Continuous synthesis method of glufosinate-ammonium

Abstract

The invention relates to the technical field of fine chemical engineering, in particular to a continuous synthesis method of glufosinate ammonium, which comprises the following steps: A) mixing diethyl methylphosphonite, acrolein and acetic acid for condensation reaction to obtain a compound a-1; b) mixing the compound a-1 with water, and carrying out a first hydrolysis reaction under the action of a catalyst to obtain a first system; c) returning a part of the first system to the condensation reaction system in the step A), and respectively reacting ethanol and acetic acid with diethyl methylphosphonite and acrolein to generate a compound a; mixing the unreturned part in the first system with an acidic compound, and carrying out a second hydrolysis reaction to obtain a compound c; d) the compound c, an ammonia source and a cyanide source are subjected to a cyanamide reaction to obtain a compound d, the ammonia source is selected from ammonia water or a mixture of ammonia water and ammonium chloride, and the cyanide source is selected from sodium cyanide or hydrogen cyanide, and E) the compound d is subjected to a third hydrolysis reaction to generate glufosinate-ammonium.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fine chemical technology, in particular to a continuous synthesis method of glufosinate-ammonium. BACKGROUND

[0002] Glufosinate-ammonium, commonly known as glufosinate, is a low-toxicity and high-efficiency herbicide. Glufosinate-ammonium has a variety of synthetic routes, and the Strecker method is the most commonly used route in industrial production.

[0003] At present, most of the production of glufosinate-ammonium is carried out by batch kettle synthesis, which requires frequent material transfer and temperature rising and lowering operations, and the product quality will fluctuate due to the operation differences between batches.

[0004] There have been reports on the continuous synthesis method of glufosinate-ammonium, which mainly uses diethyl methyl phosphonite or monoalkyl methyl phosphonate as raw material to continuously synthesize glufosinate-ammonium or key intermediates in the process. The most prominent problem in the current synthesis method of glufosinate-ammonium is the low atomic economy. In particular, in the diethyl methyl phosphonite route, the ethoxy group in the structure of the raw material diethyl methyl phosphonite will generate ethanol in the subsequent reaction; and the equivalent of acetic acid raw material to the diethyl ester will be regenerated as acetic acid or corresponding salt in the subsequent reaction, and finally ethanol and acetic acid will continue to exist in the reaction material in the form of by-products. In addition, the hydrolysis process of aminocarbonitrile requires the use of excess acid, and all the above-mentioned substances must be separated through additional steps into waste gas, waste water or solid waste. Therefore, effectively utilizing the excess ethanol, acetic acid, hydrochloric acid and other by-products generated in the reaction process can improve the overall atomic economy of the reaction, reduce the unit consumption and raw material cost, and reduce the additional separation steps and three-waste treatment links, which is of great significance to the realization of the continuous flow synthesis of glufosinate-ammonium. SUMMARY

[0005] Therefore, the present application aims to solve the technical problem of providing a continuous synthesis method of glufosinate-ammonium, which realizes the continuous production of glufosinate-ammonium.

[0006] To achieve the above-mentioned purpose, the present application provides a continuous synthesis method of glufosinate-ammonium, comprising the following steps:

[0007] A) mixing diethyl methyl phosphonate, acrolein and acetic acid to carry out a condensation reaction to obtain compound a-1;

[0008] B) mixing compound a-1 with water to carry out a first hydrolysis reaction under the action of a catalyst to obtain a first system; the first system comprises compound b, compound c, ethanol, acetic acid and unreacted compound a-1;

[0009] C) A portion of the first system is returned to the condensation reaction system of step A), where ethanol and acetic acid react with diethyl methylphosphonite and acrolein, respectively, to generate compound a;

[0010] The portion of the first system that was not returned was mixed with an acidic compound and subjected to a second hydrolysis reaction to obtain compound c;

[0011] D) Compound c undergoes a cyanamide reaction with an ammonia source and a cyanide source to obtain compound d;

[0012] E) Compound d undergoes a third hydrolysis reaction to produce glufosinate;

[0013]

[0014] R1 is -COCH3;

[0015] R is either -CH2CH3 or -COCH3.

[0016] The reaction equation for step A) is as follows:

[0017]

[0018] Wherein, R1 is -COCH3.

[0019] After undergoing step B), the first system obtained by compound a includes compound b, compound c, ethanol, acetic acid, and unreacted compound a.

[0020] The preferred molar ratio of diethyl methylphosphonate, acrolein, and acetic acid is 1:1:1.

[0021] The condensation reaction is preferably carried out in a continuous flow reactor.

[0022] The preferred temperature for the condensation reaction is 5~45℃, more preferably 10~25℃.

[0023] The reaction equation for step B) is as follows:

[0024]

[0025] In the above reaction, the hydrolysis of a-1 is divided into two stages. In the first stage, compound a-1 hydrolyzes to generate compound b and produces one molecule of acetic acid. In the second stage, compound b hydrolyzes to generate compound c and produces one molecule of ethanol. Since the added H2O is insufficient to completely hydrolyze a-1, the first system in step B) includes compound b, compound c, ethanol, acetic acid and unreacted compound a-1.

[0026] The present invention returns a portion of the first system to the condensation reaction system of step A), where ethanol and acetic acid undergo condensation reactions with diethyl methylphosphonite and acrolein, respectively, to generate compound a:

[0027]

[0028] Where R is -CH2CH3 or -COCH3.

[0029] Returning a portion of the first system to the condensation reaction system in step A) allows the generated ethanol and acetic acid to be reused in the condensation reaction system for the synthesis of compound a. This reduces the amount of ethanol and acetic acid transported, thereby reducing consumption and waste generation.

[0030] The portion is preferably 10% to 70% of the total, more preferably 30% to 60% of the total. The total is the total volume of the first system.

[0031] In this invention, a portion of the first system returned is denoted as stream II. After returning a portion of the first system (i.e., stream II) to the condensation reaction system in step A), the system obtained by the condensation reaction is denoted as stream I. Stream I includes compound a, compound b, compound c, ethanol, and acetic acid.

[0032] At this point, the system includes the reactions of diethyl methylphosphonite, acrolein, and acetic acid, as well as the reactions of diethyl methylphosphonite, acrolein, and ethanol.

[0033] The molar ratio of diethyl methylphosphonite, acrolein, acetic acid, and flow strand II is preferably 1:(0.95~1.15):(0.3~1.0):(0.1~3.0), more preferably 1:(0.98~1.02):(0.4~0.6):(0.5~1.5), and even more preferably 1:1:0.5:1.0.

[0034] In the above molar ratio, the molar amount of stream II refers to the sum of the molar amounts of ethanol and acetic acid that can be used as reactants.

[0035] Stream I is then repeated in step B), mixed with water, and undergoes the first hydrolysis reaction under the action of a catalyst to obtain the first system. A portion is then separated and designated as stream II, which is returned to step A) for reuse. The remaining portion undergoes the second hydrolysis reaction. This cycle is repeated to achieve continuous production.

[0036] At this point, step B) is: mixing compound a with water and carrying out the first hydrolysis reaction under the action of a catalyst to obtain the first system; the first system includes compound b, compound c, ethanol, acetic acid and unreacted compound a.

[0037] The equation for the first hydrolysis reaction is as follows:

[0038]

[0039] The catalyst in step B) is preferably a supported acidic catalyst that enables compound a or compound a-1 to undergo sufficient primary hydrolysis with a small amount of water. Preferably, the catalyst includes, but is not limited to, molecular sieves, preferably ZSM-5 molecular sieve catalysts, more preferably mesoporous ZSM-5 molecular sieve catalysts with a silica-alumina ratio of less than 10. In some embodiments of the present invention, the catalyst is a ZSM-5 molecular sieve with a silica-alumina ratio of about 5.0.

[0040] The molar amount of water is preferably 0 to 50% of the molar amount of compound a or compound a-1 in stream I, more preferably 15% to 25%.

[0041] The preferred reaction temperature for the first hydrolysis is 20~80℃, more preferably 40~60℃.

[0042] The equation for the second hydrolysis reaction is as follows:

[0043]

[0044] The acidic compound is preferably hydrochloric acid. The concentration of the hydrochloric acid is preferably 0.5% to 5.0%, more preferably 1.0% to 3.0%. The molar amount of the acidic compound in the second hydrolysis reaction is preferably 1% to 5% of the total molar amount of compound a and compound b in stream II, more preferably 2%.

[0045] The system formed after the second hydrolysis reaction is designated as flow stream III. This reaction stage includes the complete hydrolysis of compounds a and b under acid catalysis to generate compound c.

[0046] The preferred reaction temperature for the second hydrolysis reaction is 20~60℃, more preferably 25~45℃.

[0047] Then, stream III is mixed with an ammonia source and a cyanide source for a cyanamation reaction to generate stream IV. The reaction equation is as follows:

[0048]

[0049] In the above reaction process, compound c reacts to generate α-aminonitrile compound d in the presence of both an ammonia source and a cyanide source.

[0050] The ammonia source is preferably ammonia water or a mixture of ammonia water and ammonium chloride.

[0051] The molar amount of the ammonia source is preferably 1 to 6 times that of compound c in stream III, more preferably 5 times.

[0052] The preferred cyanide source is sodium cyanide or hydrogen cyanide.

[0053] The molar amount of the cyanide source is preferably 0.99 to 1.2 times that of compound c in stream III, and more preferably 1.01 times.

[0054] The preferred temperature for the cyanamide reaction is 10-30°C, more preferably 15-25°C.

[0055] Preferably, the cyanamide reaction process further includes: removing ammonia gas.

[0056] The methods for removing ammonia include, but are not limited to, depressurization removal.

[0057] In the process of removing ammonia under reduced pressure, the endpoint pH is preferably used as the control index. Preferably, the endpoint pH value is controlled at 7-8.

[0058] Removing ammonia can improve the utilization rate of ammonia, reduce the consumption of ammonia and acid, and reduce the production of ammonium chloride.

[0059] The compound d undergoes a third hydrolysis reaction to produce glufosinate. The reaction equation for this process is as follows:

[0060]

[0061] The third hydrolysis reaction is preferably carried out in an acidic aqueous solution, and more preferably in an aqueous solution of hydrochloric acid.

[0062] The molar ratio of hydrochloric acid to compound d is preferably 2~8:1, more preferably 4~6:1.

[0063] In this invention, the excess hydrochloric acid used during the hydrolysis of compound d can be recovered in stages and reused as hydrochloric acid raw material for the hydrolysis of compound d.

[0064] Preferably, the third hydrolysis reaction is carried out sequentially in reactors A and B. Specifically, stream IV is mixed with metered hydrochloric acid to form stream V, which is then sequentially introduced into reactors A and B for stirring and heating, ultimately generating stream VI. The pre-distillate produced in reactor A can be further treated as wastewater, while the post-distillate condensed in reactor B, due to its high hydrochloric acid content, is recovered and recycled. Preferably, the post-distillate recovered from reactor B accounts for 10% to 60% of the total distillate during the three hydrolysis processes, more preferably 30% to 45%.

[0065] The reaction temperature in the reactor A is preferably 80~110℃, more preferably 90~110℃.

[0066] The reaction temperature in the reactor B is preferably 100~130℃, more preferably 110~120℃.

[0067] Preferably, the stream VI enters the downstream separation system.

[0068] Figure 1 A schematic flowchart of the continuous synthesis method of glufosinate provided by the present invention.

[0069] Compared with the prior art, the present invention provides a continuous synthesis method for glufosinate, comprising the following steps: A) mixing diethyl methylphosphonite, acrolein, and acetic acid for a condensation reaction to obtain compound a-1; B) mixing compound a-1 with water and performing a first hydrolysis reaction under the action of a catalyst to obtain a first system; the first system includes compound b, compound c, ethanol, acetic acid, and unreacted compound a-1; C) returning a portion of the first system to the condensation reaction system of step A), where ethanol and acetic acid react with diethyl methylphosphonite and acrolein, respectively, to generate compound a; the portion of the first system not returned is mixed with an acidic compound for a second hydrolysis reaction to obtain compound c; D) reacting compound c with an ammonia source and a cyanide source for a cyanamide reaction to obtain compound d; the ammonia source is selected from ammonia water or a mixture of ammonia water and ammonium chloride; the cyanide source is selected from sodium cyanide or hydrogen cyanide; E) compound d undergoes a third hydrolysis reaction to generate glufosinate.

[0070] The continuous synthesis method of glufosinate provided by this invention consists of steps including condensation, primary hydrolysis, secondary hydrolysis, cyanamide formation, and tertiary hydrolysis. In particular, a portion of the material generated after the primary hydrolysis is recycled into the condensation reaction, serving both as a solvent dilution and allowing the byproducts such as acetic acid and ethanol to be reused as raw materials for the condensation reaction. This reduces the amount of ethanol and acetic acid transported and improves the raw material conversion rate. Attached Figure Description

[0071] Figure 1 A schematic flowchart of the continuous synthesis method of glufosinate provided by the present invention;

[0072] Figure 2 The GC spectrum of the system obtained from the second hydrolysis reaction is shown. Detailed Implementation

[0073] To further illustrate the present invention, a detailed description is provided below with reference to embodiments. However, it should be understood that these descriptions are merely for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims.

[0074] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0075] Example 1

[0076] 5.89 g acrolein (0.10 mol, 95%) and 6.06 g acetic acid (0.10 mol, 99%) were pre-mixed and then simultaneously injected into a continuous flow reactor with 14.32 g (0.10 mol, 95%) diethyl methyl phosphite via pumps for condensation reaction. The feed flow rates were set to 12.85 ml / min (0.1 mol / min) and 15.91 ml / min (0.1 mol / min), respectively, and the reactor temperature was controlled at 22 °C.

[0077] The reactor for primary hydrolysis was filled with self-made ZSM-5 molecular sieves with a silica-to-alumina ratio of approximately 5.0, with a packing density of d = 6 mm × 5 m. The water feed rate was set to 0.36 ml / min (0.02 mol / min), and the primary hydrolysis reaction temperature was controlled at 40 °C. Initially, the three-way valve at the reactor outlet was switched to full circulation mode, and the vent valve was opened to allow all of stream II generated from the primary hydrolysis to return. Once the returned stream II filled the pipeline and reached the vent valve, the vent valve was closed.

[0078] Replace the feed material at the inlet pump with a sufficient amount of acrolein and acetic acid premixed in a 1:0.5 molar ratio, and a sufficient amount of diethyl methylphosphonate. Set the feed flow rates to 28.79 ml / min (0.3 mol / min for acrolein and 0.15 mol / min for acetic acid) and 47.72 ml / min (0.3 mol / min for diethyl methylphosphonate), respectively. Simultaneously open the outlet three-way valve to control the water feed flow rate at 1.08 ml / min, and control the return stream II flow rate at 146.1 ml / min via the circulation pump. Continue to control the condensation reaction temperature at 22°C and the primary hydrolysis reaction temperature at 40°C.

[0079] The feed flow rate of 2% dilute hydrochloric acid was set at 10.95 ml / min, and it, along with the material from the outlet of the primary hydrolysis three-way valve, entered the continuous flow reactor for secondary hydrolysis. The reaction temperature was controlled at 42℃. The material at the outlet was sampled and analyzed by GC, as shown in the attached figure. Figure 2 As shown, the main component is the intermediate phosphonic aldehyde, with an RT of 14.18 min and a content of 79.5%. Other substances are mainly ethanol (9.2%, RT=3.19 min), acetic acid (6.1%, RT=4.10 min), and water (no peak observed).

[0080] Ammonia and cyanide source compounds were pumped into the reactor at a flow rate of 104.15 ml / min. The ammonia and cyanide source compounds were a pre-stirred mixed aqueous solution of ammonium chloride, ammonia water, and sodium cyanide in a molar ratio of 1.0:4.0:1.01. This mixture was mixed with stream III from the previous reactor and then entered the reactor to carry out the cyanamation reaction. The reaction temperature was controlled at 20°C to generate stream IV.

[0081] The 960.95g (1.5mol) of material accumulated over 5 minutes in the above steps was received into a 2000ml jacketed reactor. 760.4g of 36% hydrochloric acid was added, and the mixture was heated and stirred to 105℃. 517.6g of the initial fraction was removed, and the mixture was then transferred to another 2000ml jacketed reactor. The temperature was gradually increased to 115℃ over 6 hours, and 282.2g of fraction was obtained by condensation. The remaining liquid in the jacketed reactor was 915.04g. Analysis showed a glufosinate content of 28.7%, and the overall reaction yield was calculated to be 88.36%.

[0082] Example 2

[0083] In this embodiment, the initial filling of the reactor with material is basically the same as in Example 1, but the water feed flow rate is set to 0.43 ml / min (0.024 mol / min).

[0084] A sufficient amount of acrolein:acetic acid premixed solution with a molar ratio of 1:0.6 was prepared according to the ratio of acrolein (58.9 g, 1.0 mol, 95%) to acetic acid (36.4 g, 0.6 mol, 99%). This premixed solution, along with diethyl methyl phosphite (95%), was then simultaneously injected into a continuous flow reactor via separate pumps for condensation reaction. The feed flow rates were set to 30.75 ml / min (0.3 mol / min for acrolein and 0.18 mol / min for acetic acid) and 47.73 ml / min (0.3 mol / min for acetic acid), respectively. The reactor temperature was controlled at 22℃. The three-way valve was opened, and the primary hydrolysis influent flow rate was controlled at 0.86 ml / min, while the return material flow rate was controlled at 117.5 ml / min.

[0085] The feed flow rate of 2% dilute hydrochloric acid was set at 10.95 ml / min, and it was fed into the continuous flow reactor together with the material from the outlet of the primary hydrolysis three-way valve for secondary hydrolysis. The reaction temperature was controlled at 42°C. The material at the outlet was sampled and analyzed by GC. The chromatogram was similar to that of Example 1, with phosphonaldehyde (80.1%, RT=14.18 min), ethanol (9.0%, RT=3.19 min), and acetic acid (7.15%, RT=4.10 min).

[0086] The cyanamide reaction and the three-stage hydrolysis reaction were performed in the same manner as in Example 1. The initial fraction (507.0 g) was removed by heating to 105°C, and the final fraction (300.3 g) was obtained by heating to 115°C. The remaining liquid in the reactor was 910.6 g. Analysis showed that the glufosinate content was 29.1%, and the overall reaction yield was calculated to be 89.10%.

[0087] Example 3

[0088] In this embodiment, the initial filling of the reactor with material is basically the same as in Example 1, but the water feed flow rate is set to 0.29 ml / min (0.016 mol / min).

[0089] A sufficient amount of acrolein:acetic acid premixed solution with a molar ratio of 1:0.4 was prepared according to the ratio of acrolein (58.9 g, 1.0 mol, 95%) to acetic acid (24.2 g, 0.4 mol, 99%). This premixed solution, along with diethyl methyl phosphite (95%), was then simultaneously injected into a continuous flow reactor via separate pumps for condensation reaction. The feed flow rates were set to 26.84 ml / min (0.3 mol / min for acrolein and 0.12 mol / min for acetic acid) and 47.73 ml / min (0.3 mol / min for acetic acid), respectively. The reactor temperature was controlled at 22℃. The three-way valve was opened, and the primary hydrolysis influent flow rate was controlled at 1.3 ml / min, while the return material flow rate was controlled at 182.2 ml / min.

[0090] The feed flow rate of 2% dilute hydrochloric acid was set at 10.95 ml / min, and it was fed into the continuous flow reactor together with the material from the outlet of the primary hydrolysis three-way valve for secondary hydrolysis. The reaction temperature was controlled at 42°C. The material at the outlet was sampled and analyzed by GC. The chromatogram was similar to that of Example 1, with phosphonaldehyde (78.3%, RT=14.18 min), ethanol (8.7%, RT=3.19 min), and acetic acid (5.2%, RT=4.10 min).

[0091] The cyanamide reaction and the three-stage hydrolysis reaction were performed in the same manner as in Example 1. The temperature was raised to 105°C to remove 520.2 g of the initial fraction, and then raised to 115°C to obtain 280.7 g of the final fraction. The remaining liquid in the reactor was 913.6 g. Analysis showed that the glufosinate content was 28.6%, and the overall reaction yield was calculated to be 87.80%.

[0092] Example 4

[0093] In this embodiment, the operation of initially filling the reactor with material and the ratio of raw materials for the condensation reaction are the same as in Example 1.

[0094] The feed flow rates of the acetic acid and acrolein mixture and the diethyl methyl phosphite feed pump were set to 57.58 ml / min (0.6 mol / min for acrolein and 0.6 mol / min for acetic acid) and 95.44 ml / min (0.6 mol / min for acetic acid), respectively, and the reactor temperature was controlled at 22℃. The three-way valve was opened, and the primary hydrolysis influent flow rate was controlled at 2.16 ml / min, while the return material flow rate was controlled at 293.0 ml / min.

[0095] The feed flow rate of 2% dilute hydrochloric acid was set at 21.90 ml / min, and it was fed into the continuous flow reactor together with the material from the outlet of the primary hydrolysis three-way valve for secondary hydrolysis. The reaction temperature was controlled at 42°C. The material at the outlet was sampled and analyzed by GC. The spectrum was similar to that of Example 1, with phosphonaldehyde (77.0%, RT=14.18 min), ethanol (9.0%, RT=3.19 min), and acetic acid (6.6%, RT=4.10 min).

[0096] Example 5

[0097] In this embodiment, the operation of initially filling the reactor with material, the condensation reaction, and the secondary hydrolysis reaction are the same as in Example 1. The difference is that the influent flow rate for the primary hydrolysis is controlled at 2.16 ml / min, and the return material flow rate is controlled at 146.1 ml / min. In the GC spectrum of the secondary hydrolysis products, phosphonaldehyde (76.9%, RT=14.18 min), ethanol (9.0%, RT=3.19 min), and acetic acid (7.15%, RT=4.10 min) are present.

[0098] Example 6

[0099] In this embodiment, all other operations are the same as in Example 1. The difference is that the material after the cyanamide reaction is completed is transferred to a container and depressurized to -0.95 MPa to continuously remove ammonia from the liquid. After maintaining the temperature at 25°C and depressurizing for 2.5 hours, the final pH of the liquid is measured to be 7.5.

[0100] Add 494.1g of 36% hydrochloric acid to 884.20g of the above material (total 1.5mol), heat and stir to 105℃, remove the initial fraction 291.564g, and continue heating to 115℃ to obtain 167.4g of fraction. The remaining liquid in the reactor is 895.8g. Sampling analysis shows that the glufosinate content is 29.4%, and the overall reaction yield is calculated to be 88.50%.

[0101] Example 7

[0102] In this embodiment, all other operations are the same as in Example 1, except that the hydrochloric acid used for the three hydrolysis cycles is a mixture of the latter fraction (436.5 g, 9.5% hydrochloric acid concentration) and 36% hydrochloric acid (645.2 g) collected under the conditions of Example 1, totaling 1081.7 g. After adding the hydrochloric acid, the mixture was heated and stirred to 105°C to remove 790.5 g of the former fraction. The temperature was then further increased to 115°C to obtain 298.6 g of the fraction. The remaining liquid in the reactor was 920.3 g. Sampling analysis showed that the glufosinate content was 28.5%, and the overall reaction yield was calculated to be 88.25%.

[0103] Comparative Example 1

[0104] Using the reaction apparatus described in Example 1, the primary hydrolysis reactor was removed, and its outlet three-way valve was switched to a straight-through state. A sufficient amount of acrolein:acetic acid premixed solution with a molar ratio of 1:1 was prepared according to the ratio of acrolein (58.9 g, 1.0 mol, 95%) to acetic acid (60.6 g, 1.0 mol, 99%). This premixed solution, along with diethyl methyl phosphite (95%), was then simultaneously injected into a continuous flow reactor via pumps for condensation reaction. The feed flow rates were set to 38.57 ml / min (0.3 mol / min) and 47.73 ml / min (0.3 mol / min), respectively, and the reactor temperature was controlled at 22°C.

[0105] The feed flow rate of 2% dilute hydrochloric acid was set at 12.0 ml / min, and the reaction temperature was controlled at 42℃. The material at the outlet was sampled and analyzed by GC. The results showed that phosphonaldehyde (73.2%, RT=14.18 min), ethanol (1.2%, RT=3.19 min), and acetic acid (18.9%, RT=4.10 min).

[0106] A pre-stirred mixed aqueous solution of ammonium chloride, ammonia, and sodium cyanide in a molar ratio of 1.0:4.0:1.01 was pumped into the reactor at a flow rate of 104.15 ml / min to carry out the cyanamation reaction, and the reaction temperature was controlled at 20℃.

[0107] Add 760.4 g of 36% hydrochloric acid to 941.0 g (1.5 mol) of material accumulated over 5 minutes in the above steps. Heat and stir to 105°C, removing 506.8 g of the initial fraction. Continue heating for 6 hours to 115°C, removing 274.1 g of the final fraction. The remaining liquid is 902.6 g. Sampling analysis shows a glufosinate content of 25.3%, and the overall reaction yield is calculated to be 76.27%.

[0108] Comparative Example 2

[0109] Using the reaction apparatus and feed flow rate from Comparative Example 1, the temperature inside the condensation reactor was controlled at 6°C. GC analysis was performed on phosphonaldehyde (76.9%, RT=14.18 min), ethanol (0.9%, RT=3.19 min), and acetic acid (17.9%, RT=4.10 min). 760.4 g of 36% hydrochloric acid was added to the cyanamide-treated feed collected over 5 min, and the mixture was heated and stirred to 105°C. 501.0 g of the initial fraction was removed. The temperature was gradually increased to 115°C over 6 h, and 275.5 g of the final fraction was removed. The remaining 910.7 g of feed was sampled and analyzed; the glufosinate content was 27.2%, and the overall reaction yield was calculated to be 83.44%.

[0110] Comparative Example 3

[0111] Using the reaction apparatus, feed flow rate, and reaction conditions described in Comparative Example 1, the mixture was directly stirred and gradually heated to 115°C over 6 hours, yielding 790.7 g of fraction. The remaining liquid was 900.6 g; analysis showed a glufosinate content of 25.3%, and the overall reaction yield was calculated to be 76.8%.

[0112] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A continuous synthesis method for glufosinate, comprising the following steps: A) Diethyl methylphosphonite, acrolein and acetic acid were mixed and subjected to a condensation reaction to obtain compound a-1; B) Compound a-1 is mixed with water and subjected to a first hydrolysis reaction in the presence of a catalyst to obtain the first system; the first system includes compound b, compound c, ethanol, acetic acid and unreacted compound a-1; C) A portion of the first system is returned to the condensation reaction system of step A), where ethanol and acetic acid react with diethyl methylphosphonite and acrolein, respectively, to generate compound a; The portion of the first system that was not returned was mixed with an acidic compound and subjected to a second hydrolysis reaction to obtain compound c; D) Compound c undergoes a cyanamide reaction with an ammonia source and a cyanide source to obtain compound d; E) Compound d undergoes a third hydrolysis reaction to produce glufosinate; R1 is -COCH3; R is either -CH2CH3 or -COCH3.

2. The continuous synthesis method of glufosinate according to claim 1, characterized in that, In step C), a portion of the first system is 10% to 70% of the total.

3. The continuous synthesis method of glufosinate according to claim 1, characterized in that, A portion of the first system is returned as stream II. After stream II is returned to the condensation reaction system in step A), the system obtained by the condensation reaction is denoted as stream I. Stream I is then repeated in step B) to undergo the first hydrolysis reaction to obtain the first system. A portion of this system is then denoted as stream II and returned to step A) for reuse. The remaining portion undergoes the second hydrolysis reaction, and this cycle continues.

4. The continuous synthesis method of glufosinate according to claim 1, characterized in that, The condensation reaction is carried out in a continuous flow reactor; The condensation reaction occurs at a temperature of 5~45℃.

5. The continuous synthesis method of glufosinate according to claim 1, characterized in that, The catalyst for the first hydrolysis reaction is a supported acidic catalyst.

6. The continuous synthesis method of glufosinate according to claim 4, characterized in that, The catalyst for the first hydrolysis reaction is a ZSM-5 molecular sieve catalyst.

7. The continuous synthesis method of glufosinate according to claim 1, characterized in that, The temperature of the first hydrolysis reaction is 20~80℃.

8. The continuous synthesis method of glufosinate according to claim 1, characterized in that, The reaction temperature for the second hydrolysis reaction is 20~60℃.

9. The continuous synthesis method of glufosinate according to claim 1, characterized in that, The ammonia source is selected from ammonia water or a mixture of ammonia water and ammonium chloride; the cyanide source is selected from sodium cyanide or hydrogen cyanide; The molar amount of the ammonia source is 1 to 6 times that of compound c; The molar amount of the cyanide source is 0.99 to 1.2 times that of compound c.

10. The continuous synthesis method of glufosinate according to claim 1, characterized in that, The third hydrolysis reaction was carried out sequentially in reactors A and B; The reaction temperature in reactor A is 80~110℃; The reaction temperature in reactor B is 100~130℃.

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