and then 20ml of 0.2% NaOH was added. The resulting mixture was warmed in a water bath at 45°C for 30 minutes and then cooled to room temperature using cool water. The sample was then neutralised and adjusted to the 50 ml mark with 0.08 M acetic acid. The samples were then analysed by HPLC using a Cl 8 reverse phase silica column. The mobile phase was 45/10/45 (by volume) methanol/acetonitrile/pH 7.8 buffer, with a flow rate of 0.5 ml/min. The detector wavelength was set at 260 nm. AU analyses were performed isocratically at 30 ⁰ C.

General Procedure B:

The extraction apparatus comprised a steel biomass cylinder, a glass receiver vessel and a steel recovery cylinder which were removably connectable to one another through an arrangement of pipes equipped with suitable couplings. The biomass cylinder was equipped at its inlet end with removable valve assembly V3. The piping that was used to couple the biomass cylinder to the receiver vessel was provided with an in-line filter, followed by an in-line, two-way valve Vl. The

piping that was used to connect the receiver vessel to the recovery cylinder was also equipped with an in-line, two-way valve V2. The folly assembled apparatus is depicted in Figure 2. When so assembled, each vessel could be brought into fluid communication with its neighbours by opening the valves in the connecting pipe work.

In use, valve V3 at the inlet side of the biomass cylinder was removed and the biomass to be extracted charged to the biomass cylinder. The valve was then replaced and a mobile vacuum pump was connected to valve V3 and used to remove air from the biomass cylinder. The biomass cylinder was weighed and then filled with solvent from a solvent cylinder through valve V3. The vacuum in the biomass cylinder helped to draw the solvent into the cylinder. The weight of the biomass cylinder was monitored during the solvent transfer process to ensure that the desired quantity of solvent was transferred to the vessel.

Once the transfer of solvent was complete, valve V3 was closed and the biomass cylinder shaken for 10 to 30 seconds to thoroughly mix the biomass with the solvent. The biomass cylinder was then connected to the receiver vessel and recovery cylinder as shown in Figure 2 and allowed to stand for approximately 30 minutes. The recovery cylinder was weighed and evacuated prior to assembly and liquid nitrogen was then placed in a bath arranged around the recovery cylinder to allow it to act as a condenser for recovered solvent.

After 30 minutes, valve V2 was opened folly and then valve Vl opened slowly until a steady flow of material into the receiver vessel was observed. If the solvent formed a separate liquid layer in the receiver vessel, then a container of warm (25- 35°C) water was placed around the vessel to gently warm the vessel and evaporate the solvent.

Once the flow of material into the receiver vessel stopped, valve Vl was closed, followed by valve V2 and the receiver vessel was then removed from the rig and fitted with a bung. A second receiver vessel was then assembled onto the rig and valve V2 followed by valve Vl opened. The biomass cylinder was then warmed using a hair-dryer to ensure that the majority of the solvent remaining in the biomass cylinder was vaporised and transferred to the recovery cylinder. After about 5 minutes of warming, valve Vl followed by valve V2 were closed.

The recovery cylinder was then detached from the rig and re-weighed to check that the majority of the solvent had been recovered. If more than approximately 10 g of solvent remained on the biomass, then the biomass warming process described above was repeated.

The extract collected in the first receiver flask was weighed and a small sample, dissolved in methanol analysed, using a Varian Saturn GCMS fitted with a CIP- SIL 8 CB column of 30 m length and 0.25 mm internal diameter. The temperature program that was run for the GCMS was as follows:

( 1 ) Starting Temperature 60 ⁰ C (2) Ramping to 24O ⁰ C at 3°C/minute

(3) Ramping to 250 ⁰ C at 20°C/minute

(4) Hold at 250°C for 6 minutes

Examples 1 to 8:

General procedure A described above was used to examine the extraction of ground cardamom pods, ground cloves, ground ginger and ground Artemisia using 1,1,1,2-tetrafluoropropene (R-1234yf) and 1,1,1,2,3-pentafluoropropene (R- 1225ye - E/Z mixture) as the extraction solvents. The results are shown in the table below.

The cardamom, clove and ginger extracts were analysed by GCMS. The GCMS traces for the cardamom extracts are shown in Figure 3, those for the clove extracts in Figure 4 and those for the ginger extracts in Figure 5. In Figure 5, the upper trace is for the extract obtained using R- 1225 ye and the lower trace is for the extract obtained using R- 1234 yf.

The Artemisia extracts were analysed by HPLC. The HPLC traces are shown in Figure 6. The upper trace is for the extract obtained using R-1234yf and the lower trace is for the extract obtained using R-1225 ye.

Example 9:

General procedure B described above was used to examine the extraction of ground cardamom pods using 1,1-difluorocyclopropane as the extraction solvent. The results are shown in the table below.

The GCMS trace for the cardamom extract is shown in Figure 7.