Synthesis method of glyphosate

Abstract

The invention discloses a synthesis method of glyphosate. The synthesis method comprises the following steps: carrying out a depolymerization reaction on paraformaldehyde, formaldehyde and a catalyst in methanol to obtain a depolymerization solution; adding glycine, methanol and triethylamine into the depolymerization liquid for catalytic reaction to obtain addition liquid; dimethyl phosphite is added into the addition liquid, triethylamine is supplemented, and a condensation liquid is obtained through a reaction; adding the condensation liquid into a supercritical extraction kettle, and extracting methanol and triethylamine hydrochloride; and adding hydrochloric acid into the extracted condensation liquid for acidolysis to remove chloromethane, hydrogen chloride, water or other light components, adding alkali to adjust pH, crystallizing, filtering and drying to obtain glyphosate. According to the method, a typical glycine method production process is improved, methanol, triethylamine hydrochloride and water in condensation reaction liquid can be quickly removed at low temperature by adopting a supercritical extraction technology, acidolysis energy consumption and hydrochloric acid consumption are reduced, a removed triethylamine and methanol mixed solution is recycled, and the yield of the product is improved. And the effects of recycling resources and reducing energy consumption are achieved. Meanwhile, the catalyst B is added, so that free aldehyde in a reaction system can be eliminated, side reactions are reduced, and the quality of the glyphosate active compound is improved.

Description

Technical Field

[0001] The invention belongs to the field of pesticide chemicals, and specifically relates to a method for synthesizing glyphosate. Background Art

[0002] Glyphosate is a globally recognized non-residue herbicide. It not only has excellent weed control effects, but also has the advantages of high efficiency, low toxicity and low residue, making it an important pesticide production material. my country is the world's largest glyphosate production market. Domestic companies have a glyphosate production capacity of about 813,000 tons / year, accounting for 68.72% of the world's current glyphosate production capacity. Some foreign regions restrict or prohibit the use of glyphosate, but only restrict the use of glyphosate in non-agricultural fields such as public places, and do not restrict the use of glyphosate in the agricultural field. With the further increase in the area of ​​genetically modified crops, pesticides such as paraquat will gradually withdraw from the herbicide market, and the global market demand for glyphosate will also increase further.

[0003] At present, the main methods for the production of glyphosate include: one is the production method using glycine and alkyl esters as raw materials; the other is the production method using iminodiacetic acid (IDA) as raw material. Among them, the glycine production route mainly uses polyformaldehyde, glycine, dimethyl phosphite as raw materials, triethylamine as catalyst, and methanol as solvent. It is prepared through four steps of depolymerization, addition, condensation and hydrolysis. At present, through the exploration of the synthesis reaction mechanism and the continuous optimization of process parameters, the yield of glyphosate based on glycine is generally more than 78%, and the total yield is stable at more than 82%. However, the effective utilization rate of phosphorus is only about 60-65%, which is relatively low. The reason for the low phosphorus utilization rate is that side reactions occur during the resynthesis process, generating phosphorus-containing compounds such as phosphorous acid, hydroxymethyl phosphonic acid, methyl glyphosate and glyphosate, among which methyl glyphosate and glyphosate are generated by the reaction of glyphosate with free formaldehyde during high-temperature acid hydrolysis. In addition, the glycine-based glyphosate synthesis process still has problems such as high energy consumption, large solvent usage, long production cycle, large acid consumption in acid hydrolysis, and large alkali consumption in mother liquor treatment to recover triethylamine. Summary of the invention

[0004] The invention provides a method for synthesizing glyphosate, which improves the traditional glycine method, adopts supercritical extraction technology to quickly remove methanol, triethylamine and water in the condensation reaction solution at low temperature, reduces the energy consumption of acidolysis and the amount of hydrochloric acid used, recycles triethylamine and methanol solvents, and reduces the amount of alkali used in crystallization, thereby achieving the effect of resource recycling and energy consumption reduction. At the same time, adding a catalyst B can decompose the content of free aldehydes in the reaction system, reduce the generation of side reactions, and improve the quality of glyphosate original medicine. The technical solution of the present invention is as follows: A method for synthesizing glyphosate, the method comprising the following steps: I. reacting paraformaldehyde, formaldehyde and catalyst A in methanol at a temperature of 35-42°C until the solution becomes colorless and transparent to obtain a depolymerization solution; II. Add glycine, methanol and triethylamine to the depolymerization solution to obtain an addition solution, control the reaction temperature at 46-48°C, and the reaction time for 30-90 minutes; III. Add dimethyl phosphite to the addition liquid and add triethylamine to obtain a condensation solution, the reaction temperature is controlled at 54-60 ° C, the reaction time is 30-90 minutes; IV. Adding the catalyst B to the condensed liquid, after a period of reaction, transferring to a supercritical CO2 extraction kettle to extract methanol and triethylamine; V. Add hydrochloric acid to the condensed liquid after extraction to remove light components such as methyl chloride, hydrogen chloride, and water, add alkali to adjust the pH, crystallize, filter and dry to obtain glyphosate.

[0005] In the step I, the molar ratio of paraformaldehyde, methanol and catalyst is 1:(2-2.3):(0.4-0.8), preferably 1:2.1:0.4, 1:2:0.5.

[0006] In the step I, the catalyst is a methanol solution of one or more of sodium methoxide, potassium methoxide, triethylamine, and trimethylamine, with a concentration of 5-10 mol / L.

[0007] The molar ratio of glycine, methanol and triethylamine in step II is 1:(4-10):(0.4-0.8), preferably 1:6:0.5, 1:5:0.6.

[0008] In step III, the molar ratio of dimethyl phosphite to glycine is (1.10-1.2):1, preferably 1.14:1, 1.18:1, and the molar ratio of the added triethylamine to glycine is (0.2-0.6):1, preferably 0.3:1, 0.2:1.

[0009] The catalyst B used in step IV is one or more of sodium sulfite, sodium bisulfite, sodium phosphite and sodium hydrogen phosphite, preferably sodium bisulfite: sodium sulfite = 2:3, and the ratio of the added amount to glycine is (0.1-0.5):1, preferably 0.10:1.

[0010] In the present invention, the main component of the depolymerization liquid in step I of the synthesis of glyphosate is hemiacetal and the amount is excessive. The hemiacetal can reversibly generate methanol and formaldehyde. In the acidolysis process of step V, formaldehyde and the generated glyphosate can react under high temperature conditions to generate by-products such as formulas (2) and (3). The catalyst B can react with free formaldehyde to achieve the effect of removing free formaldehyde and reducing side reactions. .

[0011] The extractant for supercritical extraction in step IV is one of carbon dioxide, ethane, ethylene, propane and propylene, preferably carbon dioxide.

[0012] The carrier for supercritical extraction in step IV is a 5-10% dilute hydrochloric acid solution and one or a mixed solution of methanol, ethanol and water, preferably methanol.

[0013] The pressure of supercritical extraction is 7.5-20 MPa, the temperature is controlled at 35-45°C, and the extraction time is 30-50 minutes.

[0014] Supercritical extraction can extract 40-60% of the total mass of the condensation reaction solution, of which methanol accounts for 60-70%, triethylamine accounts for 30-40%, and others account for 5-10%. The mixed solution obtained by extraction can be applied to the step of adding triethylamine.

[0015] The molar ratio of hydrochloric acid used in the acidolysis in step V to glycine is (2.8-4.5):1, preferably 3.5:1. The acidolysis removal temperature is 95-115°C, preferably 110°C.

[0016] In step V, alkali is added to adjust the pH to 2.0-2.5, preferably 2.5, and the amount of alkali added is 35-50 g of 30-40% sodium hydroxide solution.

[0017] Beneficial effects of the present invention: The present invention adopts supercritical extraction technology in the process of glyphosate synthesis, and uses sodium sulfate and sodium bisulfite mixed binary catalytic decomposition reaction of free formaldehyde. Supercritical extraction technology can quickly extract the solvent in the reaction at low temperature, reduce the maximum reaction temperature, and effectively recycle the reaction solvent. Compared with single catalysis, the mixed binary catalyst of sodium sulfate and sodium bisulfite has a better catalytic decomposition effect, avoids the side reaction of free formaldehyde in the process of glyphosate synthesis, improves the purity of the prepared glyphosate original drug, and more effectively utilizes phosphorus resources. The supercritical extraction technology can quickly remove methanol, triethylamine and water in the condensation reaction liquid at low temperature, and based on 0.8 mol of glycine, the amount of hydrochloric acid used in the acid hydrolysis process is reduced by 30-50%, the maximum temperature of the acid hydrolysis is reduced by 10-25°C, and the reaction time is reduced by 10-20 minutes. The extracted methanol triethylamine mixed solution can be directly recycled and reused, reducing energy consumption and improving reaction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Supercritical CO2 extraction process flow chart.

[0019] Figure 2 Process flow chart of glyphosate synthesis method. DETAILED DESCRIPTION

[0020] The following will be combined with the specific embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. The embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the protection scope of the present invention.

[0021] Example 1 To a 1000mL four-necked reaction bottle, add 490.01g of paraformaldehyde, 90.03g of methanol, and 20.05g of a 5mol / L catalyst solution in sequence, raise the temperature to 40°C, keep the temperature at 40-42°C, and stir for 35 minutes to obtain a depolymerization reaction liquid; add 75.06g of glycine, 50.15g of triethylamine, and 160.03g of methanol to the depolymerization reaction liquid, control the temperature at 42°C, and stir for 65 minutes to complete the addition reaction to obtain an addition reaction liquid; add 100g of dimethyl phosphite to the addition reaction liquid; 01.02g, 65.03g of methanol, control the temperature at 55℃, stir for 20 minutes, add 30.51g of triethylamine, control the temperature at 58℃, react for 30 minutes, complete the condensation reaction, and obtain a condensation reaction liquid; add 10.41g of catalyst B (the mass ratio of sodium bisulfite and sodium sulfite is 2:3) to the condensation reaction liquid, react for 15 minutes, then transfer the condensation reaction liquid to a supercritical extraction reactor, use CO2 as the extractant, 20.03g of methanol as the carrying agent, the extraction temperature is 35℃, the extraction pressure is 8.00 MPa, the extraction time is 70 minutes, and 295.62g of extract and 300.25g of raffinate are obtained. 260.08 g of 30% hydrochloric acid was added to the raffinate for acidification, and the solution was desolventized and hydrolyzed for 1.8 hours. When the temperature reached 110°C, 90.02 g of water was added, and the solution was kept warm for 30 minutes, then cooled to below 85°C, and liquid alkali was added dropwise to adjust the pH to 2.0. The solution was stirred for 2 hours and allowed to stand for crystallization. The solution was washed, filtered, and dried to obtain 110.18 g of glyphosate powder with a mass fraction of 95.2%. The yield of glyphosate powder was 78.86% based on glycine, and the total yield was 81.97%.

[0022] Example 2 The experimental operation steps of Example 3 are similar to those of Example 1, except that catalyst B is not added, and the other operation steps are the same as those of Example 1. 110.05 g of glyphosate dry powder is obtained, and the glyphosate dry powder yield is 78.53% based on glycine, and the total yield is 82.26%.

[0023] Example 3 The experimental operation steps of Example 2 are similar to those of Example 1, except for the step of adding catalyst B. In Example 2, catalyst B is added after supercritical extraction, and a mixture of sodium bisulfite and sodium sulfite (the mass ratio of sodium bisulfite to sodium sulfite is 2:3) of 10.41 g is added. After the reaction, 110.22 g of glyphosate dry powder is obtained, and the glyphosate dry powder yield is 78.36% based on glycine, and the total yield is 82.23%.

[0024] Example 4 The experimental operation steps of Example 3 are similar to those of Example 1, except that the supercritical extraction conditions (extraction temperature 45°C, extraction pressure 20.00 MPa) are different in extraction pressure and temperature, and 10.41 g of catalyst B sodium bisulfite and sodium sulfite mixed catalyst B (the mass ratio of sodium bisulfite to sodium sulfite is 2:3) are added before extraction. The extraction conditions of Example 3 are that the extractant is CO2, the carrier is 20.05 g of methanol, the extraction temperature is 45°C, the extraction pressure is 20.00 MPa, the extraction time is 45 minutes, and 300.13 g of extract and 298.60 g of raffinate are obtained. 260.23 g of 30% hydrochloric acid is added for acidification. 110.15 g of glyphosate dry powder is obtained, and the glyphosate dry powder yield is 79.16% based on glycine, and the total yield is 82.26%.

[0025] Comparative Example 1 To a 1000mL four-necked reaction bottle, 49.03g of paraformaldehyde, 90.05g of methanol, and 20.13g of a 5mol / L catalyst solution were added in sequence, the temperature was raised to 40°C, kept at 40°C, and stirred for 35 minutes to obtain a depolymerization reaction liquid; 75.08g of glycine, 50.25g of triethylamine, and 160.13g of methanol were added to the depolymerization reaction liquid, the temperature was controlled at 42°C, and stirred for 65 minutes to complete the addition reaction to obtain an addition reaction liquid; 101.01g of dimethyl phosphite and 65.04g of methanol were added to the addition reaction liquid, the temperature was controlled at 55°C, stirred for 20 minutes, and the addition reaction was completed. Add 30.45 g of triethylamine, control the temperature at 58°C, react for 30 minutes, complete the condensation reaction, and obtain a condensation reaction liquid; add 320.05 g of 30% hydrochloric acid to the condensation reaction liquid for acidification, desolventize and hydrolyze for 2.5 hours, the temperature reaches 118°C, add 75.13 g of water, keep warm for 30 minutes, cool to below 85°C, add liquid alkali dropwise to adjust the pH to 2.0, continue stirring for 2 hours, and stand for crystallization; wash, filter, and dry to obtain 110.83 g of glyphosate dry powder with a mass fraction of 95.8%. Calculated on the basis of glycine, the glyphosate dry powder yield is 78.39%, and the total yield is 82.12%.

[0026] Comparative Example 2 The difference from the operation steps of Comparative Example 1 is that 10.43 g of catalyst B (sodium bisulfite and sodium sulfite) is added to the condensation reaction solution before acid hydrolysis, and 320.08 g of 30% hydrochloric acid is added for acidification after 15 minutes of reaction. 110.78 g of glyphosate dry powder with a mass fraction of 95.8% is obtained. The yield of glyphosate dry powder is 78.88% based on glycine, and the total yield is 82.23%.

[0027] Table 1 Serial number Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Catalyst B Catalyst B: glycine = 0.1:1 (before extraction) none Catalyst B: glycine = 0.1:1 (after extraction) Catalyst B: glycine = 0.1:1 (before extraction) none Catalyst B: glycine = 0.1:1 Extraction temperature, °C 35.0 35.0 35.0 45.0 / / Extraction pressure, MPa 8.00 8.00 8.00 20.00 / / Methyl glyphosate content, % 0.18 0.26 0.16 0.10 0.35 0.25 Glyphosate content, % 0.68 1.28 0.96 0.75 1.53 0.78 Glyphosate content, % 96.81 96.52 96.16 97.20 95.67 96.31 The testing instrument for glyphosate in the above embodiment is an ultraviolet spectrophotometer, and the testing is performed using the technical means of the national standard GB / T20684-2017.

[0028] It can be seen from the experimental data in Table 1 that the introduction of catalyst B in the synthesis process of glyphosate can effectively reduce the content of methyl glyphosate and glyphosate in the original drug. In addition, the use of supercritical extraction technology can recycle the solvent, reduce acid and alkali consumption, and further reduce the temperature of side reactions, reduce the generation of methyl glyphosate and glyphosate, and make the original drug glyphosate higher in purity. The technical solution of the present invention is explained through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above specific embodiments to be implemented. Any improvements made by technicians in the relevant field based on the present invention, or equivalent replacement of the materials selected by the present invention, etc., fall within the scope of protection of the patent.

Claims

1. A method for synthesizing glyphosate, characterized in that: The method comprises the following steps: Step I. performing a depolymerization reaction on paraformaldehyde, formaldehyde and catalyst A in methanol to obtain a depolymerization liquid; Step II. Add glycine, methanol and triethylamine to the depolymerization solution to obtain an addition solution; Step III. Add dimethyl phosphite to the addition liquid and add triethylamine to react to obtain a condensation liquid; Step IV. Adding the catalyst B to the condensed liquid, and transferring the mixture to a supercritical extraction kettle for extraction after the reaction; Step V. Add hydrochloric acid to the condensed liquid after extraction to remove methyl chloride, hydrogen chloride, water or other light components, cool it down, add alkali to adjust the pH, crystallize, filter and dry to obtain glyphosate.

2. A method for synthesizing glyphosate according to claim 1, characterized in that: In step I, the molar ratio of paraformaldehyde, methanol and catalyst is 1:(2-2.3):(0.4-0.8), and catalyst A is a methanol solution of one or more of sodium methoxide, potassium methoxide, triethylamine and trimethylamine.

3. A method for synthesizing glyphosate according to claim 1, characterized in that: In step I, the depolymerization reaction temperature is controlled at 35-40°C.

4. A method for synthesizing glyphosate according to claim 1, characterized in that: The molar ratio of glycine in step II to the paraformaldehyde in step II is 1:1.5-2.2, the molar ratio of glycine, methanol and triethylamine is 1:(4-10):(0.4-0.8), and the reaction temperature is controlled not higher than 48°C.

5. A method for synthesizing glyphosate according to claim 1, characterized in that: In step III, the molar ratio of dimethyl phosphite to glycine is (1.10-1.2):1, the molar ratio of the added triethylamine to glycine is (0.2-0.6):1, and the reaction temperature is controlled at 54-60°C.

6. A method for synthesizing glyphosate according to claim 1, characterized in that: The catalyst B in step IV is one or more of sodium sulfite, sodium bisulfite, sodium phosphite and sodium hydrogen phosphite, and the molar ratio of the catalyst B to glycine is (0.1-0.5):1, and the reaction takes 5-20 minutes.

7. A method for synthesizing glyphosate according to claim 1, characterized in that: The extractant for supercritical extraction in step IV is one of carbon dioxide, ethane, ethylene, propane, and propylene, the carrier is one of methanol and ethanol or a mixed solution, the pressure is 7.5-20 MPa, the temperature is controlled at 35-45°C, and the extraction time is 30-90 minutes.

8. A method for synthesizing glyphosate according to claim 1, characterized in that: In step V, the molar ratio of the mass of hydrochloric acid used in the acidolysis to glycine is (2.8-4.5):1, the concentration of the hydrochloric acid is 25-35%, and the acidolysis removal temperature is 95-120°C.

9. A method for synthesizing glyphosate according to claim 1, characterized in that: Step V: add alkali to adjust pH to 2.0-2.5.

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