Oxidation synthesis process of di (2-ethylhexyl) phosphate

Abstract

The invention belongs to the technical field of organic synthesis, and particularly relates to an oxidation synthesis process of di (2-ethylhexyl) phosphate ester, which comprises the following steps: by taking di (2-ethylhexyl) phosphite ester as a raw material and dimethyl sulfoxide as an oxidant, carrying out oxidation reaction in a reaction solvent under the catalysis of a catalyst to prepare the di (2-ethylhexyl) phosphate ester, the catalyst is periodic acid or iodine simple substance. According to the method, hydrolysis of phosphate can be avoided, so that the content of the impurity mono (2-ethylhexyl) phosphate is controlled, the quality of the di (2-ethylhexyl) phosphate product is improved, the yield of the di (2-ethylhexyl) phosphate can reach 90.5%, and the content of the mono (2-ethylhexyl) phosphate is less than 0.1%; the method has the advantages of simple process, easily available raw materials, mild reaction conditions and simple post-treatment, and is suitable for industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and specifically relates to an oxidation synthesis process of di(2-ethylhexyl) phosphate. Background Art

[0002] Dialkyl phosphates are a class of compounds with special applications. Among them, di(2-ethylhexyl) phosphate (codenamed P204), also known as bis(2-ethylhexyl) phosphate, diisooctyl phosphate, and dioctyl phosphate, is an extractant mainly used for rare earths, non-ferrous metals (cobalt, nickel, gold, copper, indium, etc.), and electrolytic metals. It is widely used in nuclear fuel (uranium) extraction, rare earth element separation, and non-ferrous metal extraction.

[0003] At present, Chinese invention CN105440072A discloses a method for preparing di(2-ethylhexyl) phosphate, which uses phosphorus oxychloride and 2-ethylhexanol as raw materials to prepare di(2-ethylhexyl) phosphate, but the preparation of the catalyst used in the preparation method is relatively complicated, and the synthesized di(2-ethylhexyl) phosphate contains more mono(2-ethylhexyl) phosphate impurities, which affects its extraction performance. Another Chinese invention CN102911203A discloses a method for preparing alkyl phosphate, which uses 2-ethylhexanol as a raw material, adds a phosphorylation reagent in batches to carry out a phosphorylation reaction, and finally adds deionized water to carry out a hydrolysis reaction to obtain a target product; but the effective content of di(2-ethylhexyl) phosphate obtained by the preparation method is difficult to reach more than 90%, and the yield is not ideal. In addition, the "Organophosphorus Extractant P" published by Cao Ruzhen's team at Nankai University 204 The following method is disclosed in the article "Synthesis Research": 2-ethylhexanol is used as a raw material, reacted with phosphorus trichloride to prepare di(2-ethylhexyl) phosphite, and then chlorinated with chlorine and hydrolyzed to obtain di(2-ethylhexyl) phosphate. However, the above method has a long synthesis process, and the last step of hydrolysis will also produce mono(2-ethylhexyl) phosphate, which affects the product quality.

[0004] Therefore, the content of the synthetic di(2-ethylhexyl) phosphate product in the prior art is not high, and the mono(2-ethylhexyl) phosphate accounts for a large proportion, which restricts the application and development of the product. It is necessary to design a better di(2-ethylhexyl) phosphate synthesis route. Summary of the invention

[0005] The present invention aims to provide an oxidation synthesis process of di(2-ethylhexyl) phosphate to solve the problem of high content of mono(2-ethylhexyl) phosphate in the di(2-ethylhexyl) phosphate product synthesized in the prior art.

[0006] In order to achieve the above-mentioned purpose, the scheme of the present invention is: an oxidation synthesis process of di(2-ethylhexyl) phosphate, comprising the following steps: using di(2-ethylhexyl) phosphite as a raw material and dimethyl sulfoxide as an oxidant, an oxidation reaction occurs under the catalysis of a catalyst to obtain di(2-ethylhexyl) phosphate, wherein the catalyst is periodic acid or elemental iodine.

[0007] Optionally, the following steps are included:

[0008] S1, reaction stage: di(2-ethylhexyl)phosphite, dimethyl sulfoxide, a catalyst and a reaction solvent are mixed, the reaction temperature is 25-30°C, the reaction time is 2.5-24h, and a crude reaction solution is obtained;

[0009] S2, post-treatment stage: the crude reaction solution is added dropwise to the quenching aqueous solution, the water temperature is maintained at 10-30°C and stirred for 0.5-2h during the dropping process, the layers are allowed to stand, the organic phase is taken, and di(2-ethylhexyl) phosphate is obtained through drying and concentration; wherein the quenching aqueous solution is a sodium thiosulfate aqueous solution or a sodium bisulfite aqueous solution.

[0010] Optionally, in step S1, the molar ratio of di(2-ethylhexyl)phosphite, catalyst and dimethyl sulfoxide is 1:(0.1-0.001):1.2.

[0011] Optionally, in step S1, the reaction solvent is one of toluene, dichloromethane, tetrahydrofuran and petroleum ether.

[0012] Optionally, in step S2, the mass ratio of the reaction solvent to di(2-ethylhexyl)phosphite is 10 to 0.5:1.

[0013] Optionally, in step S2, the quenching aqueous solution is a 10 wt % sodium thiosulfate aqueous solution or a 10 wt % sodium bisulfite aqueous solution.

[0014] The working principle and beneficial effect of this scheme are: no water is added in the reaction stage of this scheme, and no water is generated, thereby avoiding the hydrolysis of phosphate, and then controlling the content of the impurity mono(2-ethylhexyl) phosphate, and improving the quality of the di(2-ethylhexyl) phosphate product; and, in the post-processing stage of this scheme, the quenching environment is a neutral environment, room temperature conditions, under which no hydrolysis of di(2-ethylhexyl) phosphate will occur. Therefore, in this scheme, the yield of di(2-ethylhexyl) phosphate can reach 90.5%, and the content of mono(2-ethylhexyl) phosphate is less than 0.1%. Secondly, the reaction selectivity in this scheme is high, no special impurities are generated, and the crude reaction solution can obtain qualified products after simple quenching, drying, and concentration, that is, this scheme has a simple process, easy-to-obtain raw materials, reaction conditions and temperature, and simple post-processing, which is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the reaction equation of the oxidation synthesis process of di(2-ethylhexyl) phosphate in an embodiment of the present invention;

[0016] Figure 2 is the hydrogen nuclear magnetic resonance spectrum of di(2-ethylhexyl) phosphate prepared in Example 2 of the present invention;

[0017] Figure 3 is the nuclear magnetic resonance phosphorus spectrum of di(2-ethylhexyl) phosphate prepared in Example 2 of the present invention;

[0018] Figure 4 The nuclear magnetic resonance phosphorus spectrum of di(2-ethylhexyl) phosphate prepared in the comparative example of the present invention is shown. DETAILED DESCRIPTION

[0019] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0020] The present invention provides an oxidation synthesis process of di(2-ethylhexyl) phosphate, wherein di(2-ethylhexyl) phosphite is used as a raw material and dimethyl sulfoxide is used as an oxidant, and an oxidation reaction is carried out under the catalysis of a catalyst to obtain di(2-ethylhexyl) phosphate, wherein the catalyst is periodic acid or iodine. The oxidation synthesis process of di(2-ethylhexyl) phosphate specifically comprises the following steps:

[0021] S1, reaction stage: di(2-ethylhexyl)phosphite, dimethyl sulfoxide, catalyst and reaction solvent are mixed, the reaction temperature is 0-50°C, the reaction time is 6-24h, and the reaction is returned to room temperature after the reaction is completed to obtain a crude reaction solution. In this step, the molar ratio of di(2-ethylhexyl)phosphite, catalyst and dimethyl sulfoxide is 1:(0.1-0.001):1.2, the mass ratio of reaction solvent to di(2-ethylhexyl)phosphite is 10-0.5:1, and the reaction solvent is one of toluene, dichloromethane, tetrahydrofuran and petroleum ether.

[0022] S2, post-treatment stage: adding the crude reaction solution dropwise to the quenching aqueous solution, maintaining the water temperature at 10-30°C and stirring for 0.5-2h during the dropping process, standing to separate the layers, taking the organic phase, drying and concentrating to obtain di(2-ethylhexyl) phosphate; wherein the quenching aqueous solution is a sodium thiosulfate aqueous solution or a sodium bisulfite aqueous solution, and the concentration of the sodium thiosulfate aqueous solution or the sodium bisulfite aqueous solution is preferably 10wt%.

[0023] Among them, di(2-ethylhexyl)phosphite can be prepared by reacting phosphorus trichloride with isooctyl alcohol (reference: "Synthesis of di(2-ethylhexyl)phosphoric acid thioate", Chemical Reagents, 1993, 15(1), P41, Liu Xingzhi, Ge Yongcheng, Song Yulin), and the obtained di(2-ethylhexyl)phosphite has a purity of ≥97%; in addition, the catalyst, dimethyl sulfoxide, reaction solvent and solute of the quenching aqueous solution are all reagent grade.

[0024] The following specific examples are given to illustrate the present invention in detail. It should also be understood that the following examples are only used to specifically illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are also only examples within a suitable range, that is, those skilled in the art can make a selection within a suitable range according to the description herein, and are not limited to the specific values ​​​​exemplified below.

[0025] In addition, the titration method involved in the present invention is as follows:

[0026] Prepare 0.1 mol / L sodium hydroxide standard solution (calibrated according to GBT601); 75% ethanol aqueous solution; 10 g / L phenolphthalein indicator (solvent is ethanol); 5 g / L methyl red indicator (solvent is ethanol).

[0027] Accurately weigh 0.23-0.25g (accurate to 0.0001g) of di(2-ethylhexyl) phosphate sample in a 100mL beaker, add 50mL 75% ethanol aqueous solution, 2 drops (about 0.1mL) 5g / L methyl red indicator and 2 drops (about 0.1mL) 10g / L phenolphthalein indicator, then add a magnetic stirrer, then place the beaker on a magnetic stirrer, insert the electrode into the beaker liquid, turn on stirring, and after the pH displayed on the pH meter stabilizes, titrate with 0.1mol / L sodium hydroxide standard solution. Until the first jump point appears (the solution changes from red to yellow), record the volume of 0.1mol / L sodium hydroxide standard solution consumed at this time as V1. Continue to titrate with 0.1mol / L sodium hydroxide standard solution, and record the volume of 0.1mol / L sodium hydroxide standard solution consumed at the second jump point (the solution changes from yellow to red) as V2.

[0028] Result calculation formula: Di(2-ethylhexyl) phosphate content = [(2V1-V2)*C*0.3224 / m]*100%

[0029] Mono(2-ethylhexyl)phosphate content = [(V1-V2)*C*0.2102 / m]*100%

[0030] Where:

[0031] C-concentration of sodium hydroxide standard solution, mol / L;

[0032] V1-the volume of sodium hydroxide standard solution consumed when titrating to the first jump point, mL;

[0033] V2-the volume of sodium hydroxide standard solution consumed when titrating to the second jump point, mL;

[0034] m-di(2-ethylhexyl) phosphate sample mass, g;

[0035] 0.3224-Di(2-ethylhexyl)phosphate molar mass, g / mmol;

[0036] 0.210 2-Mono(2-ethylhexyl)phosphate molar mass, g / mmol.

[0037] Example 1

[0038] This embodiment provides an oxidation synthesis process of di(2-ethylhexyl) phosphate, and its reaction equation is as follows: Figure 1 As shown, the specific steps include:

[0039] (1) Reaction stage: 30.6 g of di(2-ethylhexyl)phosphite, 9.4 g of dimethyl sulfoxide and 306.6 g of toluene were added to a three-necked flask, and 0.57 g of periodic acid was added under stirring. After the addition was completed, the temperature of the liquid in the three-necked flask was maintained at room temperature (the room temperature in the laboratory was 25-30° C.). After about 2.5 hours, it was determined by TLC that the reaction had reached the end point, and a crude reaction solution was obtained.

[0040] (2) Post-treatment stage: Add 10 wt% sodium bisulfite aqueous solution to another reaction bottle and start stirring, and drop the crude reaction solution obtained in step (1) into 10 wt% sodium bisulfite aqueous solution for quenching, and maintain the water temperature at 10-30°C and stir for 0.5-1h during the dropping process. After the stirring is completed, stand and separate, take the organic phase, dry and filter it with anhydrous sodium sulfate, first control the vacuum pressure value within 2.5-3.5 KPa, and the concentration temperature within 80-90°C, distill the excess solvent from the organic phase, and continue to reduce the vacuum to 500-800 Pa after almost no distillation, and control the temperature at 90-100°C to completely desolventize and concentrate. When the mass of the organic phase is constant, it can be considered that the concentration is complete, thereby obtaining 27.7 g of di(2-ethylhexyl) phosphate, with a yield of 86%, a titration content of 96.5% (the titration method is as described above), and a mono(2-ethylhexyl) phosphate content of <0.3%.

[0041] Example 2

[0042] This embodiment provides an oxidation synthesis process of di(2-ethylhexyl) phosphate, which specifically comprises the following steps:

[0043] (1) Reaction stage: 183.6 g of di(2-ethylhexyl)phosphite, 56.2 g of dimethyl sulfoxide and 1836.2 g of petroleum ether were added to a three-necked flask, and 154.1 mg of iodine was added under stirring. After the addition was completed, the temperature of the liquid in the three-necked flask was maintained at room temperature for reaction. After about 6 hours, TLC was used to determine that the reaction had reached the end point, and a crude reaction solution was obtained. In this step, the molar ratio of di(2-ethylhexyl)phosphite, iodine and dimethyl sulfoxide was 1:0.001:1.2.

[0044] (2) Post-treatment stage: Add 10 wt% sodium bisulfite aqueous solution to another reaction bottle and start stirring, and drop the crude reaction solution obtained in step (1) into 10 wt% sodium bisulfite aqueous solution for quenching, and maintain the water temperature at 10-30°C and stir for 0.5-1h during the dropping process. After the stirring is completed, stand and separate, take the organic phase, dry and filter it with anhydrous sodium sulfate, first control the vacuum pressure value within 5.5-8.5 KPa, and the concentration temperature within 45-55°C, distill the excess solvent from the organic phase, and continue to reduce the vacuum to 500-800 Pa after almost no distillation, and control the temperature at 90-100°C to completely desolventize and concentrate. After the mass of the organic phase is constant, it can be considered that the concentration is complete, thereby obtaining 174.8 g of di(2-ethylhexyl) phosphate, with a yield of 90.5%, a titrated content of 96.8%, and a mono(2-ethylhexyl) phosphate content of <0.1%.

[0045] The hydrogen nuclear magnetic resonance spectrum of the di(2-ethylhexyl) phosphate prepared in this example is as follows: Figure 2Its nuclear magnetic resonance phosphorus spectrum is shown in Figure 3 As shown, through Figure 2 and Figure 3 It can be verified that the product obtained in this example is di(2-ethylhexyl) phosphate.

[0046] Example 3

[0047] The difference between the present embodiment and the embodiment 1 is only that: in the step (1) of the present embodiment, the catalyst is replaced by iodine element by periodic acid, and in addition, in the present embodiment, the consumption of di(2-ethylhexyl)phosphite is 10.2g, the consumption of dimethyl sulfoxide is 3.2g, the consumption of toluene is 102.2g, and the consumption of iodine element is 0.8g, so that the molar ratio between di(2-ethylhexyl)phosphite, iodine element and dimethyl sulfoxide is 1:0.1:1.2. All the others are the same. The present embodiment obtains 8.7g di(2-ethylhexyl)phosphate, and the yield is 82.3%, the titration content is 96.1%, and the content of mono(2-ethylhexyl)phosphate is less than 0.2%.

[0048] Example 4

[0049] The difference between the present embodiment and the embodiment 1 is only that: in the step (1) of the present embodiment, the catalyst is replaced by iodine element by periodic acid. In addition, in the present embodiment, the consumption of di(2-ethylhexyl)phosphite is 30.6g, the consumption of dimethyl sulfoxide is 9.4g, the consumption of toluene is 306.6g, and the consumption of iodine is 0.25g. In this way, the molar ratio between di(2-ethylhexyl)phosphite, periodic acid and dimethyl sulfoxide is 1:0.01:1.2. All the others are the same. The present embodiment obtains 28.05g di(2-ethylhexyl)phosphate, and the yield is 87.1%, the titration content is 96.2%, and the content of mono(2-ethylhexyl)phosphate is less than 0.1%.

[0050] Comparative Example

[0051] Add 30.7g of phosphorus oxychloride and 70mL of toluene to a three-necked flask, start stirring and gradually add a mixed solution of 46.9g of isooctyl alcohol and 36.4g of triethylamine, and keep the reaction temperature no more than 35°C during the addition. After the addition is complete, maintain the reaction at 25-35°C, and detect the reaction by TLC until the end point is reached. After the reaction is completed, filter the reaction solution, wash the reaction solution with 30.7g of clean water, separate the organic phase, wash the aqueous phase twice with 16.4g of toluene, combine all organic phases and dry with anhydrous sodium sulfate, and filter to obtain a toluene solution of diisooctyl chlorophosphate.

[0052] The obtained diisooctyl chlorophosphate toluene solution was placed in a reaction bottle, and 40g30% sodium hydroxide aqueous solution was gradually added after stirring. The reaction temperature was maintained at no more than 60°C during the addition. After the addition was completed, the temperature was gradually raised to 90-95°C for reaction. The reaction end point was detected by TLC. After the reaction was completed, 20wt% hydrochloric acid aqueous solution was added to adjust the pH to 3-4, and then the liquid was separated by standing. The organic phase was obtained and then washed with saturated salt water to separate the organic phase and dried and filtered with anhydrous sodium sulfate. When the filtrate was concentrated, the vacuum pressure value was first controlled within 2.5-3.5Kpa, and the temperature was distilled out at 80-90°C to distill out excess solvent. After almost no distillation, the vacuum was continued to be reduced to 500-800Pa, and the temperature was controlled at 90-100°C to completely desolventize and concentrate. After the reaction liquid mass was constant, it was considered that the concentration was complete. Finally, 47.1g of di(2-ethylhexyl) phosphate was obtained, with a yield of 81.1%, a titration content of 93.2%, and a single(2-ethylhexyl) phosphate content of 2.8%. The di(2-ethylhexyl) phosphate prepared in this comparative example has a nuclear magnetic resonance phosphorus spectrum as shown in Figure 4 As shown, Figure 4 This indicates that the product of this comparative example contains impurities and has a lower purity than the product of Example 2.

[0053] The above are only embodiments of the present invention. The invention is not limited to the fields involved in this implementation case. The common sense such as the known specific structures and characteristics in the scheme is not described in detail here. The ordinary technicians in the relevant field know all the common technical knowledge in the technical field to which the invention belongs before the application date or priority date, can obtain all the existing technologies in the field, and have the ability to apply the conventional experimental means before that date. The ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the protection scope of the present invention, which will not affect the effect of the implementation of the present invention and the practicality of the present invention. The protection scope required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to explain the content of the claims.

Claims

1. An oxidation synthesis process for di(2-ethylhexyl) phosphate, characterized in that: The following steps are involved: Di(2-ethylhexyl) phosphate is prepared by oxidation reaction with di(2-ethylhexyl) phosphite as a raw material and dimethyl sulfoxide as an oxidant under the catalysis of a catalyst, wherein the catalyst is periodic acid or iodine.

2. The oxidation synthesis process of di(2-ethylhexyl)phosphate according to claim 1, characterized in that: The following steps are involved: S1, reaction stage: di(2-ethylhexyl)phosphite, dimethyl sulfoxide, a catalyst and a reaction solvent are mixed, the reaction temperature is 25-30°C, the reaction time is 2.5-24h, and a crude reaction solution is obtained; S2, post-treatment stage: the crude reaction solution is added dropwise to the quenching aqueous solution, the water temperature is maintained at 10-30°C and stirred for 0.5-2h during the dropping process, the layers are allowed to stand, the organic phase is taken, and di(2-ethylhexyl) phosphate is obtained through drying and concentration; wherein the quenching aqueous solution is a sodium thiosulfate aqueous solution or a sodium bisulfite aqueous solution.

3. The oxidation synthesis process of di(2-ethylhexyl)phosphate according to claim 2, characterized in that: In step S1, the molar ratio of di(2-ethylhexyl)phosphite, catalyst and dimethyl sulfoxide is 1:(0.1-0.001):1.

2.

4. The oxidation synthesis process of di(2-ethylhexyl)phosphate according to claim 2, characterized in that: In step S1, the reaction solvent is one of toluene, dichloromethane, tetrahydrofuran and petroleum ether.

5. The oxidation synthesis process of di(2-ethylhexyl)phosphate according to claim 2, characterized in that: In step S2, the mass ratio of the reaction solvent to di(2-ethylhexyl)phosphite is 10 to 0.5:

1.

6. The oxidation synthesis process of di(2-ethylhexyl)phosphate according to claim 2, characterized in that: In step S2, the quenching aqueous solution is a 10 wt % sodium thiosulfate aqueous solution or a 10 wt % sodium bisulfite aqueous solution.

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