A method for preparing glufosinate-ammonium salt

Abstract

This invention provides a method for preparing refined glufosinate. Unlike existing technologies that use glufosinate as a raw material, this method specifically uses crude 4-(hydroxymethylphosphono)-2-carbonylbutyric acid (containing oxalic acid) as the raw material. Based on this raw material, this invention specifically adds an alkaline reaction to pre-remove oxalate, resulting in oxalic acid residue <0.05%. When the specific alkaline is not ammonia, ammonia of at least the molar amount of the raw material needs to be added. Further alkaline is added to adjust the pH, and the mixture is continuously fed into a one-step enzymatic conversion system to obtain the corresponding refined glufosinate. Compared to the traditional process of preparing refined glufosinate using racemic glufosinate technical powder through a two-step enzymatic catalysis, this method features simpler processes, lower production costs, and greater applicability.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, specifically relating to a method for preparing glufosinate-ammonium salt. Background Technology

[0002] L-glufosinate, also known as L-form glufosinate, is a broad-spectrum, contact, and non-selective herbicide. As an L-amino acid, it binds to the active site of glutamine synthase (GS), inhibiting glutamine synthesis, leading to excessive ammonia accumulation in plants, nitrogen metabolism disorders, chloroplast disintegration, and ultimately, plant death. Compared to glufosinate, L-glufosinate has advantages such as higher herbicidal activity, lower dosage, and greater environmental friendliness. Current technologies for the preparation of L-glufosinate have been researched.

[0003] Patent CN107502647A uses D,L-glufosinate as a raw material, oxidizing it to 4-(hydroxymethylphosphono)-2-carbonylbutyric acid via D-amino acid oxidase, and then catalytically reducing it back to L-glufosinate via amino acid dehydrogenase. However, the oxidation of D-glufosinate to 4-(hydroxymethylphosphono)-2-carbonylbutyric acid by D-amino acid oxidase generates hydrogen peroxide, which easily leads to the inactivation of the enzyme protein and the decomposition of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid. Although hydrogen peroxide can be removed by adding additional catalase, it cannot completely eliminate the adverse effects of hydrogen peroxide, and the use of catalase increases additional costs.

[0004] US patent application US20180030487A1 also oxidizes D-glufosinate to 4-(hydroxymethylphosphono)-2-carbonylbutyric acid using D-amino acid oxidase, and then uses a stereoselective transamination reaction catalyzed by L-amino acid transaminase (L-TA) to convert 4-(hydroxymethylphosphono)-2-carbonylbutyric acid into glufosinate. The transaminase process described in this patent document has advantages such as high enzyme activity and high stereoselectivity, but it also has two major drawbacks: First, the transaminase catalytic step is an equilibrium reaction, requiring an excess of amino donors (amino acids or organic amines) to ensure a high conversion rate (3 equivalent amino donors, 90% conversion). Excess amino donors and corresponding byproducts will severely affect subsequent separation and purification steps. Second, in the synthesis of glufosinate, material decomposition can affect the smooth progress of the reaction, thus impacting the conversion rate. Furthermore, if the reaction system contains impurities, such as oxalic acid, which cannot be effectively removed, it may trigger multiple chain reactions, affecting key indicators such as enzyme catalytic activity, product purity, and physicochemical stability. Currently, the preparation of different types of glufosinate salts also faces certain challenges. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for preparing glufosinate-ammonium salts. This preparation method can simplify the synthesis steps, solve the problem of material decomposition and improve the conversion rate, and realize the effective preparation of different glufosinate-ammonium salts, which has important theoretical and practical application value.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] This invention provides a method for preparing glufosinate-ammonium salt, comprising the following steps:

[0008] S1: Adjust the pH of the aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid to 3-6 using a desalting alkali. The solid precipitates out, and the solution is filtered to obtain an aqueous solution of PPO.

[0009] The desalting alkali includes ammonia, and the molar amount of ammonia in the obtained PPO aqueous solution is not less than the molar amount of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid;

[0010] Alternatively, the desalting alkali does not include ammonia. After filtration, ammonia is added separately to the PPO aqueous solution, and the molar amount of ammonia in the PPO aqueous solution is controlled to be not less than the molar amount of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid.

[0011] S2: Adjust the pH of an aqueous PPO solution with an ammonia molar amount not less than that of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid molar amount to 6-9 using an alkali to obtain a PPO salt solution;

[0012] S3: PPO salt solution is continuously fed into the enzyme catalytic conversion system and subjected to heat preservation reaction. After post-processing, glufosinate is obtained.

[0013] Preferably, in the aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid, the mass content of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid is 5~80 wt%.

[0014] Preferably, in the aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid, the mass content of oxalic acid is 0.1~10 wt%.

[0015] Preferably, the desalting alkali or alkali is independently selected from any one or more of ammonia, ammonia water, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, monomethylamine, dimethylamine, isopropylamine, or monoethanolamine.

[0016] Preferably, the desalting alkali or alkali is introduced independently in the form of a solid or an aqueous solution, wherein the mass concentration of the aqueous solution is 5-99.9%.

[0017] Preferably, the temperature for adjusting the pH using desalination alkali in step S1 is 0~35℃.

[0018] Preferably, step S2 is carried out in a continuous reactor.

[0019] Preferably, in the continuous reactor, the PPO aqueous solution and the alkali are mixed at a temperature of 0~35°C.

[0020] Preferably, the enzyme catalytic conversion system is a solution containing amino acid dehydrogenase, isopropanol dehydrogenase, isopropanol, and coenzyme.

[0021] Preferably, the mass of the amino acid dehydrogenase or isopropanol dehydrogenase is 1-15% of the mass of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid, the mass of the coenzyme is 0.01-5% of the mass of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid, and the mass of the isopropanol is 33-100% of the mass of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid.

[0022] Preferably, the continuous feeding time is 1~24 h, and the temperature of the heat preservation reaction is 35~45℃.

[0023] Preferably, the post-processing is as follows: after filtration and concentration, glufosinate-ammonium salt technical material is obtained, and then crystallized to obtain glufosinate-ammonium salt.

[0024] Preferably, the solvent used for crystallization is selected from any one or more of methanol, ethanol, isopropanol, n-butanol, n-hexane, acetonitrile, or toluene.

[0025] Preferably, the glufosinate is any one or more of glufosinate ammonium salt, glufosinate sodium salt, glufosinate potassium salt, glufosinate monomethylamine salt, glufosinate dimethylamine salt, glufosinate isopropylamine salt, or glufosinate monoethanolamine salt.

[0026] Preferably, the purity of the glufosinate is above 98.5%, the oxalic acid content is below 0.05%, and the yield is above 97%.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] The method for preparing refined glufosinate salt provided by this invention differs from existing technologies that use glufosinate as a raw material. This invention specifically uses crude 4-(hydroxymethylphosphono)-2-carbonylbutyric acid (containing oxalic acid) as the raw material. This method offers advantages such as a wide availability of raw materials, low cost, direct connection to upstream synthesis processes, elimination of complex purification processes, and significant reduction in raw material pretreatment costs. Based on this raw material, this invention further incorporates a desalination alkali reaction to pre-remove oxalate, resulting in oxalic acid residue of <0.05%. Then, alkali is added to adjust the pH and the mixture is continuously fed into a one-step enzymatic catalytic conversion system to obtain the corresponding refined glufosinate salt. Compared to the traditional process of preparing refined glufosinate using racemic glufosinate technical powder via a two-step enzymatic catalysis, this method is simpler, has lower production costs, and is more applicable. Attached Figure Description

[0029] Figure 1 The chromatogram of glufosinate prepared in Example 1 was obtained after testing according to the national standard GB / T 43172-2023.

[0030] Figure 2 The chromatogram of the sample prepared in Example 1 using the oxalic acid quantitative test method of the present invention is shown below.

[0031] Figure 3 The chromatogram of the oxalic acid standard obtained by the quantitative oxalic acid test method of the present invention is shown. Detailed Implementation

[0032] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0033] It should be noted that 4-(hydroxymethylphosphono)-2-carbonylbutyric acid is abbreviated as PPO.

[0034] In this invention, the “PPO aqueous solution” mentioned below refers to the aqueous solution obtained after filtering out the oxalate from an aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid.

[0035] This invention provides a method for preparing glufosinate-ammonium salt, comprising the following steps:

[0036] S1: Adjust the pH of the aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid to 3-6 using a desalting alkali. The solid precipitates out and is filtered to obtain an aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid.

[0037] It should be noted that desalination and alkali removal fall into the following two categories:

[0038] When the desalting alkali includes ammonia, it is preferable to control the molar amount of ammonia in the obtained PPO aqueous solution to be not less than the molar amount of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid;

[0039] Alternatively, when the desalting alkali does not include ammonia, after filtration, it is preferable to add ammonia separately to the PPO aqueous solution, controlling the molar amount of ammonia in the PPO aqueous solution to be not less than the molar amount of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid;

[0040] The purpose of the above operation is to control the molar amount of ammonia in the PPO aqueous solution to be no less than the molar amount of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid, because the conversion of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid to glufosinate requires at least an ammonia molar amount equal to that of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid;

[0041] S2: Adjust the pH of an aqueous PPO solution with an ammonia molar amount not less than that of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid molar amount to 6-9 using an alkali to obtain a PPO salt solution;

[0042] S3: PPO salt solution is continuously fed into the enzyme catalytic conversion system and subjected to heat preservation reaction. After post-processing, glufosinate is obtained.

[0043] According to this invention, the raw material is first provided as an aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid, which can be prepared using oxalate ester as a raw material. Compared with the conventional prior art that uses glufosinate as a raw material, this invention specifically uses crude 4-(hydroxymethylphosphono)-2-carbonylbutyric acid (containing oxalic acid) as a raw material, which can directly utilize the feed solution from the upstream synthesis, eliminating the separation, purification, and drying steps in the preparation of solid glufosinate, significantly reducing raw material costs and the complexity of pretreatment processes.

[0044] The present invention does not impose any particular limitation on the method for preparing an aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid from oxalate esters; the preparation can be carried out in accordance with methods well known to those skilled in the art.

[0045] In some embodiments of the present invention, the aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid has a mass content of 5-80 wt%, such as 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, or 80 wt%. The aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid has a mass content of 0.1-10 wt%, such as 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%.

[0046] According to this invention, preferably, the pH of an aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid is adjusted to 3-6 using a desalting alkali. The pH can be 3, 3.5, 4, 4.5, 5, 5.5, or 6, etc., causing solid precipitation. After filtration, a desalted PPO aqueous solution is obtained. The reason for adjusting the pH to 3-6 in this invention is to utilize the common ion effect and the stronger acidity of oxalic acid compared to other carboxylic acids. The solubility of oxalate in the presence of carboxylic acid compounds varies with pH. By controlling the amount of alkali, oxalic acid can be precipitated out as oxalate, thereby achieving efficient separation of oxalate from 4-(hydroxymethylphosphono)-2-carbonylbutyric acid in the system, resulting in oxalic acid residue of <0.05% after removal.

[0047] In some embodiments of the present invention, it is preferred that the pH of the aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid is adjusted using a desalting alkali at a temperature of 0~35°C, preferably 0~30°C, more preferably 0~20°C, even more preferably 0~10°C, and even more preferably 2~10°C.

[0048] The present invention preferably controls the above temperature to be 0~35℃, because the decomposition rate of PPO is slow in this temperature range. If it is below 0℃, the solution will freeze; conversely, if it is above 35℃, the decomposition rate of PPO will be accelerated.

[0049] The desalination alkali can be selected from any one or more of ammonia gas, ammonia water, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, monomethylamine, dimethylamine, isopropylamine, or monoethanolamine. The mass fraction of the ammonia water is 5-30%, such as 5%, 10%, 15%, 20%, 25%, or 30%.

[0050] Specifically, the desalination alkali can be introduced in the form of a solid or an aqueous solution. When introduced in the form of an aqueous solution, the mass concentration of the aqueous solution is preferably 5-99.9%, more preferably 5-80%, and even more preferably 5-60%.

[0051] In the above-mentioned desalination process, this invention utilizes the common ion effect and the stronger acidity of oxalic acid compared to other carboxylic acids. It also examines the pH variation of oxalate solubility in the presence of carboxylic acid compounds. By controlling the amount of alkali, oxalic acid can be precipitated as a solid oxalate, thus achieving efficient separation from 4-(hydroxymethylphosphono)-2-carbonylbutyric acid in the system. Generally, after filtration, the residual oxalic acid in the obtained PPO aqueous solution is <0.05 wt%.

[0052] To reiterate, when ammonia is used as the desalting alkali to remove oxalate, and the pH is adjusted to 3-6, the ammonia source in the system is sufficient. After solid precipitation and filtration, a PPO aqueous solution with an ammonia molar amount not less than that of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid can be obtained.

[0053] However, when the desalination alkali does not include ammonia, after the solid precipitates and is filtered, ammonia of no less than the molar amount of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid needs to be added. This is because the conversion of PPO to glufosinate requires at least an amount of ammonia equal to the molar amount of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid.

[0054] Then, according to the present invention, the pH of the PPO aqueous solution, with a molar amount of ammonia not less than that of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid, is adjusted to 6-9 using an alkali, preferably 7-9, more preferably 7-8.5, and even more preferably 7.8-8.5, such as 6, 6.5, 7, 7.5, 7.8, 8, 8.5, or 9, to obtain a PPO salt solution. In this step, the alkali added and its form of introduction are the same as the selection range of the desalting alkali in step S1 above, and will not be repeated here. The pH is controlled to 6-9 in this step because the enzyme's catalytic activity is optimal within this range. The PPO salt can be any one or more of ammonium salts, sodium salts, potassium salts, monomethylamine salts, dimethylamine salts, isopropylamine salts, or monoethanolamine salts, and the specific type of salt is related to the type of alkali added.

[0055] It should be noted that the alkali and the desalting alkali mentioned can be the same or different, and there are no special restrictions.

[0056] In some embodiments of the present invention, it is preferred that an aqueous solution of PPO with a molar amount of ammonia not less than the molar amount of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid is mixed with an alkali in a continuous reactor, wherein the mixing temperature is 0~35°C, preferably 0~30°C, more preferably 0~20°C, more preferably 0~10°C, and even more preferably 2~10°C.

[0057] The present invention does not particularly limit the type of continuous reactor, such as including but not limited to tubular reactors.

[0058] Then, the obtained PPO salt solution is continuously fed into the enzyme catalytic conversion system and subjected to a heat preservation reaction. After post-processing, glufosinate is obtained.

[0059] In some embodiments of the present invention, it is preferable to continuously feed the PPO salt solution generated in the continuous reactor into the enzyme catalytic conversion system. The continuous feeding time depends on the mixing time of the continuous reactor and is 1 to 24 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 15 hours, 18 hours, 21 hours, 24 hours, etc.

[0060] In this invention, the enzyme-catalyzed conversion system is a solution containing amino acid dehydrogenase, isopropanol dehydrogenase, isopropanol, and a coenzyme; the mass of the amino acid dehydrogenase and isopropanol dehydrogenase is 1-15% of the mass of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid, such as 1%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%; the coenzyme can specifically be NADP (nicotinamide adenine dinucleotide phosphate) or NAD. Nicotinamide adenine dinucleotide, the mass of which is 0.01~5% of the mass of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid, such as 0.01%, 0.05%, 0.1%, 0.5%, 1%, 2%, 3%, 4% or 5%; the mass of which isopropanol is 33~100% of the mass of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid, such as 33%, 35%, 40%, 50%, 60%, 70%, 80%, 90% or 100%.

[0061] After the PPO salt solution is continuously fed into the enzyme-catalyzed conversion system, the reaction is preferably carried out at 35-45°C for 1-24 h, more preferably at 35-40°C for 5-12 h. The reaction is considered complete when 4-(hydroxymethylphosphono)-2-carbonylbutyric acid is completely consumed, as detected by LC-MS. During the reaction, the PPO salt reacts with ammonia to form an imine intermediate, which, under the catalysis of isopropanol and coenzyme, produces glufosinate and acetone as a byproduct.

[0062] After the above reaction is completed, post-processing is preferably performed. The post-processing refers to: filtering and concentrating the reaction product to obtain glufosinate-ammonium technical, and then crystallizing it to obtain glufosinate-ammonium salt.

[0063] The mass concentration of the glufosinate-ammonium technical material is 5-70%, such as 5%, 10%, 20%, 30%, 40%, 50%, 60% or 70%, etc.

[0064] The solvent used for the above crystallization is selected from any one or more of methanol, ethanol, isopropanol, n-butanol, n-hexane, acetonitrile, or toluene.

[0065] In this invention, the final glufosinate salt prepared is any one or more of glufosinate ammonium salt, glufosinate sodium salt, glufosinate potassium salt, glufosinate monomethylamine salt, glufosinate dimethylamine salt, glufosinate isopropylamine salt, or glufosinate monoethanolamine salt.

[0066] Further refining this application, in some specific embodiments of the present invention, the desalting alkali added in step S1 is ammonia water, the alkali added in step S2 is ammonia water, and the final glufosinate is glufosinate.

[0067] Alternatively, the desalting alkali added in step S1 is sodium hydroxide, the alkali added in step S2 is sodium hydroxide, and the final glufosinate is glufosinate sodium salt.

[0068] Alternatively, the desalting alkali added in step S1 is potassium hydroxide, the alkali added in step S2 is potassium hydroxide, and the final glufosinate is glufosinate potassium salt.

[0069] Alternatively, the desalting alkali added in step S1 is isopropylamine, the alkali added in step S2 is isopropylamine, and the final glufosinate-ammonium salt obtained is glufosinate-ammonium isopropylamine salt.

[0070] Alternatively, the desalting alkali added in step S1 is ammonia water, and the alkali added in step S2 is sodium hydroxide, so that the final glufosinate is a mixture of glufosinate and sodium salt.

[0071] Alternatively, the alkali added in step S1 is concentrated ammonia, and the alkali added in step S2 is sodium hydroxide, and the final glufosinate is a mixture of glufosinate and sodium salt.

[0072] Alternatively, the desalting alkali added in step S1 is ammonia water, and the alkali added in step S2 is potassium hydroxide, and the final glufosinate is a mixture of glufosinate and potassium salt.

[0073] Alternatively, the desalting alkali added in step S1 is ammonia water, and the alkali added in step S2 is isopropylamine, and the final glufosinate is a mixture of glufosinate and isopropylamine.

[0074] Alternatively, the desalting alkali added in step S1 is sodium hydroxide, and the alkali added in step S2 is ammonia water, and the final glufosinate is a mixture of glufosinate and sodium salt.

[0075] Alternatively, the desalting alkali added in step S1 may be sodium carbonate, and the alkali added in step S2 may be potassium carbonate, resulting in a final glufosinate-ammonium salt mixture of potassium and sodium glufosinate-ammonium salts.

[0076] According to the test results, the purity of the glufosinate prepared according to the method provided by the present invention is above 98.5%, the oxalic acid content is below 0.05%, and the yield is above 97%.

[0077] It is evident that the preparation method provided by this invention not only simplifies the synthesis steps but also avoids the problem of material decomposition, effectively improving the conversion rate and successfully achieving the effective preparation of different glufosinate salts, thus possessing significant theoretical and practical application value.

[0078] To further illustrate the present invention, the following examples provide a detailed description. All experimental materials used in the following examples are commercially available products. Unless otherwise specified, all "%" in the following examples and comparative examples refer to mass percentages.

[0079] Example 1

[0080] Take 180.1 g of an aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid (4-(hydroxymethylphosphono)-2-carbonylbutyric acid content 30%, 4-(hydroxymethylphosphono)-2-carbonylbutyric acid 0.3 mol, oxalic acid content 4.9%), adjust the pH to 3.0 with 15% ammonia water (for desalination), control the temperature at 2~10℃ during the process, the solid precipitates out, and filter to obtain a desalted PPO aqueous solution. The obtained PPO aqueous solution and 15% ammonia (alkali) were continuously premixed in a tubular reactor at 2-10℃ until the pH reached 7.5. This mixture was then continuously added to a solution containing 21.6 g isopropanol, 5.0 g isopropanol dehydrogenase, 5.0 g amino acid dehydrogenase, 0.3 g NAD, and 100 g water for 2 hours, maintaining the system temperature at 40℃. After the addition was complete, the mixture was kept at this temperature for 6 hours. LC-MS analysis was performed until 4-(hydroxymethylphosphono)-2-carbonylbutyric acid was completely consumed. The solution was concentrated, filtered to remove protein, and crystallized from methanol to obtain 59.6 g of refined glufosinate-phosphonium salt with a purity of 98.8% (oxalic acid content 0.01%) and a total yield of 99.1%. The chromatogram obtained after testing according to the national standard GB / T 43172-2023 is shown below. Figure 1 As shown, the retention time of the prepared glufosinate-ammonium salt is consistent with that of the glufosinate-ammonium standard, and the spectrum is clean with no extraneous peaks.

[0081] Furthermore, this invention employs a quantitative oxalic acid testing method to determine the oxalic acid content in the glufosinate-ammonium salt prepared in Example 1, as detailed below:

[0082] In Example 1, glufosinate was prepared and dissolved in deionized water as a sample. Oxalic acid in the sample was separated and determined using an anion exchange column, and quantification was performed using the external standard method.

[0083] Water: Deionized water conductivity ≥18.2 MΩ·cm;

[0084] Rinse solution: potassium hydroxide;

[0085] Anhydrous oxalic acid standard: 99.72%;

[0086] Chromatographic conditions for ion chromatography:

[0087] Column: 250 mm × 4 mm (id) IonPac AS11-HC anion analyzer column;

[0088] Guard column: 50 mm × 4 mm (id) IonPac AG11-HC anion guard column;

[0089] Suppressor: ASRS-4mm;

[0090] Flow rate: 1.0 mL / min;

[0091] Injection volume: 25 μL;

[0092] Column temperature: 30℃±2℃;

[0093] Retention time: Oxalic acid approximately 14.6 min;

[0094] The gradient elution conditions are shown in Table 1 below:

[0095] Table 1

[0096]

[0097] 1. Preparation of standard: Weigh about 0.1 g of anhydrous oxalic acid standard into a 250 mL volumetric flask, dilute with water to the mark and shake well. Transfer 1 mL of the standard into a 100 mL volumetric flask, dilute with water to the mark and shake well (about 4 mg / L).

[0098] 2. Sample preparation: Weigh approximately 5.0 g of the sample into a 100 mL volumetric flask, dilute with water to the mark, and shake well;

[0099] 3. Calculation method:

[0100] .

[0101] Test results are as follows Figure 2 and Figure 3 As shown, the peak area of ​​the standard sample is 4.314, and the peak area of ​​the sample is 5.418. The calculated oxalic acid content is 0.01%.

[0102] Examples 2-10

[0103] Referring to Example 1, the results of using different desalination alkalis and bases, and the yields are shown in Table 2.

[0104] The specific steps are the same as in Example 1, except that the desalting alkali and the type of alkali are different (when the desalting alkali is not ammonia, ammonia of the same molar amount as 4-(hydroxymethylphosphono)-2-carbonylbutyric acid is added). The sodium hydroxide and potassium hydroxide used in Examples 2 to 10 are solids. The other parameters and steps are the same as in Example 1. The yield is calculated based on the amount of glufosinate in the finished enzymatic conversion solution, and the oxalic acid content is the content in the finished solution.

[0105] Table 2

[0106]

[0107] by 1 Example 3: Except for sodium hydroxide (non-ammonia), an ammonia solution was added in an amount equal to the molar amount of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid. After adjusting the pH of the PPO aqueous solution to 3.0 with sodium hydroxide, a solid precipitated out. After filtration, 34.1 g of 15% ammonia (0.3 mol of ammonia) was added to the solution to obtain a PPO aqueous solution with an ammonia molar amount not less than that of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid. The obtained PPO aqueous solution with an ammonia molar amount not less than that of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid and the alkali, i.e., sodium hydroxide, were continuously premixed until the pH was equal to 7.5 and continuously added to the enzyme catalytic system for reaction. After the reaction was completed, the reaction was analyzed and quantified.

[0108] In other embodiments, when the salt alkali is not ammonia, an equimolar amount of ammonia equal to that of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid is added, referring to the above. 1 The steps in Example 3 are sufficient.

[0109] Examples 11-17

[0110] Referring to Example 1, the yield of the product and the removal of oxalic acid were investigated by adjusting 15% ammonia water to different pH values ​​for desalination. The results are shown in Table 3.

[0111] The specific steps are the same as in Example 1, except that the pH value is adjusted to a different value. All other parameters and steps are the same as in Example 1. The yield is calculated based on the amount of glufosinate in the feed solution after enzyme conversion.

[0112] Table 3

[0113]

[0114] As shown in Table 2, oxalic acid can be removed efficiently when the desalination pH is not lower than 3.0, and the yield is greater than 99%. However, when the desalination pH is lower than 3.0, such as when the pH is 2.5, a large amount of oxalic acid residue affects the enzyme catalytic efficiency, and the yield is only 90.1%, indicating that the oxalic acid removal rate has a significant impact on the yield.

[0115] Examples 18-26

[0116] Referring to Example 1, the yield of the product was investigated when the alkali was adjusted to different pH values, as shown in Table 4.

[0117] The specific steps are the same as in Example 1, except that the alkali is adjusted to different pH values. All other parameters and steps are the same as in Example 1. The yield is calculated based on the amount of glufosinate in the feed solution after enzyme conversion.

[0118] Table 4

[0119]

[0120] in, 1 Example 25 refers to adjusting the pH to 3.0 using 15% ammonia water (for desalination), causing solid precipitation. After filtration to obtain a desalinated PPO aqueous solution, the obtained PPO aqueous solution was adjusted to the corresponding pH in Table 3 using solid sodium hydroxide. The remaining steps and parameters were consistent with those in Example 1.

[0121] 2 Example 26 refers to adjusting the pH to 3.0 using sodium hydroxide (for desalination). After desalination, the solid precipitates, is filtered, and ammonia is added to obtain a PPO aqueous solution with an ammonia molar amount not less than the molar amount of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid. The obtained PPO aqueous solution is then adjusted to the corresponding pH in Table 3 using solid sodium hydroxide. The remaining steps and parameters are consistent with those in Example 1.

[0122] As shown in Table 3, the enzyme catalytic efficiency varies at different pH values. The results indicate that the catalytic effect is better at pH 6-9, with a yield greater than 92%; at pH 7-9, the yield is greater than 96%; at pH 7-8.5, the yield is greater than 97%; and the catalytic effect is best at pH 7.8-8.5, with a yield greater than 99%. Too low or too high pH values ​​will affect the yield and show varying degrees of decrease.

[0123] Example 27

[0124] Take 108.1 g of an aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid (4-(hydroxymethylphosphono)-2-carbonylbutyric acid content 50%, 4-(hydroxymethylphosphono)-2-carbonylbutyric acid 0.3 mol, oxalic acid content 8.2%), pass ammonia gas (to remove salt and alkali) to adjust the pH to 6.0, and control the temperature at 2~10℃ during the process. The solid precipitates out, and the solution is filtered to obtain a desalted PPO aqueous solution. The obtained PPO aqueous solution and ammonia (alkali) were continuously premixed in a tubular reactor at 2-10℃ until the pH reached 7.5. The mixture was then continuously added to a solution containing 54.0 g isopropanol, 0.5 g isopropanol dehydrogenase, 0.5 g amino acid dehydrogenase, 0.1 g NAD, and 100 g water for 2 hours, maintaining the system temperature at 35℃. After the addition was completed, the mixture was kept at this temperature for 24 hours. LC-MS analysis was performed until 4-(hydroxymethylphosphono)-2-carbonylbutyric acid was completely consumed. The mixture was concentrated, filtered to remove protein, and crystallized from isopropanol to obtain 58.9 g of refined glufosinate-phosphonium salt with a purity of 98.2% (oxalic acid content 0.01%), and a total yield of 97.3%.

[0125] Example 28

[0126] Take 1080.6 g of an aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid (4-(hydroxymethylphosphono)-2-carbonylbutyric acid content 5%, 4-(hydroxymethylphosphono)-2-carbonylbutyric acid 0.3 mol, oxalic acid content 0.1%), and pass methylammonium (for desalting) through it to adjust the pH to 3.0. During the process, control the temperature at 2~10℃. The solid precipitates out, and the solution is filtered to obtain a desalted PPO aqueous solution. The obtained PPO aqueous solution and monomethylamine (alkali) were continuously premixed in a tubular reactor at 2-10℃ until the pH reached 7.5. The mixture was then continuously added to a solution containing 21.6 g isopropanol, 8.1 g isopropanol dehydrogenase, 8.1 g amino acid dehydrogenase, 2.7 g NAD, and 100 g water for 12 hours, maintaining the system temperature at 45℃. After the addition was completed, the mixture was kept at this temperature for 1 hour. LC-MS analysis confirmed complete consumption of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid. The solution was concentrated, filtered to remove protein, and crystallized in acetonitrile to obtain 63.8 g of glufosinate monomethylamine salt with a purity of 98.3% (oxalic acid content 0.01%), and a total yield of 98.5%.

[0127] Example 29

[0128] Take 180.1 g of an aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid (4-(hydroxymethylphosphono)-2-carbonylbutyric acid content 30%, 4-(hydroxymethylphosphono)-2-carbonylbutyric acid 0.3 mol, oxalic acid content 4.9%), and pass dimethylamine (for desalination) to adjust the pH to 3.0. During the process, control the temperature at 2~10℃. The solid precipitates out, and the solution is filtered to obtain a desalted PPO aqueous solution. The obtained PPO aqueous solution and dimethylamine (alkali) were continuously premixed in a tubular reactor at 2-10℃ until the pH reached 7.5. The mixture was then continuously added to a solution containing 21.6 g isopropanol, 5.0 g isopropanol dehydrogenase, 5.0 g amino acid dehydrogenase, 0.3 g NAD, and 100 g water for 2 hours, maintaining the system temperature at 40℃. After the addition was completed, the mixture was kept at this temperature for 12 hours. LC-MS analysis showed that the 4-(hydroxymethylphosphono)-2-carbonylbutyric acid was completely consumed. The solution was concentrated, filtered to remove protein, and crystallized from methanol to obtain 67.7 g of glufosinate-phosphonium dimethylamine salt with a purity of 98.5% (oxalic acid content 0.01%) and a total yield of 98.3%.

[0129] Example 30

[0130] Take 180.1 g of an aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid (4-(hydroxymethylphosphono)-2-carbonylbutyric acid content 30%, 4-(hydroxymethylphosphono)-2-carbonylbutyric acid 0.3 mol, oxalic acid content 4.9%), and introduce monoethanolamine (for desalination) to adjust the pH to 3.0. During the process, control the temperature at 2~10℃. The solid precipitates out, and the solution is filtered to obtain a desalted PPO aqueous solution. The obtained PPO aqueous solution and monoethanolamine (base) were continuously premixed in a tubular reactor at 2-10℃ until the pH reached 7.5. The mixture was then continuously added to a solution containing 21.6 g isopropanol, 5.0 g isopropanol dehydrogenase, 5.0 g amino acid dehydrogenase, 0.3 g NAD, and 100 g water for 2 hours, maintaining the system temperature at 40℃. After the addition was completed, the mixture was kept at this temperature for 6 hours. LC-MS analysis showed complete consumption of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid. The solution was concentrated, filtered to remove protein, and crystallized from methanol to obtain 72.4 g of glufosinate monoethanolamine salt with a purity of 98.5% (oxalic acid content 0.01%), and a total yield of 98.1%.

[0131] Example 31

[0132] Take 180.1 g of an aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid (4-(hydroxymethylphosphono)-2-carbonylbutyric acid content 30%, 4-(hydroxymethylphosphono)-2-carbonylbutyric acid 0.3 mol, oxalic acid content 4.9%), add 15% sodium carbonate (for desalination) to adjust the pH to 3.0, and control the temperature at 2~10℃ during the process. The solid precipitates out, and the solution is filtered to obtain a desalted PPO aqueous solution. The obtained PPO aqueous solution and 50% potassium carbonate (alkali) were continuously premixed in a tubular reactor at 2-10℃ until the pH reached 7.5. This mixture was then continuously added to a solution containing 21.6 g isopropanol, 5.0 g isopropanol dehydrogenase, 5.0 g amino acid dehydrogenase, 0.3 g NAD, and 100 g water for 2 hours, maintaining the system temperature at 40℃. After the addition was completed, the mixture was kept at this temperature for 6 hours. LC-MS analysis confirmed complete consumption of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid. The mixture was concentrated, filtered to remove protein, and crystallized from methanol to obtain 62.6 g of a mixture of sodium and potassium glufosinate-ammonium salts. The glufosinate-ammonium acid content was 85.3% (oxalic acid content 0.01%), with a total yield of 98.3%.

[0133] Comparative Example 1 - PPO aqueous solution does not remove oxalic acid

[0134] Referring to Example 1, 180.1 g of an aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid (4-(hydroxymethylphosphono)-2-carbonylbutyric acid content 30%, 0.3 mol of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid, oxalic acid content 4.9%) was taken. The pH was adjusted to 7.5 with 15% ammonia water. The temperature was controlled at 2~10℃ during the process. Filtration and desalting were not performed. The solution was continuously added to a solution containing 21.6 g isopropanol, 5.0 g isopropanol dehydrogenase, 5.0 g amino acid dehydrogenase, 0.3 g NAD, and 100 g water for 2 hours, maintaining the system temperature at 40℃. After the addition was completed, the solution was kept at this temperature for 6 hours. LC-MS was used to monitor the reaction until the 4-(hydroxymethylphosphono)-2-carbonylbutyric acid was completely consumed. The solution was concentrated, filtered to remove protein, and crystallized from methanol to obtain 50.2 g of the solution. g-grade glufosinate-phosphonium salt, purity 98.1% (oxalic acid content 0.50%), total yield 82.8%.

[0135] Comparative Example 2 - Using a batch reaction

[0136] Referring to Example 1, 180.1 g of an aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid (4-(hydroxymethylphosphono)-2-carbonylbutyric acid content 30%, 4-(hydroxymethylphosphono)-2-carbonylbutyric acid 0.3 mol, oxalic acid content 4.9%) was taken. The pH was adjusted to 3.0 with 15% ammonia water (for desalination). The temperature was controlled at 2~10℃ during the process. The solid precipitated out and was filtered to obtain a desalted PPO aqueous solution. The obtained PPO aqueous solution and 15% ammonia (alkali) were added to a glass flask and mixed at 2-10℃ until the pH was 7.5. Then, the mixture was added to a solution containing 21.6 g isopropanol, 5.0 g isopropanol dehydrogenase, 5.0 g amino acid dehydrogenase, 0.3 g NAD and 100 g water for 2 hours, maintaining the system temperature at 40℃. After the addition was completed, the mixture was kept at this temperature for 6 hours. LC-MS was used to detect the reaction until 4-(hydroxymethylphosphono)-2-carbonylbutyric acid was completely consumed. The mixture was concentrated, filtered to remove protein, and crystallized from methanol to obtain 52.3 g of refined glufosinate-phosphonium salt with a purity of 98.7% (oxalic acid content 0.02%) and a total yield of 86.8%.

[0137] Comparative Example 3 - Temperature during pH adjustment process not controlled

[0138] Referring to Example 1, 180.1 g of an aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid (4-(hydroxymethylphosphono)-2-carbonylbutyric acid content 30%, 4-(hydroxymethylphosphono)-2-carbonylbutyric acid 0.3 mol, oxalic acid content 4.9%) was taken. The pH was adjusted to 3.0 with 15% ammonia water (for desalination). The temperature was not controlled during the process, and the temperature reached a maximum of 52°C. After cooling to room temperature, the solution was filtered to obtain a desalinated PPO aqueous solution. The resulting PPO aqueous solution was adjusted to pH 7.5 with 15% ammonia water without temperature control and continuously added to a solution containing 21.6 g isopropanol, 5.0 g isopropanol dehydrogenase, 5.0 g amino acid dehydrogenase, 0.3 g NAD, and 100 g water for 2 hours, maintaining the system temperature at 40℃. After the addition was completed, the system was kept at this temperature for 6 hours. LC-MS was used to detect the reaction until 4-(hydroxymethylphosphono)-2-carbonylbutyric acid was completely consumed. The solution was concentrated, filtered to remove protein, and crystallized from methanol to obtain 49.3 g of refined glufosinate-phosphonium salt with a purity of 97.5% (oxalic acid content 0.02%), and an overall yield of 80.9%.

[0139] The comparison of Comparative Examples 1, 2, and 3 shows that the oxalic acid impurity content in the PPO aqueous solution affects the catalytic effect of the reaction enzyme, thus leading to a decrease in yield. Furthermore, in the batch reaction, the high concentration of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid in the initial catalytic stage prevents its timely conversion to glufosinate, resulting in reduced selectivity and a lower yield. Simultaneously, if the temperature is not controlled during pH adjustment, the increased exothermic neutralization temperature will cause some 4-(hydroxymethylphosphono)-2-carbonylbutyric acid to decompose, further reducing the yield.

[0140] Therefore, this application, through the above-mentioned process design of temperature control, pH adjustment, and desalination coupled with continuous reaction, effectively eliminates the inhibitory effect of oxalic acid impurities on enzyme catalysis and avoids the selectivity and yield losses caused by local high concentration and thermal decomposition of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid; at the same time, relying on the differentiated alkali neutralization strategy, it can directionally synthesize glufosinate-ammonium of different salt types, which not only greatly improves the product yield but also enriches the preparation method system of glufosinate-ammonium salt products.

[0141] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a salt of glufosinate-ammonium, characterized in that, Includes the following steps: S1: Adjust the pH of the aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid to 3-6 using a desalting alkali. The solid precipitates out, and the solution is filtered to obtain an aqueous solution of PPO. The desalting alkali includes ammonia, and the molar amount of ammonia in the obtained PPO aqueous solution is not less than the molar amount of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid; Alternatively, the desalting alkali does not include ammonia. After filtration, ammonia is added separately to the PPO aqueous solution, and the molar amount of ammonia in the PPO aqueous solution is controlled to be not less than the molar amount of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid. S2: Adjust the pH of an aqueous PPO solution with an ammonia molar amount not less than that of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid molar amount to 6-9 using an alkali to obtain a PPO salt solution; S3: PPO salt solution is continuously fed into the enzyme catalytic conversion system and subjected to heat preservation reaction. After post-processing, glufosinate is obtained.

2. The production method according to claim 1, characterized by, In the aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid, the mass content of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid is 5~80 wt%; The aqueous solution of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid containing oxalic acid has a mass content of 0.1~10 wt%.

3. The production method according to claim 1 or 2, characterized by, The desalting alkali or base is independently selected from any one or more of ammonia, ammonia water, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, monomethylamine, dimethylamine, isopropylamine, or monoethanolamine; The desalination alkali or alkali is introduced independently in the form of a solid or an aqueous solution, wherein the aqueous solution has a mass concentration of 5-99.9%.

4. The production method according to any one of claims 1 to 3, characterized by, In step S1, the temperature for adjusting the pH using desalination alkali is 0~35℃.

5. The preparation method according to any one of claims 1 to 3, characterized in that, Step S2 is carried out in a continuous reactor; In the continuous reactor, PPO aqueous solution and alkali are mixed at a temperature of 0~35℃.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The enzyme catalytic conversion system is a solution containing amino acid dehydrogenase, isopropanol dehydrogenase, isopropanol, and coenzyme. The mass of the amino acid dehydrogenase or isopropanol dehydrogenase is 1-15% of the mass of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid, the mass of the coenzyme is 0.01-5% of the mass of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid, and the mass of the isopropanol is 33-100% of the mass of 4-(hydroxymethylphosphono)-2-carbonylbutyric acid.

7. The preparation method according to any one of claims 1 to 6, characterized in that, The continuous feeding time is 1~24 h, and the temperature of the heat preservation reaction is 35~45℃.

8. The preparation method according to any one of claims 1 to 7, characterized in that, The post-processing is as follows: after filtration and concentration, glufosinate-ammonium salt mother stock is obtained, and then crystallized to obtain glufosinate-ammonium salt.

9. The preparation method according to claim 8, characterized in that, The solvent used for crystallization is selected from any one or more of methanol, ethanol, isopropanol, n-butanol, n-hexane, acetonitrile, or toluene; The glufosinate salt is any one or more of glufosinate ammonium salt, glufosinate sodium salt, glufosinate potassium salt, glufosinate monomethylamine salt, glufosinate dimethylamine salt, glufosinate isopropylamine salt, or glufosinate monoethanolamine salt.

10. The preparation method according to any one of claims 1 to 9, characterized in that, The purity of the glufosinate is above 98.5%, the oxalic acid content is below 0.05%, and the yield is above 97%.

Images