Comprehensive recycling methods for byproducts of alkyl dichlorophosphine production

Abstract

This invention discloses a comprehensive recycling method for byproducts of alkyl dichlorophosphine production. The method includes: reacting an alkanoic acid compound with the alkyl dichlorophosphine in the byproduct to generate a phosphorus-containing flame retardant or its intermediate, obtaining a post-reaction mixture; then, gradually separating sodium chloride and precipitates in the form of hydrated aluminum trichloride by progressively increasing the hydrogen chloride content in the system, obtaining a mixture containing the phosphorus-containing flame retardant or its intermediate, a small amount of aluminum chloride, sodium chloride, and hydrochloric acid; distilling and concentrating the mixture, adding sodium hydroxide, filtering, acidifying and concentrating the filtrate, and then extracting and purifying. This method yields pure sodium chloride, pure hydrated aluminum chloride, and the phosphorus-containing flame retardant or its intermediate. The steps are clear, the function is well-defined, and the method is simple and easy to control, completely solving the problem of comprehensive utilization of complex salts in the production of methyl dichlorophosphine.

Description

Technical Field

[0001] This invention relates to the field of recycling and utilizing phosphorus-containing byproducts from the production process of organophosphorus intermediate alkyl dichlorophosphine, specifically to a comprehensive utilization method for phosphorus-containing complex salts. Background Technology

[0002] Alkyl dichlorophosphine, also known as alkyl dichloride, is an important intermediate in organophosphine compounds, especially methyl dichlorophosphine, which is the core raw material for the synthesis of diethyl methylphosphonite, an intermediate in the herbicide glufosinate. Currently, there are three main methods for producing methyl dichlorophosphine:

[0003] 1. Phosphorus trichloride and methane are reacted with a catalyst at high temperature and pressure to produce methyl dichlorophosphine through a tubular reactor, condenser and fractionation unit. This method is prone to producing deposits that can cause blockage of the tubular reactor and condenser, resulting in production interruption. In addition, the product conversion rate is low and the energy consumption is high.

[0004] 2. Phosphorus trichloride, aluminum trichloride, and chloromethane undergo a complexation reaction in a pressure vessel to generate a ternary complex. The ternary complex is reduced by aluminum powder to obtain a complex of methyl dichlorophosphine and aluminum trichloride. This complex dissociates into methyl dichlorophosphine under the action of sodium chloride, and the remaining byproduct is a complex salt of sodium chloride and aluminum chloride.

[0005] 3. Chloromethane reacts with aluminum alloy to produce a mixture of methyl aluminum chloride and dimethyl aluminum chloride. This mixture reacts with phosphorus trichloride to produce a complex of methyl dichlorophosphine and aluminum chloride. This complex reacts with sodium chloride to dissociate methyl dichlorophosphine, with the remaining byproduct being a complex salt of sodium chloride and aluminum chloride.

[0006] In the methods described above, although methods 2 and 3 do not involve high temperature and high pressure, the insufficient dissociation of methyldichlorophosphine and aluminum trichloride by sodium chloride results in a high residual methyldichlorophosphine content in the aluminum chloride and sodium chloride composite salt. This hinders the effective recovery and utilization of the aluminum chloride and sodium chloride composite salt, posing a significant obstacle to the production of methyldichlorophosphine. To address this problem, existing technologies have proposed several different solutions, such as:

[0007] Chinese invention patent CN105217667B mentions using a mixture of alcohol and ether as a decomposition agent to decompose sodium chloride and aluminum chloride to obtain aluminum chloride for reuse. However, this method does not mention the treatment of phosphorus-containing compounds in sodium chloride and sodium tetrachloroaluminate, and therefore cannot recover phosphorus-containing compounds and sodium chloride.

[0008] Chinese invention patent CN108238621A mentions dissolving a composite salt and then adding ferric chloride, hydrochloric acid, sodium hydroxide, sodium aluminate, etc. to carry out a polymerization reaction. After cooling and filtration, a polyaluminum chloride solution is obtained. This method provides a method for preparing polyaluminum chloride from composite salts. However, this method will result in a large amount of sodium chloride and a small amount of phosphorus-containing compounds entering the polyaluminum chloride system. Because the polyaluminum chloride produced by this method contains phosphorus-containing compounds, its application is limited.

[0009] Chinese invention patent CN111187297A discloses a method for recovering and treating phosphorus-containing industrial byproducts. The method involves placing the byproducts generated during the production of diethyl methyl phosphite in a reaction vessel, adding phenolic compounds, di- or higher aromatic amine compounds, or compounds containing ethylene oxide functional groups, and heating the reaction under air-isolated conditions. After cooling to room temperature, the resulting solid is slowly dissolved in water. Since this water dissolution process is exothermic, the addition rate needs to be controlled, and the mixture must be stirred evenly. The mixture is then cooled and filtered. The resulting filter residue is used as a phosphorus-based flame retardant. The first filter residue... The liquid continues solid-liquid separation. Specifically, the first filtrate is heated to 100-120 degrees Celsius until crystals appear and their quantity stops increasing. Heating is then stopped, and the solution is filtered while hot. The resulting solid is sodium chloride crystals. Water is slowly added to the second filtrate, which is then cooled to room temperature. The pH of the second filtrate is adjusted to prepare polyaluminum chloride. Specifically, ferric chloride and hydrochloric acid are added to the second filtrate, and the mixture is stirred until homogeneous. The reaction temperature is maintained above 85 degrees Celsius. Then, aluminum hydroxide and calcium aluminate are added sequentially, and the reaction temperature is maintained at 100 degrees Celsius to obtain polyaluminum chloride. Although this method can recover methyldichlorophosphine, the added phenolic substances, di- or higher aromatic amines, or epoxides will enter the polyaluminum chloride system, causing contamination and rendering the polyaluminum chloride unusable. In addition, a large amount of phenolic substances will dissolve in the filtrate, creating new wastewater treatment problems. Moreover, this method is complex, difficult to control, and inconvenient to operate.

[0010] Chinese invention patent CN111689508A discloses a method for treating sodium tetrachloroaluminate solid residue, comprising: (1) mixing sodium tetrachloroaluminate solid residue with water for dissociation, then adding a separating agent to precipitate aluminum chloride hexahydrate, or directly mixing sodium tetrachloroaluminate solid residue with a separating agent for dissociation and precipitating aluminum chloride hexahydrate, and then obtaining aluminum chloride hexahydrate solid and a primary filtrate through a first solid-liquid separation; (2) concentrating and crystallizing the primary filtrate obtained in step (1), followed by a second solid-liquid separation to obtain sodium chloride solid and a secondary filtrate, with the secondary filtrate returned to step (1) to provide the separating agent required for the precipitation of aluminum chloride hexahydrate. This method has been verified to separate sodium chloride and aluminum chloride. However, the scheme reported in this patent contains errors. Specifically, in step (1), sodium chloride is obtained first, not aluminum chloride hexahydrate. The sodium chloride and aluminum chloride obtained in the end do not meet the standard requirements due to contamination from phosphorus-containing compounds in the solid residue mother liquor.

[0011] In summary, existing technologies cannot fully and effectively utilize the complex salts generated during the production of methyldichlorophosphine, and some utilization methods also suffer from problems such as complex processes and high control difficulty. Summary of the Invention

[0012] To address the technical problem of comprehensive utilization of by-products in the production of methyldichlorophosphine, this invention provides a method for comprehensive utilization of by-products in the production process of methyldichlorophosphine. This method can fully and effectively recover and utilize by-products from the production of methyldichlorophosphine, and the process is simple and easy to control.

[0013] To solve the above problems, the present invention adopts the following technical solution:

[0014] A comprehensive recycling method for byproducts of alkyl dichlorophosphine production, wherein the byproducts comprise a complex salt of sodium chloride and aluminum chloride, and alkyl dichlorophosphine, the method comprising the following steps:

[0015] S1. The alkyl dichlorophosphine produced as a byproduct of the alkyl dichlorophosphine production is reacted with an olefinic compound in the presence of water to generate a phosphorus-containing flame retardant or an intermediate thereof, thereby obtaining a first mixture containing the phosphorus-containing flame retardant or an intermediate thereof, sodium chloride, and aluminum chloride.

[0016] S2. Pass hydrogen chloride and / or add hydrochloric acid into the first mixture to make the mass percentage of hydrogen chloride in the mixture solution reach 5%-15%, so that sodium chloride crystals out, filter, wash the filter cake with hydrochloric acid, and obtain pure sodium chloride solid. The filtrate is a second mixture containing a very small amount of sodium chloride, aluminum trichloride, phosphorus-containing flame retardant or its intermediate, and hydrochloric acid.

[0017] S3. Pass hydrogen chloride gas and / or add hydrochloric acid into the filtrate after filtration in step S2, so that the mass content of hydrogen chloride in the mixture solution is greater than or equal to 35%, so that aluminum chloride precipitates in the form of hydrated aluminum trichloride. Filter, wash the filter cake with hydrochloric acid, and dry to obtain hydrated aluminum trichloride. The filtrate is a third mixture containing a phosphorus-containing flame retardant or its intermediate, aluminum chloride and sodium chloride, and hydrochloric acid.

[0018] S4. The third mixture in step S3 is concentrated by distillation to obtain concentrated hydrochloric acid and a phosphorus-containing flame retardant or its intermediate mixed with aluminum chloride and sodium chloride.

[0019] S5. Separate and remove aluminum chloride and sodium chloride from a phosphorus-containing flame retardant or its intermediate containing aluminum chloride and sodium chloride to obtain a phosphorus-containing flame retardant or its intermediate.

[0020] Further, in step S1, the by-product of the alkyl dichlorophosphine production, the olefinic compound, and dilute hydrochloric acid are mixed and reacted at a temperature of 40 to 100 degrees Celsius, wherein the mass percentage of the dilute hydrochloric acid is less than or equal to 10%.

[0021] According to a preferred aspect of the present invention, in step S1, the by-product of the alkyl dichlorophosphine production is added to the dilute hydrochloric acid in batches, and the system temperature is maintained at 40-100 degrees Celsius during the addition process. After the by-product of the alkyl dichlorophosphine production is added, an olefinic compound or an aqueous solution containing the olefinic compound is added, and the mixture is stirred to obtain the first mixture.

[0022] Furthermore, in steps S2 and S3, the hydrochloric acid used for washing is concentrated hydrochloric acid with a mass percentage of 30% to 37%.

[0023] Further, in step S1, the olefin compound is a 2-olefin compound, more preferably a C4-C20 olefin compound, and even more preferably a C4-C12 olefin compound.

[0024] According to the present invention, the olefinic compounds have the structure shown in the following general formula (1):

[0025]

[0026] Among them, R 1 R 2 R 3 The phenyl group is independently hydrogen, a C1-C12 branched or straight-chain alkyl group, a C3-C12 cycloalkyl group, a C3-C12 cycloalkyl group with a C1-C12 alkyl side chain, or an unsubstituted or substituted phenyl group.

[0027] Furthermore, in general formula (1), R 1 R2 R 3 It can be independently hydrogen, methyl, ethyl, propyl, cyclopropyl, isopropyl, butyl, isobutyl, pentyl, hexyl, cyclobutyl, cyclopentyl, cyclohexyl, phenyl, methylphenyl, or ethylphenyl, wherein R 1 R 2 R 3 At most one of them is a cyclic substituent.

[0028] In step S1, typical olefinic compounds include, but are not limited to, acrylic acid and / or methacrylic acid.

[0029] According to some preferred aspects of the present invention, before step S1, the content of alkyl dichlorophosphine in the phosphorus-containing complex salt is obtained, and in step S1, the alkyl dichlorophosphine to olefinic acid compound is fed in a molar ratio of 1:1.01 to 1.3.

[0030] More preferably, in step S1, the alkyl dichlorophosphine to olefinic acid compound is fed in a molar ratio of 1:1.01 to 1.1.

[0031] According to some preferred aspects of the present invention, in step S1, the amount of dilute hydrochloric acid used is 1-10 times that of the phosphorus-containing complex salt. More preferably, in step S1, the amount of dilute hydrochloric acid used is 1-5 times that of the phosphorus-containing complex salt.

[0032] According to some preferred aspects of the present invention, in step S1, the mass percentage of the dilute hydrochloric acid is 2% to 5%; in step S2, the mass percentage of the hydrochloric acid used for washing the filter cake is 30% to 37%.

[0033] According to some preferred aspects of the present 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, hydrogen chloride is introduced to make the mass percentage of hydrogen chloride in the mixture solution 35%-45%.

[0034] According to some preferred aspects of the present invention, the alkyl dichlorophosphine is methyl dichlorophosphine, and the phosphorus-containing complex salt is a byproduct of methyl dichlorophosphine production. The comprehensive recycling method for the byproduct of alkyl dichlorophosphine production further includes: S6, using the sodium chloride solid obtained in step S2 in the methyl dichlorophosphine production process.

[0035] According to some preferred aspects of the present invention, the comprehensive recycling method for the by-products of alkyl dichlorophosphine production further includes: S7, using the hydrated aluminum chloride obtained in step S3 in the casting and wastewater treatment industries.

[0036] According to some preferred aspects of the present invention, the comprehensive recycling method for the by-products of alkyl dichlorophosphine production further includes: S8, further separating the concentrated hydrochloric acid obtained in step S4 into hydrogen chloride gas and dilute hydrochloric acid for use in step S1.

[0037] Further, in step S8, the method for separating concentrated hydrochloric acid is either the calcium chloride method or the sulfuric acid method; wherein, the calcium chloride method uses calcium chloride solution as a dehydrating agent to continuously separate hydrogen chloride, and continuously distills the calcium chloride solution to obtain dilute hydrochloric acid; the concentrated calcium chloride solution continues to be used as a dehydrating agent to separate hydrogen chloride; the sulfuric acid method uses concentrated sulfuric acid as a dehydrating agent to continuously separate hydrogen chloride, and continuously distills the sulfuric acid solution to obtain dilute hydrochloric acid and concentrated sulfuric acid, and the concentrated sulfuric acid continues to be used as a dehydrating agent to separate hydrogen chloride.

[0038] Preferably, in step S1, after sodium chloride crystallizes and before filtration, the system is kept at 70–90 degrees Celsius for 1–2 hours. This temperature maintenance facilitates the subsequent filtration and separation of sodium chloride.

[0039] According to a preferred aspect of the invention, step S5 further includes:

[0040] S50: Add sodium hydroxide to the phosphorus-containing flame retardant or its intermediate containing aluminum chloride and sodium chloride obtained in step S4, so that the dissolved aluminum chloride is converted into sodium chloride and aluminum hydroxide, and a mixture containing aluminum hydroxide, sodium chloride, sodium salt of phosphorus-containing flame retardant or its intermediate is obtained. Filter, and the filtrate is an aqueous solution of sodium salt of phosphorus-containing flame retardant or its intermediate and sodium chloride.

[0041] S51: Add hydrochloric acid to the filtrate obtained in step S50 to acidify it so that the sodium salt of the phosphorus-containing flame retardant or its intermediate is released into the phosphorus-containing flame retardant or its intermediate. Then concentrate it until anhydrous to obtain the phosphorus-containing flame retardant or its intermediate and sodium chloride. Add organic solvent and stir evenly. Filter the solution. After concentrating the filtrate, distill it under reduced pressure or recrystallize it to obtain the phosphorus-containing flame retardant or its intermediate. Wash the filter cake with organic solvent and dry it to obtain sodium chloride.

[0042] According to some preferred aspects of the present invention, the comprehensive recycling method for byproducts of alkyl dichlorophosphine production further includes one or more of the following steps:

[0043] S9. Dissolve the sodium chloride obtained in step S5 in water to obtain an aqueous solution of sodium chloride, and then return to step S1 to mix it with dilute hydrochloric acid to dissolve the complex salt.

[0044] S10. The filter cake, i.e. aluminum hydroxide, filtered in step S50 is returned to step S2 to generate aluminum chloride.

[0045] S11. The phosphorus-containing flame retardant intermediate obtained in step S51 is further processed into a phosphorus-containing flame retardant.

[0046] The present invention also provides a method for producing alkyl dichlorophosphine, comprising:

[0047] (1) Obtain alkyl dichlorophosphine and sodium chloride and aluminum chloride complex salt byproducts containing alkyl dichlorophosphine.

[0048] (2) The above-mentioned comprehensive recycling method for byproducts of alkyl dichlorophosphine production is used to recover sodium chloride, hydrated aluminum chloride, phosphorus-containing flame retardant or its intermediates.

[0049] Furthermore, the production method further includes (3) using the sodium chloride recovered in (2) above as a raw material in step (1).

[0050] In one specific embodiment of the present invention, the alkyl dichlorophosphine includes methyl dichlorophosphine, phenyl dichlorophosphine, etc.

[0051] In this invention, unless otherwise specified, the mass percentage concentrations of dilute hydrochloric acid, concentrated sulfuric acid, hydrogen chloride, and sulfuric acid are all within the conventional definition range of the prior art.

[0052] The beneficial effects of the technical solution provided by this invention are as follows:

[0053] The processing method described in this invention can convert residual alkyl dichlorophosphine in compound salts into phosphorus-containing flame retardants or intermediates with high added value; it can also obtain sodium chloride with a content of 99.5% or higher, which can be recycled in the production process of methyl dichlorophosphine; and it can obtain hydrated aluminum chloride with a content of 97% or higher, fully meeting the standards for superior grade hydrated aluminum chloride; the hydrochloric acid used can be separated into hydrogen chloride and dilute hydrochloric acid, which can be recycled for the treatment of compound salts. Compared with the prior art, the method of this invention can achieve efficient recovery of all useful substances, and the entire process generates no waste liquid, has low recovery costs, is simple in process and easy to operate, and can truly and thoroughly solve the problem of comprehensive utilization of by-products from the production of alkyl dichlorophosphine. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 This is the hydrogen spectrum of the flame retardant prepared in Example 1. Detailed Implementation

[0056] The following section uses the comprehensive utilization method of by-products (phosphorus-containing complex salts) in the production process of methyl dichlorophosphine as an example to further elaborate on the present invention.

[0057] According to some specific embodiments of the present invention, a method for comprehensive utilization of byproducts in the production process of methyldichlorophosphine includes the following steps:

[0058] S1. The byproducts of alkyl dichlorophosphine production are added in batches to dilute hydrochloric acid, maintaining the system temperature at 40–100 degrees Celsius during the addition process. After the byproducts of alkyl dichlorophosphine production are completely added, an olefinic acid compound or an aqueous solution containing an olefinic acid compound is added, and the mixture is stirred to obtain a first mixture. In this step, the amount of olefinic acid compound added is preferably in excess relative to phosphorus-containing components such as methyl dichlorophosphine. Preferably, the molar ratio of olefinic acid compound to methyl dichlorophosphine is 1.01–1.3:1, more preferably 1.01–1.1:1, and even more preferably 1.03–1.05:1. Preferably, the reaction temperature is 40–100 degrees Celsius, more preferably 40–70 degrees Celsius, and even more preferably 45–60 degrees Celsius. The concentration of the dilute hydrochloric acid used is preferably less than or equal to 10%, more preferably less than or equal to 5%, and its amount used is generally 1-10 times that of the phosphorus-containing complex salt, preferably 1-5 times; in addition, the dilute hydrochloric acid used can be produced by separating the concentrated hydrochloric acid obtained in subsequent steps.

[0059] S2. Utilizing the ionic effect, a certain amount of hydrogen chloride is added to the first mixture to significantly reduce the solubility of sodium chloride by increasing chloride ions, causing crystallization. Preferably, the mixture is kept at a certain temperature (to facilitate crystal transformation of sodium chloride for subsequent filtration). After filtration, the filter cake is washed with hydrochloric acid of a certain concentration to obtain pure sodium chloride solid. After drying, it can be used for the production of methyldichlorophosphine. The filtrate is a second mixture containing trace amounts of sodium chloride, aluminum trichloride, a phosphorus-containing flame retardant or its intermediate, and hydrochloric acid. Preferably, hydrogen chloride is added to bring the hydrogen chloride concentration in the mixture solution to 6%-10%. The temperature for holding the mixture can be 70-90 degrees Celsius, and the holding time can be 1-2 hours. The concentration of hydrochloric acid used for washing is preferably concentrated hydrochloric acid, specifically, for example, 30-37%.

[0060] S3. Continue to pass hydrogen chloride gas through the second mixture obtained in step S2 to further increase the chloride ion content and make the hydrogen chloride content greater than 35%, causing aluminum chloride to precipitate as hydrated aluminum trichloride. Filter the mixture, wash the filter cake with concentrated hydrochloric acid, combine the filtrates, and dry the filter cake to obtain hydrated aluminum trichloride. The filtrate is a third mixture containing a phosphorus-containing flame retardant or its intermediate, a small amount of aluminum chloride, sodium chloride, and hydrochloric acid. The hydrogen chloride introduced can be hydrogen chloride produced by separating concentrated hydrochloric acid obtained in subsequent steps. Preferably, the hydrogen chloride content is 35%-45%.

[0061] S4. The third mixture obtained in step S3 is concentrated by distillation to obtain concentrated hydrochloric acid and a phosphorus-containing flame retardant or its intermediate mixed with a small amount of aluminum chloride and sodium chloride. Preferably, the distillation concentration is a vacuum multi-effect distillation concentration;

[0062] S5. Separating phosphorus-containing flame retardants or their intermediates from phosphorus-containing flame retardants or their intermediates mixed with small amounts of aluminum chloride and sodium chloride, specifically including:

[0063] S50: The phosphorus-containing flame retardant or its intermediate obtained in step S4, which contains a small amount of aluminum chloride and sodium chloride, is neutralized with sodium hydroxide (the dissolved aluminum chloride is converted into sodium chloride and aluminum hydroxide to effectively separate the phosphorus-containing flame retardant and inorganic salts), to obtain a mixture of aluminum hydroxide, sodium chloride, and sodium salt of phosphorus-containing flame retardant or its intermediate. The mixture is filtered, and the filtrate is an aqueous solution of sodium salt of phosphorus-containing flame retardant or its intermediate and sodium chloride.

[0064] S51: Acidify the filtrate from the previous step by adding hydrochloric acid (to release the sodium salt of the phosphorus-containing flame retardant into the phosphorus-containing flame retardant or its intermediate, facilitating solvent extraction), then concentrate to anhydrous to obtain the phosphorus-containing flame retardant or its intermediate and sodium chloride. Add an organic solvent, stir until homogeneous, filter, concentrate the filtrate, and then distill under reduced pressure (mainly suitable for liquid low-boiling-point flame retardants) or recrystallize using a suitable solvent (mainly suitable for solid flame retardants) to obtain the phosphorus-containing flame retardant. Wash the filter cake with an organic solvent and dry to obtain sodium chloride. The organic solvent used is not limited to a single organic solvent or a mixture of several organic solvents; appropriate selection can be made for different phosphorus-containing flame retardants.

[0065] This invention, through the above steps, yields pure sodium chloride, pure hydrated aluminum chloride, and a phosphorus-containing flame retardant or its intermediate. The steps are clear and the functions are well-defined. Sodium chloride can be used in the production of methyldichlorophosphine; the hydrated aluminum chloride has high purity, meeting the standards for superior-grade hydrated aluminum chloride, and can be used in the foundry and wastewater treatment industries. This invention completely solves the problem of comprehensive utilization of complex salts in the production of methyldichlorophosphine, resolving an industry challenge and laying the foundation for the large-scale industrialization of methyldichlorophosphine.

[0066] The comprehensive utilization method of the present invention preferably further includes one or more of the following steps:

[0067] S6. Use the sodium chloride solid obtained in step S2 in the methyldichlorophosphine production process.

[0068] S7. Use the hydrated aluminum chloride obtained in step S3 in the casting and wastewater treatment industries.

[0069] S8. The concentrated hydrochloric acid obtained in step S4 is further separated into hydrogen chloride gas and dilute hydrochloric acid for use in step S1. The method for separating the concentrated hydrochloric acid can be, for example, the calcium chloride method or the sulfuric acid method. Specifically, the calcium chloride method uses calcium chloride solution as a dehydrating agent to continuously separate hydrogen chloride, and continuously distills the calcium chloride solution to obtain dilute hydrochloric acid; the concentrated calcium chloride solution continues to be used as a dehydrating agent to separate hydrogen chloride; the sulfuric acid method uses concentrated sulfuric acid as a dehydrating agent to continuously separate hydrogen chloride, and continuously distills the sulfuric acid solution to obtain dilute hydrochloric acid and concentrated sulfuric acid, and the concentrated sulfuric acid continues to be used as a dehydrating agent to separate hydrogen chloride.

[0070] S9. Dissolve the sodium chloride obtained in step S51 in water to obtain an aqueous solution of sodium chloride, and return to step S1;

[0071] S10. The filter cake obtained in step S50, i.e. aluminum hydroxide, is returned to step S2 to generate aluminum chloride.

[0072] S11. The phosphorus-containing flame retardant intermediate obtained in step S51 is further processed into a phosphorus-containing flame retardant.

[0073] According to a preferred aspect of the present invention, the olefinic compound in step S1 is an olefinic compound as described below:

[0074]

[0075] Among them, R 1 R 2 R 3 The phenyl group is independently hydrogen, a C1-C12 branched or straight-chain alkyl group, a C3-C12 cycloalkyl group, a C3-C12 cycloalkyl group with a C1-C12 alkyl side chain, or an unsubstituted or substituted phenyl group.

[0076] Furthermore, in general formula (1), R 1 R 2 R 3 It can be independently hydrogen, methyl, ethyl, propyl, cyclopropyl, isopropyl, butyl, isobutyl, pentyl, hexyl, cyclobutyl, cyclopentyl, cyclohexyl, phenyl, methylphenyl, or ethylphenyl, wherein R 1 R 2 R 3 At most one of them is a cyclic substituent.

[0077] In step S1, typical olefinic compounds include, but are not limited to, acrylic acid and / or methacrylic acid.

[0078] The equation for the reaction of olefinic compounds with methyldichlorophosphine to produce phosphorus-containing flame retardants or their intermediates is as follows:

[0079]

[0080] Through extensive experimental verification, optimization, and simplification, the inventors have innovatively discovered a comprehensive utilization method for the above-mentioned byproducts. This invention is applicable not only to the complex salts generated during the production of methyl dichlorophosphine but also to the complex salts generated during the production of phenyl dichlorophosphine via a Friedel-Crafts reaction.

[0081] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0082] It should be noted that the terms "comprising" and "having" and any variations thereof in this invention are intended to cover non-exclusive inclusion, for example, a composition, process, method, apparatus, product or device that includes a series of substances, steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to these processes, methods, products or devices.

[0083] In the following embodiments, the implementation conditions may be further adjusted according to specific requirements. Implementation conditions not specified are generally those used in routine experiments. Unless otherwise specified, all raw materials used in the embodiments are industrial grade. The percentage (%) of a grade refers to a mass percentage unless otherwise specified.

[0084] In the following examples, the phosphorus-containing complex salt is a byproduct of the production process of methyl dichlorophosphine, including a complex of sodium chloride and aluminum chloride and methyl dichlorophosphine, etc.

[0085] The composition and phosphorus content of the phosphorus-containing compound salt were determined as follows: 1.05 g of the compound salt sample was weighed, dissolved in 50 mL of water, and diluted to a volumetric flask of 100 mL. Then, 1 mL of this solution was measured and diluted to a volumetric flask of 1 L with water. The phosphorus content was determined to be 0.205 mg / L using the ammonium molybdate spectrophotometric method, which translates to a phosphorus content of 19.5 g / kg, equivalent to 0.629 mol / kg. The sodium ion content was determined to be 12.23% by ion chromatography, equivalent to 31.11% sodium chloride, and the aluminum chloride content was determined to be 61.53% by titration.

[0086] Example 1

[0087] This example provides a method for recycling phosphorus-containing complex salts, implemented as follows:

[0088] S1. Weigh 1000g of the same batch of compound salt as the test sample, and add it in portions to 2100g of 4.3% hydrochloric acid solution. Maintain the system temperature at approximately 50°C during the addition process. After the compound salt has been completely added, add 50g of acrylic acid and continue stirring for 30 minutes to obtain the first mixture. The reaction equation is as follows:

[0089]

[0090] S2. 105 g of hydrogen chloride is introduced into the first mixture of step S1, and stirring is continued for 30 minutes to precipitate sodium chloride. The mixture is heated to 80 degrees Celsius and kept at that temperature for 1 hour. After filtration, the filter cake is washed with 650 g of 20% hydrochloric acid, filtered, and dried to obtain 299.5 g of sodium chloride. The sodium chloride content is determined to be 99.63% by ion chromatography and 16.3 ppm by ammonium molybdate spectrophotometry, with a recovery rate of 96.2%.

[0091] S3. Combine the filtrates from step S2, and continue to pass 720 g of hydrogen chloride through them. After filtration, wash the filter cake with 1100 g of 36.6% hydrochloric acid. After drying, the filter cake weighs 1105 g. The content of hydrated aluminum chloride is determined to be 98.2% by complexation method, the sodium ion content is determined to be 0.56% (equivalent to sodium chloride) by ion chromatography, and the phosphorus content is determined to be 21.4 ppm by ammonium molybdate spectrophotometry, with a recovery rate of 99.3%.

[0092] S4. Combine the filtrate and washing liquid from step S3 and perform vacuum distillation. Absorb the vacuum tail gas with the cooled distilled hydrochloric acid to obtain 3544 grams of 37% hydrochloric acid.

[0093] S5. The remaining 97.3 g of the distillate from step S4 was neutralized with sodium hydroxide, filtered, and the filtrate was acidified to pH 1 with concentrated hydrochloric acid. The solution was then distilled under reduced pressure to evaporate the water. 150 g of acetone was added and refluxed to dissolve the residue. The solution was filtered while hot, and the solid was washed with 50 g of hot acetone to obtain solid sodium chloride and an acetone solution containing phosphorus flame retardant. The solution was cooled to 5°C, filtered, and vacuum dried to obtain 88.2 g (MP 98-100°C) of solid flame retardant (compound I-1), with a recovery rate of 92.3%. The 1H NMR spectrum of the flame retardant is shown below. Figure 1 As shown, the spectrum matches the proton spectrum of compound I-1, proving that compound I-1 was successfully synthesized.

[0094] Example 2

[0095] This example provides a method for recycling phosphorus-containing complex salts, implemented as follows:

[0096] S1. Weigh 1000g of the same batch of compound salt as the test sample, and add it in portions to 2100g of 5.1% hydrochloric acid solution. Maintain the system temperature at approximately 50°C during the addition process. After the compound salt has been completely added, add 60g of methacrylic acid and continue stirring for 30 minutes to obtain the first mixture. The reaction equation is as follows:

[0097]

[0098] S2. 105 g of hydrogen chloride is introduced into the first mixture of step S1, and stirring is continued for 30 minutes to precipitate sodium chloride. The mixture is heated to 70 degrees Celsius and kept at that temperature for 1.5 hours. After filtration, the filter cake is washed with 650 g of 20% hydrochloric acid, filtered, and dried to obtain 305.4 g of sodium chloride. The sodium chloride content is determined to be 99.57% by ion chromatography and 22.1 ppm by ammonium molybdate spectrophotometry, with a recovery rate of 98.2%.

[0099] S3. Combine the filtrates from step S2, and continue to pass 720 g of hydrogen chloride through them. After filtration, wash the filter cake with 1100 g of 37% hydrochloric acid. After drying, the filter cake weighs 1095 g. The content of hydrated aluminum chloride is determined to be 98.6% by complexation method, the sodium ion content is determined to be 0.47% (equivalent to sodium chloride) by ion chromatography, and the phosphorus content is determined to be 19.7 ppm by ammonium molybdate spectrophotometry, with a recovery rate of 98.4%.

[0100] S4. Combine the filtrate and washing liquid from step S3 and perform vacuum distillation. Absorb the vacuum tail gas with the cooled distilled hydrochloric acid to obtain 3574 grams of 36.8% hydrochloric acid.

[0101] S5. The remaining 104.3 g of the distillate from step S4 was neutralized with sodium hydroxide, filtered, and the filtrate was acidified with concentrated hydrochloric acid to pH 1. The solution was then distilled under reduced pressure to evaporate the water. 150 g of acetone was added and refluxed to dissolve the residue. The solution was filtered while hot, and the solid was washed with 50 g of hot acetone to obtain solid sodium chloride and an acetone solution containing phosphorus flame retardant. The solution was cooled to 5°C, filtered, and vacuum dried to obtain 98.1 g of solid flame retardant (compound I-2) (MPa 105-106°C), with a recovery rate of 94%. This flame retardant was dissolved in 500 g of water, 15.5 g of aluminum hydroxide was added, and the solution was refluxed for 4 hours. After filtration and drying, the weight was 97.9 g (yield 95.2%).

[0102] Flame retardancy test

[0103] Flame retardancy test: To facilitate the testing of the flame retardant performance of the flame retardant, epoxy resin was used as the polymer base material. Specifically, bisphenol A epoxy resin (CYD-127) and curing agent diaminodiphenylmethane (DDM) were used. 100 grams of epoxy resin were added to the flame retardant obtained in the example, with the flame retardant addition amounts being 10% and 15%, respectively. After dispersion using a high-speed disperser, 26 grams of curing agent were added, and the temperature was raised to 145 degrees Celsius. Dispersion was continued using a high-speed disperser until uniform dispersion. The mixture was then poured into a mold, placed in an oven, and kept at 160 degrees Celsius for 4 hours. After cooling, the sample was removed from the mold for testing. The flame retardant data (residual carbon rate and oxygen index at 600 degrees Celsius) were measured as shown in Table 1 below.

[0104] Table 1

[0105]

[0106] The flame retardancy test data above show that the flame retardant recovered by the method of the present invention has excellent flame retardant properties, which are comparable to those of the same flame retardant produced normally.

[0107] Comparative Example 1

[0108] The treatment of phosphorus-containing complex salts was carried out according to the method reported in CN111689508A, and the process is as follows:

[0109] Weigh 2000g of water and heat it to 80°C. Take 500g of phosphorus-containing compound salt and add it to the 2000g of water in batches. Control the reaction system temperature at 80°C and keep the reaction at this temperature for 1 hour. Then, introduce 350g of hydrogen chloride. A solid precipitates out. Filter the solution. After vacuum drying at 70°C for 7 hours, the solid weighs 102.6g. Analysis shows that the sodium chloride content is 95.5%, the hydrated aluminum chloride content is 3.8%, and the total phosphorus content is 0.278%, equivalent to 2780ppm. Concentrate the filtrate under normal pressure to crystallize. When the system temperature reaches 110°C, stop the concentration, cool and crystallize. Filter the solution. After vacuum drying at 70°C for 7 hours, the solid weighs 494.6g. Analysis shows that the sodium chloride content is 8.68%, the hydrated aluminum chloride content is 90.0%, and the total phosphorus content is 0.52%, equivalent to 5200ppm.

[0110] Comparative Example 2

[0111] This example provides a method for processing phosphorus-containing complex salts, employing a process essentially the same as in Example 1. The difference is that the substance added in S1 is not acrylic acid, but p-methylphenol. The specific implementation process is as follows.

[0112] S1. Weigh 1000g of phosphorus-containing compound salt from the same batch as the test sample, add it in batches to 2100g of 4% hydrochloric acid solution, then add 100g of p-methylphenol. During the addition process, keep the system temperature at about 50 degrees Celsius to obtain the first mixture.

[0113] S2. 105 g of hydrogen chloride was introduced into the first mixture, and stirring was continued for 30 minutes. The temperature was raised to 80 degrees Celsius and kept at that temperature for 1 hour. The mixture was filtered, and the filter cake was washed with 650 g of 20% hydrochloric acid. After filtration and drying, 295.3 g of sodium chloride was obtained. The sodium chloride content was determined to be 99.38% by ion chromatography and the phosphorus content was determined to be 19.2 ppm by ammonium molybdate spectrophotometry. The recovery rate of sodium chloride was 94.9%.

[0114] S3. Combine the filtrates from the filtration step in S2, and continue to pass 720 g of hydrogen chloride through the filter. After filtration, the filter cake is washed with 1100 g of 35% hydrochloric acid, dried, and weighed to 1046.9 g, which is hydrated aluminum chloride. The content of hydrated aluminum chloride was determined by complexation method to be 97.9%, the sodium ion content was determined by ion chromatography to be 0.41% (equivalent to sodium chloride content), and the phosphorus content was determined by ammonium molybdate spectrophotometry to be 15.4 ppm. The recovery rate of hydrated aluminum chloride was 94.1%.

[0115] S4. After combining the filtrate and washing liquid filtered in S3, perform vacuum distillation. The vacuum tail gas is absorbed by the cooled distilled hydrochloric acid to obtain 3542 grams of 36.7% hydrochloric acid.

[0116] S5. The remaining 196.5 g of the vacuum distillation residue from S4 was neutralized with sodium hydroxide, filtered, and the filtrate was acidified with concentrated hydrochloric acid to pH 1. Vacuum distillation was then carried out to evaporate the water. 100 g of ethanol was added to dissolve the residue, and the mixture was filtered. The filter cake was washed with 40 g of ethanol to obtain solid sodium chloride. The filtrate and washing liquid were combined to obtain a phosphorus-containing flame retardant ethanol solution. After removing the ethanol, vacuum distillation was carried out to obtain 90.5 g of p-methylphenol. The fraction at 175-178 degrees Celsius was collected under a vacuum of 5 Pa, yielding 12.4 g of liquid flame retardant. The remaining high-boiling fraction was 60.2 g, representing a phosphorus recovery rate of 11.6%.

[0117] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A comprehensive recycling method of by-products of alkyl dichlorophosphine production, said by-products of alkyl dichlorophosphine production comprising a complex salt of sodium chloride and aluminum chloride and alkyl dichlorophosphine, said alkyl dichlorophosphine being methyldichlorophosphine, characterized in that, The method comprises the following steps: ​ S1, mixing the alkyl dichlorophosphine production by-product, olefinic acid compound and dilute hydrochloric acid, and reacting at a temperature of 40-100 DEG C to generate a phosphorus-containing flame retardant or an intermediate thereof, to obtain a first mixture comprising the phosphorus-containing flame retardant or the intermediate thereof, sodium chloride and aluminum chloride, wherein the mass percentage of the dilute hydrochloric acid is less than or equal to 10%; The olefinic acid compound has the structure shown in the following general formula (1): ， Among them, R 1 R 2 R 3 Independently, it is hydrogen, methyl, ethyl, propyl, cyclopropyl, isopropyl, butyl, isobutyl, pentyl, hexyl, cyclobutyl, cyclopentyl, cyclohexyl, phenyl, methylphenyl, or ethylphenyl, wherein R 1 R 2 R 3 At most one of them is a cyclic substituent; S2, introducing hydrogen chloride into the first mixture and / or adding hydrochloric acid to make the mass percentage of hydrogen chloride in the mixture solution reach 5%-15%, so that sodium chloride is crystallized and precipitated, and the mixture is filtered, the filter cake is washed with hydrochloric acid to obtain pure sodium chloride solid, and the filtrate is a second mixture comprising a small amount of sodium chloride, aluminum chloride, the phosphorus-containing flame retardant or the intermediate thereof and hydrochloric acid; S3, introducing hydrogen chloride gas into the filtrate after the step S2 and / or adding hydrochloric acid to make the mass percentage of hydrogen chloride in the mixture solution be greater than or equal to 35%, so that aluminum chloride is precipitated in the form of hydrated aluminum chloride, the mixture is filtered, the filter cake is washed with hydrochloric acid, and the hydrated aluminum chloride is obtained after drying, and the filtrate is a third mixture comprising the phosphorus-containing flame retardant or the intermediate thereof, aluminum chloride and sodium chloride and hydrochloric acid; S4, concentrating the third mixture in the step S3 by distillation to obtain concentrated hydrochloric acid and the phosphorus-containing flame retardant or the intermediate thereof mixed with aluminum chloride and sodium chloride; S5, adding sodium hydroxide to the phosphorus-containing flame retardant or the intermediate thereof mixed with aluminum chloride and sodium chloride obtained in the step S4, so that the aluminum chloride in a dissolved state generates sodium chloride and aluminum hydroxide, to obtain a mixture comprising aluminum hydroxide, sodium chloride and the sodium salt of the phosphorus-containing flame retardant or the intermediate thereof, the mixture is filtered, the filtrate is an aqueous solution of the sodium salt of the phosphorus-containing flame retardant or the intermediate thereof and sodium chloride, hydrochloric acid is added to acidify the sodium salt of the phosphorus-containing flame retardant or the intermediate thereof to release the phosphorus-containing flame retardant or the intermediate thereof, and then the mixture is concentrated to be water-free, to obtain the phosphorus-containing flame retardant or the intermediate thereof and sodium chloride, an organic solvent is added and stirred uniformly, the mixture is filtered, the filtrate is concentrated, and then distilled under reduced pressure or recrystallized, to obtain the phosphorus-containing flame retardant or the intermediate thereof, and the filter cake is washed with the organic solvent and dried to obtain sodium chloride.

2. The method for comprehensive recovery of by-products of alkyl dichlorophosphine production according to claim 1, characterized in that, In the step S1, the alkyl dichlorophosphine production by-product is added to the dilute hydrochloric acid in batches, the temperature of the system is kept at 40-100 DEG C during the addition, after the addition of the alkyl dichlorophosphine production by-product is completed, the olefinic acid compound or an aqueous solution in which the olefinic acid compound is dispersed is added, and the mixture is stirred and reacted to obtain the first mixture.

3. The method for comprehensive recovery of by-products of alkyl dichlorophosphine production according to claim 1, characterized in that, In the steps S2 and S3, the hydrochloric acid used for washing has a mass percentage of 30%-37%.

4. The method for comprehensive recovery of by-products of alkyl dichlorophosphine production according to claim 1, characterized in that, In the step S1, the olefinic acid compound is acrylic acid and / or methacrylic acid.

5. The method for comprehensive recovery of by-products of alkyl dichlorophosphine production according to claim 1, characterized in that, Before the step S1 is performed, the content of alkyl dichlorophosphine in the alkyl dichlorophosphine production by-product is obtained, and in the step S1, the alkyl dichlorophosphine and the olefinic acid compound are added according to a molar ratio of 1:1.01-1.

3.

6. The method for comprehensive recovery of by-products of alkyl dichlorophosphine production according to claim 5, characterized in that, In the step S1, the alkyl dichlorophosphine and the olefinic acid compound are added according to a molar ratio of 1:1.01-1.

1.

7. The method for comprehensive recovery of by-products of alkyl dichlorophosphine production according to claim 1, characterized in that, In step S1, the amount of dilute hydrochloric acid used is 1-10 times the amount of by-product of alkyl dichlorophosphine; and / or, the reaction temperature is 45-60 degrees Celsius.

8. The method for comprehensive recovery of by-products of alkyl dichlorophosphine production according to claim 1, characterized in that, In step S1, the mass percentage of dilute hydrochloric acid is 2%-5%; and / or, in step S2, the mass percentage of hydrogen chloride in the mixture solution is 6%-10% after the hydrogen chloride is introduced; and / or, in step S3, the mass percentage of hydrogen chloride in the mixture solution is 35%-45% after the hydrogen chloride is introduced.

9. The method for comprehensive recovery of by-products of alkyl dichlorophosphine production according to claim 1, characterized in that, In step S1, after the sodium chloride is crystallized and precipitated, the system is incubated at 70-90 degrees Celsius for 1-2 hours before filtration.

10. The method for comprehensive recovery of by-products of alkyl dichlorophosphine production according to claim 9, characterized in that, The comprehensive recycling method further comprises one or more of the following steps: S7, using the aluminum chloride hydrate obtained in step S3 in the foundry and sewage treatment industries; S8, further separating the concentrated hydrochloric acid obtained in step S4 into hydrogen chloride gas and dilute hydrochloric acid, which is used in step S1; S9, dissolving the sodium chloride obtained in step S5 in water to obtain a sodium chloride aqueous solution, which is returned to step S1 and mixed with dilute hydrochloric acid to dissolve the complex salt; S10, returning the filter cake, i.e. aluminum hydroxide, obtained by filtering in step S5 to step S2 to generate aluminum chloride; S11, further processing the phosphorus-containing flame retardant intermediate obtained in step S5 into a phosphorus-containing flame retardant.

11. The method for comprehensive recovery of by-products of alkyl dichlorophosphine production according to claim 1, characterized in that, The comprehensive recycling method further comprises: S6, using the sodium chloride solid obtained in step S2 in the production process of methyl dichlorophosphine.

12. A process for the production of an alkyl dichlorophosphine comprising: (1) obtaining alkyl dichlorophosphine and sodium chloride, aluminum chloride complex salt by-products containing alkyl dichlorophosphine, characterized in that the production method further comprises (2): using the comprehensive recycling method according to any one of claims 1-11 to recycle and obtain sodium chloride, aluminum chloride hydrate, phosphorus-containing flame retardant or its intermediate.

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