阅读说明：本技术 一种含磷复合盐的回收利用方法 (Recycling method of phosphorus-containing composite salt ) 是由 成贞辉 曹凌云 颜新天 孙素丽 蔡华胜 于 2020-12-10 设计创作，主要内容包括：本发明公开了一种含磷复合盐的回收利用方法,含磷复合盐包含氯化钠和氯化铝复合盐以及烷基二氯膦,该方法包括：利用烯烃类化合物与含磷复合盐中的烷基二氯膦反应生成含磷阻燃剂或其中间体,获得反应后混合物,然后通过分步分级地提高体系中的氯化氢含量以逐步分离出氯化钠以及以水合三氯化铝形式的析出物,并获得包含含磷阻燃剂或其中间体、少量氯化铝和氯化钠、盐酸的混合物,蒸馏浓缩后加入氢氧化钠,过滤,滤液酸化浓缩后萃取,提纯。本发明方法得到了纯净的氯化钠、纯净的水合氯化铝、并得到了含磷阻燃剂或其中间体,步骤清晰功能明确,且方法简单易于控制,完全解决了甲基二氯膦生产过程中复合盐的回收利用问题。(The invention discloses a recycling method of a phosphorus-containing composite salt, wherein the phosphorus-containing composite salt comprises sodium chloride, aluminum chloride composite salt and alkyl dichlorophosphine, and the method comprises the following steps: the method comprises the steps of utilizing an olefin compound to react with alkyl dichlorophosphine in a phosphorus-containing composite salt to generate a phosphorus-containing flame retardant or an intermediate thereof, obtaining a mixture after reaction, then gradually separating sodium chloride and a precipitate in the form of aluminum trichloride hydrate by increasing the content of hydrogen chloride in a system step by step in a grading manner, obtaining a mixture containing the phosphorus-containing flame retardant or the intermediate thereof, a small amount of aluminum chloride, sodium chloride and hydrochloric acid, adding sodium hydroxide after distillation and concentration, filtering, acidifying and concentrating a filtrate, then extracting, and purifying. The method of the invention obtains pure sodium chloride, pure aluminum chlorohydrate and phosphorus-containing flame retardant or intermediate thereof, has clear and definite steps and functions, is simple and easy to control, and completely solves the problem of recycling the composite salt in the production process of the methyldichlorophosphine.)

1. A method for recycling a phosphorus-containing composite salt, which comprises a sodium chloride and aluminum chloride composite salt and an alkyl dichlorophosphine, characterized by comprising the following steps:

s1, reacting the phosphorus-containing composite salt with an olefin compound in the presence of water and a catalyst to generate a phosphorus-containing flame retardant or an intermediate thereof, and obtaining a first mixture containing the phosphorus-containing flame retardant or the intermediate thereof, sodium chloride, aluminum chloride and hydrochloric acid; or reacting the phosphorus-containing composite salt with an olefin compound in hydrochloric acid in the presence of a catalyst to obtain a first mixture containing a phosphorus-containing flame retardant or an intermediate thereof, sodium chloride, aluminum chloride and hydrochloric acid; the olefin compound has a structure shown in the following general formula (1) or formula (2):

wherein R is₁、R₂、R₃、R₄、R₅、R₆Independently hydrogen, C1-C12 branched chain or straight chain alkyl, C3-C12 cycloalkyl, C3-C12 cycloalkyl with C1-C12 alkyl side chain, phenyl which is unsubstituted or substituted by one or more C1-C12 branched chain or straight chain alkyl, and n is an integer between 2 and 8;

s2, introducing hydrogen chloride into the first mixture to enable the mass percentage of the hydrogen chloride in the mixture solution to reach 5% -15%, crystallizing and separating out the sodium chloride, and filtering to obtain a filtrate, wherein the filtrate is a second mixture containing a very small amount of sodium chloride, aluminum trichloride, a phosphorus-containing flame retardant or an intermediate thereof and hydrochloric acid;

s3, continuously introducing hydrogen chloride gas into the second mixture in the step S2 to ensure that the mass content of the hydrogen chloride in the mixture solution is more than or equal to 35%, so that the aluminum chloride is precipitated in the form of aluminum trichloride hydrate, and filtering to obtain a filtrate, wherein the filtrate is a third mixture containing the phosphorus-containing flame retardant or an intermediate thereof, aluminum chloride, sodium chloride and hydrochloric acid;

s4, distilling and concentrating the third mixture obtained in the step S3 to obtain concentrated hydrochloric acid and a phosphorus-containing flame retardant mixed with aluminum chloride and sodium chloride or an intermediate thereof;

s5, adding sodium hydroxide into the phosphorus-containing flame retardant mixed with aluminum chloride and sodium chloride or the intermediate thereof obtained in the step S4 to enable the dissolved aluminum chloride to generate sodium chloride and aluminum hydroxide, obtaining a mixture containing the aluminum hydroxide, the sodium chloride, the phosphorus-containing flame retardant or the sodium salt of the intermediate thereof, filtering, adding hydrochloric acid into filtrate to acidify the filtrate to enable the phosphorus-containing flame retardant or the sodium salt of the intermediate thereof to be dissociated into the phosphorus-containing flame retardant or the intermediate thereof, then concentrating until the filtrate is anhydrous to obtain the phosphorus-containing flame retardant or the phosphorus-containing flame retardant intermediate and the sodium chloride, adding an organic solvent to stir uniformly, filtering, concentrating the filtrate, and distilling under reduced pressure or recrystallizing to obtain the phosphorus-containing flame retardant or the intermediate thereof.

2. The method according to claim 1, wherein in step S1, R in the general formula (1) or (2)₁、R₂、R₃、R₄、R₅、R₆Independently hydrogen, methyl, ethyl, propyl, cyclopropyl, isopropyl, butyl, isobutyl, pentyl, hexyl, cyclobutyl, cyclopentyl, cyclohexyl, phenyl, methylphenyl, ethylphenyl; n is 3, 4, 5, 6 or 7.

3. The method of claim 1, wherein in step S1, the olefin compound is one or more selected from the group consisting of ethylene, propylene, butylene, cyclopentene, cyclohexene, styrene, and methyl styrene.

4. The method for recycling the phosphorus-containing composite salt according to claim 1, wherein in step S1, the reaction is carried out at a temperature of 40 to 100 ℃; and/or the catalyst is a free radical initiator, and the free radical initiator is azobisisobutyronitrile or di-tert-butyl peroxide; and/or in step S1, the reaction of the phosphorus-containing composite salt and the olefin compound is carried out in dilute hydrochloric acid, wherein the mass percentage of the dilute hydrochloric acid is less than or equal to 10%.

5. The method for recycling the phosphorus-containing composite salt according to claim 1, wherein in step S1, the amount of hydrochloric acid used is 1-10 times of the amount of the phosphorus-containing composite salt, and the mass percentage of the hydrochloric acid is 2-5%.

6. The method according to claim 1, wherein the content of the alkyl dichlorophosphine in the phosphorus-containing composite salt is obtained before the step S1 is performed, and in step S1, the content of the alkyl dichlorophosphine in the phosphorus-containing composite salt is determined according to the molar ratio of the alkyl dichlorophosphine to the olefin compound of 1: 1.01-1.3, feeding.

7. The method of claim 1, further comprising: in step S2, after filtering, washing the filter cake with hydrochloric acid, filtering after washing, and drying to obtain pure sodium chloride solid; wherein the mass percentage of the hydrochloric acid used for washing the filter cake is 30-37%, and the second mixture comprises a filtrate obtained by filtering after sodium chloride is crystallized and separated out and a filtrate obtained by filtering after the filter cake is washed; the recycling method of the phosphorus-containing composite salt also comprises the step S6 of selectively using the sodium chloride solid obtained by filtering in the step S2 in the production process of the methyldichlorophosphine;

and/or in step S3, after filtering, washing a filter cake with hydrochloric acid, and drying to obtain aluminum trichloride hydrate; the third mixture comprises filtrate obtained after precipitation of aluminum trichloride hydrate and washing liquid obtained after washing the filter cake, and the method for recycling the phosphorus-containing composite salt selectively comprises a step S7, wherein the aluminum chlorohydrate obtained by filtering in the step S3 is used in the casting and sewage treatment industries.

8. The method of claim 1, further comprising: in step S2, the step of controlling the crystallization of sodium chloride is carried out at the temperature of 70-90 ℃ for 1-2 h.

9. The method for recycling the phosphorus-containing composite salt according to claim 1, wherein in the step S2, hydrogen chloride is introduced to make the mass percentage of hydrogen chloride in the mixture solution reach 6% -10%; in step S3, hydrogen chloride is introduced to make the mass content of hydrogen chloride in the mixture solution 35% -45%.

10. The method for recycling the phosphorus-containing composite salt according to claim 1, wherein in step S5, the method further comprises: adding an organic solvent, uniformly stirring and filtering to obtain a filter cake, washing the filter cake with the organic solvent, and drying to obtain sodium chloride; and mixing the washing liquid obtained after washing with the filtrate obtained after adding the organic solvent, uniformly stirring and filtering, concentrating, and carrying out reduced pressure distillation or recrystallization to obtain the phosphorus-containing flame retardant or the intermediate thereof.

11. The method for recycling a phosphorus-containing composite salt according to any one of claims 1 to 10, wherein the alkyl dichlorophosphine is methyldichlorophosphine, and the phosphorus-containing composite salt is a by-product from the production of methyldichlorophosphine;

and/or the recycling method of the phosphorus-containing composite salt further comprises one or more of the following steps:

s8, further separating the concentrated hydrochloric acid obtained in the step S4 into hydrogen chloride gas and dilute hydrochloric acid for use in the step S1; the method for separating the concentrated hydrochloric acid is a calcium chloride method or a sulfuric acid method; the calcium chloride method comprises the steps of continuously separating out hydrogen chloride by using a calcium chloride solution as a dehydrating agent, continuously distilling the calcium chloride solution to obtain dilute hydrochloric acid, and continuously separating the hydrogen chloride by using a calcium chloride concentrated solution as the dehydrating agent; the sulfuric acid method comprises the steps of continuously separating hydrogen chloride by using concentrated sulfuric acid as a dehydrating agent, continuously distilling a sulfuric acid solution to obtain dilute hydrochloric acid and concentrated sulfuric acid, and continuously separating the hydrogen chloride by using the concentrated sulfuric acid as the dehydrating agent;

s9, adding the organic solvent in the step S5, stirring uniformly, filtering, dissolving the obtained sodium chloride with water to obtain a sodium chloride aqueous solution, returning to the step S1, mixing with hydrochloric acid, and dissolving the complex salt;

s10, returning the filter cake filtered in the first step in the step S5, namely the aluminum hydroxide, to the step S2 for generating aluminum chloride;

s11, further preparing the phosphorus-containing flame retardant intermediate obtained in the step S5 into a phosphorus-containing flame retardant.

Technical Field

The invention relates to the technical field of recycling of phosphorus-containing byproducts in the production process of organic phosphine intermediates, in particular to a recycling method of phosphorus-containing composite salt.

Background

Alkyl dichlorophosphine, also known as alkyl dichlorophosphine, is an important intermediate of organic phosphine compounds, particularly methyl dichlorophosphine, and is a core raw material for synthesizing herbicide glufosinate-ammonium intermediate diethyl methylphosphonite. Currently, the mainstream production methods of methyldichlorophosphine mainly comprise the following three methods:

1. phosphorus trichloride and methane pass through a tubular reactor, a condenser and a fractionating device in the presence of a high-temperature high-pressure catalyst to obtain methyldichlorophosphine, deposits are easily generated in the method, the tubular reactor and the condenser are blocked, production interruption is caused, the product conversion rate is low, and the energy consumption is high.

2. Phosphorus trichloride, aluminum trichloride and chloromethane are subjected to complex reaction in a pressure kettle to generate a ternary complex, the ternary complex is reduced by aluminum powder to obtain a complex of methyldichlorophosphine and aluminum trichloride, the complex is dissociated into the methyldichlorophosphine under the action of sodium chloride, and a byproduct of composite salt of sodium chloride and aluminum chloride is remained.

3. Methyl chloride reacts with aluminum alloy to generate a mixture of methyl dichloroaluminum and dimethyl aluminum chloride, the mixture reacts with phosphorus trichloride to generate a complex of methyl dichlorophosphine and aluminum chloride, the complex reacts with sodium chloride to dissociate the methyl dichlorophosphine, and a byproduct of a complex salt of the sodium chloride and the aluminum chloride is remained.

In the above methods, methods 2 and 3 do not have high temperature and high pressure, but the dissociation of sodium chloride to methyldichlorophosphine and aluminum trichloride is insufficient, so that the content of the residual methyldichlorophosphine in the aluminum chloride and sodium chloride composite salt is relatively high, and the aluminum chloride and sodium chloride composite salt cannot be well recycled, which is a great obstacle in the production of methyldichlorophosphine. To address this problem, the prior art proposes a number of different solutions, for example:

the Chinese patent CN105217667B mentions that the sodium chloride and the aluminum chloride are decomplexed by a mixture of decomplexer alcohol and ether to obtain the aluminum chloride for reuse, and the method does not mention the treatment of the phosphorus-containing compound and the sodium chloride in the sodium chloride and the compound salt sodium tetrachloroaluminate, so that the phosphorus-containing compound and the sodium chloride cannot be recovered.

Chinese patent CN108238621A discloses a method for preparing polyaluminium chloride by dissolving compound salt, adding ferric chloride, hydrochloric acid, sodium hydroxide, sodium metaaluminate and the like to carry out polymerization reaction, cooling and filtering to obtain polyaluminium chloride solution.

Chinese invention patent CN111187297A discloses a method for recovering and treating phosphine-containing industrial by-products, which comprises placing the by-products generated in the production process of diethyl methylphosphite into a reaction vessel, adding phenolic compounds or binary and above arylamine compounds or compounds containing oxirane functional groups, heating to react under the condition of isolating air, cooling to room temperature, slowly dissolving the obtained solid in water, and controlling the adding speed and stirring uniformly because the process of dissolving water is a heat release process; cooling and filtering, wherein the obtained filter residue is used as a phosphorus flame retardant, the obtained first filtrate is continuously subjected to solid-liquid separation, specifically, the first filtrate is heated to 100-120 ℃ until crystals appear and the amount of the crystals is not increased any more, the heating is stopped, the hot first filtrate is filtered, and the obtained solid is sodium chloride crystals; and (3) slowly adding water into the obtained second filtrate, cooling to room temperature, adjusting the pH value of the second filtrate to prepare the polyaluminium chloride, specifically, adding ferric chloride and hydrochloric acid into the second filtrate, stirring and mixing uniformly, controlling the temperature of the reaction solution to be more than 85 ℃, then sequentially adding aluminum hydroxide and calcium metaaluminate, and controlling the reaction temperature to be 100 ℃ to react to obtain the polyaluminium chloride. Although the method can recycle the methyldichlorophosphine, the added phenolic substances, or binary and above aromatic amine compounds or epoxy compounds enter a polyaluminium system to cause polyaluminium pollution, so that the method has no application value, and in addition, the phenolic substances are dissolved in the filtrate in a large amount to bring a new waste liquid treatment problem. Moreover, the method has the disadvantages of complex process, high control difficulty and inconvenient operation.

Chinese patent CN111689508A discloses a method for treating tetrachloro sodium aluminate solid slag, which comprises (1) mixing tetrachloro sodium aluminate solid slag with water for dissociation, then adding a separating agent to separate out aluminum chloride hexahydrate, or directly mixing tetrachloro sodium aluminate solid slag with the separating agent for dissociation, separating out aluminum chloride hexahydrate, and then carrying out primary solid-liquid separation to obtain aluminum chloride hexahydrate solid and primary filtrate; (2) and (3) concentrating and crystallizing the primary filtrate obtained in the step (1), and performing secondary solid-liquid separation to obtain sodium chloride solid and secondary filtrate, and returning the secondary filtrate to the step (1) to provide a separating agent required by precipitation of aluminum chloride hexahydrate. The process has proved to be capable of separating sodium chloride and aluminium chloride, however, the solution reported in this patent has errors, in particular, in step (1) it is not aluminium chloride hexahydrate but sodium chloride which is obtained first, and the sodium chloride and aluminium chloride which are finally obtained are not up to standard because of contamination from phosphorus-containing compounds in the solid residual mother liquor.

In conclusion, in the prior art, the utilization of the composite salt generated in the production process of the methyl dichlorophosphine cannot be fully and effectively realized, and some utilization methods have the problems of complex process, high control difficulty and the like.

Disclosure of Invention

In order to solve the technical problem of the comprehensive utilization of byproducts in the production of methyl dichlorophosphine, the invention provides a method for recycling a byproduct phosphorus-containing composite salt in the production process of methyl dichlorophosphine, and the method can realize the full and effective recycling of the byproduct in the production of the methyl dichlorophosphine, and has the advantages of simple process and easy control.

In order to solve the problems, the invention adopts the following technical scheme:

a method for recycling a phosphorus-containing composite salt comprising a sodium chloride and aluminum chloride composite salt and an alkyl dichlorophosphine, the method comprising the steps of:

s1, reacting the phosphorus-containing composite salt with an olefin compound in the presence of water and a catalyst to generate a phosphorus-containing flame retardant or an intermediate thereof, and obtaining a first mixture containing the phosphorus-containing flame retardant or the intermediate thereof, sodium chloride, aluminum chloride and hydrochloric acid; or reacting the phosphorus-containing composite salt with an olefin compound in hydrochloric acid in the presence of a catalyst to obtain a first mixture containing a phosphorus-containing flame retardant or an intermediate thereof, sodium chloride, aluminum chloride and hydrochloric acid; the olefin compound has a structure shown in the following general formula (1) or formula (2):

wherein R is₁、R₂、R₃、R₄、R₅、R₆Independently hydrogen, C1-C12 branched chain or straight chain alkyl, C3-C12 cycloalkyl, C3-C12 cycloalkyl with C1-C12 alkyl side chain, phenyl which is unsubstituted or substituted by one or more C1-C12 branched chain or straight chain alkyl, and n is an integer between 2 and 8;

s2, introducing hydrogen chloride into the first mixture to enable the mass percentage of the hydrogen chloride in the mixture solution to reach 5% -15%, crystallizing and separating out the sodium chloride, and filtering to obtain a second mixture containing a very small amount of sodium chloride, aluminum trichloride, a phosphorus-containing flame retardant or an intermediate thereof and hydrochloric acid;

s3, continuously introducing hydrogen chloride gas into the second mixture in the step S2 to ensure that the mass content of the hydrogen chloride in the mixture solution is more than or equal to 35%, precipitating aluminum chloride in the form of aluminum trichloride hydrate, and filtering to obtain a third mixture containing the phosphorus-containing flame retardant or the intermediate thereof, aluminum chloride, sodium chloride and hydrochloric acid;

s4, distilling and concentrating the third mixture obtained in the step S3 to obtain concentrated hydrochloric acid and a phosphorus-containing flame retardant mixed with aluminum chloride and sodium chloride or an intermediate thereof;

s5, adding sodium hydroxide into the phosphorus-containing flame retardant mixed with aluminum chloride and sodium chloride or the intermediate thereof obtained in the step S4 to enable the dissolved aluminum chloride to generate sodium chloride and aluminum hydroxide, obtaining a mixture containing the aluminum hydroxide, the sodium chloride, the phosphorus-containing flame retardant or the sodium salt of the intermediate thereof, filtering, adding hydrochloric acid into filtrate to acidify the filtrate to enable the phosphorus-containing flame retardant or the sodium salt of the intermediate thereof to be dissociated into the phosphorus-containing flame retardant or the intermediate thereof, then concentrating until the filtrate is anhydrous to obtain the phosphorus-containing flame retardant or the phosphorus-containing flame retardant intermediate and the sodium chloride, adding an organic solvent to stir uniformly, filtering, concentrating the filtrate, and distilling under reduced pressure or recrystallizing to obtain the phosphorus-containing flame retardant or the intermediate thereof.

According to a further preferred aspect of the present invention, in step S1, in the general formula (1) or (2), R₁、R₂、R₃、R₄、R₅、R₆Independently hydrogen, methyl, ethyl, propyl, cyclopropyl, isopropyl, butyl, isobutyl, pentyl, hexyl, cyclobutyl, cyclopentyl, cyclohexyl, phenyl, methylphenyl, ethylphenyl; n is 3, 4, 5, 6 or 7.

According to some preferred and specific aspects of the present invention, in step S1, the olefin compound is one or more selected from the group consisting of ethylene, propylene, butylene, cyclopentene, cyclohexene, styrene and methyl styrene.

According to some preferred aspects of the present invention, before performing step S1, the content of alkyl dichlorophosphine in the phosphorus-containing composite salt is obtained, and in step S1, the content of alkyl dichlorophosphine in the phosphorus-containing composite salt is determined according to the feeding molar ratio of alkyl dichlorophosphine to the olefin-based compound of 1: 1.01-1.3, feeding. Further preferably, in step S1, the molar ratio of alkyl dichlorophosphine to olefin compound is 1: 1.01-1.1, feeding.

According to some preferred aspects of the present invention, in step S1, the reaction of the phosphorus-containing complex salt with the olefinic compound is performed in dilute hydrochloric acid, wherein the mass percentage of the dilute hydrochloric acid is less than or equal to 10%. Further, in step S1, the diluted hydrochloric acid is 2% to 5% by mass.

According to some preferred aspects of the present invention, in step S1, the hydrochloric acid is used in an amount of 1 to 10 times as much as the phosphorus-containing complex salt. Further preferably, in step S1, the amount of hydrochloric acid used is 1 to 5 times that of the phosphorus-containing complex salt.

Further, in step S1, the reaction may be performed at a temperature of 40 to 100 ℃, and preferably, the reaction is performed at a temperature of 80 to 100 ℃.

Further, in step S1, the catalyst may be any of various known radical initiators, including, but not limited to, azobisisobutyronitrile, peroxy compounds such as di-t-butylperoxide, and the like.

According to some preferred aspects of the present invention, the method for recycling the phosphorus-containing complex salt further comprises: in step S2, the step of controlling the precipitation of sodium chloride crystals is performed by keeping the temperature at 70-90 ℃.

Further, in step S2, the heat preservation is performed at 70-85 ℃.

Further, in step S2, the heat preservation time is 1-2 hours.

According to some preferred aspects of the present invention, in step S2, after the filtering, the filter cake is washed with hydrochloric acid, and then filtered and dried to obtain pure solid sodium chloride; wherein the mass percentage of the hydrochloric acid used for washing the filter cake is 30-37%, and the second mixture comprises a filtrate obtained by filtering after sodium chloride is crystallized and separated out and a filtrate obtained by filtering after the filter cake is washed.

According to some preferred aspects of the present invention, in step S3, after the filtering, the filter cake is washed with hydrochloric acid and dried to obtain aluminum trichloride hydrate; wherein the mass percentage of the hydrochloric acid used for washing the filter cake is 30-37%, and the third mixture comprises a filtrate obtained by separating out aluminum trichloride hydrate and filtering and a washing liquid obtained by washing the filter cake.

According to some preferred aspects of the invention, in step S2, hydrogen chloride is introduced to make the mass percentage of hydrogen chloride in the mixture solution reach 6% -10%; and/or in step S3, introducing hydrogen chloride to ensure that the mass content of the hydrogen chloride in the mixture solution is 35-45%.

According to some preferred aspects of the present invention, in step S5, the method for recycling the phosphorus-containing composite salt further comprises: adding an organic solvent, uniformly stirring and filtering to obtain a filter cake, washing the filter cake with the organic solvent, and drying to obtain sodium chloride; and mixing the washing liquid obtained after washing with the filtrate obtained after adding the organic solvent, uniformly stirring and filtering, concentrating, and carrying out reduced pressure distillation or recrystallization to obtain the phosphorus-containing flame retardant or the intermediate thereof.

According to some preferred aspects of the invention, the alkyl dichlorophosphine is methyldichlorophosphine and the phosphorus-containing complex salt is a by-product from the production of methyldichlorophosphine. The recycling method of the phosphorus-containing composite salt further comprises the following steps: s6, the sodium chloride solid obtained by filtering in the step S2 is used in the process of producing the methyl dichlorophosphine.

According to some preferred aspects of the present invention, the method for recycling the phosphorus-containing complex salt further comprises: s7, the aluminum chlorohydrate obtained by filtering in the step S3 is used for casting and sewage treatment industries.

According to some preferred aspects of the present invention, the method for recycling the phosphorus-containing complex salt further comprises: s8, the concentrated hydrochloric acid obtained in step S4 is further separated into hydrogen chloride gas and dilute hydrochloric acid, and used in step S1.

Further, in step S8, the method of separating concentrated hydrochloric acid is a calcium chloride method or a sulfuric acid method; the calcium chloride method comprises the steps of taking a calcium chloride solution as a dehydrating agent, continuously separating out hydrogen chloride, and continuously distilling the calcium chloride solution to obtain dilute hydrochloric acid; the calcium chloride concentrated solution is continuously used as a dehydrating agent to separate hydrogen chloride; the sulfuric acid method is characterized in that concentrated sulfuric acid is used as a dehydrating agent to continuously separate hydrogen chloride, and a sulfuric acid solution is continuously distilled to obtain dilute hydrochloric acid and concentrated sulfuric acid, and the concentrated sulfuric acid is used as the dehydrating agent to continuously separate the hydrogen chloride.

According to some preferred aspects of the present invention, the method for recycling the phosphorus-containing complex salt further comprises one or more of the following steps:

s9, adding the organic solvent in the step S5, stirring uniformly, filtering, dissolving the obtained sodium chloride with water to obtain a sodium chloride aqueous solution, returning to the step S1, mixing with hydrochloric acid, and dissolving the complex salt;

s10, returning the filter cake filtered in the first step in the step S5, namely the aluminum hydroxide, to the step S2 for generating aluminum chloride;

s11, further preparing the phosphorus-containing flame retardant intermediate obtained in the step S5 into a phosphorus-containing flame retardant.

The invention also provides a production method of methyldichlorophosphine, which comprises the following steps:

(1) obtaining methyl dichlorophosphine and sodium chloride and aluminum chloride composite salt byproducts containing the methyl dichlorophosphine,

(2) the method for recycling the phosphorus-containing composite salt is adopted to recycle and obtain sodium chloride, aluminum chlorohydrate, a phosphorus-containing flame retardant or an intermediate thereof;

(3) the sodium chloride recovered in step S2 in the above-mentioned step (2) is used as a dissociation agent in the step (1) to dissociate methyldichlorophosphine.

In the invention, if the mass percent concentration is not specified, the mass percent contents of the hydrogen chloride and the sulfuric acid in the related dilute hydrochloric acid and the concentrated hydrochloric acid are all the conventional defined ranges in the prior art.

The technical scheme provided by the invention has the following beneficial effects:

the treatment method can prepare the methyl dichlorophosphine residual in the composite salt into the phosphorus-containing flame retardant or the intermediate thereof; sodium chloride with the content of 99.5 percent or more can be obtained and can be reused in the production process of the methyldichlorophosphine; and can obtain the hydrated aluminum chloride with the content of 97 percent or more, which completely accords with the standard of the superior product of the hydrated aluminum chloride; the hydrochloric acid used can be separated to obtain hydrogen chloride and dilute hydrochloric acid, and the hydrogen chloride and dilute hydrochloric acid can be reused for treating the compound salt. Compared with the prior art, the method can realize the high-efficiency recovery of all useful substances, has no waste liquid in the whole process, lower recovery cost, simple process and simple and convenient operation, and can really and completely solve the problem of comprehensive utilization of the phosphorus-containing composite salt.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is an RSC thermogram of an aluminum methylcyclohexylphosphinate salt prepared in example 3;

FIG. 2 is an RSC thermogram of aluminum methylcyclohexylphosphinate salt produced by a normal production process;

FIG. 3 is an analytical spectrum of TG-DTG which is a zinc salt of methylethylphosphinic acid prepared in example 4;

FIG. 4 is an analytical spectrum of TG-DTG produced by a normal production method.

Detailed Description

The invention provides a method for comprehensively utilizing byproducts in the production process of methyldichlorophosphine, which comprises the following steps:

s1, reacting the phosphorus-containing composite salt with an olefin compound in the presence of water and a catalyst at a certain temperature to generate a phosphorus-containing flame retardant or an intermediate thereof, and obtaining a first mixture containing the phosphorus-containing flame retardant or the intermediate thereof, sodium chloride, aluminum chloride and hydrochloric acid; or reacting the phosphorus-containing composite salt with an olefin compound in diluted hydrochloric acid in the presence of a catalyst to obtain a first mixture containing a phosphorus-containing flame retardant or an intermediate thereof, sodium chloride, aluminum chloride and hydrochloric acid; the mass percentage content of the dilute hydrochloric acid is less than or equal to 10 percent; in this step, the amount of the olefin compound is preferably in excess relative to the amount of the phosphorus-containing component such as methyldichlorophosphine, and the molar ratio of the olefin compound to the methyldichlorophosphine is preferably 1.01 to 1.3: 1, more preferably 1.01 to 1.1: 1. preferably, the reaction temperature is 40-100 ℃, further preferably 50-100 ℃, and further preferably 80-100 ℃. The concentration of the dilute hydrochloric acid used is preferably 10% or less, more preferably 5% or less, and the amount used is generally 1 to 10 times, preferably 1 to 5 times, that of the phosphorus-containing complex salt; the catalyst may be azobisisobutyronitrile or a peroxy compound such as di-t-butylperoxide or like free radical initiator.

Furthermore, the dilute hydrochloric acid used can be produced by separation from the concentrated hydrochloric acid obtained in the subsequent step.

S2, supplementing certain hydrogen chloride into the first mixture by utilizing the ionic effect, fully reducing the solubility of sodium chloride by utilizing a mode of increasing chloride ions, crystallizing and separating out, preserving heat to convert the crystal form of the sodium chloride, filtering, washing a filter cake by hydrochloric acid with certain concentration to obtain pure sodium chloride solid, drying the pure sodium chloride solid to be used for producing the methyldichlorophosphine, wherein the filtrate is a second mixture containing a small amount of sodium chloride, aluminum trichloride, phosphorus-containing flame retardant or intermediate thereof and hydrochloric acid. Preferably, the hydrogen chloride is supplemented to make the concentration of the hydrogen chloride in the mixture solution reach 6-10%. Preferably, the heat preservation is performed at 70-90 ℃, specifically, 80 ℃, for example, and the heat preservation time is, for example, 1-2 hours.

S3, continuously introducing hydrogen chloride gas into the second mixture obtained in the step S2, continuously increasing the content of chloride ions, enabling the content of hydrogen chloride to be more than 35%, enabling aluminum chloride to be precipitated in the form of aluminum trichloride hydrate, filtering, washing a filter cake with concentrated hydrochloric acid, combining filter liquor, and drying the filter cake to obtain the aluminum trichloride hydrate. The filtrate is a third mixture comprising the phosphorus-containing flame retardant or its intermediate, a small amount of aluminum chloride and sodium chloride, hydrochloric acid. The introduced hydrogen chloride can be hydrogen chloride generated by separating concentrated hydrochloric acid obtained in the subsequent step. Preferably, introducing hydrogen chloride to ensure that the content of the hydrogen chloride is 35-45%;

s4, distilling and concentrating the third mixture obtained in the step S3 to obtain concentrated hydrochloric acid and a phosphorus-containing flame retardant mixed with a small amount of aluminum chloride and sodium chloride or an intermediate thereof. Preferably, the distillation concentration is reduced pressure multi-effect distillation concentration;

s5, neutralizing the phosphorus-containing flame retardant mixed with a small amount of aluminum chloride and sodium chloride or the intermediate thereof obtained in S4 with sodium hydroxide (preparing the dissolved aluminum chloride into sodium chloride and aluminum hydroxide to effectively separate the phosphorus-containing flame retardant from inorganic salt substances) to obtain aluminum hydroxide, sodium chloride, phosphorus-containing flame retardant or a mixture of the intermediate sodium salt thereof, filtering, adding hydrochloric acid into the filtrate to acidify the filtrate, namely adding hydrochloric acid to dissociate the phosphorus-containing flame retardant sodium salt into the phosphorus-containing flame retardant or the intermediate thereof so as to facilitate solvent extraction, then concentrating to be anhydrous to obtain the phosphorus-containing flame retardant or the phosphorus-containing flame retardant intermediate and sodium chloride, adding an organic solvent to stir uniformly, filtering, concentrating the filtrate, distilling under reduced pressure (mainly suitable for liquid low-boiling point flame retardants) or selecting suitable solvents to recrystallize (mainly suitable for solid flame retardants), obtaining the phosphorus-containing flame retardant, washing a filter cake by using an organic solvent, and drying to obtain sodium chloride. The organic solvent is not limited to a certain organic solvent or a mixture of several organic solvents, and can be properly selected according to different phosphorus-containing flame retardants.

Pure sodium chloride, pure aluminum chloride hydrate and phosphorus-containing flame retardant or an intermediate thereof are obtained through the steps, the steps are clear, the function is clear, and the sodium chloride can be used for producing the methyldichlorophosphine; the aluminum chlorohydrate has high purity, reaches the standard of high-grade aluminum chlorohydrate, and can be used in casting and sewage treatment industries. The method of the invention completely solves the problem of comprehensive utilization of the composite salt in the production process of the methyldichlorophosphine, solves the industrial problem and lays a foundation for large-scale industrialization of the methyldichlorophosphine.

The comprehensive utilization method of the present invention preferably further comprises one or more of the following steps:

s6, the sodium chloride solid obtained in the step S2 is used in the methyl dichlorophosphine production process.

S7, the aluminum chlorohydrate obtained in the step S3 is used for casting and sewage treatment industries.

S8, further separating the concentrated hydrochloric acid obtained in the step S4 into hydrogen chloride gas and dilute hydrochloric acid, and using the hydrogen chloride gas and dilute hydrochloric acid in the step S1, wherein the method for separating the concentrated hydrochloric acid can be, for example, a calcium chloride method or a sulfuric acid method, specifically, the calcium chloride method is a method of continuously separating hydrogen chloride by using a calcium chloride solution as a dehydrating agent, and continuously distilling the calcium chloride solution to obtain dilute hydrochloric acid; the calcium chloride concentrated solution is continuously used as a dehydrating agent to separate hydrogen chloride; the sulfuric acid method is characterized in that concentrated sulfuric acid is used as a dehydrating agent to continuously separate hydrogen chloride, and a sulfuric acid solution is continuously distilled to obtain dilute hydrochloric acid and concentrated sulfuric acid, and the concentrated sulfuric acid is used as the dehydrating agent to continuously separate the hydrogen chloride.

S9, dissolving the sodium chloride obtained in the step S5 with water to obtain a sodium chloride aqueous solution, returning to the step S1, mixing with dilute hydrochloric acid, and dissolving the complex salt;

s10, returning the filter cake filtered in the first step in the step S5, namely the aluminum hydroxide, to the step S2 for generating aluminum chloride.

S11, further preparing the phosphorus-containing flame retardant intermediate obtained in the step S5 into a phosphorus-containing flame retardant.

According to a preferred aspect of the present invention, the olefinic compound of step S1 of the present invention is an olefinic compound as follows:

wherein in the general formula (1), R₁、R₂、R₃、R₄Independently hydrogen, C1-C12 branched or straight chain alkyl, C3-C12 cycloalkyl, C3-C12 cycloalkyl with a C1-C12 alkyl side chain, phenyl which is unsubstituted or substituted with one or more C1-C12 branched or straight chain alkyl, and the like, preferably hydrogen, C1-C6 branched or straight chain alkyl, cyclohexyl, cyclopentyl, phenyl, and the like. Further, R₁、R₂、R₃、R₄Independently hydrogen, methyl, ethyl, propyl, cyclopropyl, isopropyl, butyl, isobutyl, pentyl, hexyl, cyclobutyl, cyclopentyl, cyclohexylPhenyl, methylphenyl, ethylphenyl.

The equation for the reaction of olefinic compounds with methyldichlorophosphine to form phosphorus-containing flame retardants or intermediates thereof is as follows:

according to another preferred aspect of the present invention, the olefinic compound of step S1 of the present invention is an olefinic compound as follows:

wherein in the general formula (2), R₅、R₆Independently hydrogen, C1-C12 branched or straight chain alkyl, C3-C12 cycloalkyl, C3-C12 cycloalkyl with a C1-C12 alkyl side chain, phenyl which is unsubstituted or substituted with one or more C1-C12 branched or straight chain alkyl, etc., preferably hydrogen, C1-C6 branched or straight chain alkyl, cyclohexyl, cyclopentyl, phenyl, etc.; further, R₅、R₆Independently hydrogen, methyl, ethyl, propyl, cyclopropyl, isopropyl, butyl, isobutyl, pentyl, hexyl, cyclobutyl, cyclopentyl, cyclohexyl, phenyl, methylphenyl, ethylphenyl; n is an integer of 2 to 8, and specifically may be 3, 4, 5, 6 or 7, etc.

The equation for the reaction of olefinic compounds with methyldichlorophosphine to form phosphorus-containing flame retardants or intermediates thereof is as follows:

according to still another preferred aspect of the present invention, the olefin compound in step S1 of the present invention may be one or more selected from ethylene, propylene, butylene, cyclopentene, cyclohexene, styrene, and methyl styrene.

The inventor of the invention innovatively provides the comprehensive utilization method of the compound salt through a large number of experimental verifications and experimental optimization and simplified operations. The present invention is suitable for the production of composite salt of methyl dichloro phosphine and phenyl dichloro phosphine.

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It is noted that the terms "comprises" and "comprising," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a composition, process, method, apparatus, article, or apparatus that comprises a list of elements, steps, or components is not necessarily limited to those elements or components expressly listed, but may include other elements or steps not expressly listed or inherent to such process, method, article, or apparatus.

In the following examples, the conditions used may be further adjusted according to specific requirements, and the conditions not specified are generally those in routine experiments. The raw materials used in the examples are all industrial products unless otherwise specified. The% mentioned means mass% unless otherwise specified.

In the following examples, the phosphorus-containing complex salt is a by-product from the production of methyldichlorophosphine, and includes a complex of sodium chloride and aluminum chloride, methyldichlorophosphine, and the like.

The components and phosphorus content of the phosphorus-containing composite salt are detected as follows: weighing 1.05 g of the compound salt sample, dissolving the compound salt sample in 50 ml of water, fixing the volume in a 100 ml volumetric flask, measuring 1 ml of the compound salt sample, fixing the compound salt sample in a 1 l volumetric flask with water, and measuring the phosphorus content of 0.205 mg/l by using an ammonium molybdate spectrophotometry, wherein the phosphorus content of the compound salt sample is 19.5 g/kg in terms of conversion. The reduced phosphorus content was 0.629 mol/kg. The sodium ion content was 12.23% as determined by ion chromatography, the reduced sodium chloride content was 31.11%, and the aluminum chloride content was 61.53% as determined by titration.

Example 1

The embodiment provides a recycling method of phosphorus-containing composite salt, which comprises the following steps:

s1, weighing 1000 g of phosphorus-containing composite salt in the same batch as the detection sample, controlling the temperature, adding the phosphorus-containing composite salt in batches into 2100 g of 4% hydrochloric acid solution containing 0.5 g of azobisisobutyronitrile, simultaneously dropwise adding 52 g of cyclohexene, and keeping the system temperature at about 80-85 ℃ in the adding process to obtain a first mixture, wherein the related reaction equation is as follows:

s2, introducing 105 g of hydrogen chloride into the first mixture, continuing stirring for 30 minutes, raising the temperature to 80 ℃, preserving the temperature for 1 hour, filtering, pulping and washing a filter cake with 650 g of 20% hydrochloric acid, filtering and drying to obtain 297.5 g of sodium chloride, calibrating the sodium chloride content to 99.56% by detecting sodium ions by using ion chromatography, calibrating the phosphorus content to 14.5ppm by using an ammonium molybdate spectrophotometry, and ensuring that the recovery rate of the sodium chloride is 95.6 percent

S3, combining the filtrate obtained in the filtering step in the S2 step, continuously introducing 720 g of hydrogen chloride, filtering, washing a filter cake by 1100 g of 35% hydrochloric acid, drying, weighing 1096.7 g of the dried filter cake to obtain aluminum chlorohydrate, detecting the content of the aluminum chlorohydrate to be 97.9% by using a complexation method, detecting the content of sodium ions converted into the content of sodium chloride to be 0.41% by using an ion chromatography, detecting the content of phosphorus to be 15.4ppm by using an ammonium molybdate spectrophotometry, and determining the recovery rate of the aluminum chlorohydrate to be 98.5%;

s4, combining the filtrate filtered in S3 with a washing solution, distilling under reduced pressure, and absorbing vacuum tail gas by cooled distilled hydrochloric acid to obtain 3550 g of 36.7% hydrochloric acid;

s5, neutralizing 115.6 g of residual liquid obtained by reduced pressure distillation in S4 with sodium hydroxide, filtering, adding concentrated hydrochloric acid into filtrate to acidify until the pH value is 1, carrying out reduced pressure distillation, evaporating water, adding 100 g of ethanol to dissolve residues, filtering, and washing filter cakes with 40 g of ethanol to obtain sodium chloride solid; the filtrate and the washing liquid are combined to be phosphorus flame retardant ethanol solution, after ethanol is evaporated, the fraction of 154 ℃ and 156 ℃ is collected under the vacuum degree of 5Pa by reduced pressure distillation, 95.5 g of liquid flame retardant (compound I-1) is obtained, and the recovery rate of the converted phosphorus is 93.7 percent.

Example 2

The embodiment provides a recycling method of phosphorus-containing composite salt, which comprises the following steps:

s1, weighing 1000 g of phosphorus-containing composite salt in the same batch as the detection sample, controlling the temperature, adding the phosphorus-containing composite salt into 2100 g of 3.5% hydrochloric acid solution in batches, adding 1 g of ditert-butyl peroxide after the phosphorus-containing composite salt is completely added, introducing ethylene to keep the system pressure at 0.05MPa until the system pressure is unchanged, continuing stirring for 30 minutes, and discharging residual ethylene to obtain a first mixture, wherein the related reaction equation is as follows:

s2, introducing 105 g of hydrogen chloride into the first mixture, continuously stirring for 30 minutes, raising the temperature to 75 ℃, preserving the temperature for 1.5 hours, filtering, pulping and washing a filter cake by 650 g of 20% hydrochloric acid, filtering and drying to obtain 296.7 g of sodium chloride, detecting the sodium ion by using an ion chromatography to calibrate the sodium chloride content to 99.46%, detecting the phosphorus content by using an ammonium molybdate spectrophotometry to be 17.5ppm, and recovering the rate to 95.3%;

s3, combining the filtrate obtained in the filtering step in the S2 step, continuously introducing 720 g of hydrogen chloride, washing a filter cake by 1100 g of 36.7% hydrochloric acid after filtering, weighing 1078 g of the dried filter cake, detecting the content of aluminum chlorohydrate to be 98.4% by a complexation method, detecting the content of sodium ions to be converted into the content of sodium chloride to be 0.46% by an ion chromatography method, detecting the content of phosphorus to be 18.8ppm by an ammonium molybdate spectrophotometry method, and recovering the rate to be 97.8%;

s4, combining the filtrate filtered in S3 with a washing solution, distilling under reduced pressure, and absorbing vacuum tail gas by cooled distilled hydrochloric acid to obtain 3547 g of 36.5% hydrochloric acid;

s5, neutralizing 72.1 g of residual liquid obtained by reduced pressure distillation in S4 with sodium hydroxide, filtering, adding concentrated hydrochloric acid into the filtrate to acidify until the pH value is 1, carrying out reduced pressure distillation, evaporating to remove water, adding 150 g of acetone, refluxing and dissolving the residue, filtering while the filtrate is hot, washing the filter cake with 50 g of hot acetone to obtain sodium chloride solid, combining the filtrate and the washing liquid to obtain a phosphorus-containing flame retardant acetone solution, carrying out reduced pressure distillation under the vacuum degree of 10Pa to collect 146℃ fraction at 147 ℃, obtaining 62.3 g of liquid flame retardant (compound I-2), and recovering 91.7% of the phosphorus by reduced pressure distillation.

Example 3

Methylcyclohexylphosphinic acid (compound I-1) obtained in example 1 was dissolved in 500 g of water, neutralized to neutrality by adding sodium hydroxide, added with a solution of 66 g of aluminum sulfate octadecahydrate in 300 g of water, stirred for reaction for 2 hours, filtered, washed with water, and dried to obtain 98.5 g of methylcyclohexylphosphinic acid aluminum salt flame retardant, with a yield of 98.3%, and the reaction equation was as follows:

the obtained product is analyzed by RSC heat, the result is shown in figure 1, and the RSC chart is compared with the RSC chart (shown in figure 2) of the normally produced aluminum methylcyclohexyl phosphinate, and the following results can be seen: the methyl cyclohexyl aluminium hypophosphite obtained by the method of the invention is consistent with the normally produced product.

Example 4

The methyl ethyl phosphinic acid (compound I-2) obtained in example 2 is dissolved in 300 g of water, sodium hydroxide is added for neutralization to neutrality, 39.4 g of anhydrous zinc chloride solution in 200 g of water is added for stirring reaction for 1.5 hours, and 78.6 g of the methyl ethyl phosphinic acid zinc flame retardant is obtained after filtration, water washing and drying, the yield is 97.5 percent, and the reaction equation is as follows:

the obtained product was analyzed by TG-DTG analysis, and the results are shown in FIG. 3, compared with RSC chart of normally produced zinc methyl ethyl phosphinate (shown in FIG. 4), and it can be seen that: the zinc salt of methyl ethyl phosphinic acid obtained by the method of the invention is consistent with the normally produced product.

Comparative example 1

The treatment of the phosphorus-containing complex salt was carried out according to the method reported in CN111689508A, as follows:

weighing 2000 g of water, heating to 80 ℃, taking 500 g of phosphorus-containing composite salt, adding the phosphorus-containing composite salt into 2000 g of water in batches, controlling the temperature of a reaction system to be 80 ℃, carrying out heat preservation reaction for 1 hour, introducing 350 g of hydrogen chloride, separating out solids, filtering, drying the solids at 70 ℃ in vacuum for 7 hours to obtain 102.6 g of solids, analyzing the weight of the solids to be 95.5 percent, the content of aluminum chlorohydrate to be 3.8 percent, the content of total phosphorus to be 0.278 percent, converting the solids into 2780ppm, concentrating and crystallizing the filtrate at normal pressure, stopping concentrating the filtrate at 110 ℃, cooling the crystals, filtering, drying the solids at 70 ℃ in vacuum for 7 hours to obtain 494.6 g of solids, analyzing the content of sodium chloride to be 8.68 percent, the content of aluminum chlorohydrate to be 90.0 percent, the content of total phosphorus to be 0.52 percent and converting the solids into 5200 ppm.

Comparative example 2

This example provides a method for treating a complex salt containing phosphorus according to the method reported in CN 111187297A.

Adding 200 g of phosphorus-containing composite salt into a 1L reaction bottle, adding 20 g of p-methylphenol, vacuumizing and replacing with nitrogen, heating to 135 ℃ by using a heating jacket under stirring, continuously keeping the temperature and stirring for 2 hours, transferring into a glass culture dish, cooling to obtain a gray black solid, crushing the solid, adding the crushed solid into 400 ml of water in batches, controlling the adding speed to keep the temperature below 40 ℃, continuously stirring for 30 minutes after the adding is finished, cooling to below 20 ℃, filtering, washing the solid with water, drying to obtain 15.6 g of a solid compound, wherein the yield is 47.7%, and detecting that the phosphorus content in the filtrate is 1200ppm and the p-methylphenol content is 15 g/L.

Comparative example 3

Substantially the same procedure as in example 1 was conducted, except that the substance charged in S1 was not cyclohexene, but p-methylphenol. The specific implementation process is as follows.

S1, weighing 1000 g of phosphorus-containing composite salt in the same batch as the detection sample, adding the phosphorus-containing composite salt into 2100 g of 4% hydrochloric acid solution in batches, adding 100 g of p-methylphenol, and keeping the system temperature at about 50 ℃ in the adding process to obtain a first mixture;

s2, introducing 105 g of hydrogen chloride into the first mixture, continuously stirring for 30 minutes, heating to 80 ℃, preserving heat for 1 hour, filtering, pulping and washing a filter cake with 650 g of 20% hydrochloric acid, filtering, and drying to obtain 295.3 g of sodium chloride, wherein the sodium chloride content is 99.38% by detecting sodium ions through ion chromatography, the phosphorus content is 19.2ppm by ammonium molybdate spectrophotometry, and the recovery rate of the sodium chloride is 94.9%;

s3, combining the filtrate obtained in the filtering step in the S2 step, continuously introducing 720 g of hydrogen chloride, filtering, washing a filter cake by 1100 g of 35% hydrochloric acid, drying, weighing 1046.9 g of the dried filter cake to obtain aluminum chlorohydrate, detecting the content of the aluminum chlorohydrate to be 97.9% by a complexation method, detecting the content of sodium ions to be 0.41% by ion chromatography, detecting the content of phosphorus to be 15.4ppm by an ammonium molybdate spectrophotometry, and recovering the recovery rate of the aluminum chlorohydrate to be 94.1%;

s4, combining the filtrate filtered in S3 with a washing solution, distilling under reduced pressure, and absorbing vacuum tail gas by cooled distilled hydrochloric acid to obtain 3542 g of 36.7% hydrochloric acid;

s5, neutralizing 196.5 g of residual liquid obtained by reduced pressure distillation in S4 with sodium hydroxide, filtering, adding concentrated hydrochloric acid into filtrate to acidify until the pH value is 1, carrying out reduced pressure distillation, evaporating water, adding 100 g of ethanol to dissolve residues, filtering, and washing filter cakes with 40 g of ethanol to obtain sodium chloride solid; the filtrate and the washing liquid are combined to obtain phosphorus-containing fire retardant ethanol solution, after ethanol is evaporated, 90.5 g of p-methylphenol is obtained by reduced pressure distillation, the fraction at 175 ℃ and 178 ℃ is collected under the vacuum degree of 5Pa to obtain 12.4 g of liquid fire retardant, the residual high boiling point fraction is 60.2 g, and the recovery rate of the converted phosphorus is 11.6%.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.