METHOD AND APPARATUS FOR EXTRACTION USING CARBON DIOXIDE

Abstract

The invention provides a method for extraction of at least one extract compound from a material, comprising: a. contacting carbon dioxide with the material to dissolve an amount of the at least one extract compound from the material into the carbon dioxide; b. contacting the carbon dioxide comprising the at least dissolved extract compound with a sorbent to sorb the at least one extract compound onto the sorbent and for regenerating the carbon dioxide; c. recirculating the regenerated carbon dioxide; and d. repeating said recirculating at a constant density of said carbon dioxide of between 100 and 1000 kg/m.sup.3, and repeating said recirculating for at least 10 cycles.

Claims

1. A method for extraction of at least one extract compound from a material, comprising: a. contacting carbon dioxide with the material to dissolve an amount of the at least one extract compound from the material into the carbon dioxide; b. contacting the carbon dioxide comprising the at least dissolved extract compound with a sorbent to sorb the at least one extract compound onto the sorbent and for regenerating the carbon dioxide; c. recirculating the regenerated carbon dioxide; and d. repeating said recirculating at a constant density of said carbon dioxide of between 100 and 1000 kg/m.sup.3, and repeating said recirculating for at least 10 cycles.

2. The method according to claim 1, wherein during said recirculating said carbon dioxide has a pressure drop for one cycle less than 1 MPa (10 bar).

3. The method according to claim 1, wherein during said recirculating said carbon dioxide is maintained at a constant temperature, wherein said temperature is maintained constant within a range of less than ±20 degrees.

4. The method according to claim 1, wherein said constant temperature is between 10 and 140° C..

5. The method according to claim 1, wherein said sorbent is selected from the group consisting of activated carbon, silicates, natural and synthetic mineral clays, aluminosilicates, phyllosilicates, aluminium phyllosilicates, zeolite material, maltodextrins, super absorbing polymers, and a combination thereof.

6. The method according to claim 1, wherein a weight ratio of said carbon dioxide to material from which the at least one extract compound is extracted of between 10:1 and 1:1.

7. The method according to claim 1, wherein the material is plant material, wherein the plant material before extraction comprises 1 wt. % or less extract compound, and wherein a ratio of material to sorbent is between 5:1 and 1000:1.

8. The method according to claim 4, wherein the carbon dioxide comprises between 10 and 100% of the maximum solubility of water in carbon dioxide at said constant density and temperature.

9. The method according to claim 1, wherein the material is a plant material selected from tree bark, root, needles, beans, pods, seeds, hard fruit, flowers, woods, and mixtures thereof, wherein the beans are selected from coffee beans, cocoa beans, soy beans, and peas, and wherein the plant material comprises pre-processed plant material.

10. The method according to claim 1, wherein the at least one extract compound is selected from at least one polycyclic aromatic compound, a halogenated compound, a terpenoid, a cannabinoid, a triterpenoids, a pesticide, a converted pesticide and combination thereof, wherein the converted pesticide is selected from a microbially, enzymatically, chemically, photo-chemically, and incompletely combusted pesticide.

11. An assembly for extraction of at least one extract compound from a material, comprising a pressure vessel enclosing: a pump in said pressure vessel for circulating carbon dioxide through said pressure vessel; a sorbent container in said pressure vessel for holding a sorbent, and a material container in said pressure vessel for holding the material comprising the at least one extract compound, said pump fluidly coupled to said material container and to said sorbent container for circulating said carbon dioxide through said material and through said sorbent at a density of between 100 and 1000 kg/m.sup.3.

12. The assembly of claim 11, wherein at least one of the sorbent container and the material container each comprises a permeable wall allowing said carbon dioxide to respectively at least one of entering the respective sorbent container, entering the material container, exiting the sorbent container, exiting the material container, and a combination thereof.

13. The assembly of claim 11, wherein said sorbent container and said material container are fluidly coupled in series to one another, in particular wherein said actuator, said sorbent container and said material container are fluidly coupled in series to one another.

14. The assembly of claim 11, where the pump is adapted to overcome a pressure drop over the assembly of maximum 5 bar.

15. An extract plant material comprising less than 1 ppm pesticide.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

[0046] FIG. 1 schematically depicts an embodiment of the assembly;

[0047] FIG. 2 a graph showing a relation between maximum solubility of water in carbon dioxide.

[0048] The drawings are not necessarily on scale.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0049] In FIG. 1, an example of the assembly is schematically depicted. A pressure vessel 1 holds a pump 2, and a first containers 3 and a second container 4. The pump 2 and the containers are mutually coupled in series. One of the containers 3, 4 can hold the material, and the other container 4, 3 can hold the sorbent. In an embodiment, more than one sorbent can be used for sorbing different extract compounds. In such an embodiment, a container can be divided into subcontainers each holding a separate sorbent.

[0050] In this embodiment, the pump is fluidly coupled with first container 3. The first container is in turn fluidly coupled with the second container 4. A space between an inner surface of a wall of the pressure vessel 1 and an outer surface of at least one of the first and second container 3, 4 can provide a conduit for a return flow of carbon dioxide, fluidly coupling the second container 4 and an inlet of the pump 2.

[0051] In an embodiment, the pressure vessel 1 is circle cylindrical. In a further embodiment, the first and second container 3, 4 and circle cylindrical. In depicted embodiment, flows of carbon dioxide are indicated with arrows, showing a flow direction. In the embodiment, each container 3, 4 has a radial flow opening and an axial flow opening. In the depicted embodiment, the first container comprises a radial ingress provision, here a permeable circumferential wall. The first container comprises an axial outlet opening. In an embodiment, a permeable conduit may be provided. In an embodiment, the inlet opening may be fluidly coupled to the permeable, axial conduit and the outlet opening may be provided by the permeable circumferential wall.

[0052] In the depicted embodiment, the second container has its inlet opening be fluidly coupled to a permeable, axial conduit and its outlet opening may be provided by the permeable circumferential wall. For a compact build, the first and second containers have reverse inlet and outlet provisions.

[0053] At least part of one or more walls of the first and/or second container are permeable to carbon dioxide. Here, the circumferential walls of both first and second container are permeable. The walls may comprise for instance comprise a perforated part, a sieve part. In an embodiment, one or more parts of one or more container wall parts may comprise a cloth, nonwoven part, or a mesh. For the permeable circumferential wall and/or axial permeable conduit, in order to provide a homogeneous flow, the permeability in axial direction may increase.

[0054] Other configurations may be possible. The depicted embodiment or the alternative with first and second containers with mutually reverse inlet and outlet provisions allow a compact build.

[0055] Pump 2 can have a capacity and limited headspace for providing a pressure increase of less than 5 bar.

[0056] FIG. 2 shows a relation between water solubility of water in carbon dioxide an the density of the carbon dioxide. In this graph, the temperature of carbon dioxide is 40° C.

Examples

[0057] 1. Cleaning of Cork

[0058] Unprocessed cork (200 g) was cut to granules with size of about mm, having 11.8 ppt (parts per trillion!) TCA and a moisture content of ca. 10%. These cork dices were placed in a 600 ml canister in a vertically placed 2 litre stainless steel pressure vessel. This canister was made from stainless steel with a two layer mesh-perforated plate top and bottom parts. A second, bag-like, canister was placed in the same pressure vessel and on top of the first canister. The second canister contained 100 g. of active carbon.

[0059] Carbon dioxide was introduced in the system to a pressure of 140 bar and a temperature 40° C. The carbon dioxide was subsequently circulated from top to bottom over the two canisters for 1 hour, using a centrifugal pump at a max. pressure drop of 0.8 bar and a flow rate of 126 kg/h. TCA contents were determined after depressurization of the vessel in both the cork and active carbon. TCA contents were measured after extraction by SPME-GC-MS according to International Standard ISO 20752.

[0060] In a second trial, two sets of first and second canisters were placed into the pressure vessel and the process was continued for 1.5 h.

[0061] In both runs, TCA level in the cork was reduced to below 0.5 ppt (parts per trillion).

[0062] 2. Cleaning of Cocoa Beans

[0063] Cocoa beans may have contaminants such as fungi, pesticides, heavy metals and PAHs on their shell. These contaminants may get into the chocolate production process and contaminate the final chocolate product, which is unhealthy for consumers. Supercritical CO.sub.2 was used to clean the cocoa beans and remove these contaminants from the cocoa bean shell.

[0064] To remove the contaminants from the cocoa beans a drying equipment was used, which is a system which circulates supercritical CO.sub.2 through two pressure vessels. These two pressure vessels can be brought into a fluid communication.

[0065] Some options for the configuration of the two vessels, where the far right one is the preferred version. The left one was used in this example. Supply and discharge of supercritical CO.sub.2 is not shown here.

[0066] In the larger vessel of these two vessels, a measured amount of cocoa beans was put in a cloth bag functioning as a canister, to prevent beans or parts/dust of the bean to enter and circulate through the system. In the smaller of the two vessels, an excess of active carbon was placed in a cloth holder, again to prevent dust to circulate through the system. The system was pressurised, and the CO.sub.2 was circulated through the bags functioning as beds and the system comprising the two pressure vessels for 1 hour at a flow rate of 237 kg/h and a maximum pressure drop of 0.8 bar. The temperature of the carbon dioxide in the system was 40° C. and the pressure was 150 bars.

[0067] With this method very little water or fat is extracted from the beans and there is a significant decrease in pesticides and polyaromatic hydrocarbons, as the table below illustrates.

TABLE-US-00001 TABLE Before After Pyrethrins (sum) 2.43 mg/kg ND Fenvalerate (sum) 1.81 mg/kg 0.4 mg/kg Sample weight 100.2 g 99.6 g Active carbon weight 10.0 g 10.1 g

[0068] The pyrethrins are a class of organic compounds normally derived from Chrysanthemum cinerariifolium that have potent insecticidal activity by targeting the nervous systems of insects. Pyrethrin naturally occurs in chrysanthemum flowers and is often considered an organic insecticide.

[0069] Fenvalerate (CAS 51630-58-1) is a pyrethroid insecticide. It is a mixture of four optical isomers which have different insecticidal activities. The 2-S alpha (or SS) configuration, known as esfenvalerate, is the most insecticidally active isomer. Fenvalerate consists of about 23% of this isomer.

[0070] 3. Taxane Removal from Hazelnut Shells

[0071] Hazelnut shells contain taxane derivatives (Miele et al., Phytochem. Rev. 11: 211-225 (2012) that may limit new applications (Ref: Luisa Cruz-Lopes, Jorge Manuel Martins, Bruno Esteves, B. Lemos. ECOWOOD 2012 conference 5th International Conference on Environmentally-Compatible Forest Products. 05-7 Sep. 2012 Oporto, Portugal) by the presence of taxanes (paclitaxel derivatives/precursors), which by itself could be relevant pharmaceutical products or building blocks.

[0072] Hazelnut in shell were obtained from a regional wholesaler and dehulled. Shells were dried for 24 h before further use. Shells further crushed to sizes of ca. 3-5 mm, and further milled in a blender and mortar. A 92 g of the crushed shells was packed in a cloth container and placed in a cylindrical high pressure container of 1 litre, together with 9 g of active carbon (Cabot, granules) placed on top. After adding 5 ml of ethanol as co-solvent/entrainer, precooled CO.sub.2 was pump using a Lewa membrane pump type EK1 and heated till 40° C. by a tube-in-tube heater exchanger and added to the high pressure container till a pressure of 160 bar was reached. CO.sub.2 was recirculated at a rate of 100 kg/h over the two beds (top-to-bottom) via and internal high static pressure centrifugation pump for 1 hour, which keeping the temperature of the high pressure container maintained at 40° C. through a hot water hose jacketed around the container. The overall pressure drop was measured using a pressure difference meter to be 35 mbar over the system.

[0073] Pressure was released during 7 min from a bottom connection of the vertically placed container into a second container where the residuals were retrieved at the bottom.

[0074] Initial and residual contents as well as the yield in active carbon was determined for taxane derivative (baccatin III) via HPLC-UV at 225 nm after 200 injection on a reversed phase column (Phenomenex Luna, 250×4.6 mm, 5 nm) eluted with water:methanol: acetonitril 50:30:20.

TABLE-US-00002 TABLE Initial taxane content in the shells 35 mg/kg Final taxane content in the shells 6 mg/kg Taxane content in active carbon 2.2 mg

[0075] Results in the table above show that the levels in the shell was significantly reduced and the taxane was largely captured on the active carbon in concentrated form, allowing the CO.sub.2 to be safely released, the shell to be safely used and the pharmaceutically active component to be further used.

[0076] 4. Extraction of Rose Bud Oil

[0077] Freshly harvested rose bud petals were treated to obtain rose oil which is present in low level amounts. A 600 ml canister was filled with 90 g of petals. A separate bag was filled with 10 g fine powdered hardened rapeseed RP70 (Cargill). Both were brought into a high pressure vessel, which was kept at 25° C. and subsequently pressurised to 70 bars using dense carbon dioxide. Carbon dioxide was circulated over the two beds placed in series, flow rate 100 kg/h, for 1.5 h. After circulation the system was depressurised during 10 minutes. In this process, the water content was close to 100% of the water of the maximum solubility of water in carbon dioxide at the given temperature and pressure.

[0078] Processed Rose petals and RP70 were subsequently extracted with acetone for 5 days at −18° C. for analysis. Rose oil contents were determined in duplicate on the base of its principle component, citronellol, using GC Varian 430-GC equipped with a Agilent VF-1 ms column and FID detector. See the results in the table below, showing amounts in rose petals before extraction, after extraction (“processed”) and amounts in rapeseed fat. Thus, rose oil is obtained in a commercially viable method, that is selective.

TABLE-US-00003 Citronellol content (mg/g) Rose petals 0.34 +/− 0.04 Processed rose petals 0.06 +/− 0.03 Fat 2.53 +/− 0.07

[0079] It will also be clear that the above description and drawings are included to illustrate some embodiments of the invention, and not to limit the scope of protection. Starting from this disclosure, many more embodiments will be evident to a skilled person. These embodiments are within the scope of protection and the essence of this invention and are obvious combinations of prior art techniques and the disclosure of this patent.