CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This patent application claims priority to U.S. Provisional Application No.

62/868,966, filed June 30, 2019, and U.S. Provisional Application No. 62/880,967, filed July 31, 2019, the entire contents of each of which are hereby incorporated by reference.

TECHNICAL FIELD

[0002] The present disclosure relates to systems and methods for separating cannabinoids. In some aspects, methods disclosed and contemplated herein relate to separating cannabinoids from plant extract using one or more membranes at ambient conditions.

INTRODUCTION

[0003] ABC (Alternative Biotech Crops) is a term that has been used to describe to the Cannabis family of plants and includes Cannabis and Industrial Hemp. Cannabis is rich in THC (Tetrahydrocannabinol), which is the psychoactive agent, whereas Industrial Hemp is rich in CBD (Cannabidiol) which is non-psychoactive and popularly known as medical marijuana.

[0004] Broadly, there are two major extraction routes: Supercritical Carbon Dioxide (SCF) route and the Solvent Route. Within the Solvent Route, typically ethanol is used but non-polar solvents such as heptane and butane are also used. Ethanol extraction is the most popular and prevalent. One of the major issues for both the SCF and Solvent routes is the“winterization” step that is required. After extraction with, for example ethanol, the extract is chilled, typically, to - 40°C to -80C to precipitate the waxes and lipids. This process is highly energy intensive and it does not eliminate the waxes completely. The chilling step is followed by filtration and other particulate removal steps. All these steps can lead to significant yield losses of the valuable products like THC and CBD.

[0005] Until recently, molecular separations using membrane technology were almost exclusively based on aqueous systems. Originally, nanofiltration (NF) was used for water treatments or for water softening. Like reverse osmosis (RO), the use of NF has broadened from waste-water treatment and sea-water desalination to milk and juice production. With the development of solvent-stable Organic Solvent Nanofiltration (OSN) membranes, the application fields for NF membranes can now be extended to the chemical process industries, e.g.,

Pharmaceuticals, Fine Chemicals, Natural Oils (including Essential Oils), Bulk Chemicals and Oil & Gas.

[0006] Operating separation processes at room temperature and carrying out gentle molecular separation can reduce process cost and increase efficiency. Various nanofiltration membranes disclosed herein are solvent stable and compatible with a wide range of organic solvents and organic/aqueous solvent mixtures, including polar and polar aprotic solvents such as acetone, tetrahydrofuran (THF), and ethanol.

SUMMARY

[0007] In one aspect, a method for separating a cannabinoid from a plant extract is disclosed. The example method includes providing a plant extract in a solvent, the solvent being selected from the group consisting of ethanol, methanol, acetone, butanol, isopropyl alcohol, water, and mixtures thereof, the plant extract comprising wax material and a cannabinoid compound;

subjecting the plant extract to a first nanofiltration operation with a first nanofiltration membrane thereby providing a first retentate enriched in the wax material and a first permeate comprising the cannabinoid compound; and subjecting the first permeate to a second nanofiltration operation with a second nanofiltration membrane, thereby providing a second retentate enriched in the cannabinoid compound and a second permeate including the solvent. The first nanofiltration operation is performed at an input fluid pressure of from 20 bar to 60 bar and a temperature of at least 15°C and no greater than 50°C. The first nanofiltration membrane comprises a silicone acrylate membrane layer on a polyimide support and has a molecular weight cut off of from 400 g/mol to 900 g/mol. The second nanofiltration operation is performed at an input fluid pressure of from 20 bar to 60 bar and a temperature of at least 15°C and no greater than 50°C. The second nanofiltration membrane has a molecular weight cut off of from 150 g/mol to 350 g/mol.

[0008] In another aspect, a system for separating cannabinoid from plant extract is disclosed. The example system can include a feed tank including polar solvent and plant extract, the plant extract including wax material and cannabinoid and a conduit in fluid communication with the feed tank, the conduit including a nanofiltration membrane and configured to discharge both a permeate stream and a retentate stream. The filtration membrane has a polyimide support layer and a silicon-based active membrane; the feed tank is configured to provide the polar solvent at a temperature and at a pressure to the conduit; the nanofiltration membrane having a molecular weight cut off of from 400 g/mol to 900 g/mol; the permeate stream including the solvent and the cannabinoid, the permeate stream sent to a holding tank; the retentate stream including wax material and being sent back to the feed tank; the pressure being no less than 20 bar and no greater than 60 bar; and the temperature being at least 15°C and no greater than 50°C.

[0009] There is no specific requirement that a material, technique or method relating to suspensions include all of the details characterized herein, in order to obtain some benefit according to the present disclosure. Thus, the specific examples characterized herein are meant to be exemplary applications of the techniques described, and alternatives are possible.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 shows an example method for separating a cannabinoid from a plant extract.

[0011] FIG. 2 shows a schematic diagram of a system for separating cannabinoid from plant extract.

DETAILED DESCRIPTION

[0012] Systems and methods disclosed and contemplated herein relate to separating cannabinoid from plant extract at ambient conditions. In some applications, plant extract in a solvent is passed through a first membrane that includes a silicone acrylate membrane layer on a polyimide support. A resulting retentate can include wax material, and possibly lipids and chlorophyll, and a resulting permeate can include the polar solvent and the cannabinoid compound. Subsequently, the cannabinoid compound can be separated from the solvent using various methods.

I. Example Materials

[0013] Systems, methods and techniques disclosed and contemplated herein can be applied using various materials. Certain aspects of various materials used in those systems and methods are described below.

[0014] In various implementations, exemplary systems and methods can have one or more of the following improvements or advantages: little or no lipids fouling on the membrane; potential elimination of winterization and associated unit operations; non-thermal (ambient temperature) concentration (significantly reduces the need for evaporation steps and thus all those rotavaps); non-thermal processing also helps to maintain product purity and quality; non-thermal processing also allows more product flexibility, i.e., avoidance of decarboxylation due to heat helps in having more product options; improvement in CAPEX from elimination of winterization and reduction in the need for evaporation/distillation units; improvement in OPEX from reduced need for cartridge filtration, solvent recycle, and significantly reduced energy costs.

A. Example Plant Components

[0015] Systems, methods and techniques disclosed herein separate cannabinoid from plant extract. Typically, the plant is a cannabis plant and various techniques may be applied to generate plant extract from the cannabis plant. As used herein, cannabinoid is meant to refer broadly to a class of compounds. Example cannabinoid compounds include, for instance, tetrahydrocannabinol (THC) and cannabidiol (CBD).

[0016] In some instances, plant extract may include one or more components in addition to cannabinoid compounds. For example, plant extract may include cannabinoid compounds, wax material, terpenes, lipids, and chlorophyll.

B. Example Solvents

[0017] Various solvents may be used with the systems, methods and techniques disclosed and contemplated herein. Typically, solvents are polar. Example solvents include ethanol, methanol, acetone, butanol, isopropyl alcohol, water, and mixtures thereof. In some instances, the solvent used is ethanol. In some instances, the solvent used is a mixture of ethanol and water. Other solvents are possible.

II. Exemplary Filtration Membranes

[0018] Exemplary filtration membranes used with systems and methods disclosed herein are nanofiltration membranes. Broadly, the nanofiltration membranes selectively allow material to pass through, called the permeate, and selectively prevent material from passing through, called the retentate. As used herein, the term“nanofiltration” means membrane filtration which separates molecules having molar masses ranging from about 150 Da to about 1,500 Da.

Typically, methods and systems disclosed herein use a first nanofiltration membrane and a second nanofiltration membrane.

A. Exemplary First Nanofiltration Membranes

[0019] Exemplary first nanofiltration membranes are selected to provide a retentate enriched in wax and/or lipid and phospholipid material, and to provide a permeate including cannabinoid compound(s) and solvent.

[0020] Exemplary first nanofiltration membranes typically include a silicone acrylate membrane layer on a polyimide support. Example silicone acrylates usable for the membranes are described in U.S. Pat. No. 6,368,382, U.S. Pat. No. 5,733,663, JP 62-136212, P 59-225705, DE 102009047351 and in EP 1741481 Al, the contents of which are hereby incorporated by reference in their entirety.

[0021] Example polyimide membranes may be made of P84 (CAS No. 9046-51-9), P84HT

(CAS No. 134119-41-8) and/or mixtures thereof. Polyimide membranes optionally may be crosslinked according to GB 2437519, which is hereby incorporated by reference in its entirety. In some instances, first nanofiltration membranes are organic coated polyimide membranes, which may include crosslinked or non-crosslinked P84 and/or P84HT membranes

[0022] Exemplary first nanofiltration membranes usually have a molecular weight cut off from 400 g/mol to 900 g/mol. In various instances, exemplary first nanofiltration membranes have a molecular weight cut off of from 400 g/mol to 700 g/mol; from 500 g/mol to 700 g/mol; from 400 g/mol to 600 g/mol; or from 500 g/mol to 650 g/mol. As used herein,“molecular weight cut off’ is defined according to the methodology of See-Toh et al (2007) (Journal of Membrane Science, 291 (1-2), pp. 120-125), where the molecular weight cut-off is taken to be the molecular weight at which 90% rejection is achieved of a series of styrene oligomers.

[0023] Example first nanofiltration membranes are typically hydrophobic. For the purposes of this application,“hydrophobic” means that the selective membrane should provide a contact angle for water of more than 70° at 25° C., as measured using the static sessile drop method described in ASTM D7334. In some instances, first nanofiltration membranes have a contact angle for water of more than 75° at 25° C. In some instances, first nanofiltration membranes have a contact angle for water of more than 90° at 25° C, and in some instances the water contact angle is more than 95° at 25° C.

[0024] Example first nanofiltration membranes are commonly understood to be used with non-polar solvents and should not be used with polar solvents (such as ethanol, water, methanol, acetone, and mixtures thereof). However, in contrast to that understanding, systems and methods disclosed herein utilize first nanofiltration membranes with solvents such as ethanol, water, methanol, acetone, and mixtures thereof. It has been discovered that membranes commonly understood to be optimized for use with ethanol, water, methanol, acetone, and mixtures thereof can experience fouling from lipids and phospholipids, which can greatly diminish performance. Examples of these membranes include membranes with a polyimide active membrane on a polypropylene support.

[0025] Exemplary commercially available membranes suitable for use as first nanofiltration membranes include PuraMem® S600 and PuraMem® Flux from Evonik MET Ltd. (Parsippany, New Jersey). Each of these membranes are noted as being not recommended for use in aqueous/water mixtures or aqueous/organic solvent mixtures.

B. Exemplary Second Nanofiltration Membranes

[0026] Exemplary second nanofiltration membranes selectively remove cannabinoid compounds from permeate obtained from the first nanofiltration membrane. That is, exemplary second nanofiltration membranes typically provide a retentate enriched in cannabinoid compound(s) and a permeate including the solvent. Because the first permeate is little to no lipids or little to no phospholipids, exemplary second nanofiltration membranes suitable for polar solvents may be used.

[0027] Second nanofiltration membranes usually have a lower molecular weight cut off than first nanofiltration membranes. In some instances, second nanofiltration membranes have a molecular weight cut off of from 150 g/mol to 350 g/mol. In various implementations, second nanofiltration membranes have a molecular weight cut off of from 150 g/mol to 250 g/mol; from 200 g/mol to 350 g/mol; from 250 g/mol to 350 g/mol; or from 200 g/mol to 300 g/mol.

[0028] In some instances, second nanofiltration membranes include a polyimide active membrane on a polypropylene support. Examples of commercially available membranes suitable for use as second nanofiltration membranes include the DuraMem® 300 and the DuraMem® 200 available from Evonik (Parsippany, New Jersey).

III. Exemplary Operating Conditions

[0029] Systems and methods disclosed herein can be used to separate cannabinoids from plant extract without cooling operations, such as winterization, and/or without heating operations. Typically, separation operations are performed at ambient temperature. As used herein,“ambient temperature” includes a temperature between 10°C and 50°C. In various implementations, ambient temperature is a temperature between 10°C and 40°C; between 15°C and 35°C; between 15°C and 35°C; or between 20°C and 30°C. Performing separation operations at ambient temperature means that one or more of the following are at ambient temperature during execution of one or more operations: fluid in the system (e.g., solvent with plant extract), system components, and an environment surrounding the system components.

[0030] In some instances, the first nanofiltration membrane is optimized to perform under conditions with a fluid pressure of from 20 bar to 60 bar. In various implementations, the first nanofiltration membrane is optimized to perform under conditions where the pressure is from 25 bar to 55 bar; from 30 bar to 50 bar; from 40 bar to 60 bar; from 35 bar to 55 bar; from 35 bar to 50 bar; from 45 bar to 60 bar; from 35 bar to 40 bar; from 40 bar to 45 bar; from 45 bar to 50 bar; or from 50 bar to 55 bar.

[0031] In some instances, the second nanofiltration membrane is optimized to perform under conditions with a fluid pressure of from 20 bar to 60 bar. In various implementations, the second nanofiltration membrane is optimized to perform under conditions where the pressure is from 25 bar to 55 bar; from 30 bar to 50 bar; from 40 bar to 60 bar; from 35 bar to 55 bar; from 35 bar to 50 bar; from 45 bar to 60 bar; from 35 bar to 40 bar; from 40 bar to 45 bar; from 45 bar to 50 bar; or from 50 bar to 55 bar.

IV. Exemplary Methods of Operation

[0032] FIG. 1 shows example method 100 for separating a cannabinoid from a plant extract. Example method 100 includes providing plant extract in solvent (operation 102), performing a first nanofiltration operation (operation 104), and performing a second nanofiltration operation (operation 106). Typically, example method 100 does not include chilling the solvent with the plant extract to remove the wax, a process known as“winterization.” Other implementations can include more or different operations.

[0033] Example method 100 begins by providing plant extract in solvent. The plant extract includes wax material and one or more cannabinoid compounds. In some instances, the plant extract also includes lipids and chlorophyll. The solvent is selected from ethanol, methanol, acetone, water, and mixtures thereof. In some instances, the solvent is ethanol. In some instances, the solvent is a mixture of ethanol and water.

[0034] In some instances, example method 100 includes one or more operations to generate the plant extract in solvent (not shown in FIG. 1). For example, method 100 may additionally include extracting plant extract using supercritical carbon dioxide. Then the carbon dioxide may be removed to provide a solid extract. After removing the carbon dioxide, the solid extract may be dissolved in the solvent, thereby providing the plant extract in solvent. Other methods for providing plant extract in solvent are contemplated.

[0035] After providing plant extract in solvent (operation 102), a first nanofiltration operation is performed (operation 104). The first nanofiltration operation (operation 104) includes passing the plant extract in solvent to a first nanofiltration membrane, thereby generating a first retentate and a first permeate. The first retentate is enriched in wax material and the first permeate includes the solvent and one or more cannabinoid compounds. The first nanofiltration operation is performed at an input fluid pressure of from 20 bar to 60 bar and at a temperature of at least 15°C and no greater than 35°C.

[0036] Example first nanofiltration membranes are described in greater detail above, and include a silicone acrylate membrane layer on a polyimide support. The first nanofiltration membrane has a molecular weight cut off of from 400 g/mol to 900 g/mol.

[0037] In some instances, a decolorization operation is performed on the first permeate (not shown in FIG. 1) before performing the second nanofiltration operation (operation 106).

Broadly, decolorization includes one or more processes to remove unwanted pigments from the permeate. Example decolorization techniques include, for instance, passing the permeate over a substrate where pigment particles can adsorb, such as an activated carbon substrate. [0038] Next, a second nanofiltration operation is performed (operation 106). The second nanofiltration operation (operation 106) can include passing the first permeate from operation 104 through a second nanofiltration membrane, thereby providing a second retentate enriched in one or more cannabinoid compounds and a second permeate including the solvent.

[0039] Example second nanofiltration membranes are described in greater detail above, and typically have a molecular weight cut off of from 150 g/mol to 350 g/mol . Because the molecular weight of many cannabinoid compounds are in the range of about 350 Da, the second nanofiltration membrane can retain one or more cannabinoid compounds. The second permeate can also include terpenes.

[0040] In some instances, second permeate can be recycled and used in a subsequent process for separating cannabinoid from plant extract. In some instances, second permeate may be recycled back to an extraction stage. Recycling second permeate can significantly reduce the evaporation duty that is typically performed by rotavaps.

V. Exemplary Systems

[0041] FIG. 2 is a schematic diagram of example system 200 for separating cannabinoid from plant extract. Example system 200 may be used to perform one or more operations of method 100, discussed above. Other embodiments can include more or fewer components.

[0042] Example system 200 includes feed tank 202 that includes polar solvent and plant extract. The plant extract includes wax material and cannabinoid. Feed tank 202 can be configured to provide its contents to conduit 202, such as by one or more pumps, at a desired pressure. For instance, feed tank 202 can provide fluid to conduit 204 at a pressure of 20 bar to 60 bar. Typically, feed tank 202 provides fluid to conduit 204 at ambient temperature, which can include a temperature of at least 15°C and no greater than 35°C.

[0043] Conduit 204 is in fluid communication with feed tank 202 and includes a first nanofiltration membrane. Example first nanofiltration membranes are discussed in greater detail above. The first nanofiltration membrane has a molecular weight cut off of from 400 g/mol to 900 g/mol.

[0044] Conduit 204 discharges a first permeate and a first retentate. In some instances, the first permeate is provided to conduit 206. In some instances, the first permeate is sent to a tank (not shown) and then the first permeate is provided from the tank to conduit 206. The first permeate includes solvent and one or more cannabinoid compounds.

[0045] In some instances, the first retentate can be provided to feed tank 202. In some instances, the first retentate is sent to a waste collection apparatus. The first retentate can include wax material.

[0046] Conduit 206 includes a second nanofiltration membrane and separates one or more cannabinoid compounds from the solvent. Conduit 206 receives the first permeate at ambient temperature and at a pressure of from 20 bar to 60 bar.

[0047] Example second nanofiltration membranes are discussed in greater detail above. The second nanofiltration membrane has a molecular weight cut off of from 150 g/mol to 350 g/mol.

[0048] Conduit 206 discharges a second permeate and a second retentate. In some instances, the second permeate is provided to feed tank 202. In some instances, second permeate is provided to a waste collection apparatus. The second permeate typically is primarily solvent.

[0049] In some instances, the second retentate is provided to a collection tank. The second retentate includes one or more cannabinoid comounds.

VI. Example Experimental Data

[0050] Various experiments were conducted and are discussed below. Each test used the indicated membrane for separation of cannabinoid from waxes/lipids in plant extract, and none of the feeds were winterized prior to testing. These data are meant to be instructive and in no way are limiting.

A. Trial 1.

[0051] Evonik DuraMem 500 was used as the first nanofiltration membrane at pilot unit scale, using a spiral-wound module of the membranes. DuraMem 500 has a molecular weight cut off of 500 g/mol and includes a polyimide active membrane on a polypropylene support.

[0052] The size of the spiral-wound membranes was 1.8 inches in diameter and 12 inches in length. Ethanol was used as solvent and the average permeate flux was 1-2 liters/m ² /hr, and the average rejection of CB was 80%-85%. It was observed that the membranes experienced fouling and, once fouled, the membranes could not be cleaned effectively and the performance continued to be poor. It was hypothesized that the waxes and/or lipids in the plant extract caused irreversible fouling of the DuraMem membranes when used as a first nanofiltration membrane.

B. Trial 2

[0053] Fluid including waxes, lipids, and cannabinoid compounds was provided to a first nanofiltration membrane at the pilot scale, using a spiral-wound module of the membranes. The membrane was Evonik PuraMem S600, which is a membrane with a silicone acrylate membrane layer on a polyimide support. Evonik PuraMem S600 has a molecular weight cut-off of 600 g/mol.

[0054] The size of the spiral-wound membranes was 1.8 inches in diameter and 12 inches in length. Ethanol was used as solvent and the average permeate flux was 6.1 liters/m ² /hr (LMH). The CBD rejection rate was 0-2% and the waxes/lipids rejection rate was >99.0%. The pressure used was 40 bar.

C. Trial 3

[0055] Ethanol-based solvent including cannabinoid compound was provided to a second nanofiltration membrane at the pilot scale. Evonik DuraMem 300 was used as the second nanofiltration membrane. Evonik DuraMem 300 includes a polyimide membrane layer on a polypropylene support, and has a molecular weight cut off of 300 g/mol. The average permeate flux was 7.5 LMH at a pressure of 40 bar. The CBD rejection rate was 92-93%.

D. Trial 4

[0056] Ethanol-based solvent including cannabinoid compound was provided to a second nanofiltration membrane at the pilot scale. Evonik Duramem 200 was used as the second nanofiltration membrane. Evonik DuraMem 200 includes a polyimide membrane layer on a polypropylene support, and has a molecular weight cut off of 200 g/mol. The average Permeate Flux was 5.0 LMH at a pressure of 40 bar. The CBD rejection rate was >97%. E. Trial 5

[0057] Ethanol-based solvent including cannabinoid compound was provided to a second nanofiltration membrane at the pilot scale. Evonik DuraMem 500 was used as the second nanofiltration membrane. Evonik DuraMem 500 includes a polyimide membrane layer on a polypropylene support, and has a molecular weight cut off of 500 g/mol. At a feed pressure of 5 bar, the permeate flux was 1.5 LMH with a CBD rejection rate of 10%. At a feed pressure greater than 5 bar, the permeate flux was 5 LMH with a CBD rejection greater than 70%.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present document, including definitions, will control. Example methods and materials are described below, although methods and materials similar or equivalent to those described herein can be used in practice or testing of the present disclosure. The materials, methods, and examples disclosed herein are illustrative only and not intended to be limiting.

[0059] The terms“comprise(s),”“include(s),”“having,”“has, ”“can,”“contain(s),” and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that do not preclude the possibility of additional acts or structures. The singular forms“a,” “an” and“the” include plural references unless the context clearly dictates otherwise. The present disclosure also contemplates other embodiments“comprising,”“consisting of’ and “consisting essentially of,” the embodiments or elements presented herein, whether explicitly set forth or not.

[0060] For the recitation of numeric ranges herein, each intervening number there between with the same degree of precision is explicitly contemplated. For example, for the range of 6-9, the numbers 7 and 8 are contemplated in addition to 6 and 9, and for the range 6.0-7.0, the number 6.0, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9, and 7.0 are explicitly contemplated. For example, when a pressure range is described as being between ambient pressure and another pressure, a pressure that is ambient pressure is expressly contemplated.