Treatment method of rectifying still residues for preparing methyl phosphinic acid monoalkyl ester

Abstract

The invention provides a treatment method of rectifying still residues for preparing methyl phosphinic acid monoalkyl ester, which comprises the following steps: under a protective atmosphere, adding paraformaldehyde into the rectifying still residues for preparing methyl phosphinic acid monoalkyl ester, heating and stirring until the paraformaldehyde is completely dissolved, and continuously stirring to carry out a first reaction; adding toluene and alcohols into the reaction system to carry out esterification reaction; dehydrating the reaction system until no water is separated from the system, and rectifying the reacted material until no product methyl phosphinic acid monoalkyl ester is extracted; and cooling the reaction system, detecting that the content of methyl phosphine in the system is below the safety limit by using a phosphine gas detector, and transferring into a hazardous waste storage container. The process is simple to operate, low in cost and high in feasibility, the potential safety hazard in the production process of directly preparing methyl phosphinic acid monoalkyl ester by reacting methyl dichlorophosphine with alcohol in the past is solved, and the yield of the product methyl phosphinic acid monoalkyl ester can be greatly improved.

Description

Technical Field

[0001] The present application belongs to the technical field of waste treatment generated in chemical production processes, and more specifically, to a method for treating residues in a distillation kettle for preparing monoalkyl methylphosphinate. Background Art

[0002] Methylphosphinate monoalkyl ester is one of the most important intermediates for preparing glufosinate ammonium. As a herbicide, glufosinate ammonium is an alternative between glyphosate and paraquat. It is a highly efficient, low-toxic, non-selective contact-type organophosphine herbicide with partial systemic effect. It is easily soluble in water and insoluble in organic solvents. Glufosinate ammonium has low toxicity, is relatively safe, is easily degraded in the soil, is safe for crops, and has the advantages of small drift, wide herbicidal spectrum, high activity, small dosage, and low environmental pressure. In recent years, glufosinate ammonium has received more and more attention.

[0003] At present, the best process for producing glufosinate-ammonium is to carry out Michael phosphination reaction with methylphosphinate monoalkyl ester and acryl cyanohydrin acetate in the presence of peroxide as catalyst, and then obtain glufosinate-ammonium after ammoniation and hydrolysis, wherein methylphosphinate monoalkyl ester is obtained by esterification reaction with corresponding alcohol in the presence of acid binding agent (or without acid binding agent, using cyclone separator to separate generated hydrogen chloride gas) and then distillation. Although the reaction has a high conversion rate, the yield still has a large room for improvement, and the phenomenon of deflagration and fire in the still residue after the distillation is completed often occurs, the main reason is that in order to obtain a higher yield, the temperature must be increased in the later stage of distillation to overcome the continuously decreasing product vapor pressure, and the increase in temperature will cause the system's alkylphosphinate to be continuously produced, and further generate alkylphosphine gas to accumulate in the distillation still residue. At normal temperature and pressure, alkyl phosphine is a colorless, highly toxic, flammable gas that can form an explosive mixture with air. The generation of alkyl phosphine gas greatly increases the risk of the process and poses a prominent safety issue. In order to ensure safety, distillation can only be stopped in the later stage of distillation, causing part of the product to be lost in the distillation still residue, resulting in product waste. In addition, there are great safety hazards in the storage, transportation and subsequent incineration of the distillation still residue.

[0004] Patent US4549995 discloses a method for producing monoisobutyl methylphosphinate, which uses methyl dichlorophosphine as a raw material, directly esterifies with isobutyl alcohol, separates the hydrogen chloride gas produced during the reaction by a cyclone separator, and finally obtains monoisobutyl methylphosphinate by distillation. Since the hydrogen chloride gas produced during the reaction can dissolve in the reaction system, the cyclone separator cannot separate the hydrogen chloride gas in a timely and complete manner, resulting in the reaction system still being acidic after the reaction is completed. Methyl phosphine gas will be produced in the subsequent heating and distillation process, thereby causing great safety hazards. Figure 1 The specific mechanism of producing methyl phosphine gas is explained.

[0005] Patent US20180265529A1 discloses a method for preparing alkyl phosphinate monoalkyl esters by hydrolyzing alkyl phosphinates under acidic conditions and under the action of corresponding alcohols. The patent method is essentially to circumvent the problem of easy generation of alkyl phosphine in the technical solution of patent US454995, so as to better eliminate the hidden dangers of process safety. Although this method overcomes the problem of fire and deflagration, it still requires the reaction of alkyl dichlorophosphine with alcohol to first obtain alkyl phosphinate dialkyl esters, and then further hydrolyze and react with alcohol to obtain alkyl phosphinate monoalkyl esters, which undoubtedly increases the process cost and is extremely cumbersome to operate. Summary of the invention

[0006] The purpose of the present application is to provide a method for treating the residue in the distillation kettle for preparing monoalkyl methylphosphinate, so as to solve the technical problems of the safety hazard caused by the methyl phosphine produced in the production process of directly preparing monoalkyl methylphosphinate by reacting methyl dichlorophosphine with alcohol in the prior art, and the unsatisfactory yield of the monoalkyl methylphosphinate product.

[0007] To achieve the above object, the present application provides a method for treating the distillation still residue of preparing monoalkyl methylphosphinate, comprising the following steps:

[0008] Under a protective atmosphere, adding paraformaldehyde to the residue in the distillation kettle for preparing monoalkyl methylphosphinate, heating and stirring until the paraformaldehyde is completely dissolved, and then continuing stirring to carry out a first reaction;

[0009] Adding toluene and alcohol into the reaction system to carry out esterification reaction;

[0010] After the reaction system is dehydrated until no more water is separated out of the system, the materials after the reaction are subjected to rectification treatment until no product monoalkyl methylphosphinate is produced;

[0011] The reaction system was cooled and the phosphine content in the system was detected by a phosphine gas detector. When the content was below the safety limit, the system was transferred into a hazardous waste storage container.

[0012] Furthermore, the mass ratio of the added paraformaldehyde to the distillation kettle residue is 1:20 to 1:40.

[0013] Furthermore, the temperature of the first reaction is 80° C. to 100° C., and the time is 1 h to 2 h.

[0014] Furthermore, the mass ratio of the added toluene to the residue in the distillation kettle is 1:1 to 2:1.

[0015] Furthermore, the mass ratio of the added alcohols to the distillation kettle residue is 1:2 to 1:3.

[0016] Furthermore, the alcohol is any one of methanol, ethanol, n-propanol, isopropanol, n-butanol and isobutanol.

[0017] Furthermore, after the esterification reaction is completed, the distillation temperature when the methylphosphinate monoalkyl ester in the system is completely distilled out is 90° C. to 110° C., and the vacuum degree is 0.2 KPa to 0.4 KPa.

[0018] Furthermore, the method also includes the following steps: passing the tail gas in the reaction system into a decontamination tower for treatment.

[0019] Furthermore, the decontamination liquid in the decontamination tower is hydrogen peroxide with a mass concentration of 5%.

[0020] Furthermore, the distillation still residue is obtained by the following preparation process:

[0021] The methyl dichlorophosphine is reacted with the alcohols, and after the reaction is completed, ammonia gas is introduced into the system, the ammonium chloride produced in the system is filtered, the filter cake is washed with the corresponding alcohol, and the filtrate is combined, and the filtrate is subjected to vacuum distillation until no more methyl phosphinate monoalkyl ester is distilled out, thereby obtaining the distillation kettle residue.

[0022] Compared with the prior art, this application has the following technical effects:

[0023] The present invention discloses a method for treating a distillation kettle residue for preparing a monoalkyl methylphosphinate, which can effectively overcome the defects existing in the previous preparation process by adding paraformaldehyde to the distillation kettle residue. As the temperature of the reaction system rises, the methyl phosphine produced in the system can react with the paraformaldehyde, be quenched into a tertiary phosphine compound containing a hydroxymethyl group and lose its activity. Further, the corresponding alcohol and a small amount of toluene are added to the distillation kettle residue again for reaction, so that the methylphosphinic acid in the distillation kettle residue can be re-esterified to form a monoalkyl methylphosphinic acid ester. The monoalkyl methylphosphinic acid ester that could not be completely evaporated in the distillation kettle residue system and the monoalkyl methylphosphinic acid ester formed by re-esterification can be completely evaporated by increasing the temperature under a certain vacuum degree.

[0024] The method of the present application has simple process operation, low cost and strong feasibility, solves the problem that the methyl phosphine produced in the previous production process of directly preparing methyl phosphinate monoalkyl ester by reacting methyl dichlorophosphine with alcohol is extremely easy to explode and catch fire, eliminates safety hazards, and can greatly improve the yield of the product methyl phosphinate monoalkyl ester, thereby effectively avoiding the occurrence of safety accidents and increasing economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0026] Figure 1 A reaction mechanism diagram for producing methylphosphine gas provided as background technology for this application;

[0027] Figure 2 A reaction mechanism diagram for eliminating methylphosphine accumulation provided in an embodiment of the present application;

[0028] Figure 3 This is a mechanism diagram of the esterification reaction of methylphosphinic acid provided in the examples of the present application. DETAILED DESCRIPTION

[0029] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0030] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0031] The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass described in the embodiment description of the present application can be a mass unit known in the chemical industry such as μg, mg, g, kg, etc.

[0032] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0033] In the process of treating the distillation still residue in the preparation process of methylphosphinic acid monoalkyl ester, the embodiment of the present application found that adding paraformaldehyde can effectively overcome the defects existing in the previous preparation process. With the increase of temperature in the later stage, the methyl phosphine produced in the system can react with paraformaldehyde, be quenched into a tertiary phosphine compound containing hydroxymethyl and lose its activity. Further adding the corresponding alcohol and a small amount of toluene to the still residue for reaction can make the methylphosphinic acid in the distillation still residue re-esterify to form methylphosphinic acid monoalkyl ester. The methylphosphinic acid monoalkyl ester remaining in the distillation still residue system that cannot be completely evaporated due to the aforementioned reasons and the methylphosphinic acid monoalkyl ester formed by re-esterification can be completely evaporated by increasing the temperature under a certain vacuum degree.

[0034] The embodiment of the present application utilizes inexpensive and readily available paraformaldehyde to timely quench the methyl phosphine generated in the system, the process operation is simple, and the safety hazard caused by the methyl phosphine generated in the production process of directly preparing methyl phosphinate monoalkyl ester by reacting methyl dichlorophosphine with alcohol is completely eliminated, the product yield can be greatly improved, and the economic benefits are increased while effectively avoiding the occurrence of safety accidents.

[0035] The present application provides a method for treating a distillation reactor residue in the preparation of monoalkyl methylphosphinate, comprising the following steps:

[0036] (1) Methyl dichlorophosphine is added to alcohol at a certain speed, and after the addition is completed, the mixture is kept warm and stirred continuously. After the reaction is completed by GC detection, ammonia is introduced into the system, the ammonium chloride produced in the system is filtered, the filter cake is washed with corresponding alcohol, and the filtrate is combined, and the filtrate is subjected to vacuum distillation. After the excess alcohol and other light components are completely removed, methyl phosphinate monoalkyl ester is started to be removed, and the temperature in the distillation tower is kept at a certain vacuum degree so as not to exceed a specific temperature until no methyl phosphinate monoalkyl ester is distilled out, thereby obtaining a distillation still residue. According to GC analysis, the distillation still residue contains methyl phosphinate monoalkyl ester (about 40%), methyl phosphinic acid (about 30%), methyl phosphonic acid (about 10%), other salt impurities and unknown impurities (about 20%).

[0037] (2) The distillation kettle residue is transferred into a treatment container under a protective atmosphere (nitrogen can be used), and the tail gas in the material transfer process is washed through a washing tower, and then polyformaldehyde is added to the distillation kettle residue, and the temperature is raised and stirred until the paraformaldehyde is completely dissolved and then the reaction is continued by stirring, and then an appropriate amount of toluene is added to carry out esterification reaction with the corresponding alcohol and dehydration. After no more water is separated out in the system, the material is transferred to a distillation device for distillation, and after light components such as toluene are separated out, the temperature is raised under a certain vacuum degree until no product methyl phosphinate is produced. After the system is cooled, the vacuum can be directly broken by air (the tail gas is washed), and the phosphine gas detector is used to detect that the methyl phosphine content in the system is below the safety limit, which is safe and qualified distillation kettle residue, and then it is transferred to a hazardous waste storage container and handed over to an institution with hazardous waste treatment qualifications for treatment.

[0038] In the above step (2), the mass ratio of the paraformaldehyde added to the treatment container to the mass ratio of the residue in the distillation kettle is 1:20 to 1:40. The temperature of the stirring reaction after adding the paraformaldehyde is 80°C to 100°C, and the reaction time is 1h to 2h. The mass ratio of the toluene used in the further esterification of the methylphosphinic acid in the distillation kettle residue to the mass ratio of the residue in the distillation kettle is 1:1 to 2:1, and the mass ratio of the alcohol used in the further esterification to the residue in the distillation kettle is 1:2 to 1:3, and the alcohol can be any one of methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol. After the esterification reaction is completed, the distillation temperature when the monoalkyl methylphosphinic acid ester in the system is completely distilled out is 90°C to 110°C, and the vacuum degree is 0.2KPa to 0.4KPa. The decontamination liquid in the decontamination tower is hydrogen peroxide with a mass concentration of 5%.

[0039] The reaction mechanism of eliminating the accumulation of methylphosphine in the embodiment of the present application is as follows Figure 2 shown.

[0040] The mechanism of the esterification reaction of methylphosphinic acid in the present embodiment is as follows Figure 3 shown.

[0041] A method for treating a distillation reactor residue for preparing monoalkyl methylphosphinate according to an embodiment of the present application is illustrated below by using a plurality of specific embodiments.

[0042] Example 1

[0043] Example 1 of the present application provides a method for treating a distillation reactor residue for preparing monoalkyl methylphosphinate, comprising the following steps:

[0044] 1170g of methyl dichlorophosphine was slowly added to 960g of methanol at a speed to maintain the internal temperature of the reaction at 0°C. After the addition was completed, the internal temperature was maintained at 25°C for 2h and the reaction was completed. Ammonia was introduced into the system under recooling at a speed to maintain the internal temperature at 0°C. When the pH value of the system reached 6.5, the introduction of ammonia was stopped. The ammonium chloride generated in the system was filtered, the filter cake was washed with 480g of methanol, and the filtrate was combined and subjected to vacuum distillation to extract light components such as methanol and the product methyl phosphinate. The vacuum degree of the system at the end of extraction was 0.7KPa, the gas phase temperature was 90°C, and 799g of the product methyl phosphinate was obtained, with a yield of 85% and a GC purity of 98.6%. 96g of the distillation kettle residue was obtained, and GC analysis showed that it contained 41% methyl phosphinate, 28% methyl phosphinic acid, and the rest were methyl phosphonic acid, salt impurities and unknown impurities.

[0045] The residue of the above distillation kettle is transferred to the treatment device through nitrogen, and the tail gas in the transfer process is washed through the washing tower to absorb the gas phase part of methylphosphine in the quenching system. The washing tower is stored with a mass concentration of 5% hydrogen peroxide. 3.2g of polyformaldehyde is added to the treatment device, stirred and heated to 90°C for reaction for 1.5h, and then cooled to room temperature, and then 144g of toluene and 38.4g of methanol are added, stirred and heated to 110°C for reflux, and no water is taken out of the water separator, and then the material is transferred to the distillation device, and after separating toluene and excess methanol, the product is received under the conditions of gas phase temperature of 90°C to 95°C and vacuum degree of 0.2KPa to 0.4KPa, and 64.5g of methylphosphinate is obtained, and the purity is 98.5% after GC detection. The combined product is 863.5g in total, and the total yield is 91.9%.

[0046] The residue after the secondary distillation is tested with a phosphine gas detector and the methyl phosphine content in the system is found to be below the safety limit, making it a safe and qualified distillation kettle residue. It is then transferred to a hazardous waste storage container and handed over to an institution with hazardous waste treatment qualifications for disposal.

[0047] Example 2

[0048] Example 2 of the present application provides a method for treating the distillation reactor residue for preparing monoalkyl methylphosphinate, comprising the following steps:

[0049] 2340g of methyl dichlorophosphine was slowly added to 3220g of ethanol, and the speed of addition maintained the internal temperature of the reaction at 5°C. After the addition was completed, the internal temperature was maintained at 27°C for 1.5h, and the reaction was completed. Ammonia was introduced into the system under recooling, and the speed of introducing ammonia maintained the internal temperature at 5°C. When the pH value of the system reached 7, the introduction of ammonia was stopped, and the ammonium chloride generated in the system was filtered, and the filter cake was washed with 1000g of ethanol. After the filtrate was combined, vacuum distillation was performed to extract light components such as ethanol and the product methyl phosphinate. The vacuum degree of the system at the end of extraction was 0.65KPa, and the gas phase temperature was 98°C. The product methyl phosphinate was obtained. 1879.2g, the yield was 87%, and the GC purity was 99.1%. 198g of the distillation kettle residue was obtained, and GC analysis showed that it contained 39% methyl phosphinate, 32% methyl phosphinic acid, and the rest were methyl phosphonic acid, salt impurities and unknown impurities.

[0050] The residue of the above distillation kettle is transferred to the treatment device through nitrogen, and the tail gas in the transfer process is washed through the washing tower to absorb the gas phase part of methylphosphine in the quenching system. The washing tower is stored with a mass concentration of 5% hydrogen peroxide. 6.6g of polyformaldehyde is added to the treatment device, stirred and heated to 95°C for reaction for 1.8h, and then cooled to room temperature, and then 336g of toluene and 71g of ethanol are added, stirred and heated to 110°C for reflux, and no water is taken out of the water separator, and then the material is transferred to the distillation device, and after separating toluene and excess ethanol, the product is received under the conditions of gas phase temperature of 95°C to 100°C and vacuum degree of 0.2KPa to 0.4KPa, and 146.3g of product methylphosphinate monoethyl ester is obtained, and the purity is 98.8% after GC detection, and the combined product is 2025.5g in total, with a total yield of 93.8%.

[0051] The residue after the secondary distillation is tested with a phosphine gas detector and the methyl phosphine content in the system is found to be below the safety limit, making it a safe and qualified distillation kettle residue. It is then transferred to a hazardous waste storage container and handed over to an institution with hazardous waste treatment qualifications for disposal.

[0052] Example 3

[0053] Example 3 of the present application provides a method for treating the distillation reactor residue for preparing monoalkyl methylphosphinate, comprising the following steps:

[0054] 1755g of methyl dichlorophosphine was slowly added to 4440g of n-butanol at a rate of maintaining the internal temperature of the reaction at -5°C. After the addition was completed, the internal temperature was maintained at 22°C for 2.5h. The reaction was completed, and ammonia gas was introduced into the system under recooling at a rate of maintaining the internal temperature at -2°C. When the pH value of the system reached 6.8, the introduction of ammonia gas was stopped. The ammonium chloride generated in the system was filtered, and the filter cake was washed with 1110g of n-butanol. The filtrate was combined and subjected to vacuum distillation to respectively extract light components such as n-butanol and the product methyl phosphinic acid mono-n-butyl ester. The vacuum degree of the system at the end of extraction was 0.6KPa, and the gas phase temperature was 100°C. 1805.4g of the product methyl phosphinic acid mono-n-butyl ester was obtained with a yield of 88.5% and a GC purity of 98.4%. 135 g of the distillation still residue was obtained, and GC analysis showed that it contained 38.7% of methylphosphinic acid mono-n-butyl ester, 31.6% of methylphosphinic acid, and the rest were methylphosphonic acid, salt impurities and unknown impurities.

[0055] The residue of the above distillation kettle is transferred to the treatment device through nitrogen, and the tail gas in the transfer process is washed through the washing tower to absorb the gas phase part of methylphosphine in the quenching system. The washing tower is stored with a mass concentration of 5% hydrogen peroxide. 4.9g of polyformaldehyde is added to the treatment device, stirred and heated to 100°C for reaction for 2h, and then cooled to room temperature, and then 216g of toluene and 61.4g of n-butanol are added, stirred and heated to 110°C for reflux, until no water is taken out of the water separator, and then the material is transferred to the distillation device, toluene and excess n-butanol are separated, and the product is received under the conditions of gas phase temperature of 100°C to 110°C and vacuum degree of 0.2KPa to 0.4KPa, and 118.5g of methylphosphinate mono-n-butyl ester is obtained, and the purity is 98.3% after GC detection, and the combined product is 1923.9g in total, with a total yield of 94.3%.

[0056] The residue after the secondary distillation is tested with a phosphine gas detector and the methyl phosphine content in the system is found to be below the safety limit, making it a safe and qualified distillation kettle residue. It is then transferred to a hazardous waste storage container and handed over to an institution with hazardous waste treatment qualifications for disposal.

[0057] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A method for treating a distillation still residue in the preparation of monoalkyl methylphosphinate, characterized in that: The following steps are involved: Under a protective atmosphere, adding paraformaldehyde to the residue in the distillation kettle for preparing monoalkyl methylphosphinate, heating and stirring until the paraformaldehyde is completely dissolved, and then continuing stirring to carry out a first reaction; Adding toluene and alcohol into the reaction system to carry out esterification reaction; After the reaction system is dehydrated until no more water is separated out of the system, the materials after the reaction are subjected to rectification treatment until no product monoalkyl methylphosphinate is produced; The reaction system was cooled and the phosphine content in the system was detected by a phosphine gas detector. When the content was below the safety limit, the system was transferred into a hazardous waste storage container.

2. The method for treating the distillation still residue of preparing monoalkyl methylphosphinate according to claim 1, characterized in that: The mass ratio of the added paraformaldehyde to the residue in the distillation kettle is 1:20 to 1:

40.

3. The method for treating the distillation still residue of preparing methylphosphinate monoalkyl ester according to claim 1, characterized in that: The temperature of the first reaction is 80° C. to 100° C., and the time is 1 h to 2 h.

4. The method for treating the distillation still residue of preparing methylphosphinate monoalkyl ester according to claim 1, characterized in that: The mass ratio of the added toluene to the residue in the distillation kettle is 1:1 to 2:

1.

5. The method for treating the distillation still residue of preparing methylphosphinate monoalkyl ester according to claim 1, characterized in that: The mass ratio of the added alcohols to the residue in the distillation kettle is 1:2 to 1:

3.

6. The method for treating the distillation still residue in the preparation of monoalkyl methylphosphinate according to claim 5, characterized in that: The alcohol is any one of methanol, ethanol, n-propanol, isopropanol, n-butanol and isobutanol.

7. The method for treating the distillation still residue of preparing monoalkyl methylphosphinate according to claim 1, characterized in that: After the esterification reaction is completed, the distillation temperature when the methylphosphinate monoalkyl ester in the system is completely distilled out is 90° C. to 110° C., and the vacuum degree is 0.2 KPa to 0.4 KPa.

8. The method for treating the distillation still residue in the preparation of monoalkyl methylphosphinate according to claim 1, characterized in that: The method also includes the following steps: passing the tail gas in the reaction system into a decontamination tower for treatment.

9. The method for treating the distillation still residue in the preparation of monoalkyl methylphosphinate according to claim 8, characterized in that: The decontamination liquid in the decontamination tower is hydrogen peroxide with a mass concentration of 5%.

10. A method for treating a distillation still residue in the preparation of monoalkyl methylphosphinate according to any one of claims 1 to 9, characterized in that: The distillation still residue is obtained by the following preparation process: The methyl dichlorophosphine is reacted with the alcohols, and after the reaction is completed, ammonia gas is introduced into the system, the ammonium chloride produced in the system is filtered, the filter cake is washed with the corresponding alcohol, and the filtrate is combined, and the filtrate is subjected to vacuum distillation until no more methyl phosphinate monoalkyl ester is distilled out, thereby obtaining the distillation kettle residue.

Images