A method for extracting glyphosate from glyphosate mother liquor using high-pressure supercritical carbon dioxide

Abstract

The present invention provides a method for extracting glyphosate from a glyphosate mother liquor using high-pressure supercritical carbon dioxide. After carbon dioxide is pumped into the glyphosate mother liquor, supercritical carbon dioxide extraction is performed under high-pressure conditions to separate glyphosate from the glyphosate mother liquor. The pH value of the glyphosate mother liquor is adjusted to 2-6 before the carbon dioxide is pumped into the glyphosate mother liquor, and the pH regulator includes an alkali metal hydroxide. The present invention improves the extraction rate of glyphosate in the mother liquor through supercritical carbon dioxide extraction. The method is simple to operate, uses less solvent, is easy to separate, has low environmental pollution during the production process, is suitable for industrial production, can effectively extract glyphosate from the mother liquor, and the obtained product has high purity. Glyphosate crystals are directly obtained after cooling and crystallization. Compared with traditional extraction techniques, the method of the present invention adopts high-pressure supercritical carbon dioxide extraction technology, which increases the polarity range of the extract, reduces the operating temperature, shortens the extraction time, and improves the extraction efficiency.

Description

Technical Field

[0001] The invention discloses a method for extracting glyphosate from glyphosate mother liquor with high-pressure supercritical carbon dioxide, belonging to the technical field of extraction and separation. Background Art

[0002] Glyphosate is currently the most widely used herbicide in the world. It boasts high efficacy, low toxicity, a broad spectrum, and a non-selective nature. It dissolves the waxy surface layer of weed leaves, branches, and stems, allowing the drug to rapidly enter the plant's transport system and kill the weeds. Its excellent biological properties have established its position in the pesticide market and rapidly gained industry adoption. According to literature, glyphosate can be synthesized using a variety of methods, with the two most prevalent domestic production processes being the alkyl ester method (glycine method) and the iminodiacetic acid method (IDA method). In my country, approximately 70% of glyphosate production capacity is produced using the alkyl ester method. The production process primarily involves depolymerization, addition, condensation, acid hydrolysis, and crystallization. The basic principle is that paraformaldehyde, glycine, and dimethyl phosphite react in the presence of methanol as a solvent and triethylamine as a catalyst to produce a synthetic solution primarily composed of an organophosphorus intermediate. This solution is then hydrolyzed under acidic conditions to produce glyphosate, which is then crystallized and separated to yield glyphosate technical that meets national standards. The acid mother liquor is the liquid obtained after solid-liquid separation of the glyphosate. After analysis and testing, the content of glyphosate in the mother liquor under the process conditions is about 0.8~1.5%.

[0003] Previous research on glyphosate mother liquors has mostly used traditional extraction processes, using triethylamine as the extractant. The specific process involves adding an excess of triethylamine to the mother liquor, which results in the mother liquor separating into two layers: a lower layer containing concentrated glyphosate mother liquor and an upper layer containing a triethylamine salt solution. Key challenges with traditional extraction techniques include high operating temperatures (approximately 100°C), low glyphosate extraction yields, and a low glyphosate content (2-3%) in the resulting concentrated mother liquor. This makes direct conversion to glyphosate products difficult, hindering scale-up production and cost control.

[0004] Supercritical CO2 extraction is an advanced separation technology widely used in the pharmaceutical, food, fragrance, petrochemical, and environmental fields. It boasts high efficiency, environmental friendliness, and low energy consumption. By utilizing the properties of supercritical fluids, the desired components are dissolved under high-density conditions (low temperature, high pressure). These components are then separated from the extractant under reduced density conditions.

[0005] To date, there have been no reports on the extraction of glyphosate from glyphosate mother liquor using supercritical carbon dioxide extraction technology. Therefore, utilizing the advantages of supercritical carbon dioxide extraction technology to extract glyphosate components from mother liquor is a topic that urgently needs research. Summary of the Invention

[0006] The invention provides a method for extracting glyphosate from a glyphosate mother liquor using high-pressure supercritical carbon dioxide. The method is simple to operate and easy to control parameters, suitable for scaled-up production, and has a high glyphosate extraction transfer rate and few impurity components.

[0007] The technical solution of the present invention provides a method for extracting glyphosate from a glyphosate mother liquor using high-pressure supercritical carbon dioxide. After carbon dioxide is pumped into the glyphosate mother liquor, supercritical carbon dioxide extraction is performed under high-pressure conditions to separate glyphosate from the glyphosate mother liquor.

[0008] For those skilled in the art, the extraction is carried out in an extraction kettle, which is an extraction reactor conventionally understood by those skilled in the art, such as a high-pressure extraction kettle. The present invention uses a two-extraction two-part circulation high-pressure extraction kettle, the equipment model is HA220-50-06, and the working pressure is ≤50 Mpa.

[0009] In the extraction process, the glyphosate mother liquor is first charged into the extraction kettle, and then the extraction process is carried out.

[0010] The pH value of the glyphosate mother liquor is adjusted to 2-6 before being pumped into the carbon dioxide, and the pH regulator includes an alkali metal hydroxide.

[0011] In some preferred embodiments, the pH of the glyphosate mother liquor in the extraction kettle can be adjusted to any value between 2 and 6. In some preferred embodiments, the pH is adjusted to 5 to 5.5. The pH adjuster can be sodium hydroxide or potassium hydroxide; it can also be a sodium or potassium alkoxide, such as sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium propoxide, potassium propoxide, sodium butoxide, or potassium butoxide. The mass concentration of the sodium hydroxide or potassium hydroxide can be 30-50% to achieve the desired pH condition.

[0012] During the supercritical carbon dioxide extraction process, the material temperature is adjusted to 40-100°C, and the pressure in the extraction kettle is 20-50 MPa. In some embodiments, this process is achieved by first adjusting the glyphosate mother liquor in the extraction kettle to a temperature anywhere between 40-100°C, then pumping carbon dioxide into the extraction kettle. The pressure in the extraction kettle is then controlled to 20-50 MPa while maintaining the temperature at 40-100°C, and the extraction process is carried out under this stable pressure. Furthermore, the extraction time can be calculated based on the controlled temperature and pressure conditions.

[0013] More preferably, the temperature in the extraction kettle is controlled at 50° C. and the pressure is controlled at 40 MPa.

[0014] The extraction time is 20 to 60 minutes, and more preferably the extraction time is 40 minutes.

[0015] After the extraction is completed, the carbon dioxide fluid containing the saturated target separation substance (glyphosate) enters the separation kettle. Due to the pressure drop and temperature change, the carbon dioxide and glyphosate quickly become two phases (gas-liquid separation) and are immediately separated. The gaseous carbon dioxide flows into the storage tank for recycling, and the liquid glyphosate extract is directly discharged from the lower layer of the separation kettle. After cooling and crystallization, glyphosate is filtered to obtain glyphosate.

[0016] In some embodiments, the separation is performed in a separation kettle, which can be a distillation reactor or a separation tower.

[0017] Specifically, the materials after extraction and stratification are pumped into a separation kettle for separation. The temperature during the separation process is 40-100°C and the pressure is 20-50 MPa. That is, the temperature of the materials in the separation kettle is controlled at 40-100°C and the pressure in the separation kettle is controlled at 20-50 MPa.

[0018] More preferably, the temperature of the material in the separation kettle is controlled at 55° C., and the pressure in the separation kettle is controlled at 35 MPa.

[0019] In some embodiments, the extraction process further includes pumping an entrainer into the extraction kettle after achieving stable extraction temperature and pressure, and separating the temperature and pressure during the separation process, to achieve a stable cyclic extraction process. The entrainer can be pumped into the glyphosate mother liquor together with carbon dioxide for extraction.

[0020] The entrainer is a mixed solution of triethylamine and alcohol, wherein the volume percentages of triethylamine and alcohol are 85-95% and 15-5% respectively; the alcohol is selected from a C1-C5 alcohol solution.

[0021] More preferably, the entrainer is a mixed solution of methanol and triethylamine, with the volume percentages of methanol and triethylamine being 90% and 10%.

[0022] The volume ratio of the entrainer to the glyphosate mother solution is 1-5: 1. More preferably, the volume ratio of the entrainer to the glyphosate mother solution is 2:1.

[0023] In some embodiments, a conventional cooling crystallization step of glyphosate is also included, that is, a step well known in the art of cooling the obtained glyphosate extract in water to below 10° C. for crystallization.

[0024] Another object of the present invention is to provide a method for cyclically extracting glyphosate from a glyphosate mother liquor using high-pressure supercritical carbon dioxide. After carbon dioxide is pumped into the glyphosate mother liquor, supercritical carbon dioxide extraction is performed under high-pressure conditions, followed by separation. After separation, glyphosate technical and an isolate are obtained. The isolate is then injected into the glyphosate mother liquor together with carbon dioxide to achieve cyclic extraction.

[0025] In some embodiments, a glyphosate mother liquor is charged into an extraction kettle of a high-pressure supercritical carbon dioxide extraction device. The temperatures of the extraction kettle and the separation kettle are waited for to reach set values, carbon dioxide is pumped into the extraction kettle, and after adjusting the pressure valves to stabilize the pressures in the extraction kettle and the separation kettle, a cyclic extraction is started. After the set temperature and pressure parameters in the extraction kettle and the separation kettle are stabilized, an entrainer is pumped in and a timer is started. The amount of entrainer used is 1 to 3 ml per 1 ml of glyphosate mother liquor. After extraction and separation, the resulting material is separated and fed into the separation kettle. The glyphosate extract is discharged from the separation kettle and collected. Glyphosate crystals are obtained after cooling and crystallization. The remaining material after extraction and separation is returned to the carbon dioxide feed device and fed into the extraction kettle together with the material, completing the cyclic process.

[0026] The extraction is carried out in an extraction kettle, which is an extraction reactor conventionally understood by those skilled in the art, such as a high-pressure extraction kettle. The present invention uses a two-extraction two-part circulation high-pressure extraction kettle, the equipment model is HA220-50-06, and the working pressure is ≤50 Mpa.

[0027] In the extraction process, the glyphosate mother liquor is first charged into the extraction kettle, and then the extraction process is carried out.

[0028] The pH value of the glyphosate mother liquor is adjusted to 2-6 before being pumped into the carbon dioxide, and the pH regulator includes an alkali metal hydroxide.

[0029] The pH of the glyphosate mother liquor in the extraction kettle is adjusted to any value between 2 and 6. In some preferred embodiments, the pH is adjusted to 2. The pH adjuster can be sodium hydroxide or potassium hydroxide; it can also be sodium or potassium alkoxides, such as sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium propoxide, potassium propoxide, sodium butoxide, or potassium butoxide. The mass concentration of the sodium hydroxide or potassium hydroxide can be 30-50% to achieve the desired pH.

[0030] During the supercritical carbon dioxide extraction process, the material temperature is adjusted to 40-100°C, and the pressure in the extraction kettle is 20-50 MPa. In some embodiments, this process is achieved by first adjusting the glyphosate mother liquor in the extraction kettle to a temperature anywhere between 40-100°C, then pumping carbon dioxide into the extraction kettle. The pressure in the extraction kettle is then controlled to 20-50 MPa while maintaining the temperature at 40-100°C, and the extraction process is carried out under this stable pressure. Furthermore, the extraction time can be calculated based on the controlled temperature and pressure conditions.

[0031] More preferably, the temperature in the extraction kettle is controlled at 50° C. and the pressure is controlled at 40 MPa.

[0032] The extraction time is 20 to 60 minutes, and more preferably the extraction time is 40 minutes.

[0033] After the extraction is completed, the carbon dioxide fluid containing the saturated target separation substance (glyphosate) enters the separation kettle. Due to the pressure drop and temperature change, the carbon dioxide and glyphosate quickly become two phases (gas-liquid separation) and are immediately separated. The gaseous carbon dioxide flows into the storage tank for recycling, and the liquid glyphosate extract is directly discharged from the lower layer of the separation kettle. After cooling and crystallization, glyphosate is filtered to obtain glyphosate.

[0034] In some embodiments, the separation is performed in a separation kettle, which can be a distillation reactor or a separation tower.

[0035] Specifically, the materials after extraction and stratification are pumped into a separation kettle for separation. The temperature during the separation process is 40-100°C and the pressure is 20-50 MPa. That is, the temperature of the materials in the separation kettle is controlled at 40-100°C and the pressure in the separation kettle is controlled at 20-50 MPa.

[0036] More preferably, the temperature of the material in the separation kettle is controlled at 55° C., and the pressure in the separation kettle is controlled at 35 MPa.

[0037] In some embodiments, the extraction process further includes pumping an entrainer into the extraction kettle after achieving stable extraction temperature and pressure, and separating the temperature and pressure during the separation process, to achieve a stable cyclic extraction process. The entrainer can be pumped into the glyphosate mother liquor together with carbon dioxide for extraction.

[0038] The entrainer is a mixed solution of triethylamine and alcohol, wherein the volume percentages of triethylamine and alcohol are 85-95% and 15-5% respectively; the alcohol is selected from a C1-C5 alcohol solution.

[0039] More preferably, the entrainer is a mixed solution of methanol and triethylamine, with the volume percentages of methanol and triethylamine being 90% and 10%.

[0040] The volume ratio of the entrainer to the glyphosate mother solution is 1-5: 1. More preferably, the volume ratio of the entrainer to the glyphosate mother solution is 2:1.

[0041] In some embodiments, a conventional cooling crystallization step of glyphosate is also included, that is, a step well known in the art of cooling the obtained glyphosate extract in water to below 10° C. for crystallization.

[0042] Compared with the prior art, the present invention has the following beneficial effects: The present invention improves the extraction rate of glyphosate from the mother liquor through supercritical carbon dioxide extraction. The method is simple to operate, uses less solvent, is easy to separate, and has low environmental pollution during the production process. It is suitable for industrial production and can effectively extract glyphosate from the mother liquor. The resulting product is high in purity, and glyphosate crystals are directly obtained after cooling and crystallization. Compared with traditional extraction techniques, the method of the present invention utilizes high-pressure supercritical carbon dioxide extraction technology, which increases the polarity range of the extract, reduces the operating temperature, shortens the extraction time, and improves the extraction efficiency. Using the technical solution of the present application, a glyphosate extraction rate of 70% or more can be achieved, more preferably 80% or more, more preferably 82% or more, and even more preferably 90% or more can be achieved. DETAILED DESCRIPTION

[0043] The present invention is further described below with reference to the following examples. However, the scope of protection claimed in the present invention is not limited to the scope described in the examples.

[0044] The glyphosate mother liquor described in the present invention is obtained from the glycine process production workshop of Yichang Taisheng Chemical Co., Ltd., and contains approximately 1.0-2.0% glyphosate and has a pH of approximately 1.0. The method for extracting glyphosate from the glyphosate mother liquor using high-pressure supercritical carbon dioxide employs a cyclic extraction process. The extraction kettles are parallel-separated, and the extracted material enters a separation kettle. The separation kettles are two-stage, series-connected separation kettles.

[0045] Comparative Example 1

[0046] 500 ml of glyphosate acid mother liquor was collected and tested for a glyphosate content of 1.20%. 150.31 g of 50% sodium hydroxide solution was added for neutralization, and the pH was measured to be 5.5. The mixture was heated to 100°C, and 570 g of triethylamine was added as an extractant. The mixture was allowed to stand for separation, and the upper layer, after separation, became a triethylamine salt solution. After stirring, the pH was measured to be 8.2. After standing for 2 hours and cooling, the glyphosate mother liquor separated into two layers: the upper layer was a triethylamine salt solution, and the lower layer was a concentrated glyphosate mother liquor with a content of approximately 2.44%. Based on the glyphosate content in the glyphosate mother liquor and the extracted glyphosate content, the glyphosate extraction yield in this example was 66.38% and the content was 94.85%. The triethylamine salt solution obtained by separation was conventionally recovered to form a triethylamine-containing solution, which was then reused. After 13 cycles, the content was 89.85% and the extraction yield was 34.25%.

[0047] Example 1

[0048] A method for extracting glyphosate from a glyphosate mother liquor using high-pressure supercritical carbon dioxide is disclosed. 500 ml of glyphosate acid mother liquor is measured to contain 1.24% glyphosate. 145.78 grams of 50% sodium hydroxide solution is added for neutralization, and the pH is measured to be 5.0. The extraction kettle and separation kettle are heated separately. When the temperatures of the extraction kettle and separation kettle reach 50°C and 55°C, respectively, carbon dioxide is pumped into the extraction kettle using a high-pressure pump. The valves are adjusted to achieve pressures of 40 MPa and 35 MPa, respectively, and a cyclic extraction process is initiated. The extraction process lasts for 40 minutes. After completion of the extraction, the upper layer of the extraction kettle is transferred to the separation kettle. After separation, the glyphosate extract is discharged from the separation kettle and collected. After cooling and crystallization, the glyphosate extract is filtered to obtain glyphosate. Analysis and testing revealed that the extracted glyphosate technical weighed 3.90 g and contained 96.56% glyphosate. The calculated glyphosate extraction yield for this example is 70.53%.

[0049] Example 2

[0050] A method for extracting glyphosate from a glyphosate mother liquor using high-pressure supercritical carbon dioxide is disclosed. 500 ml of glyphosate acid mother liquor is taken, and the glyphosate content is determined to be 1.25%. 145.25 g of 50% sodium hydroxide solution is added for neutralization, and the pH is determined to be 5.3. The extraction kettle and separation kettle are heated separately. When the temperatures of the extraction kettle and separation kettle reach 50°C and 55°C, respectively, carbon dioxide is pumped into the extraction kettle using a high-pressure pump. The valves are adjusted to achieve pressures of 40 MPa and 35 MPa, respectively, and a cyclic extraction process is initiated. After the pressure and temperature of the extraction kettle and separation kettle stabilize, an entrainer (a mixed solution of methanol and triethylamine, with the volume percentages of methanol and triethylamine being 90% and 10% respectively) is pumped in, and a timer is started. The entrainer dosage is 2 ml per 1 ml of mother liquor, and the extraction time is 40 minutes. After the extraction is completed, the upper layer of the extraction kettle is transferred to the separation kettle. After separation, the glyphosate extract is discharged from the separation kettle and collected. The glyphosate extract is cooled, crystallized, and filtered to obtain glyphosate. Analysis and testing revealed that the extracted glyphosate technical weighed 5.07 g and contained 97.50% glyphosate, resulting in a calculated glyphosate extraction yield of 91.78% for this example. After 20 cycles, 4.96 g of glyphosate was extracted from the same batch of mother liquor, with a content of 96.98% and an extraction yield of 89.36%.

[0051] Example 3

[0052] A method for extracting glyphosate from a glyphosate mother liquor using high-pressure supercritical carbon dioxide is disclosed. 500 ml of glyphosate acid mother liquor is taken, and the glyphosate content is determined to be 1.18%. 149.15 g of 50% sodium hydroxide solution is added for neutralization, and the pH is determined to be 5.1. The extraction kettle and separation kettle are heated separately. When the temperatures of the extraction kettle and separation kettle reach 40°C and 50°C, respectively, carbon dioxide is pumped into the extraction kettle using a high-pressure pump. The valves are adjusted to achieve pressures of 50 MPa and 40 MPa, respectively, and a cyclic extraction process is initiated. After the pressure and temperature of the extraction kettle and separation kettle stabilize, an entrainer (a mixed solution of methanol and triethylamine, with the volume percentages of methanol and triethylamine being 90% and 10%, respectively) is pumped in, and a timer is started. The entrainer dosage is 2 ml per 1 ml of mother liquor, and the extraction time is 40 minutes. After the extraction is completed, the upper layer of the extraction kettle is transferred to the separation kettle. After separation, the glyphosate extract is discharged from the separation kettle and collected. The glyphosate extract is cooled, crystallized, and filtered to obtain glyphosate. Analysis revealed that the extracted glyphosate technical weighed 4.31 g and contained 97.31% glyphosate, resulting in a calculated glyphosate extraction yield of 82.53% for this example. After 20 cycles, 4.18 g of glyphosate was extracted from the same batch of mother liquor, with a content of 97.18% and an extraction yield of 79.81%.

[0053] Example 4

[0054] A method for extracting glyphosate from a glyphosate mother liquor using high-pressure supercritical carbon dioxide is disclosed. 500 ml of glyphosate acid mother liquor is taken, and the glyphosate content is determined to be 1.21%. 146.75 grams of 50% sodium hydroxide solution is added for neutralization, and the pH is determined to be 5.5. The extraction kettle and separation kettle are heated separately. When the temperatures of the extraction kettle and separation kettle reach 50°C and 55°C, respectively, carbon dioxide is pumped into the extraction kettle using a high-pressure pump. The valves are adjusted to achieve pressures of 40 MPa and 35 MPa, respectively, and a cyclic extraction process is initiated. After the pressures and temperatures of the extraction kettle and separation kettle stabilize, an entrainer (a mixed solution of methanol and triethylamine, with the volume percentages of methanol and triethylamine being 90% and 10%, respectively) is pumped in, and a timer is started. The entrainer dosage is 2 ml per ml of mother liquor, and the extraction time is 20 minutes. After the extraction is completed, the upper layer of the extraction kettle is transferred to the separation kettle. After separation, the glyphosate extract is discharged from the separation kettle and collected. The glyphosate extract is cooled, crystallized, and filtered to obtain glyphosate. Analysis and testing revealed that the extracted glyphosate technical weighed 4.31 g and contained 96.92% glyphosate, resulting in a calculated glyphosate extraction rate of 80.11% for this example. After 20 cycles, 4.21 g of glyphosate was extracted from the same batch of mother liquor, with a content of 96.88% and an extraction rate of 78.21%.

[0055] The above embodiments are merely preferred technical solutions of the present invention and should not be construed as limiting the present invention. The embodiments and features in the embodiments of this application may be arbitrarily combined with each other unless they conflict. The scope of protection of the present invention shall be the technical solutions described in the claims, including equivalent alternatives to the technical features of the technical solutions described in the claims. Equivalent alternatives and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for extracting glyphosate from glyphosate mother liquor using high-pressure supercritical carbon dioxide, characterized in that: After carbon dioxide is pumped into the glyphosate mother liquor, the material temperature is adjusted to 40-100°C, and supercritical carbon dioxide extraction is performed at a pressure of 20-50 MPa in the extraction kettle to separate glyphosate from the glyphosate mother liquor. The pH value of the glyphosate mother liquor is adjusted to 2-6 before carbon dioxide is pumped into the glyphosate mother liquor.

2. The method for extracting glyphosate from glyphosate mother liquor using high-pressure supercritical carbon dioxide according to claim 1, characterized in that: The pH adjuster includes an alkali metal hydroxide.

3. The method for extracting glyphosate from glyphosate mother liquor using high-pressure supercritical carbon dioxide according to claim 2, characterized in that: After the extraction is completed, the extracted and layered materials are separated to obtain a glyphosate extract. The glyphosate extract is cooled, crystallized, and then filtered to obtain glyphosate.

4. The method for extracting glyphosate from glyphosate mother liquor using high-pressure supercritical carbon dioxide according to claim 3, characterized in that: The temperature during the separation process is 40-100° C. and the pressure is 20-50 MPa.

5. The method for extracting glyphosate from glyphosate mother liquor using high-pressure supercritical carbon dioxide according to claim 1, characterized in that: The extraction process is a cyclic extraction process, and the extraction process also includes adding an entrainer, and the entrainer is selectively pumped into the glyphosate mother liquor together with carbon dioxide for extraction.

6. The method for extracting glyphosate from glyphosate mother liquor using high-pressure supercritical carbon dioxide according to claim 5, characterized in that: The entrainer is a mixed solution of triethylamine and alcohol, and the volume percentages of triethylamine and alcohol are 15%-5%:85-95%.

7. The method for extracting glyphosate from glyphosate mother liquor using high-pressure supercritical carbon dioxide according to claim 6, characterized in that: The alcohol is selected from C1-C5 alcohol solutions.

8. The method for extracting glyphosate from glyphosate mother liquor using high-pressure supercritical carbon dioxide according to claim 5, characterized in that: The volume ratio of the entrainer to the glyphosate mother liquor is 1-5:

1.

9. The method for extracting glyphosate from glyphosate mother liquor with high-pressure supercritical carbon dioxide according to any one of claims 1 to 8, characterized in that: After carbon dioxide is pumped into the glyphosate mother liquor, supercritical carbon dioxide extraction and separation are performed under high-pressure conditions. After separation, glyphosate technical and isolate are obtained. The isolate is injected into the glyphosate mother liquor together with carbon dioxide to achieve cyclic extraction.