System for synthesizing N, N-bis (2-ethoxyl) aminomethyl diethyl phosphonate with low formaldehyde content

Abstract

The utility model discloses a system for synthesizing N, N-bis (2-ethoxyl) aminomethyl diethyl phosphonate with low formaldehyde content, which comprises a reaction kettle I and a reaction kettle II, the reaction kettle I and the reaction kettle II are jacketed reaction kettles, and the reaction kettle I and the reaction kettle II are respectively provided with a top feed port and a bottom discharge port. A bottom discharge port of the reaction kettle I is communicated with a top feed port of the reaction kettle II, a reflux cooling assembly is arranged at the top of the reaction kettle I, and a bottom discharge port of the reaction kettle II is connected with a product storage tank. After diethanol amine and paraformaldehyde are reacted in a reaction kettle I, a water-carrying agent is added for azeotropic reflux water separation so as to realize azeotropic separation of water generated in the reaction, so that the purpose of rapidly and efficiently preparing the MHPZ intermediate is achieved, excessive formaldehyde is removed in the water-carrying process, and synthesis and preparation of N, N-bis (2-ethoxyl) aminomethyl diethyl phosphonate with low formaldehyde content are realized.

Description

Technical Field

[0001] The utility model relates to the technical field of organic synthesis, in particular to a system for synthesizing N,N-bis(2-hydroxyethyl)aminomethylphosphonic acid diethyl ester with low formaldehyde content. Background Art

[0002] The flame retardant N,N-bis(2-hydroxyethyl)aminomethylphosphonic acid diethyl ester (PFR-306) is a reactive flame retardant suitable for rigid polyurethane foams. It can be used as a polyol to replace some polyethers in foam formulations, imparting excellent flame retardancy to products at a dosage of only 5-15%. It utilizes a synergistic flame retardancy mechanism between N and P, and can act as a monomer in the polymerization reaction, achieving excellent flame retardancy without affecting material properties.

[0003] US Patent No. 3076010 uses diethanolamine to react with aqueous formaldehyde to produce the intermediate 3-(2-hydroxyethyl)-1,3-azacyclopentane. This intermediate then reacts with diethyl phosphite to produce N,N-bis(2-hydroxyethyl)aminomethylphosphonic acid diethyl ester. The product is extracted with ether and then separated by vacuum distillation. This solution reduces yields due to the presence of water, which can cause ester hydrolysis of the diethyl phosphite and the product. Furthermore, the use of ether, a low-boiling, low-flash-point solvent, poses a risk.

[0004]

[0005] Many domestic patents such as CN1583768A, CN102276645A, and CN1291992C have optimized the synthesis process, or used solid acid as a catalyst to improve the yield, or used an alcohol solution of paraformaldehyde instead of an aqueous formaldehyde solution, and used a desiccant for drying to reduce the effect of moisture to improve the yield, or achieved drying by removing water through high vacuum reduced pressure distillation. However, none of these patents mentions the removal of excess formaldehyde that does not participate in the reaction. Utility Model Content

[0006] The utility model aims to provide a system for synthesizing N,N-bis(2-hydroxyethyl)aminomethylphosphonic acid diethyl ester with low formaldehyde content. A reflux cooling component is arranged on the top of a reactor I. After the reaction of diethanolamine and paraformaldehyde in the reactor I is completed, a water-carrying agent is added to azeotropically reflux and separate the water generated by the reaction, thereby achieving the purpose of quickly and efficiently preparing an MHPZ intermediate. In addition, excess formaldehyde is removed during the water-carrying process, thereby realizing the synthesis and preparation of N,N-bis(2-hydroxyethyl)aminomethylphosphonic acid diethyl ester with low formaldehyde content.

[0007] In order to achieve the above-mentioned purpose of the invention, the technical solution of the present utility model is as follows:

[0008] A system for synthesizing N,N-bis(2-hydroxyethyl)aminomethylphosphonic acid diethyl ester with low formaldehyde content comprises a reactor I and a reactor II. Both the reactor I and the reactor II are jacketed reactors. The reactor I and the reactor II are respectively provided with a top feed port and a bottom discharge port. The bottom discharge port of the reactor I is connected to the top feed port of the reactor II. A reflux cooling component is provided on the top of the reactor I. The bottom discharge port of the reactor II is connected to a product storage tank. The reactor II is connected to a vacuum pump. A vacuum buffer tank is provided on the connecting pipe between the vacuum pump and the reactor II.

[0009] The reflux cooling assembly includes a condenser I and a water separator, the inlet of the condenser I is connected to the top reflux outlet of the reactor I, the top of the water separator is provided with an inlet, the top side of the water separator is provided with a reflux outlet, the bottom of the water separator is provided with a waste liquid outlet, the outlet of the condenser I is connected to the top inlet of the water separator; the reflux outlet of the water separator is connected to the reflux inlet at the top of the reactor.

[0010] The jackets of the reactors I and II are respectively provided with a top steam inlet and a bottom steam outlet.

[0011] A condenser II is provided on the top of the reactor II, the inlet of the condenser II is connected to the top of the reactor II, and the outlet of the condenser II is connected to the vacuum buffer tank.

[0012] The vacuum pump is a circulating water vacuum pump.

[0013] The bottom discharge port of the reactor I is connected to the top feed port of the reactor II through a metering pump.

[0014] A liquid level observation tube is provided on one side of the water separator.

[0015] The waste liquid outlet of the water distributor is connected with a tubular sight glass and a discharge valve.

[0016] The reactor I is provided with a sampling port and a temperature sensor I; the reactor II is provided with a temperature sensor II and a pressure sensor II.

[0017] The vacuum buffer tank is provided with a pressure sensor 1.

[0018] A stop valve is provided between the vacuum buffer tank and the vacuum pump.

[0019] Beneficial effects of the utility model:

[0020] 1. In this utility model, azeotropic reflux water separation technology effectively removes excess formaldehyde generated during the reaction, as well as trace amounts of water remaining after the reaction. This ensures that the formaldehyde content of the final product, MHPZ, is below 0.1 mg / g. The "Indoor Air Quality Standard" (GB / T 18883-2022) requires formaldehyde levels to be ≤ 0.08 mg / m³. Long-term exposure to high formaldehyde concentrations may cause dizziness, headaches, tearing, nausea and vomiting, coughing, chest tightness, leukemia, and, in severe cases, death. As a key indicator of environmental and human health, the free formaldehyde content in the product should be controlled to no more than 0.1 mg / g.

[0021] 2. The utility model has a reasonable design of the entire process, and the reaction conditions are mild and easy to control. In particular, the steps of azeotropic dehydration and staged temperature increase accelerate the reaction process, improve the yield of the final product, and achieve efficient synthesis.

[0022] 3. In the present invention, except for a very small amount of waste water produced in the entire process, the remaining raw materials such as the water-containing agent and the low-boiling diethyl phosphite distilled out under reduced pressure can be recovered and reused. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic structural diagram of a system for synthesizing diethyl N,N-bis(2-hydroxyethyl)aminomethylphosphonate with low formaldehyde content in Example 1 of the present invention.

[0024] Among them, 1. Reactor I; 2. Reactor II; 3. Product storage tank; 4. Vacuum pump; 5. Vacuum buffer tank; 6. Condenser I; 7. Water separator; 8. Condenser II; 9. Metering pump; 10. Liquid level observation tube; 11. Tubular sight glass; 12. Discharge valve. DETAILED DESCRIPTION

[0025] The present invention will be further described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto.

[0026] Example 1

[0027] The present embodiment provides a system for synthesizing N,N-bis(2-hydroxyethyl)aminomethylphosphonic acid diethyl ester with low formaldehyde content, including a reactor I1 and a reactor II2, wherein the reactor I1 and the reactor II2 are both jacketed reactors, and the reactor I1 and the reactor II2 are respectively provided with a top feed port and a bottom discharge port, the bottom discharge port of the reactor I1 is connected to the top feed port of the reactor II2, and a reflux cooling assembly is provided on the top of the reactor I1, and the reflux cooling assembly includes a condenser I6 and a water separator 7, the inlet of the condenser I6 is connected to the top reflux outlet of the reactor I1, and the top of the water separator 7 is provided with inlet, a reflux outlet is provided on the top side of the water separator 7, a waste liquid outlet is provided at the bottom of the water separator 7, the outlet of the condenser I6 is connected to the top inlet of the water separator 7; the reflux outlet of the water separator 7 is connected to the reflux inlet at the top of the reactor, and the bottom discharge port of the reactor II2 is connected to the product storage tank 3; the jackets of the reactor I1 and the reactor II2 are respectively provided with a top steam inlet and a bottom steam outlet; a condenser II8 is provided on the top of the reactor II2, the inlet of the condenser II8 is connected to the top of the reactor II2, the outlet of the condenser II8 is connected to the vacuum buffer tank 5, and the vacuum buffer tank 5 is connected to the vacuum pump 4.

[0028] In this embodiment, the synthesis of low-formaldehyde-content N,N-bis(2-hydroxyethyl)aminomethylphosphonic acid diethyl ester is achieved by the following steps:

[0029] S1: Add 4.24 kg (1 equivalent) of diethanolamine and 1.33 kg (1.05-1.10 equivalents) of paraformaldehyde to reactor I1, raise the temperature to 60°C, stir, and react until the paraformaldehyde is completely dissolved and clear, then continue the reaction for 2-4 hours;

[0030] S2: After the reaction is completed, 7.20 kg of n-hexane is added to azeotropically reflux and separate the water produced by the reaction, and excess formaldehyde is removed in the process of carrying water; the azeotropic water and the water-carrying agent are condensed by the condenser I6 and then enter the water separator 7 for liquid separation. The water-carrying agent in the water separator 7 is in the upper layer and the water is in the lower layer. The water-carrying agent and water are discharged into different containers by opening the waste liquid outlet of the water separator 7. After azeotropic drying to a water content of less than 300 ppm, the water-carrying agent is evaporated under reduced pressure and the temperature is lowered to 65°C;

[0031] The water-carrying agent can be an organic non-polar solvent: n-hexane, cyclohexane, n-heptane, toluene, etc., preferably n-hexane or n-heptane;

[0032] S3: After cooling, the product obtained by reducing S2 is transferred to reactor II2 for decompression and distillation to remove the residual water-carrying agent. 24 g of anhydrous aluminum chloride is added, and 5.64 kg (1 equivalent) of diethyl phosphite is added dropwise while controlling the temperature within the range of 65-75°C. There is a violent exothermic phenomenon during the addition. After the addition is completed, the temperature is increased by 10°C every 30 minutes until the temperature reaches 105°C for maturation. The catalyst is solid Lewis acid: sodium bisulfate, strong acidic cationic resin, aluminum chloride, etc.

[0033] S4: Low boiling point products were removed under reduced pressure at 105°C and -0.095 MPa for 1 h. After cooling, 10.1 kg of dark amber product was obtained with a yield of 98% and a formaldehyde content of less than 0.1 mg / g.

[0034] The amount of the residual water-carrying agent in step S3 and the low-boiling substances in step S4 is very small and can be directly distilled into the buffer tank.

[0035] Example 2

[0036] Compared with Example 1, the present embodiment differs in that, in the present embodiment, a nitrogen vent valve is provided on the top of the vacuum buffer tank 5; a liquid level observation tube 10 is provided on one side of the water separator 7, and the vacuum pump 4 is a water circulation vacuum pump 4; the remaining structures are the same as those in Example 1.

[0037] In this embodiment, by providing a nitrogen vent valve at the top of the vacuum buffer tank 5, pressure can be increased. Adding nitrogen to the buffer tank increases the pressure of the stored fluid or gas, maintaining it within the desired normal pressure range. It also acts as a buffer. When the fluid or gas enters and exits the buffer tank, the nitrogen within the tank provides a buffer zone to balance pressure changes in the pipeline or device, thereby reducing excessive flow and maintaining a stable operating state. Furthermore, it provides protection and prevents losses. Due to the inertness of nitrogen, the fluid or gas can be protected from oxidation, corrosion, or contamination. Furthermore, nitrogen acts as a protective layer, preventing damage or loss due to leakage or splashing of fluid or gas along the pipeline or device during pipeline or device maintenance.

[0038] A liquid level observation tube 10 is provided on one side of the water separator 7 to observe the interface height of the water phase and the oil phase in the water separator 7 to prevent the liquid level of the water phase from being too high, causing the water phase to return to the reactor I1.

[0039] In this embodiment, the synthesis of low-formaldehyde-content N,N-bis(2-hydroxyethyl)aminomethylphosphonic acid diethyl ester is achieved by the following steps:

[0040] S1: Add 5.10 kg of diethanolamine and 1.52 kg of paraformaldehyde to the reactor I1, raise the temperature to 60°C and stir until the paraformaldehyde is completely dissolved and clear, then continue the reaction for 3 hours;

[0041] S2: After the reaction is completed, 8.0 kg of n-heptane is added, and the temperature is continued to be raised to 61 ° C. azeotropic reflux water separation is carried out to azeotropically separate the water produced by the reaction. After the temperature reaches 69 ° C, azeotropic drying is carried out until the water content is lower than 300 ppm, and 0.84 kg of water is separated. The material is transferred to the reactor II 2 through the metering pump 9 to reduce the pressure and evaporate the water-carrying agent, and the temperature is lowered to 65 ° C.

[0042] S3: Add 250g of strong acidic cation exchange resin to reactor II2, and control the temperature in the range of 65-75℃ to add 7.04kg of diethyl phosphite dropwise. There is a strong exothermic phenomenon during the addition. After the addition is completed, increase the temperature by 10℃ every 30min until the temperature reaches 105℃ for maturation.

[0043] S4: Remove the low boiling point under reduced pressure at 105°C and -0.095 MPa for 1 h. After cooling, 12.32 kg of dark amber product was obtained with a yield of 98% and a formaldehyde content of 0.070 mg / g.

[0044] Example 3

[0045] Compared with Example 2, the present embodiment differs in that, in the present embodiment, the bottom discharge port of the reactor I1 is connected to the top feed port of the reactor II2 via a metering pump 9; the waste liquid outlet of the water separator 7 is connected to a tubular sight glass 11 and a discharge valve 12; a sampling port and a temperature sensor I are provided in the reactor I1; a temperature sensor II and a pressure sensor II are provided in the reactor II2; the vacuum buffer tank 5 is provided with a pressure sensor I; a stop valve is provided between the vacuum buffer tank 5 and the vacuum pump 4, and the remaining structures are the same as those in Example 1.

[0046] In this embodiment, a temperature sensor 1 monitors the temperature in the reactor 11 in real time. An operator takes samples from the reactor through a sampling port to detect the reaction progress in the reactor 11. A tubular sight glass 11 is provided at the waste liquid outlet of the water separator 7. During discharge, the interface between the water phase and the oil phase is observed through the tubular sight glass 11, and the container is replaced in a timely manner to recycle the water-carrying agent in the oil phase separately.

[0047] A discharge valve 12 is provided at the waste liquid outlet of the water divider 7, and the discharge valve 12 is used to realize the opening and closing of the waste liquid outlet of the water divider 7;

[0048] The temperature and pressure in the reactor Ⅱ2 are monitored in real time by the temperature sensor Ⅱ and the pressure sensor Ⅱ, and the reaction conditions in the reactor Ⅱ2 are monitored in real time;

[0049] The pressure sensor 1 monitors the pressure in the vacuum buffer tank 5 in real time. When the pressure in the vacuum buffer tank 5 is too low, the vacuum pump 4 and the stop valve between the vacuum buffer tank 5 and the vacuum pump 4 are opened to pressurize the vacuum buffer tank 5.

[0050] In this embodiment, the synthesis of low-formaldehyde-content N,N-bis(2-hydroxyethyl)aminomethylphosphonic acid diethyl ester is achieved by the following steps:

[0051] S1: Add 4.28 kg of diethanolamine and 1.27 kg of paraformaldehyde to the reactor I1, raise the temperature to 60°C and stir until the paraformaldehyde is completely dissolved and clear, then continue the reaction for 2 hours;

[0052] S2: After the reaction is completed, 7.20 kg of n-hexane is added, and the temperature is continued to rise to 61 ° C. and refluxed to separate the water produced by the reaction. After the temperature reaches 69 ° C, azeotropic drying is carried out until the water content is lower than 300 ppm, and 0.78 kg of water is separated. The material is transferred to the reactor II 2 through the metering pump 9 to evaporate the water-carrying agent under reduced pressure and then cooled to 65 ° C.

[0053] S3: Add 25g of anhydrous aluminum sulfate to reactor II2, and control the temperature in the range of 65-75℃ to add 5.64kg of diethyl phosphite dropwise. There is a violent exothermic phenomenon during the addition. After the addition is completed, increase the temperature by 10℃ every 30min until the temperature reaches 105℃ for maturation.

[0054] S4: Remove the low boiling point under reduced pressure at 105°C and -0.095 MPa for 1 h. After cooling, 10 kg of dark amber product was obtained with a yield of 98% and a formaldehyde content of 0.080 mg / g.

[0055] It is understood that the present invention is described by way of certain embodiments, and those skilled in the art will appreciate that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. Furthermore, under the guidance of the present invention, these features and embodiments may be modified to suit specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are intended to be protected by the present invention.

Claims

1. A system for synthesizing diethyl N,N-bis(2-hydroxyethyl)aminomethylphosphonate with low formaldehyde content, characterized by: The invention comprises a reactor I (1) and a reactor II (2), both of which are jacketed reactors. The reactor I (1) and the reactor II (2) are respectively provided with a top feed port and a bottom discharge port. The bottom discharge port of the reactor I (1) is connected to the top feed port of the reactor II (2). A reflux cooling component is provided on the top of the reactor I (1). The bottom discharge port of the reactor II (2) is connected to a product storage tank (3). The reactor II (2) is connected to a vacuum pump (4). A vacuum buffer tank (5) is provided on the connecting pipe between the vacuum pump (4) and the reactor II (2).

2. The system for synthesizing low-formaldehyde-content N,N-bis(2-hydroxyethyl)aminomethylphosphonic acid diethyl ester according to claim 1, characterized in that: The reflux cooling assembly comprises a condenser I (6) and a water separator (7), wherein the inlet of the condenser I (6) is connected to the top reflux outlet of the reactor I (1), the top of the water separator (7) is provided with an inlet, the top side of the water separator (7) is provided with a reflux outlet, the bottom of the water separator (7) is provided with a waste liquid outlet, the outlet of the condenser I (6) is connected to the top inlet of the water separator (7), and the reflux outlet of the water separator (7) is connected to the reflux inlet of the top of the reactor.

3. The system for synthesizing low-formaldehyde-content N,N-bis(2-hydroxyethyl)aminomethylphosphonic acid diethyl ester according to claim 1, characterized in that: The jackets of the reactor I (1) and the reactor II (2) are respectively provided with a top steam inlet and a bottom steam outlet.

4. The system for synthesizing low-formaldehyde-content N,N-bis(2-hydroxyethyl)aminomethylphosphonic acid diethyl ester according to claim 1, characterized in that: A condenser II (8) is provided on the top of the reactor II (2), the inlet of the condenser II (8) is connected to the top of the reactor II (2), and the outlet of the condenser II (8) is connected to the vacuum buffer tank (5).

5. The system for synthesizing diethyl N,N-bis(2-hydroxyethyl)aminomethylphosphonate with low formaldehyde content according to claim 1, characterized in that: The bottom discharge port of the reactor I (1) and the top feed port of the reactor II (2) are connected via a metering pump (9).

6. The system for synthesizing diethyl N,N-bis(2-hydroxyethyl)aminomethylphosphonate with low formaldehyde content according to claim 2, characterized in that: A liquid level observation tube (10) is provided on one side of the water distributor (7); and a tubular sight glass (11) and a discharge valve (12) are provided at the waste liquid outlet of the water distributor (7).

7. The system for synthesizing diethyl N,N-bis(2-hydroxyethyl)aminomethylphosphonate with low formaldehyde content according to claim 1, characterized in that: The reactor I (1) is provided with a sampling port and a temperature sensor I; the reactor II (2) is provided with a temperature sensor II and a pressure sensor II.

8. The system for synthesizing diethyl N,N-bis(2-hydroxyethyl)aminomethylphosphonate with low formaldehyde content according to claim 1, characterized in that: The vacuum buffer tank (5) is provided with a pressure sensor I.

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