Preparation method of triethyl phosphate

Abstract

The invention relates to the field of IPC C07F 9 / 11, in particular to a preparation method of triethyl phosphate. Comprising the following steps: first-stage esterification; carrying out second-stage esterification; carrying out neutralization reaction; dealcoholization is performed; rectifying under reduced pressure; according to the preparation method, a segmented reaction is matched with specific post-treatment (ammonia gas introduction), so that the purity of the obtained product is more than 99.5%, the water content is controlled to be less than 0.04, the color (APHA) is less than or equal to 10, and the acid value is controlled to be less than 0.06 mgKOH / g; according to the method, the ammonia gas is added after the reaction is finished, so that dangerous substances of chloroethane are prevented from being generated by the reaction of ethanol and hydrogen chloride, the product is prevented from being decomposed into diethyl phosphate, the product yield is increased, and the residual liquid amount is reduced.

Description

Technical Field

[0001] The invention relates to the field of IPC C07F 9 / 11, and more specifically to a method for preparing triethyl phosphate. Background Art

[0002] Triethyl phosphate is widely used, for example, as an additive in textiles and paper products, as a plasticizer in plastics and coatings, a non-reactive flame retardant, a hardener and accelerator, a lubricant, a flotation agent, a defoamer, an emulsifier, a stabilizer, and an extractant. At present, the domestic method for producing triethyl phosphate is usually to react phosphorus oxychloride with excess anhydrous ethanol.

[0003] CN102675359A discloses a method for preparing triethyl phosphate. After low-pressure esterification reaction of phosphorus oxychloride and anhydrous ethanol, excess anhydrous ethanol and part of hydrogen chloride are removed under reduced pressure, residual hydrogen chloride is removed under normal pressure, and vacuum distillation is performed to obtain a finished triethyl phosphate. A catalyst is added to reduce the temperature of the esterification reaction and increase the reaction rate from nearly 50° C. to 25-35° C. After removing excess anhydrous ethanol, ammonia is added to neutralize and remove hydrogen chloride. Adding a catalyst increases the cost of raw materials, and the catalyst remains in the product, affecting the physical properties of the material. At the same time, since the system for removing anhydrous ethanol is acidic, anhydrous ethanol will react with hydrogen chloride at a temperature higher than 40° C. to generate a dangerous substance, ethyl chloride. At the same time, the product triethyl phosphate generated will decompose to generate diethyl phosphate in an acidic environment, affecting the product yield.

[0004] CN103374028A discloses a method for preparing triethyl phosphate, which specifically comprises the following steps: firstly, using ammonia as an acid binding agent and methyl red as an indicator, phosphorus trichloride and anhydrous ethanol react to generate triethyl phosphite, filtering out the byproduct ammonium chloride, introducing a certain amount of oxygen for oxidation, and finally obtaining the target product triethyl phosphate after purification by vacuum distillation. However, in the invention, ammonia is easy to react with phosphorus trichloride and the intermediate products dichlorophosphate and monochlorophosphate in the reaction, which will increase the byproducts and affect the yield and content of the product. Summary of the invention

[0005] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing triethyl phosphate by staged reaction, by adding ammonia gas to neutralize hydrogen chloride at an appropriate stage, avoiding the generation of dangerous substance ethyl chloride and reducing the decomposition of the product. The method has a simple process, does not require high temperature, has a high content and yield of the obtained product, does not require a catalyst, does not use an organic solvent, has no three wastes discharged, is environmentally friendly, and is suitable for industrial production.

[0006] The present invention provides a method for preparing triethyl phosphate, comprising the following steps:

[0007] Step 1, one-stage esterification: add anhydrous ethanol as a base, drop phosphorus oxychloride, react under negative pressure, and keep warm after the dropwise addition;

[0008] Step 2, two-stage esterification: add anhydrous ethanol dropwise, react under negative pressure, and after the addition is completed, keep warm for reaction. When the content of monochlorophosphate is monitored to be ≤0.5%, the reaction is completed;

[0009] Step 3, neutralization reaction: neutralize the hydrogen chloride with ammonia, react, stir for 0.5 to 1 hour, filter out the generated ammonium chloride, and obtain a mother liquor;

[0010] Step 4, dealcoholization: Filter the mother liquor and remove ethanol under reduced pressure, the system negative pressure is -0.09 to -0.095 MPa, the temperature is 60 to 100°C;

[0011] Step 5, vacuum distillation: the crude triethyl phosphate is subjected to vacuum distillation to obtain the triethyl phosphate product.

[0012] The applicant has found that by adding anhydrous ethanol in stages, the molar ratio of phosphorus oxychloride to anhydrous ethanol in the first esterification is controlled to be 1:3-1:5, the molar ratio of anhydrous ethanol added in the second esterification to the phosphorus oxychloride added dropwise in the first esterification is 3:1-4:1, and the reaction time can be shortened and the reaction efficiency can be improved by gradually increasing the temperature. The reaction formula for preparing triethyl phosphate is POCl3+3C2H5OH=(C2H5O)3PO+3HCl, but the actual reaction is divided into three steps. The first step is: phosphorus oxychloride and ethanol generate dichlorophosphate and hydrogen chloride, POCl3+C2H5OH=(C2H5O)POCl2+HCl; the second step is: the product of the first step continues to react with ethanol to generate diethyl chlorophosphate (intermediate state) and hydrogen chloride, (C2H5O)POCl2+C2H5OH=(C2H5O)2POCl+HCl; the third step is: diethyl chlorophosphate and excess ethanol continue to react to generate triethyl phosphate and hydrogen chloride, (C2H5O)2POCl+C2H5OH=(C2H5O)3PO+HCl. Since the first and second steps react faster and the third step reacts slower, a specific feed ratio can control the reaction process, regulate the overall reaction, and achieve the effect of increasing the reaction rate.

[0013] However, adding anhydrous ethanol in stages will also increase the number of by-products, thereby reducing the purity. This may be due to the presence of more side reactions, such as the reaction of triethyl phosphate and hydrogen chloride to form diethyl phosphate and ethyl chloride: (C2H5O)3PO+HCl=(C2H5O)2POOH+C2H5Cl; ethanol and hydrogen chloride to form ethyl chloride and water: C2H5OH+HCl=C2H5Cl+H2O, ethanol will react with hydrogen chloride at 40°C; triethyl phosphate and water decompose into diethyl phosphate and ethanol: (C2H5O)3PO+H2O=(C2H5O)2POOH+C2H5OH. The traditional post-treatment with sodium carbonate or sodium bicarbonate not only affects the post-treatment efficiency but also cannot effectively improve the purity of triethyl phosphate.

[0014] The applicant has further studied and found that in the post-treatment neutralization reaction, ammonia is added to neutralize the generated hydrogen chloride. After the reaction is completed, ammonia is added to neutralize the hydrogen chloride to avoid the generation of ethyl chloride and the decomposition of the product, the distillation residue is reduced, and the product yield is higher than 98%, which not only improves the yield, but also protects the environment, and almost no three wastes are generated. The hydrogen chloride generated in the reaction is directly synthesized into methyl chloride, a small amount of hydrogen chloride is converted into crude ammonium chloride for sale, and a small amount of distillation residue is directionally incinerated into crude sodium pyrophosphate for sale.

[0015] The temperature of the dropwise addition in the one-stage esterification is 0-10°C.

[0016] Preferably, the temperature of the dripping in the one-stage esterification is 8-10°C.

[0017] The dripping time in the first stage of esterification is 2 to 5 hours.

[0018] The heat preservation reaction time in the first stage of esterification is 1 to 2 hours, and the temperature is 15 to 30°C.

[0019] Preferably, the heat preservation reaction time in the first stage of esterification is 1 to 2 hours, and the temperature is 15 to 20°C.

[0020] The molar ratio of phosphorus oxychloride to anhydrous ethanol in the one-stage esterification is 1:3 to 1:5.

[0021] Preferably, the molar ratio of phosphorus oxychloride to anhydrous ethanol in the one-stage esterification is 1:4 to 1:5.

[0022] The molar ratio of the anhydrous ethanol added in the second-stage esterification to the phosphorus oxychloride added dropwise in the first-stage esterification is 3:1-4:1.

[0023] The temperature of the dropwise addition in the two-stage esterification is 15 to 30°C.

[0024] Preferably, the temperature of the dripping in the second-stage esterification is 15-20°C.

[0025] The negative pressure of the first stage esterification is -0.02 to -0.05 MPa, and the negative pressure of the second stage esterification is -0.06 to -0.095 MPa.

[0026] Preferably, the negative pressure of the first-stage esterification is -0.02 to -0.03 MPa, and the negative pressure of the second-stage esterification is -0.08 to -0.095 MPa.

[0027] More preferably, the negative pressure of the first-stage esterification is -0.02 MPa, and the negative pressure of the second-stage esterification is -0.09 MPa.

[0028] The temperature of the neutralization reaction is 20-30° C., and the pH of the reaction is 7-8.

[0029] Preferably, the temperature of the vacuum distillation is 120-140°C.

[0030] Beneficial Effects

[0031] 1. The present application adopts a staged reaction with a specific post-treatment (ammonia gas), and the obtained product has a purity of more than 99.5%, a moisture content of less than 0.04, a color (APHA) ≤ 10, and an acid value of less than 0.06 mgKOH / g.

[0032] 2. The molar ratio of phosphorus oxychloride to anhydrous ethanol in the first stage of esterification is controlled to be 1:3 to 1:5, and the negative pressure of the first stage of esterification is -0.02 to -0.05 MPa. Hydrogen chloride can be removed during the reaction, so that the loss of phosphorus oxychloride is small and hydrogen chloride can be removed in time, which is beneficial to increase the reaction rate.

[0033] 3. The molar ratio of anhydrous ethanol added in the second stage esterification to phosphorus oxychloride added in the first stage esterification is controlled to be 3:1-4:1, and a higher yield (greater than 98%) can be obtained under relatively mild reaction conditions (15-30°C).

[0034] 4. The timing of adding ammonia in the present application is after the reaction is completed, which avoids the dangerous substance of ethyl chloride generated by the reaction of ethanol and hydrogen chloride, and avoids the decomposition of the product into diethyl phosphate, thereby increasing the product yield and reducing the amount of residual liquid.

[0035] 5. The by-products of the present invention have feasible treatment plans. Hydrogen chloride is used to prepare methyl chloride. A small amount of hydrogen chloride is neutralized with ammonia gas to form ammonium chloride for use as a fertilizer. The product is subjected to reduced pressure distillation and a small amount of residual liquid is incinerated to form sodium pyrophosphate, which realizes resource recycling without the discharge of three wastes and is green and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is the gas chromatogram of triethyl phosphate prepared in Example 1. DETAILED DESCRIPTION

[0037] Example 1

[0038] In a four-necked bottle, 92.14 g (1.98 mol) of anhydrous ethanol was placed, and 76.6 g (0.49 mol) of phosphorus oxychloride was added dropwise. The temperature was 8°C and the negative pressure was -0.02 MPa. The addition was continued for 2 hours. After the addition was completed, the temperature was kept at 18°C ​​for 2 hours. 69.11 g (1.49 mol) of anhydrous ethanol was continued to be added dropwise. The temperature was 18°C ​​and the negative pressure was -0.09 MPa. The temperature was kept for 3 hours. The sampling control was performed and the intermediate state was 0.3%. The reaction was terminated, ammonia was introduced, the temperature was 25°C, and the alcohol was dealcoholized by vacuum distillation. 87.98 g of triethyl phosphate was distilled out under reduced pressure.

[0039] Example 2

[0040] 92.14 g (1.98 mol) of anhydrous ethanol was placed in a four-necked bottle, and 76.6 g (0.49 mol) of phosphorus oxychloride was added dropwise. The temperature was 25°C and the negative pressure was -0.02 MPa. After the addition was completed for 2 hours, the temperature was kept at 35°C for 2 hours. 69.11 g (1.49 mol) of anhydrous ethanol was continued to be added dropwise. The temperature was 30°C and the negative pressure was -0.09 MPa. The temperature was kept for 3 hours. The sampling control was performed and the intermediate state was 0.05%. The reaction was terminated, ammonia was introduced, the temperature was 25°C, and the alcohol was dealcoholized by vacuum distillation. 82.25 g of the product triethyl phosphate was distilled out under reduced pressure.

[0041] Example 3

[0042] 92.14 g (1.98 mol) of anhydrous ethanol was placed in a four-necked bottle, and 76.6 g (0.49 mol) of phosphorus oxychloride was added dropwise. The temperature was 10°C and the negative pressure was -0.09 MPa. After the addition was completed, the temperature was kept at 20°C for 2 hours. 69.11 g (1.49 mol) of anhydrous ethanol was continued to be added dropwise. The temperature was 20°C and the negative pressure was -0.09 MPa. The temperature was kept for 3 hours. The sampling control was performed and the intermediate state was 0.4%. The reaction was terminated, ammonia was passed through, the temperature was 25°C, and the alcohol was dealcoholized by vacuum distillation. 83.98 g of triethyl phosphate was distilled out under reduced pressure.

[0043] Example 4

[0044] 92.14 g (1.98 mol) of anhydrous ethanol was placed in a four-necked bottle, and 76.6 g (0.49 mol) of phosphorus oxychloride was added dropwise. The temperature was 8°C and the negative pressure was -0.09 MPa. After the addition was completed, the temperature was kept at 20°C for 2 h. 69.11 g (1.49 mol) of anhydrous ethanol was continued to be added dropwise. The temperature was 20°C and the negative pressure was -0.09 MPa. The temperature was kept for 3 h. The sampling control was performed and the intermediate state was 0.06%. The reaction was terminated and the alcohol was dealcoholized by vacuum distillation. Ammonia was passed through. The temperature was 25°C and 80.34 g of triethyl phosphate was distilled out under reduced pressure.

[0045] Example 5

[0046] In a four-necked bottle, 92.14 g (1.98 mol) of anhydrous ethanol was placed, and 76.6 g (0.49 mol) of phosphorus oxychloride was added dropwise. The temperature was 9°C and the negative pressure was -0.02 MPa. After the addition was completed, the temperature was kept at 120°C for 2 h. 69.11 g (1.49 mol) of anhydrous ethanol was added dropwise. The temperature was 20°C and the negative pressure was -0.09 MPa. The temperature was kept for 3 h. The sampling control was performed and the intermediate state was 0.5%. The reaction was terminated and the alcohol was dealcoholized by vacuum distillation. Anhydrous sodium carbonate was added to neutralize and 79.46 g of triethyl phosphate was distilled off under reduced pressure.

[0047] Performance test methods and data

[0048] The triethyl phosphate obtained in the embodiment and the comparative example was tested. The test standards and data are shown in Table 1, wherein the purity gas chromatogram of Example 1 is shown in Table 1. Figure 1 shown.

[0049] Table 1

[0050]

Claims

1. A method for preparing triethyl phosphate, characterized in that, The following steps are involved: Step 1, one-stage esterification: add anhydrous ethanol as a base, drop phosphorus oxychloride, react under negative pressure, and keep warm after the dropwise addition; Step 2, two-stage esterification: add anhydrous ethanol dropwise, react under negative pressure, and after the addition is completed, keep warm for reaction. When the content of monochlorophosphate is monitored to be ≤0.5%, the reaction is completed; Step 3, neutralization reaction: neutralize the hydrogen chloride with ammonia, react, stir for 0.5 to 1 hour, filter out the generated ammonium chloride, and obtain a mother liquor; Step 4, dealcoholization: Filter the mother liquor and remove ethanol under reduced pressure, the system negative pressure is -0.09 to -0.095 MPa, the temperature is 60 to 100°C; Step 5, vacuum distillation: the crude triethyl phosphate is obtained by vacuum distillation.

2. A method for preparing triethyl phosphate according to claim 1, characterized in that, The temperature of the dropwise addition in the one-stage esterification is 0-10°C.

3. A method for preparing triethyl phosphate according to claim 2, characterized in that, The dripping time in the first stage of esterification is 2 to 5 hours.

4. A method for preparing triethyl phosphate according to claim 3, characterized in that, The heat preservation reaction time in the first stage of esterification is 1 to 2 hours, and the temperature is 15 to 30°C.

5. A method for preparing triethyl phosphate according to claim 4, characterized in that, The molar ratio of phosphorus oxychloride to anhydrous ethanol in the one-stage esterification is 1:3 to 1:

5.

6. A method for preparing triethyl phosphate according to claim 5, characterized in that, The molar ratio of the anhydrous ethanol added in the second-stage esterification to the phosphorus oxychloride added dropwise in the first-stage esterification is 3:1-4:

1.

7. A method for preparing triethyl phosphate according to claim 6, characterized in that, The temperature of the dropwise addition in the two-stage esterification is 15 to 30°C.

8. A method for preparing triethyl phosphate according to claim 1 or 7, characterized in that, The negative pressure of the first stage esterification is -0.02 to -0.05 MPa, and the negative pressure of the second stage esterification is -0.06 to -0.095 MPa.

9. A method for preparing triethyl phosphate according to claim 8, characterized in that, The temperature of the neutralization reaction is 20-30° C., and the pH of the reaction is 7-8.

10. A method for preparing triethyl phosphate according to any one of claims 1 to 9, characterized in that: The temperature of the vacuum distillation is 120-140°C.

Images