Preparation method of high-purity bis (2, 4, 4-trimethylpentyl) phosphinic acid

Abstract

The invention provides a preparation method of high-purity bis (2, 4, 4-trimethylpentyl) phosphinic acid, and belongs to the technical field of organic synthesis. The preparation method comprises the steps that a phosphorus source, diisobutylene, an initiator, a solvent and a catalyst are added into a sealed reaction kettle capable of being stirred and heated to be subjected to a reaction, the high-purity bis (2, 4, 4-trimethylpentyl) phosphinic acid is obtained, the phosphorus source is sodium hypophosphite or hypophosphorous acid, and the catalyst is disulfide. According to the preparation method provided by the invention, the disulfide is adopted as the catalyst to be added into the reaction, so that the reaction can be effectively promoted to shorten the reaction time and improve the yield and purity of the product, and meanwhile, the side reaction is few, the post-treatment is simple, and the product impurity content is low.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, and in particular to a method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid. Background Art

[0002] Bis(2,4,4-trimethylpentyl)phosphinic acid, trade name Cyanex272, is a special acidic phosphinic acid extractant for nickel and cobalt separation. It only needs a few extraction stages to achieve good separation effect, and it is easy to strip, with less acidic wastewater discharge. It still has excellent performance after repeated extraction. It is particularly important in the current hot field of wet recovery of waste lithium-ion cathode materials, and is the most important type of extractant in the smelting process of ternary precursor materials.

[0003] Its structure is as follows:

[0004]

[0005] The structure of bis(2,4,4-trimethylpentyl)phosphinic acid contains two CP bonds and has large steric hindrance, which makes it difficult to form. Its synthesis often requires harsh reaction conditions and cumbersome post-processing steps, which limits the development and application of this type of compound. The existing methods for preparing bis(2,4,4-trimethylpentyl)phosphinic acid are mainly divided into the following two categories:

[0006] (1) Grignard reagent method. The Grignard reagent method is to react phosphorus trichloride with ethanol to generate diethyl phosphite, which reacts with the Grignard reagent and hydrolyzes to obtain dialkyl phosphine oxide, which reacts with an oxidant and acidifies to obtain dialkyl phosphinic acid. The product purity of this method is relatively high, but the production process of this method is relatively complicated, the reaction cycle is long, and in particular, the cost is high and the yield is low, making it difficult to achieve industrial production.

[0007] (2) Free radical addition method: The molecules of hypophosphorous acid or its alkali metal salt react with the free radical molecules generated by the initiator to form highly active free radicals of hypophosphorous acid or its alkali metal salt, which then add to the olefin molecule to obtain the target product. The free radical addition method for preparing dialkylphosphinic acid and its salts is relatively simple, has a high yield, and is suitable for large-scale production.

[0008] The free radical addition method can be divided into two types according to the raw materials: the addition of olefins and phosphine or phosphinic acid and its salts. Since phosphine is a colorless, highly toxic and flammable gas, its use and operation have great safety risks. Phosphinic acid and its salts are a bulk chemical raw material, and it is of great significance to prepare dialkylphosphinic acid and its salts using phosphinic acid and its salts as raw materials.

[0009] In the extraction process, the purity of the extractant has a very important influence on its extraction effect. Excessive impurities in the extractant will lead to emulsification during the extraction process, causing difficulty in phase separation, disturbing the interface control of the extraction equipment, and a series of other problems, and its extraction efficiency will also be greatly reduced. On the contrary, the higher the purity of the extractant and the fewer impurities it contains, the better the extraction effect.

[0010] In order to synthesize high-purity di(2,4,4-trimethylpentyl)phosphinic acid, many researchers have conducted research on the free radical addition method. RORBERTSON AJ (US4374780A, 1983) disclosed that azobisisobutyronitrile was used as an initiator, 2,4,4-trimethylpentene and phosphine gas were reacted in a sealed high-pressure reactor at 3MPa and 60-90°C, and the product was purified by distillation to obtain di(2,4,4-trimethylpentyl)phosphinic acid. The obtained di(2,4,4-trimethylpentyl)phosphinic acid was subjected to oxidation reaction with hydrogen peroxide under acidic conditions at 60°C, and a product with a purity of 88% was obtained after post-treatment. Wo Shiming et al. (US7049463B2, 2006) put diisobutylene with sodium hypophosphite, acetic acid and di-tert-butyl peroxide (initiator) in a molar ratio of 2.5:1 into a high-pressure reactor at a temperature of 135°C for four 8-hour periods, added the initiator three times, and cooled after the reaction to obtain the target product. The target product content in the initial product is about 75.3%, and the product purity reaches 93.7% after alkali washing and acidification. Li Linyan et al. (CN101475588B, 2012) used a composite initiator composed of two initiators and put it into the sodium hypophosphite system, so that the reaction yield was increased to 91.5%. Xiao Jichang et al. (CN112661789A, 2021) introduced a thiol compound as a catalyst to increase the reaction rate and purity.

[0011] In addition to the purity problem of the synthetic product, the interface problem caused by the solution being divided into two phases during the product synthesis process is also one of the problems to be solved. When an organic acid or an inorganic acid is used as a solvent, the raw material diisobutylene has a low solubility in the solvent, and the reaction solution is always divided into two phases, so the reaction is mainly generated at the interface, and the phase separation is not conducive to the transfer of free radicals in the organic phase and the aqueous phase, resulting in the reaction being difficult to carry out. In order to solve the problems such as the long reaction time caused by the two-phase reaction, Wang Xiaoji (CN102020673B, 2011) accelerates the reaction process by using an initiator combination of azodiisobutylamidine hydrochloride and hydrogen peroxide, and the conditions of vigorous stirring and heating reflux of the reaction solution at normal pressure, and reacts for 5 hours to obtain the product. Chu Zhaoning et al. (CN112194676A, 2021) improve the free radical transfer rate by introducing phase transfer catalysts such as trimethylbenzyl ammonium chloride and tetrabutylammonium hydrogen sulfate in the system, promote the progress of free radical addition reaction, and react for 8 hours to obtain the product. Liu Yibiao et al. (CN117510538A, 2024) added inorganic sulfide as a catalyst to the system to promote the reaction, and heated and stirred the reaction for 9 hours to obtain the product.

[0012] From the above-mentioned patent works, in order to improve product purity and shorten reaction time, inventors have continuously optimized and improved the reaction system based on the free radical addition method, or made improvements on the initiator, or shortened the reaction process by adding catalysts to modify process conditions. However, different patents still have their own disadvantages, such as the complicated process flow caused by adding initiators in batches; the addition of composite initiators in the system is risky, the process is difficult to control and increases production costs; some types of catalysts are mixed into the system and are difficult to remove, resulting in cumbersome post-processing; at the same time, some catalysts themselves have a bad smell, which not only affects the production environment, but also creates great pressure on tail gas treatment in the production process; some catalysts need to be added in several steps, which improves purity but makes the process more complicated. In addition, most of the synthesis processes still require post-treatment methods such as alkaline washing and acidification to remove the monoalkyl hypophosphorous acid produced by the reaction to further improve purity.

[0013] Therefore, how to provide a preparation method of di(2,4,4-trimethylpentyl)phosphinic acid with simple and safe process flow, mild reaction conditions, simple post-treatment and high yield and high purity has become an urgent problem to be solved. Summary of the invention

[0014] The present invention is made to solve the above problems, and aims to provide a method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid. The preparation method provided by the present invention has simple steps, few side reactions, simple post-treatment, high product yield, high purity, and low impurity content.

[0015] The invention provides a method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid, which has the following characteristics: adding a phosphorus source, diisobutylene, an initiator, a solvent and a catalyst into a closed reaction kettle equipped with a stirrable and heatable reactor for reaction to obtain high-purity bis(2,4,4-trimethylpentyl)phosphinic acid, wherein the phosphorus source is sodium hypophosphite or hypophosphorous acid, and the catalyst is disulfide.

[0016] The method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid provided by the present invention may also have the following characteristics: wherein the molar ratio of the phosphorus source to diisobutylene is 1:2 to 1:5.

[0017] The method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid provided by the present invention may also have the following characteristics: wherein the initiator is any one or more of di-tert-butyl peroxide, tert-butyl hydroperoxide and dibenzoyl peroxide, and the molar ratio of the phosphorus source to the initiator is 1:0.05 to 1:0.2.

[0018] The method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid provided by the present invention may also have the following characteristics: when the phosphorus source is sodium hypophosphite, the solvent is one or more of sulfuric acid, hydrochloric acid, and acetic acid; when the phosphorus source is hypophosphorous acid, the solvent is any one or more of petroleum ether, ethanol, N,N-dimethylformamide, and N,N-dimethylacetamide, and the molar ratio of the phosphorus source to the solvent is 1:1 to 1:5.

[0019] In the preparation method of high-purity bis(2,4,4-trimethylpentyl)phosphinic acid provided by the present invention, the method may also have the following characteristics: wherein the catalyst is any one or more of dipentyl disulfide, methyl propyl disulfide, 3,3'-dithiobis(propane-1-ol), 4,4'-dithiodibutyric acid, 3,3-dithiodipropionic acid dimethyl ester, difurfuryl disulfide, sodium polydisulfide propane sulfonate, 1,2-dicyclohexyl disulfide, diphenyl disulfide, p-toluene disulfide, 4,4'-dithiodibenzoic acid, 2,2-difluorodiphenyl disulfide, and 2-thienyl disulfide, and the molar ratio of the phosphorus source to the catalyst is 1:0.001 to 1:0.01.

[0020] In the preparation method of high-purity bis(2,4,4-trimethylpentyl)phosphinic acid provided by the present invention, the method may also have the following characteristics: wherein the molar ratio of the phosphorus source to diisobutylene is 1:2, 1:2.5 or 1:5, the molar ratio of the phosphorus source to the solvent is 1:1, 1:1.5, 1:2, 1:2.5 or 1:5, the molar ratio of the phosphorus source to the initiator is 1:0.08, 1:0.09, 1:0.1, 1:0.11, 1:0.12 or 1:0.2, and the molar ratio of the phosphorus source to the catalyst is 1:0.002, 1:0.004 or 1:0.01.

[0021] The method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid provided by the present invention may also have the following characteristics: wherein the phosphorus source, diisobutylene, initiator, solvent and catalyst are all added at one time.

[0022] The method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid provided by the present invention may also have the following characteristics: wherein the reaction temperature is 20° C. to 200° C., and the reaction time is 2 h to 24 h.

[0023] In the preparation method of high-purity bis(2,4,4-trimethylpentyl)phosphinic acid provided by the present invention, it can also have the following characteristics: wherein the reaction temperature is 100°C, 105°C, 110°C, 115°C, 125°C, 130°C, 135°C or 140°C, and the reaction time is 5h, 6h, 10h, 8h or 12h.

[0024] The method for preparing high-purity di(2,4,4-trimethylpentyl)phosphinic acid provided by the present invention may also have the following characteristics: wherein, after the reaction is completed, post-treatment is required to obtain high-purity di(2,4,4-trimethylpentyl)phosphinic acid, and the post-treatment includes water washing and reduced pressure distillation.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The invention provides a method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid. By adding disulfide as a catalyst to the reaction, the reaction can be effectively promoted to shorten the reaction time and improve the yield and purity of the product. Meanwhile, the side reaction is small, the post-treatment is simple, and the impurity content of the product is small. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The high-purity bis(2,4,4-trimethylpentyl)phosphinic acid in Example 1 of the present invention is 31 P-NMR result diagram.

[0028] Figure 2 This is the 31P-NMR result diagram of the product after water washing and reduced pressure distillation in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0029] In order to make the technical means, creative features, objectives and effects of the present invention easy to understand, the following examples are combined with the accompanying drawings to specifically illustrate the high-purity bis(2,4,4-trimethylpentyl)phosphinic acid of the present invention.

[0030] Example 1

[0031] This embodiment provides a method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid, and the specific steps are as follows:

[0032] 8.1g NaH2PO2·H2O, 10.7g acetic acid, 22.0g diisobutylene (containing 75% α-diisobutylene and 25% β-diisobutylene), 1g di-tert-butyl peroxide, and 0.06g diamyl disulfide were placed in a 150ml pressure-resistant glass bottle, and the container was sealed and heated. The reaction was carried out at 135°C for 12 hours, and magnetic stirring was maintained during the reaction. After the reaction was completed, the mixture was naturally cooled to room temperature, washed with water, and the excess diisobutylene was removed by vacuum distillation to obtain 21.1g of colorless liquid. The P spectrum showed that there was no monosubstituted product, and the yield was 97%.

[0033] Figure 1 The high-purity bis(2,4,4-trimethylpentyl)phosphinic acid in Example 1 of the present invention is 31 P-NMR result diagram.

[0034] like Figure 1 As shown, the high-purity bis(2,4,4-trimethylpentyl)phosphinic acid prepared in this embodiment 31 The P-NMR results are:

[0035] 1 H NMR(400MHz,Chloroform-d)δ10.20(s,1H),2.12–2.00(m,2H),1.72(ddt,J=14.9,12.9,4.3Hz,2H),1.53(m ,2H),1.33(dd,J=14.1,4.7,Hz,2H),1.17(dd,J=14.0,6.0Hz,2H),1.11(m,J=6.7,1.3Hz,6H),0.91(s,18H).

[0036] 31 P NMR(162MHz,Chloroform-d)δ59.2

[0037] ESI-MS m / z:291.1[M+H] +

[0038] Example 2

[0039] This embodiment provides a method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid, and the specific steps are as follows:

[0040] 8.1g NaH2PO2·H2O, 10.7g acetic acid, 22.0g diisobutylene (containing 75% α-diisobutylene and 25% β-diisobutylene), 1g di-tert-butyl peroxide, and 0.04g methyl propyl disulfide were placed in a 150ml pressure-resistant glass bottle, and the container was sealed and heated. The reaction was carried out at 125°C for 9 hours, and magnetic stirring was maintained during the reaction. After the reaction was completed, the mixture was naturally cooled to room temperature, washed with water, and the excess diisobutylene was removed by vacuum distillation to obtain 20.7g of colorless liquid. The P spectrum showed that there was no monosubstituted product, and the yield was 95%.

[0041] Example 3

[0042] This embodiment provides a method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid, and the specific steps are as follows:

[0043] 18.9g of NaH2PO2·H2O, 10.7g of acetic acid, 56.4g of diisobutylene (containing 75% α-diisobutylene and 25% β-diisobutylene), 2.1g of di-tert-butyl peroxide, and 0.27g of sodium polydisulfide propane sulfonate were placed in a 350ml pressure-resistant glass bottle, and the container was sealed and heated. The reaction was carried out at 135°C for 12 hours, and magnetic stirring was maintained during the reaction. After the reaction was completed, the mixture was naturally cooled to room temperature, washed with water, and the excess diisobutylene was removed by vacuum distillation to obtain 50.7g of colorless liquid. The P spectrum showed that there was no monosubstituted product, and the yield was 99%.

[0044] Example 4

[0045] This embodiment provides a method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid, and the specific steps are as follows:

[0046] 8.1g NaH2PO2·H2O, 4.5g acetic acid, 22.0g diisobutylene (containing 75% α-diisobutylene and 25% β-diisobutylene), 1g di-tert-butyl peroxide, and 0.07g 1,2-dicyclohexyl disulfane were placed in a 150ml pressure-resistant glass bottle, and the container was sealed and heated. The reaction was carried out at 135°C for 12 hours, and magnetic stirring was maintained during the reaction. After the reaction was completed, the mixture was naturally cooled to room temperature, washed with water, and the excess diisobutylene was removed by vacuum distillation to obtain 20.7g of colorless liquid. The P spectrum showed that there was no monosubstituted product, and the yield was 95%.

[0047] Example 5

[0048] This embodiment provides a method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid, and the specific steps are as follows:

[0049] 8.1g of NaH2PO2·H2O, 4.5g of acetic acid, 22.0g of diisobutylene (containing 75% α-diisobutylene and 25% β-diisobutylene), 1g of di-tert-butyl peroxide, and 0.06g of diphenyl disulfide were placed in a 150ml pressure-resistant glass bottle, and the container was sealed and heated. The reaction was carried out at 135°C for 12 hours, and magnetic stirring was maintained during the reaction. After the reaction was completed, the mixture was naturally cooled to room temperature, washed with water, and the excess diisobutylene was removed by vacuum distillation to obtain 20.7g of colorless liquid. The P spectrum showed that there was no monosubstituted product, and the yield was 95%.

[0050] Example 6

[0051] This embodiment provides a method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid, and the specific steps are as follows:

[0052] 8.1g NaH2PO2·H2O, 4.5g acetic acid, 22.0g diisobutylene (containing 75% α-diisobutylene and 25% β-diisobutylene), 1g di-tert-butyl hydroperoxide, and 0.07g p-toluene disulfide were placed in a 150ml pressure-resistant glass bottle, and the container was sealed and heated. The reaction was carried out at 135°C for 12 hours, and magnetic stirring was maintained during the reaction. After the reaction was completed, the mixture was naturally cooled to room temperature, washed with water, and the excess diisobutylene was removed by vacuum distillation to obtain 21g of colorless liquid. The P spectrum showed that there was no monosubstituted product, and the yield was 97%.

[0053] Example 7

[0054] This embodiment provides a method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid, and the specific steps are as follows:

[0055] 8.1g NaH2PO2·H2O, 4.5g acetic acid, 22.0g diisobutylene (containing 75% α-diisobutylene and 25% β-diisobutylene), 1.2g benzoyl peroxide, and 0.09g 4,4'-dithiodibenzoic acid were placed in a 150ml pressure-resistant glass bottle, and the container was sealed and heated. The reaction was carried out at 135°C for 12 hours, and magnetic stirring was maintained during the reaction. After the reaction was completed, the mixture was naturally cooled to room temperature, washed with water, and the excess diisobutylene was removed by vacuum distillation to obtain 21.1g of colorless liquid. The P spectrum showed that there was no monosubstituted product, and the yield was 97%.

[0056] Example 8

[0057] This embodiment provides a method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid, and the specific steps are as follows:

[0058] 8.1g NaH2PO2·H2O, 4.5g acetic acid, 22.0g diisobutylene (containing 75% α-diisobutylene and 25% β-diisobutylene), 1g di-tert-butyl peroxide, and 0.08g 2,2-difluorodiphenyl disulfide were placed in a 150ml pressure-resistant glass bottle, and the container was sealed and heated. The reaction was carried out at 135°C for 12 hours, and magnetic stirring was maintained during the reaction. After the reaction was completed, the mixture was naturally cooled to room temperature, washed with water, and the excess diisobutylene was removed by vacuum distillation to obtain 20.9g of colorless liquid. The P spectrum showed that there was no monosubstituted product, and the yield was 96%.

[0059] Example 9

[0060] This embodiment provides a method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid, and the specific steps are as follows:

[0061] 8.1g of NaH2PO2·H2O, 4.5g of acetic acid, 22.0g of diisobutylene (containing 75% α-diisobutylene and 25% β-diisobutylene), 1g of di-tert-butyl peroxide, and 0.07g of 2-thienyl disulfide were placed in a 150ml pressure-resistant glass bottle, and the container was sealed and heated. The reaction was carried out at 135°C for 12 hours, and magnetic stirring was maintained during the reaction. After the reaction was completed, the mixture was naturally cooled to room temperature, washed with water, and the excess diisobutylene was removed by vacuum distillation to obtain 21.2g of colorless liquid. The P spectrum showed that there was no monosubstituted product, and the yield was 97%.

[0062] Example 10

[0063] This embodiment provides a method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid, and the specific steps are as follows:

[0064] 9.9g H3PO2 (50wt%), 22g diisobutylene (containing 75% α-diisobutylene and 25% β-diisobutylene), 1g di-tert-butyl peroxide, 0.05g 3,3'-dithiobis(propane-1-ol), and 45mL N,N-dimethylformamide as solvent were put into a 350ml pressure-resistant glass bottle, and the container was sealed and heated. The reaction was carried out at 100°C for 8 hours, and magnetic stirring was maintained during the reaction. After the reaction was completed, it was naturally cooled to room temperature, washed with water, and the excess diisobutylene was removed by vacuum distillation to obtain 20.9g of colorless liquid. The P spectrum showed that there was no monosubstituted product, and the yield was 96%.

[0065] Embodiment 11

[0066] This embodiment provides a method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid, and the specific steps are as follows:

[0067] 9.9g H3PO2 (50wt%), 22.0g diisobutylene (containing 75% α-diisobutylene and 25% β-diisobutylene), 1g di-tert-butyl peroxide, 0.07g 4,4'-dithiodibutyric acid, and 45mL petroleum ether as solvent were put into a 350ml pressure-resistant glass bottle, and the container was sealed and heated. The reaction was carried out at 135°C for 12 hours, and magnetic stirring was maintained during the reaction. After the reaction was completed, it was naturally cooled to room temperature, washed with water, and the excess diisobutylene was removed by vacuum distillation to obtain 20.8g of colorless liquid. The P spectrum showed that there was no monosubstituted product, and the yield was 96%.

[0068] Example 12

[0069] This embodiment provides a method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid, and the specific steps are as follows:

[0070] 9.9g H3PO2 (50wt%), 22.0g diisobutylene (containing 75% α-diisobutylene and 25% β-diisobutylene), 1g di-tert-butyl peroxide, 0.07g dimethyl 3,3-dithiodipropionate, and 45mL ethanol as solvent were placed in a 350ml pressure-resistant glass bottle, and the container was sealed and heated. The reaction was carried out at 135°C for 8 hours, and magnetic stirring was maintained during the reaction. After the reaction was completed, the mixture was naturally cooled to room temperature, washed with water, and the excess diisobutylene was removed by vacuum distillation to obtain 21.2g of colorless liquid. The P spectrum showed that there was no monosubstituted product, and the yield was 98%.

[0071] Embodiment 13

[0072] This embodiment provides a method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid, and the specific steps are as follows:

[0073] 9.9g H3PO2 (50wt%), 22.0g diisobutylene (containing 75% α-diisobutylene and 25% β-diisobutylene), 1g di-tert-butyl peroxide, 0.07g difurfuryl disulfide, 45mL N,N-dimethylacetamide as solvent were put into a 350ml pressure-resistant glass bottle, and the container was sealed and heated. The reaction was carried out at 135°C for 12 hours, and magnetic stirring was maintained during the reaction. After the reaction was completed, it was naturally cooled to room temperature, washed with water, and the excess diisobutylene was removed by vacuum distillation to obtain 20.6g of colorless liquid. The P spectrum showed that there was no monosubstituted product, and the yield was 95%.

[0074] Comparative Example 1:

[0075] This comparative example provides a comparative preparation method for synthesizing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid according to the above embodiment, and the specific steps are as follows:

[0076] 8.1g of NaH2PO2·H2O, 4.5g of acetic acid, 22g of diisobutylene (containing 75% α-diisobutylene and 25% β-diisobutylene), and 1g of di-tert-butyl peroxide were placed in a 150ml pressure-resistant glass bottle, and the container was sealed and heated. The reaction was carried out at 135°C for 12 hours, and magnetic stirring was maintained during the reaction. After the reaction was completed, the mixture was naturally cooled to room temperature, washed with water, and the excess diisobutylene was removed by vacuum distillation to obtain 12.4g of colorless liquid. The P spectrum showed that the content of monosubstituted product was 14.1%, the purity of the product was 85.9% (based on the peak value), and the yield was 57%.

[0077] Figure 2 The product after washing and vacuum distillation in Comparative Example 1 of the present invention is 31 P-NMR result diagram.

[0078] Comparative Example 2:

[0079] This comparative example provides a comparative preparation method for synthesizing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid according to the above embodiment, and the specific steps are as follows:

[0080] 9.9g H3PO2 (50wt%), 22g diisobutylene (containing 75% α-diisobutylene and 25% β-diisobutylene), 1g di-tert-butyl peroxide, and 45mL N,N-dimethylformamide as solvent were placed in a 350ml pressure-resistant glass bottle, and the container was sealed and heated. The reaction was carried out at 135°C for 12 hours, and magnetic stirring was maintained during the reaction. After the reaction was completed, the mixture was naturally cooled to room temperature, washed with water, and the excess diisobutylene was removed by vacuum distillation to obtain 10.6g of colorless liquid. The P spectrum showed that the content of the monosubstituted product was 13.9%, the product purity was 86.1% (based on the peak value), and the yield was 49%.

[0081] From the above test data, it can be found that the preparation method of high-purity bis(2,4,4-trimethylpentyl)phosphinic acid provided by the present invention can effectively improve the yield and purity of the product, and at the same time, the reaction time is short, the side reaction is less, the post-treatment is simple, and the product impurity content is low.

[0082] Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid, characterized in that: include: A phosphorus source, diisobutylene, an initiator, a solvent and a catalyst are added into a sealed reaction kettle equipped with a stirrable and heatable reactor for reaction to obtain the high-purity bis(2,4,4-trimethylpentyl)phosphinic acid. Wherein, the phosphorus source is sodium hypophosphite or hypophosphorous acid, and the catalyst is disulfide.

2. The method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid according to claim 1, characterized in that: in, The molar ratio of the phosphorus source to diisobutylene is 1:2 to 1:

5.

3. The method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid according to claim 2, characterized in that: in, The initiator is any one or more of di-tert-butyl peroxide, tert-butyl hydroperoxide and dibenzoyl peroxide. The molar ratio of the phosphorus source to the initiator is 1:0.05 to 1:0.

2.

4. The method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid according to claim 3, characterized in that: in, When the phosphorus source is sodium hypophosphite, the solvent is one or more of sulfuric acid, hydrochloric acid, and acetic acid; when the phosphorus source is hypophosphorous acid, the solvent is any one or more of petroleum ether, ethanol, N,N-dimethylformamide, and N,N-dimethylacetamide. The molar ratio of the phosphorus source to the solvent is 1:1 to 1:

5.

5. The method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid according to any one of claims 1 to 4, characterized in that: in, The catalyst is any one or more of diamyl disulfide, methyl propyl disulfide, 3,3'-dithiobis(propane-1-ol), 4,4'-dithiodibutyric acid, 3,3-dithiodipropionic acid dimethyl ester, difurfuryl disulfide, sodium polydisulfide propane sulfonate, 1,2-dicyclohexyl disulfide, diphenyl disulfide, p-toluene disulfide, 4,4'-dithiodibenzoic acid, 2,2-difluorodiphenyl disulfide, and 2-thienyl disulfide. The molar ratio of the phosphorus source to the catalyst is 1:0.001 to 1:0.

01.

6. The method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid according to claim 5, characterized in that: in, The molar ratio of the phosphorus source to the diisobutylene is 1:2, 1:2.5 or 1:5, the molar ratio of the phosphorus source to the solvent is 1:1, 1:1.5, 1:2, 1:2.5 or 1:5, the molar ratio of the phosphorus source to the initiator is 1:0.08, 1:0.09, 1:0.1, 1:0.11, 1:0.12 or 1:0.2, and the molar ratio of the phosphorus source to the catalyst is 1:0.002, 1:0.004 or 1:0.

01.

7. The method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid according to claim 1, characterized in that: in, The phosphorus source, the diisobutylene, the initiator, the solvent and the catalyst are all added at once.

8. The method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid according to claim 1, characterized in that: in, The reaction temperature is 20°C to 200°C, and the reaction time is 2h to 24h.

9. The method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid according to claim 8, characterized in that: in, The reaction temperature is 100°C, 105°C, 110°C, 115°C, 125°C, 130°C, 135°C or 140°C, and the reaction time is 5h, 6h, 10h, 8h or 12h.

10. The method for preparing high-purity bis(2,4,4-trimethylpentyl)phosphinic acid according to claim 1, characterized in that: in, After the reaction is completed, post-treatment is required to obtain the high-purity bis(2,4,4-trimethylpentyl)phosphinic acid, and the post-treatment includes water washing and reduced pressure distillation.

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