Method for recycling glyphosate membrane-passing washing water for synthesizing glyphosate

Abstract

The invention discloses a method for reusing glyphosate membrane-passing washing water for synthesis of glyphosate, which comprises the following steps: absorbing hydrogen chloride gas by the glyphosate membrane-passing washing water to obtain a hydrochloric acid solution containing glyphosate, and using the hydrochloric acid solution containing glyphosate for synthesis of glyphosate. According to the method, the glyphosate membrane-passing washing water can be directly utilized, the steam energy consumption is reduced, meanwhile, the glyphosate dissolved in the glyphosate membrane-passing washing water can be recycled, the glyphosate yield is increased, the material consumption cost of glyphosate production is remarkably reduced, and the resource utilization rate is increased.

Description

Technical Field

[0001] The invention relates to a method for recycling glyphosate washing water, in particular to a method for preparing hydrochloric acid by absorbing hydrogen chloride in glyphosate membrane washing water, and then using the obtained hydrochloric acid for glyphosate synthesis, belonging to the technical field of wastewater resource recovery and utilization. Background Art

[0002] Glyphosate is a highly effective, low-toxic, broad-spectrum, non-selective herbicide with excellent herbicidal activity. It is the largest herbicide variety in the world. There are two mainstream production routes for glyphosate: the alkyl ester method (glycine method) and the iminodiacetic acid method (IDA method). The production process abroad is mainly the IDA method of Monsanto Company in the United States; the alkyl ester method is the majority of domestic production processes, and about 70% of the production capacity is using this route. The alkyl ester method uses glycine and dimethyl phosphite as the main raw materials, methanol as the solvent, and in the presence of the catalyst triethylamine, glycine, polyformaldehyde, and dimethyl phosphite react to obtain a condensation liquid. After the condensation liquid is mixed with a certain proportion of hydrochloric acid for acidification, it is gradually heated and hydrolyzed to produce glyphosate and by-products methylal and chloromethane. The hydrolyzed liquid is crystallized, separated, washed, and dried to obtain glyphosate technical that meets the national standard.

[0003] The traditional process of synthesizing glyphosate by glycine is to obtain glyphosate powder after depolymerization, addition, condensation, acidification, acidification and hydrolysis, crystallization separation, water washing and drying. The yield of glyphosate powder in the industry is about 75%. A part of glyphosate exists in the washing water obtained by washing crystals. If this part of washing water is directly used to recover glyphosate, a large amount of water needs to be evaporated, which consumes a lot of energy, and the recovery is incomplete, the utilization rate of phosphorus is low, and the dry powder yield is low.

[0004] At present, most processes and technologies are centered around solvent recovery and reuse, and wastewater treatment technology is used to treat and recover valuable components. For example, pollutants in wastewater are removed by chemical precipitation, adsorption, membrane separation and other methods, and salts, organic matter, etc. are recovered. Or the use of methanol solution of hydrogen chloride (acid methanol) for acid hydrolysis (hydrolysis) can reduce the amount of water brought into the system, which may improve the selectivity and yield of the reaction. Or improve the reaction conditions, optimize the raw material ratio and other aspects to reduce energy consumption. Therefore, continuous process improvement is needed to improve the utilization rate of raw materials, reduce the generation of wastewater, reduce production costs, reduce energy consumption, and increase the cleanliness level of glyphosate production by the glycine method. Summary of the invention

[0005] In view of the above problems, the present invention provides a method for recycling glyphosate membrane washing water for synthesizing glyphosate. The method utilizes the membrane treatment desalination technology commonly used today, firstly performs membrane treatment desalination on the glyphosate washing water, and then uses the water to absorb hydrogen chloride to prepare hydrochloric acid, and the hydrochloric acid is used in the glyphosate synthesis process. The method realizes the direct use of the washing water and the recovery of the glyphosate dissolved therein, increases the dry powder yield of glyphosate, reduces energy consumption, reduces the synthesis cost of glyphosate, and improves the cleanliness level of glyphosate synthesis by the glycine method.

[0006] The specific technical solutions of the present invention are as follows: A method for recycling glyphosate membrane washing water for synthesizing glyphosate, comprising the following steps: (1) Use glyphosate membrane wash water to absorb hydrogen chloride gas to obtain a hydrochloric acid solution containing glyphosate.

[0007] (2) A hydrochloric acid solution containing glyphosate is used to synthesize glyphosate.

[0008] Furthermore, in step (1), the process for producing the glyphosate membrane washing water is: subjecting the water produced by washing the glyphosate crystals after cooling and crystallization in the process of synthesizing glyphosate by the glycine-dimethyl phosphite method to membrane treatment to obtain the membrane washing water.

[0009] Furthermore, membrane treatment technology is a commonly used treatment method in the field of wastewater treatment. The membrane used can be a microfiltration membrane, a nanofiltration membrane, an ultrafiltration membrane, a reverse osmosis membrane, etc. The molecular weight cutoff of the membrane is selected according to needs. The main purpose of the present invention is to remove small molecules such as sodium chloride in the wash water and leave large molecules such as glyphosate. Any membrane that achieves this purpose can be used.

[0010] Furthermore, after membrane treatment, the sodium chloride content in the obtained glyphosate membrane washing water is 0-3.0wt%, for example, 0%, 1%, 2%, 3%, and the preferred content is less than or equal to 2.0wt%.

[0011] Furthermore, in step (1), the hydrogen chloride gas may be from various sources, such as pure hydrogen chloride gas or hydrogen chloride byproducts produced during chemical synthesis in the fields of chemical industry, medicine, pesticide, etc., preferably hydrogen chloride byproducts, which are low-cost and environmentally friendly. The main component of hydrogen chloride gas is hydrogen chloride, and it may also contain a small amount of other impurities. The content of impurities should not affect the synthesis and use of glyphosate. For example, it can be hydrogen chloride byproduct produced from the preparation of dimethyl phosphite, an intermediate of the glycine method for synthesizing glyphosate.

[0012] Furthermore, in step (1), the concentration of the glyphosate-containing hydrochloric acid solution obtained by absorbing hydrogen chloride gas in the glyphosate membrane washing water is generally 25-36wt%, for example, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, preferably 28-32%.

[0013] Furthermore, in step (2), the hydrochloric acid solution containing glyphosate is used in the process of synthesizing glyphosate, so the hydrochloric acid solution contains glyphosate, which will not cause waste of glyphosate during the synthesis process, thereby improving the yield of glyphosate. The hydrochloric acid solution containing glyphosate is mainly used in the hydrolysis section of glyphosate synthesis, that is, the condensation liquid is added to the hydrochloric acid solution containing glyphosate for acidification and hydrolysis, and the condensation liquid is obtained by depolymerization, addition and condensation of glycine, polyformaldehyde and dimethyl phosphite. During hydrolysis, the molar ratio of hydrogen chloride to glycine in the hydrochloric acid solution containing glyphosate is 3.2 to 4.0:1, for example, 3.2:1, 3.3:1, 3.4:1, 3.5:1, 3.6:1, 3.7:1, 3.8:1, 3.9:1, 4.0:1.

[0014] Furthermore, the synthesis process of glyphosate is as follows: using glycine, paraformaldehyde, and dimethyl phosphite as raw materials, methanol as solvent, and triethylamine as catalyst, a condensation liquid is obtained through depolymerization, addition, and condensation reaction, and the condensation liquid is added with a hydrochloric acid solution containing glyphosate for hydrolysis, and after hydrolysis, desolventization, cooling crystallization, solid-liquid separation, water washing, and drying are performed to obtain glyphosate dry powder. The washing water obtained by water washing is subjected to membrane treatment to obtain glyphosate membrane washing water, which can be used in the next batch of glyphosate synthesis, realizing the recycling of washing water and the recovery of glyphosate.

[0015] Furthermore, during the crystallization by cooling, the pH of the crystallization solution is adjusted to 0.7-1.5, preferably 0.8-1.2, with an alkali solution.

[0016] Furthermore, when the crystals are washed with water, the molar ratio of water to glycine is 10 to 20:1, for example, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1, 20:1, preferably 12-16:1.

[0017] Compared with the prior art, the beneficial effects of this technology are: (1) Utilizing the concept of material recycling, the wash water produced in the glyphosate synthesis process is pretreated through membrane treatment technology, and then made into a hydrochloric acid solution and applied to the acid hydrolysis process of the next batch of glyphosate synthesis. This avoids the process of separate treatment of wash water, reduces water usage, and has a significant effect on energy conservation and consumption reduction in glyphosate production.

[0018] (2) The present invention directly reuses the glyphosate washing water in the glyphosate synthesis, and can directly recover the glyphosate dissolved therein, thereby reducing the energy consumption and cost of glyphosate recovery. According to the ultraviolet spectrophotometry specified in GB / T12686-2017, the yield of glyphosate dry powder obtained by the method of the present invention is greater than 79.0%, and the glyphosate dry powder content is greater than 95.0%, thereby achieving direct recovery of part of the glyphosate in the washing water, significantly improving the separation yield of glyphosate, improving the phosphorus utilization rate, and reducing the cost of glyphosate synthesis. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The figure is a process flow chart for synthesizing glyphosate using glyphosate washing water. DETAILED DESCRIPTION

[0020] The present technology is further described below with specific embodiments. The specific embodiments described herein are only used to explain the present technology, rather than all embodiments. Based on the embodiments in the present technology, all other embodiments obtained by those skilled in the art without making creative work are within the protection scope of the present technology.

[0021] Unless otherwise specified, the following reagents are commercially available and the following concentrations are percentage by mass.

[0022] Example 1 1. Take 240 g of washing water obtained by solid-liquid separation and washing crystals of glyphosate, and perform membrane treatment to remove sodium chloride therein to obtain 235 g of glyphosate membrane washing water, with a sodium chloride content of 2.3% and a glyphosate content of 1.05%.

[0023] 2. A hydrogen chloride gas passing device was built, and the glyphosate membrane wash water was used to absorb hydrogen chloride gas. The system was passed until the weight increased by 101 g. Samples were taken for testing, and the concentration of the prepared hydrochloric acid solution was measured to be 30.3%.

[0024] 3. Take 49g of polyformaldehyde solid, add 52g of methanol and 1g of triethylamine, stir and depolymerize at 50-60℃, react for 1h, and obtain depolymerization liquid; cool the depolymerization liquid to 40-42℃, add 230g of methanol, 61g of glycine (0.80mol), and 68g of triethylamine, and stir and react for 60min to obtain addition liquid. Add 108g of dimethyl phosphite and 15g of triethylamine dropwise to the addition liquid, control the temperature to 50-54℃ for condensation reaction, and keep the temperature for 1-1.5h after the addition is completed to obtain condensation liquid.

[0025] 4. After the condensation reaction is completed, 346 g of the hydrochloric acid solution prepared in step 2 is added to the condensation liquid at 30 ° C for acidification and hydrolysis. The hydrolysis time is 4 hours. After hydrolysis, the temperature is raised to 118 ° C for desolventization to obtain a hydrolyzed material. The hydrolyzed material is kept warm for reaction for 1.5 hours and then naturally cooled to 50-60 ° C. Sodium hydroxide solution is added dropwise to adjust the pH to 0.9, and the temperature is lowered to 25 ° C and stirred for crystallization for 8 hours, then filtered. The obtained crystals are washed twice with 200 g of water and dried to obtain 112.8 g of glyphosate dry powder, with a content (HPLC) of 95.0%, and a glyphosate dry powder yield of 79.2% based on glycine.

[0026] Example 2 1. Take 230 g of washing water obtained by solid-liquid separation and washing crystals of glyphosate, and perform membrane treatment to remove sodium chloride therein to obtain 226 g of glyphosate membrane washing water with a sodium chloride content of 2.2% and a glyphosate content of 1.08%.

[0027] 2. A hydrogen chloride gas passing device was built, and the glyphosate membrane wash water was used to absorb hydrogen chloride gas. The gas was passed until the system gained 107 g. Samples were taken for testing, and the concentration of the prepared hydrochloric acid solution was found to be 32.0%.

[0028] 3. Obtain the condensation solution according to the method of step 3 of Example 1.

[0029] 4. Add 318 g of the hydrochloric acid solution prepared in step 2 to the condensation liquid at 30 ° C for acidification and hydrolysis for 6 hours. After hydrolysis, heat up to 118 ° C for desolventizing to obtain a hydrolysis material. After the hydrolysis material is kept warm for 1.5 hours, the temperature is naturally lowered to 50-60 ° C, and sodium hydroxide solution is added dropwise to adjust the pH to 1.0. The temperature is lowered to 25 ° C and stirred for crystallization for 8 hours to obtain a crystalline material, which is then filtered. The obtained crystals are washed twice with 200 g of water and dried to obtain 112.7 g of glyphosate dry powder, with a content (HPLC) of 95.1%, and a glyphosate dry powder yield of 79.2% based on glycine.

[0030] Example 3 1. Take 250 g of washing water obtained by washing glyphosate crystals through solid-liquid separation, and perform membrane treatment to remove sodium chloride therein to obtain 247 g of glyphosate membrane washing water, with a sodium chloride content of 1.8% and a glyphosate content of 1.11%.

[0031] 2. A hydrogen chloride gas passing device was built, and the glyphosate membrane wash water was used to absorb hydrogen chloride gas. The gas was passed until the system gained 99 g. Samples were taken for testing, and the concentration of the prepared hydrochloric acid solution was found to be 28.5%.

[0032] 3. Obtain the condensation solution according to the method of step 3 of Example 1.

[0033] 4. Add 342 g of the hydrochloric acid solution prepared in step 2 to the condensation liquid at 30 ° C for acidification and hydrolysis. The hydrolysis time is 4 hours. After hydrolysis, the temperature is raised to 118 ° C for desolventization to obtain a hydrolysis material. The hydrolysis material is kept warm for reaction for 1.5 hours and then naturally cooled to 50-60 ° C. Sodium hydroxide solution is added dropwise to adjust the pH to 1.2. The temperature is lowered to 25 ° C and stirred for crystallization for 8 hours to obtain a crystalline material, which is then filtered. The obtained crystals are washed twice with 200 g of water and dried to obtain 112.2 g of glyphosate dry powder, with a content (HPLC) of 95.8%, and a glyphosate dry powder yield of 79.5% based on glycine.

[0034] Comparative Example 1 1. Obtain a condensation solution according to the method of step 3 of Example 1.

[0035] 2. After the condensation reaction is completed, 346 g of a commercially available 30% hydrochloric acid solution that does not contain glyphosate is added to the condensation liquid at 30°C for acidification and hydrolysis. The hydrolysis time is 4 hours. After the hydrolysis, the temperature is raised to 118°C for desolvation to obtain a hydrolysis material. The hydrolysis material is kept warm for reaction for 1.5 hours and then naturally cooled to 50-60°C. Sodium hydroxide solution is added dropwise to adjust the pH to 0.9. The temperature is lowered to 25°C and stirred for crystallization for 8 hours to obtain a crystalline material, which is then filtered. The obtained crystals are washed twice with 200 g of water and dried to obtain 110.6 g of glyphosate dry powder with a content (HPLC) of 95.5%. The yield of glyphosate dry powder is 78.1% based on glycine.

Claims

1. A method for recycling glyphosate membrane washing water for synthesizing glyphosate, characterized in that The following steps are involved: (1) Using glyphosate membrane wash water to absorb hydrogen chloride gas to obtain a hydrochloric acid solution containing glyphosate; (2) A hydrochloric acid solution containing glyphosate is used to synthesize glyphosate.

2. The method according to claim 1, characterized in that: In step (1), the process for producing the glyphosate membrane washing water is as follows: water produced by washing glyphosate crystals after cooling and crystallization in the process of synthesizing glyphosate by the glycine-dimethyl phosphite method is subjected to membrane treatment to obtain the membrane washing water.

3. The method according to claim 2, characterized in that: The membranes used in membrane treatment include microfiltration membranes, nanofiltration membranes, ultrafiltration membranes, and reverse osmosis membranes.

4. The method according to claim 2, characterized in that: After membrane treatment, the sodium chloride content in the obtained membrane washing water is 0~3.0wt%.

5. The method according to claim 1, characterized in that: In step (1), hydrogen chloride gas is a by-product produced during the chemical reaction.

6. The method according to claim 1, characterized in that: In step (1), the hydrogen chloride gas is the by-product hydrogen chloride produced during the synthesis of glyphosate by the glycine method.

7. The method according to claim 1, characterized in that: In step (1), the concentration of hydrogen chloride in the hydrochloric acid solution containing glyphosate is 25-36 wt %.

8. The method according to claim 1, characterized in that: In step (2), a hydrochloric acid solution containing glyphosate is used in the hydrolysis stage of a condensation liquid, wherein the condensation liquid is obtained by depolymerization, addition and condensation of glycine, paraformaldehyde and dimethyl phosphite; preferably, the molar ratio of hydrogen chloride to glycine in the hydrochloric acid solution containing glyphosate is 3.2 to 4.0:

1.

9. The method according to claim 8, characterized in that: The condensation liquid is hydrolyzed with a hydrochloric acid solution containing glyphosate, and after the hydrolysis, the glyphosate dry powder is obtained by desolventizing, cooling and crystallizing, solid-liquid separation, water washing and drying. The washing water obtained by water washing is treated with a membrane and then enters step (1) for reuse.

10. The method according to claim 9, characterized in that: The molar ratio of water to glycine used for water washing is 10-20:1.

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