Preparation method of dioctyl phosphate

Abstract

The invention relates to the technical field of chemical material synthesis, in particular to a preparation method of dioctyl phosphate, which comprises the following steps: (1) esterification: adding isooctanol into a reaction flask with a reflux condensing device, dropwise adding phosphorus oxychloride under negative pressure and at-5-15 DEG C, enabling the molar ratio of phosphorus oxychloride to isooctanol to be 1.0: (2.1-2.2), and enabling generated hydrogen chloride gas to enter an absorption device; (2) alkaline hydrolysis: adding 40-50% of alkali liquor into the esterification liquid, and carrying out alkaline hydrolysis at 110 + / -5 DEG C for 1-2 hours; (3) alkali washing: washing the alkaline hydrolysis solution for 2-3 times by using a dilute alkali solution; and (4) acidification and water washing: adding a hydrochloric acid solution in a hydrogen chloride device into the material subjected to alkali washing, acidifying for 15-30 minutes, and carrying out water washing distillation to obtain the product. The method has the advantages of easily available raw materials, simple operation, reasonable application of the hydrogen chloride byproduct, and no need of adding a phase transfer catalyst.

Description

Technical Field

[0001] The invention relates to the technical field of chemical material synthesis, and in particular to a method for preparing dioctyl phosphate. Background Art

[0002] Dioctyl phosphate (P204), slightly yellow transparent oily liquid, density 0.97g / cm 3 It is soluble in organic solvents such as alcohol and benzene, but insoluble in water. It is mainly used for the extraction of rare earths, non-ferrous metals (including cobalt, nickel, gold, copper, indium, etc.) and electrolytic metals.

[0003] In industry, phosphorus oxychloride and isooctyl alcohol are mainly used as raw materials to produce dioctyl phosphate. Chinese patent CN101696224A discloses a method for synthesizing dioctyl phosphate, which includes the following steps: A. Esterification reaction, add phosphorus oxychloride to a three-necked flask with magnetic stirring, start stirring, and start dripping isooctyl alcohol at 0-15°C, a large amount of heat is released, and HCl gas is generated. The dripping process takes 2-5 hours, and the molar ratio of phosphorus oxychloride to isooctyl alcohol is 1.0:1.0-3.5. B. Hydrolysis reaction process, add 0.2-0.5% of the mass of phosphorus oxychloride as a phase transfer catalyst and 1.5-2.5 times the mass of phosphorus oxychloride as sodium hydroxide solution to the reaction system, let it stand for stratification, separate the water layer, and wash the organic phase with water once; C. Acidification process, add 10% sulfuric acid 4-5 times the mass of phosphorus oxychloride to the organic phase obtained in the step. Although this invention improves the yield and product purity compared with the original tradition, the generated hydrogen chloride by-product is not properly handled, and a phase transfer catalyst needs to be added to increase production costs. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a method for preparing dioctyl phosphate to reduce the production cost of dioctyl phosphate, make full use of all atoms in the chemical reaction, and improve the product yield and purity.

[0005] Based on the above purpose, the present invention provides a method for preparing dioctyl phosphate, comprising the following steps:

[0006] Step 1, esterification: After cooling the isooctyl alcohol in an ice-salt bath, under vacuum conditions, add phosphorus oxychloride dropwise and control the reaction temperature not to exceed 20°C. After the addition is completed, under a vacuum condition of -0.06 to -0.08 MPa, heat to 30 to 40°C and react for 0.5 to 2 hours; then heat to 70 to 80°C and keep warm for 1 to 2 hours;

[0007] Step 2, alkaline hydrolysis: adding alkaline solution to the material after the esterification reaction in step 1, heating and refluxing, and removing the aqueous phase;

[0008] Step 3, alkali washing: washing the cracking liquid obtained in step 2 with alkali solution;

[0009] Step 4, acidification and water washing: the material after alkali washing is acidified, the aqueous phase is removed, washed and distilled to obtain dioctyl phosphate.

[0010] The preparation chemical formula of dioctyl phosphate is as follows:

[0011]

[0012] In step 1, the molar ratio of phosphorus oxychloride to isooctyl alcohol is 1.0:2.1-2.2.

[0013] Step 1: Cool down to -5-15°C in an ice-salt bath.

[0014] The vacuum condition when adding phosphorus oxychloride dropwise in step 1 is to control the vacuum degree to be -0.04 to -0.06 MPa.

[0015] The alkali solution in step 2 is 40-50% by mass, and the amount of alkali solution added is 1.0-1.2 times the mass of the esterified feed solution. The temperature is raised to 105-115° C. for reflux, and the reflux time is 1-2 hours.

[0016] In the alkali washing of step 3, the cracking liquid is washed 5 to 6 times with alkali solution having a mass fraction of 5-8%.

[0017] The amount of alkali solution added in step 3 is 0.8 to 1.0 times the mass of the alkaline hydrolysis solution.

[0018] The hydrogen chloride generated during the esterification process in step 1 is introduced into a hydrochloric acid absorption device to obtain a by-product hydrochloric acid solution, and the obtained by-product hydrochloric acid solution is used for acidification and water washing in step 4. The acidification temperature is 60-70° C. and the stirring acidification time is 15-30 minutes.

[0019] The concentration of hydrochloric acid used in the acidification in step 4 is 16.1-22.7%.

[0020] Beneficial effects of the present invention:

[0021] (1) The present invention starts to apply negative pressure at the beginning of the esterification reaction, and the negative pressure when phosphorus oxychloride is added dropwise is moderate, which reduces the loss rate of phosphorus oxychloride. The negative pressure is increased in the later stage of the process, which can effectively remove the generated hydrogen chloride, resulting in a faster reaction and a higher conversion rate.

[0022] (2) The present invention drips phosphorus oxychloride into isooctyl alcohol, which can effectively solve the problem of phosphorus oxychloride crystallizing due to too low temperature during the material cooling process, and at the same time reduce the volatilization of phosphorus oxychloride.

[0023] (3) The alkali washing step of the present invention can effectively wash away the sodium salt of monophosphate ester, reduce the content of monophosphate ester in the product, and improve the purity of the product.

[0024] (4) The hydrogen chloride generated in the esterification reaction is passed through an absorption device to obtain a hydrochloric acid solution, which can be directly used in the acidification reaction without treatment, so that all atoms in the entire chemical reaction are utilized, thereby reducing production costs. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0026] Figure 1 is the nuclear magnetic hydrogen spectrum of dioctyl phosphate of the present invention;

[0027] Figure 2 is the nuclear magnetic carbon spectrum of dioctyl phosphate of the present invention;

[0028] Figure 3 It is the nuclear magnetic phosphorus spectrum of dioctyl phosphate of the present invention. DETAILED DESCRIPTION

[0029] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0030] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention should have the common meanings understood by persons having ordinary skills in the field to which the present invention belongs.

[0031] The present invention provides a method for preparing dioctyl phosphate, comprising the following steps:

[0032] (1) Esterification

[0033] Add isooctyl alcohol to a reaction bottle with a reflux condenser, cool the material to -5-15°C with an ice-salt bath, and drop phosphorus oxychloride under vacuum conditions of -0.04-0.06Mpa. The molar ratio of phosphorus oxychloride to isooctyl alcohol is 1.0:2.1-2.2, and the temperature does not exceed 20°C during the dropwise addition. After the dropwise addition is completed, heat to 30-40°C under vacuum conditions of -0.06-0.08Mpa for 0.5-2h; heat to 70-80°C and keep warm for 1-2h. The hydrogen chloride gas generated during the reaction enters the hydrochloric acid absorption device.

[0034] (2) Alkaline hydrolysis

[0035] Add 40-50% concentrated alkali solution to the above esterification solution, heat the material to 110±5°C, reflux for 1-2h, and separate the water phase.

[0036] (3) Alkaline washing

[0037] Wash the alkaline solution 5 to 6 times with 5 to 8% dilute alkali solution.

[0038] (4)Acidified water washing

[0039] Add all the hydrochloric acid solution in the hydrogen chloride absorption device in the experiment to the material after alkali washing, stir and acidify at 60-70℃ for 15-30min, and separate the water phase. Wash the organic phase with an equal volume of pure water for 3-5 times, and remove water and a small amount of isooctyl alcohol by distillation to obtain the product dioctyl phosphate. The following is a detailed description through a specific example.

[0040] Example 1

[0041] Add 2.1 mol of isooctyl alcohol to a 1000 mL three-necked flask with a reflux condenser, cool the material to -5°C with an ice-salt bath, and drop 1 mol of phosphorus oxychloride under a vacuum condition of -0.04 MPa for 101 min. The temperature does not exceed 20°C during the dropwise addition. After the dropwise addition is completed, heat to 35°C under a vacuum condition of -0.08 MPa for 1 hour; heat to 70°C and keep warm for 2 hours.

[0042] 362g of 42% concentrated sodium hydroxide solution was added to the above esterification liquid, the material was heated to 112°C, refluxed for 2h, and the water phase was separated. The alkaline solution was washed twice with 310g of 5% dilute sodium hydroxide solution, and the water phase was separated. All the hydrochloric acid solution in the hydrogen chloride device in this experiment was added to the material after alkali washing, stirred and acidified at 60°C for 20min, and the water phase was separated. The organic phase was washed 3 times with an equal volume of pure water, and the product dioctyl phosphate was obtained by distillation to remove water and a small amount of isooctyl alcohol (temperature not about 150°C) 306.63g, with a yield of 95.1%, a purity of 98.56% (potentiometric titration), and a monooctyl phosphate content of 0.49% (potentiometric titration).

[0043] Example 2

[0044] Add 2.2 mol of isooctyl alcohol to a 1000 mL three-necked flask with a reflux condenser, cool the material to 0°C with an ice-salt bath, and drop 1 mol of phosphorus oxychloride under a vacuum condition of -0.06 MPa for 110 min. The temperature does not exceed 15°C during the dropwise addition. After the dropwise addition is completed, heat to 30°C and react for 2 h under a vacuum condition of -0.08 MPa; heat to 80°C and keep warm for 2 h.

[0045] Add 370g of 48% concentrated sodium hydroxide solution to the above esterification solution, heat the material to 113°C, reflux for 2h, and separate the water phase. Wash the alkaline solution 3 times with 327g of 8% dilute sodium hydroxide solution, and separate the water phase. Add all the hydrochloric acid solution in the hydrogen chloride device in this experiment to the material after alkali washing, stir and acidify at 60°C for 30min, and separate the water phase. Wash the organic phase 4 times with an equal volume of pure water, remove water and a small amount of isooctyl alcohol by distillation (temperature not about 150°C), and obtain 308.57g of dioctyl phosphate, with a yield of 95.7%, a purity of 98.86% (potentiometric titration), and a monooctyl phosphate content of 0.33% (potentiometric titration).

[0046] Example 3

[0047] Add 2.15 mol of isooctyl alcohol to a 1000 mL three-necked flask with a reflux condenser, cool the material to -2°C with an ice-salt bath, and drop 1 mol of phosphorus oxychloride under a vacuum condition of -0.05 MPa for 107 min. The temperature does not exceed 18°C ​​during the dropwise addition. After the dropwise addition is completed, heat to 30°C under a vacuum condition of -0.08 MPa for reaction for 1 hour; heat to 80°C and keep the temperature for reaction for 2 hours.

[0048] Add 365g of 50% concentrated potassium hydroxide solution to the above esterification solution, heat the material to 113°C, reflux for 1.5h, and separate the water phase. Wash the alkaline solution twice with 310g of 5% dilute potassium hydroxide solution, and separate the water phase. Add all the hydrochloric acid solution in the hydrogen chloride device in this experiment to the material after alkali washing, stir and acidify at 70°C for 20min, and separate the water phase. Wash the organic phase with an equal volume of pure water for 3 times, remove water and a small amount of isooctyl alcohol by distillation (temperature not about 150°C), and obtain 306.95g of dioctyl phosphate, with a yield of 95.2%, a purity of 98.52% (potentiometric titration), and a monooctyl phosphate content of 0.43% (potentiometric titration).

[0049] Comparative Example

[0050] The experimental conditions were consistent with those of Example 3, with alkali washing performed three times. The experimental results were: yield 96.7%, purity 96.17% (potentiometric titration), and monooctyl phosphate content 3.38% (potentiometric titration).

[0051] The data of the tests on Examples 1-3 and the comparative example are shown in Table 1 below.

[0052] Table 1: Experimental results of examples and comparative examples

[0053]

[0054] The results show that the alkali washing step can effectively reduce the content of monophosphate and improve the purity of the product. The preparation method of the present invention has high yield, high purity, low chroma and stable method.

[0055] Those skilled in the art should understand that the discussion of any of the above embodiments is only exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes in different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity. Any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing dioctyl phosphate, characterized in that: The steps include: Step 1, esterification: After cooling the isooctyl alcohol in an ice-salt bath, under vacuum conditions, add phosphorus oxychloride dropwise and control the reaction temperature not to exceed 20°C. After the addition is completed, under a vacuum condition of -0.06 to -0.08 MPa, heat to 30 to 40°C and react for 0.5 to 2 hours; then heat to 70 to 80°C and keep warm for 1 to 2 hours; Step 2, alkaline hydrolysis: adding alkaline solution to the material after the esterification reaction in step 1, heating and refluxing, and removing the aqueous phase; Step 3, alkali washing: washing the cracking liquid obtained in step 2 with alkali solution; Step 4, acidification and water washing: the material after alkali washing is acidified, the aqueous phase is removed, washed and distilled to obtain dioctyl phosphate.

2. The method for preparing dioctyl phosphate according to claim 1, characterized in that: In step 1, the molar ratio of phosphorus oxychloride to isooctyl alcohol is 1.0:2.1-2.

2.

3. The method for preparing dioctyl phosphate according to claim 1, characterized in that: Step 1: Cool down to -5-15°C in an ice-salt bath.

4. The method for preparing dioctyl phosphate according to claim 1, characterized in that: The vacuum condition when adding phosphorus oxychloride dropwise in step 1 is to control the vacuum degree to be -0.04 to -0.06 MPa.

5. The method for preparing dioctyl phosphate according to claim 1, characterized in that: The alkali solution in step 2 is 40-50% by mass, and the amount of alkali solution added is 1.0-1.2 times the mass of the esterified feed solution. The temperature is raised to 105-115° C. for reflux, and the reflux time is 1-2 hours.

6. The method for preparing dioctyl phosphate according to claim 1, characterized in that: In the alkali washing of step 3, the cracking liquid is washed 5 to 6 times with alkali solution having a mass fraction of 5-8%.

7. The method for preparing dioctyl phosphate according to claim 1 or 6, characterized in that: The amount of alkali solution added in step 3 is 0.8 to 1.0 times the mass of the alkaline hydrolysis solution.

8. The method for preparing dioctyl phosphate according to claim 1, characterized in that: The hydrogen chloride generated during the esterification process in step 1 is introduced into a hydrochloric acid absorption device to obtain a by-product hydrochloric acid solution, and the obtained by-product hydrochloric acid solution is used for acidification and water washing in step 4. The acidification temperature is 60-70° C. and the stirring acidification time is 15-30 minutes.

9. The method for preparing dioctyl phosphate according to claim 1 or 8, characterized in that: The concentration of hydrochloric acid used in the acidification in step 4 is 16.1-22.7%.

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