Preparation method and application of diethyl aluminum hypophosphite

Abstract

The invention belongs to the technical field of synthesis of diethyl aluminum hypophosphite, and particularly relates to a preparation method and application of diethyl aluminum hypophosphite. The preparation method of the diethyl aluminum hypophosphite comprises the following steps: mixing soluble hypophosphite and a first solvent in a reactor to obtain a soluble hypophosphite solution; replacing air in the reactor with nitrogen, and raising the temperature; ethylene is introduced into the soluble hypophosphite solution to obtain a reaction solution, then an initiator, a catalyst and the reaction solution are mixed and react to obtain a diethyl hypophosphite solution, and then a second solvent is added to obtain a diluted diethyl hypophosphite solution; the pH of the diluted diethyl hypophosphite solution is adjusted to be acidic, an aluminum sulfate aqueous solution is added, a reaction is conducted, and diethyl aluminum hypophosphite is prepared; the initiator comprises an oxidizing agent and a reducing agent. According to the method, the reaction temperature can be reduced to 22-50 DEG C, the energy consumption is reduced, the reaction efficiency can be improved, and the prepared diethyl aluminum hypophosphite is high in purity and high in yield.

Description

Technical Field

[0001] The invention belongs to the technical field of diethyl aluminum hypophosphite synthesis, and particularly relates to a preparation method and application of diethyl aluminum hypophosphite. Background Art

[0002] At present, polymer materials are widely used in industrial materials such as plastics, rubber and synthetic fibers, but these materials have the problem of flammability. Once burned, they often release a large amount of deadly toxic gases. Therefore, adding flame retardants to these polymer materials to give them properties such as flame retardancy, self-extinguishing and smoke suppression is one of the effective ways to improve their safety performance. Among many flame retardants, diethyl aluminum hypophosphite is highly regarded for its high phosphorus content of 23.85%. The dehydration effect produced by thermal decomposition promotes the formation of a carbon film on the polymer surface, thereby exerting an excellent flame retardant effect.

[0003] At present, the preparation of diethylaluminum hypophosphite mainly relies on two traditional methods: free radical addition method and alkylation method of elemental yellow phosphorus. However, these traditional methods have many disadvantages, such as high reaction temperature (generally above 120°C), unsatisfactory product purity and yield, low efficiency of gas-liquid heterogeneous reaction, long reaction time (generally more than 6 hours), and the generation of difficult-to-treat waste, causing serious pollution to the environment.

[0004] The free radical addition reaction process is relatively simple, and basically all of them use hypophosphite and ethylene for free radical addition reaction to produce diethyl hypophosphite. Then use aluminum sulfate to perform double decomposition reaction to generate diethyl aluminum hypophosphite. At present, all studies are to make improvements in initiators or reaction media in the hope of improving reaction efficiency, reducing reaction difficulty, and improving product purity. Jiangsu Liside New Materials Co., Ltd. proposed an innovative method in CN103951699A, using organic solvents such as butanol as additives under low-pressure reaction conditions. This method can significantly reduce the pressure of the reaction and improve the safety and operability of the reaction process. Using butanol as a solvent, the system can increase the solubility of ethylene, but the method still generates free radicals through the thermal decomposition of the initiator, thereby initiating the reaction, so the reaction still needs to be carried out under higher temperature (90-110 ° C) conditions, and the solubility of ethylene in the reaction solution at this temperature is still limited, which limits its application in industrial production to a certain extent. Hubei Hongjia Chemical Co., Ltd. proposed a new method for synthesizing diethylaluminum hypophosphite under ultraviolet light irradiation at normal pressure and low temperature in CN109608491A, but this method is difficult to implement in actual industrial production, and the light conversion efficiency is usually low. Once the equipment is enlarged, it will bring many practical problems, such as the refraction and scattering of light caused by bubbles caused by stirring and aeration devices, and it is difficult to initiate the reaction in the center of the reactor, resulting in low reaction efficiency, low purity, etc. Due to the low efficiency of light initiation, the concentration of hypophosphite is also low when preparing, resulting in low batch output.

[0005] Therefore, it is of great significance to provide a method for preparing diethyl aluminum hypophosphite with high reaction efficiency, low reaction temperature, scalable production, high purity and high yield of diethyl aluminum hypophosphite. Summary of the invention

[0006] The present invention aims to solve one or more technical problems existing in the above-mentioned prior art and at least provide a beneficial choice. Specifically, the present invention provides a method for preparing diethyl aluminum hypophosphite, which has high reaction efficiency, low reaction temperature, can be scaled up for production, and the prepared diethyl aluminum hypophosphite has high purity and high yield.

[0007] The inventive concept of the present invention: the preparation method of diethyl aluminum hypophosphite of the present invention is to mix a soluble hypophosphite with a first solvent in a reactor to obtain a soluble hypophosphite solution; replace the air in the reactor with nitrogen and heat it; pass ethylene into the soluble hypophosphite solution in the reactor to obtain a reaction solution, then mix an initiator, a catalyst and the reaction solution, react to obtain a diethyl hypophosphite solution, and then add a second solvent to obtain a diluted diethyl hypophosphite solution; adjust the pH of the diluted diethyl hypophosphite solution to acidic, add an aluminum sulfate aqueous solution, react to obtain the diethyl aluminum hypophosphite; the initiator includes an oxidant and a reductant. The present invention adopts a redox free radical initiation system under the action of a catalyst, and the initiator includes an oxidant and a reductant, which can effectively reduce the reaction temperature to 22-50°C, improve the reaction efficiency, and the prepared diethyl aluminum hypophosphite has high purity and high yield; in addition, it can also reduce energy consumption, reduce production costs, and reduce environmental pollution.

[0008] Therefore, the first aspect of the present invention provides a method for preparing diethylaluminum hypophosphite.

[0009] Specifically, the preparation method of diethyl aluminum hypophosphite comprises the following steps:

[0010] (1) mixing a soluble hypophosphite with a first solvent in a reactor to obtain a soluble hypophosphite solution;

[0011] (2) replacing the air in the reactor with nitrogen and then heating;

[0012] (3) introducing ethylene into the soluble hypophosphite solution in the reactor to obtain a reaction solution, and then mixing an initiator, a catalyst and the reaction solution to react to obtain a diethyl hypophosphite solution; and then adding a second solvent to the diethyl hypophosphite solution to obtain a diluted diethyl hypophosphite solution;

[0013] (4) adjusting the pH of the diluted diethyl hypophosphite solution obtained in step (3) to acidic, adding an aqueous solution of aluminum sulfate, reacting, and obtaining the diethyl aluminum hypophosphite;

[0014] The initiator includes an oxidizing agent and a reducing agent.

[0015] Preferably, the oxidant includes at least one of ammonium persulfate, potassium persulfate, sodium persulfate, potassium monopersulfate, sodium monopersulfate and ammonium monopersulfate; the reducing agent includes at least one of sodium sulfite, sodium bisulfite, potassium sulfite and potassium bisulfite.

[0016] Specifically, the initiator is a redox free radical initiation system composed of an oxidant and a reductant.

[0017] Preferably, the mass ratio of the initiator to the soluble hypophosphite is (0.27-1.1):100; further preferably, the mass ratio of the initiator to the soluble hypophosphite is (0.3-1):100.

[0018] Preferably, the concentration of the aqueous solution of the oxidant is 0.1-2.0 mol / L; further preferably, the concentration of the aqueous solution of the oxidant is 0.1-1.8 mol / L.

[0019] Preferably, the concentration of the aqueous solution of the reducing agent is 0.1-2.0 mol / L; further preferably, the concentration of the aqueous solution of the reducing agent is 0.1-1.8 mol / L.

[0020] Preferably, in step (1), the soluble hypophosphite includes at least one of sodium hypophosphite, potassium hypophosphite and ammonium hypophosphite.

[0021] Preferably, in step (1), the concentration of the soluble hypophosphite solution is 27-55 wt %; further preferably, in step (1), the concentration of the soluble hypophosphite solution is 30-50 wt %.

[0022] Preferably, in step (1), the first solvent comprises water and an organic solvent.

[0023] Preferably, the organic solvent includes at least one of dioxane, dimethyl sulfoxide, acetonitrile, dimethylformamide, tetrahydrofuran and acetone.

[0024] Preferably, in the first solvent, the mass proportion of water is 1-99%; further preferably, in the first solvent, the mass proportion of water is 20-80%.

[0025] Preferably, in step (2), during the replacement, the pressure in the reactor is maintained at 0.45-1.1 MPa; further preferably, in step (2), during the replacement, the pressure in the reactor is maintained at 0.5-1.0 MPa.

[0026] Preferably, in step (2), the heating temperature is 22-50°C; further preferably, in step (2), the heating temperature is 25-50°C.

[0027] Preferably, in step (3), the mass of ethylene introduced per hour is 13-60 g per mole of soluble hypophosphite in the reaction solution; further preferably, in step (3), the mass of ethylene introduced per hour is 15-56 g per mole of soluble hypophosphite in the reaction solution.

[0028] Preferably, in step (3), after the ethylene is introduced, the pressure in the reactor is maintained at 0.45-1.1 MPa, and the temperature of the reaction liquid is maintained at 22-50°C; further preferably, in step (3), after the ethylene is introduced, the pressure in the reactor is maintained at 0.5-1.0 MPa, and the temperature of the reaction liquid is maintained at 25-50°C.

[0029] Preferably, in step (3), the catalyst comprises nitrogen-doped carbon quantum dots.

[0030] Preferably, in step (3), the mass ratio of the catalyst to the soluble hypophosphite is (0.09-2.2):100; further preferably, in step (3), the mass ratio of the catalyst to the soluble hypophosphite is (0.1-2):100.

[0031] Preferably, in step (3), the reaction temperature is 22-50°C, and the reaction time is 0.9-2.5h; further preferably, in step (3), the reaction temperature is 25-50°C, and the reaction time is 1-2h.

[0032] Preferably, in step (3), the second solvent comprises water; further preferably, the water is distilled water.

[0033] Preferably, in step (3), after adding the second solvent, the concentration of the diethyl hypophosphite solution is 18-55% of the original concentration; further preferably, in step (3), after adding the second solvent, the concentration of the diethyl hypophosphite solution is 20-50% of the original concentration.

[0034] Preferably, in step (3), after adding the second solvent, the temperature is raised to obtain a diethyl hypophosphite solution, and the heating temperature is 70-95°C; further preferably, in step (3), after adding the second solvent, the temperature is raised to obtain a diethyl hypophosphite solution, and the heating temperature is 75-90°C.

[0035] Preferably, in step (4), after adjusting the pH to acidic, an aqueous solution of aluminum sulfate is added dropwise to obtain a mixed solution, which is then reacted, and the precipitate is taken and dried to obtain the diethyl aluminum hypophosphite.

[0036] Preferably, the pH is adjusted using an acid, which comprises sulfuric acid.

[0037] Preferably, the pH is 2-4; more preferably, the pH is 2-3.

[0038] Preferably, the aluminum sulfate aqueous solution is a 22-60wt% Al2(SO4)3·18H2O aqueous solution; further preferably, the aluminum sulfate aqueous solution is a 25-55wt% Al2(SO4)3·18H2O aqueous solution.

[0039] Preferably, the mass of Al2(SO4)3·18H2O aqueous solution added dropwise per hour is 60-380 g per mole of diethyl hypophosphite in the mixed solution; further preferably, the mass of Al2(SO4)3·18H2O aqueous solution added dropwise per hour is 70-350 g per mole of diethyl hypophosphite in the mixed solution.

[0040] Preferably, the dropping time is 14-65 min; more preferably, the dropping time is 15-60 min.

[0041] Preferably, the reaction time is 1.0-2.0 h; further preferably, the reaction time is 1.0-1.5 h.

[0042] The second aspect of the present invention provides an application of the preparation method of diethylaluminum hypophosphite described in the first aspect of the present invention in the field of flame retardancy.

[0043] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0044] (1) The present invention uses nitrogen-doped carbon quantum dots as catalysts. Under the action of a redox free radical initiation system including an oxidant and a reductant, the reaction temperature can be effectively reduced to 22-50°C, thereby improving the reaction efficiency. The prepared diethylaluminum hypophosphite has high purity and high yield. In addition, it can also reduce energy consumption, production costs, and environmental pollution.

[0045] (2) The present invention uses a gaseous organic solvent miscible with water as a reaction solvent, which can not only increase the concentration of ethylene in the reaction solution, but also maintain the solubility of the soluble hypophosphite in the reaction solution, which not only simplifies the reaction steps but also improves the efficiency and stability of the reaction system. DETAILED DESCRIPTION

[0046] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0047] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0048] The nitrogen-doped carbon quantum dots in the examples and comparative examples of the present invention were purchased from Xi'an Qiyue Biotechnology Co., Ltd.

[0049] Example 1

[0050] A method for preparing diethyl aluminum hypophosphite comprises the following steps:

[0051] (1) adding soluble sodium hypophosphite, water and acetonitrile to a reactor and mixing and stirring to obtain a soluble sodium hypophosphite solution with a concentration of 30 wt %, wherein the mass ratio of water to acetonitrile is 2:8; replacing the air in the reactor with nitrogen, maintaining the reactor pressure at 0.7 MPa, replacing three times, and heating to 50° C.;

[0052] (2) ethylene was introduced into the sodium hypophosphite solution in the reactor at a rate of 56 g per hour per mole of soluble sodium hypophosphite in the reaction solution, the pressure in the reactor was maintained at 0.7 MPa, and the temperature of the reaction solution was maintained at 50° C.;

[0053] (3) After exhausting the nitrogen in the kettle, a 1 mol / L sodium persulfate, a 1 mol / L sodium bisulfite and a nitrogen-doped carbon quantum dot aqueous solution accounting for 0.1 wt% of the mass ratio of soluble sodium hypophosphite are dripped into the reactor, wherein the total mass of the initiator system is 0.3% of the mass of the soluble sodium hypophosphite, and the reaction is maintained at 50° C. for 1 hour to obtain an intermediate product, and distilled water is added to the solution to dilute the solution to 50% of the original concentration and then heated to 75° C. to obtain a diethyl sodium hypophosphite solution;

[0054] (4) After adjusting the pH value of the sodium diethyl hypophosphite solution to 2 with sulfuric acid, 70 g of an Al2(SO4)3·18H2O aqueous solution with a concentration of 25 wt% per mole of sodium diethyl hypophosphite was added dropwise every hour for 60 min. After the addition was completed, the mixture was reacted for 1 hour until completion to obtain a white precipitate, which was cooled to below 50° C., filtered, and the filter cake was washed with distilled water and then heated and dried under vacuum to obtain a white powdery solid, i.e., diethyl aluminum hypophosphite. The solid product yield was 99.21%. The solid product yield was calculated as follows: based on the input of 1 mol of soluble sodium hypophosphite, the reaction was carried out at a theoretical 100% rate to obtain 1 mol of diethyl sodium hypophosphite, which was then reacted with aluminum sulfate at a theoretical 100% rate to generate 0.33 mol of diethyl aluminum hypophosphite. The molecular weight of diethyl aluminum hypophosphite was 390. Assuming that n moles of aluminum hypophosphite are added, the solid product yield = (actual solid product weight / (0.33n×390))×100%. According to nuclear magnetic resonance phosphorus spectroscopy (PNMR) analysis, the purity of diethyl aluminum hypophosphite is 99.85%.

[0055] Example 2

[0056] A method for preparing diethyl aluminum hypophosphite comprises the following steps:

[0057] (1) adding soluble potassium hypophosphite, water and dimethyl sulfoxide into a reactor and mixing and stirring to obtain a soluble potassium hypophosphite solution with a concentration of 40 wt %, wherein the mass ratio of water to dimethyl sulfoxide is 4:6; replacing the air in the reactor with nitrogen, maintaining the reactor pressure at 1.0 MPa, replacing three times, and heating to 35° C.;

[0058] (2) ethylene was introduced into the potassium hypophosphite solution in the reactor at a rate of 15 g per hour per mole of potassium hypophosphite in the reaction solution, the pressure in the reactor was maintained at 1.0 MPa, and the temperature of the reaction solution was maintained at 35° C.;

[0059] (3) After exhausting the nitrogen in the kettle, 0.1 mol / L potassium persulfate, 0.1 mol / L potassium bisulfite and a nitrogen-doped carbon quantum dot aqueous solution accounting for 0.5 wt% of the mass ratio of soluble potassium hypophosphite are dripped into the reactor, wherein the total mass of the initiator system is 1% of the total mass of the soluble potassium hypophosphite, and the reaction is maintained at 35° C. for 1.5 h to obtain an intermediate product, and distilled water is added to the solution to dilute the solution to 40% of the original concentration and then heated to 80° C. to obtain a diethyl potassium hypophosphite solution;

[0060] (4) After adjusting the pH value of the potassium diethyl hypophosphite solution to 2 with sulfuric acid, 350 g of an Al2(SO4)3·18H2O aqueous solution with a concentration of 35 wt% per mole of potassium diethyl hypophosphite was added dropwise every hour for 10 min. After the addition was completed, the mixture was reacted for 1.5 hours to obtain a white precipitate, which was cooled to below 50° C., filtered, and the filter cake was washed with distilled water and then heated and dried under vacuum to obtain a white powdery solid, i.e., diethyl aluminum hypophosphite. The solid product yield was 98.96% (the solid product yield was calculated in the same manner as in Example 1). According to PNMR analysis, the purity of the diethyl aluminum hypophosphite was 99.16%.

[0061] Example 3

[0062] A method for preparing diethyl aluminum hypophosphite comprises the following steps:

[0063] (1) adding soluble sodium hypophosphite, water, acetonitrile and dimethyl sulfoxide into a reactor and mixing and stirring to obtain a soluble sodium hypophosphite solution with a concentration of 50 wt%, wherein the mass ratio of water, acetonitrile and dimethyl sulfoxide is 3:6:1; replacing the air in the reactor with nitrogen, maintaining the pressure of the reactor at 0.5 MPa, replacing three times, and heating to 40° C.;

[0064] (2) introducing ethylene into the soluble sodium hypophosphite solution in the reactor at a rate of 20 g per hour per mole of soluble sodium hypophosphite in the reaction solution, maintaining the pressure in the reactor at 0.5 MPa and the temperature of the reaction solution at 40° C.;

[0065] (3) After exhausting the nitrogen in the kettle, 1.8 mol / L sodium persulfate, 1.8 mol / L sodium bisulfite and a nitrogen-doped carbon quantum dot aqueous solution accounting for 2 wt% of the mass ratio of soluble sodium hypophosphite are dripped into the reactor, wherein the total mass of the initiator system is 0.8% of the mass of the soluble sodium hypophosphite, and the reaction is maintained at 40° C. for 1.5 h to obtain an intermediate product, and distilled water is added to the solution to dilute the reaction solution to 45% of the original concentration and then heated to 85° C. to obtain a diethyl sodium hypophosphite solution;

[0066] (4) After adjusting the pH value of the sodium diethyl hypophosphite solution to 3 with sulfuric acid, 300 g of an Al2(SO4)3·18H2O aqueous solution with a concentration of 45 wt% per mole of sodium diethyl hypophosphite was added dropwise per hour for 15 min. After the addition was completed, the mixture was reacted for 1.5 hours to obtain a white precipitate, which was cooled to below 50° C., filtered, and the filter cake was washed with distilled water and then heated and dried under vacuum to obtain a white powdery solid, i.e., diethyl aluminum hypophosphite. The solid product yield was 98.65% (the solid product yield was calculated in the same manner as in Example 1). According to PNMR analysis, the purity of the diethyl aluminum hypophosphite was 99.77%.

[0067] Example 4

[0068] A method for preparing diethyl aluminum hypophosphite comprises the following steps:

[0069] (1) adding soluble ammonium hypophosphite, water and dimethyl sulfoxide into a reactor and mixing and stirring to obtain a soluble sodium hypophosphite solution with a concentration of 30 wt %, wherein the mass ratio of water to dimethyl sulfoxide is 7:3; replacing the air in the reactor with nitrogen, maintaining the reactor pressure at 1.0 MPa, replacing three times, and heating to 30° C.;

[0070] (2) ethylene was introduced into the soluble ammonium hypophosphite solution in the reactor at a rate of 30 g per hour per mole of ammonium hypophosphite in the reaction solution, the pressure in the reactor was maintained at 1.0 MPa, and the temperature of the reaction solution was maintained at 30° C.;

[0071] (3) After exhausting the nitrogen in the kettle, a 1.3 mol / L sodium persulfate, a 1.3 mol / L sodium bisulfite and a nitrogen-doped carbon quantum dot aqueous solution accounting for 0.5 wt% of the mass ratio of soluble hypophosphite are dripped into the reactor, wherein the total mass of the initiator system is 0.5% of the mass of the soluble sodium hypophosphite, and the reaction is maintained at 30° C. for 2 h to obtain an intermediate product, and distilled water is added to the solution to dilute the reaction solution to 35% of the original concentration and then heated to 90° C. to obtain a diethylammonium hypophosphite solution;

[0072] (4) After adjusting the pH value of the diethylammonium hypophosphite solution to 2 with sulfuric acid, 100 g of an Al2(SO4)3·18H2O aqueous solution with a concentration of 40 wt% per mole of diethylammonium hypophosphite was added dropwise every hour for 50 min. After the addition was completed, the mixture was reacted for 1 hour to obtain a white precipitate, which was cooled to below 50° C. The precipitate was filtered, the filter cake was washed with distilled water, and then heated and dried under vacuum to obtain a white powdery solid, i.e., diethylaluminum hypophosphite. The solid product yield was 99.23% (the solid product yield was calculated in the same manner as in Example 1). According to PNMR analysis, the purity of the diethylaluminum hypophosphite was 98.91%.

[0073] Example 5

[0074] A method for preparing diethyl aluminum hypophosphite comprises the following steps:

[0075] (1) adding soluble sodium hypophosphite, water and dioxane into a reactor and mixing and stirring to obtain a soluble sodium hypophosphite solution with a concentration of 30 wt %, wherein the mass ratio of water to dioxane is 3:7; replacing the air in the reactor with nitrogen, maintaining the reactor pressure at 0.8 MPa, replacing three times, and heating to 30° C.;

[0076] (2) ethylene is introduced into the soluble sodium hypophosphite solution in the reactor at a rate of 40 g per hour per mole of soluble sodium hypophosphite in the reaction solution, the pressure in the reactor is maintained at 0.8 MPa, and the temperature of the reaction solution is maintained at 30° C.;

[0077] (3) After exhausting the nitrogen in the kettle, 0.8 mol / L sodium persulfate, 0.8 mol / L sodium bisulfite and a nitrogen-doped carbon quantum dot aqueous solution accounting for 1 wt% of the mass ratio of soluble sodium hypophosphite are dripped into the reactor, wherein the total mass of the initiator system is 0.7% of the mass of the soluble sodium hypophosphite, and the reaction is maintained at 30° C. for 1.5 h to obtain an intermediate product, and distilled water is added to the solution to dilute the reaction solution to 25% of the original concentration and then heated to 75° C. to obtain a diethyl sodium hypophosphite solution;

[0078] (4) After adjusting the pH value of the sodium diethyl hypophosphite solution to 2 with sulfuric acid, 150 g of an Al2(SO4)3·18H2O aqueous solution with a concentration of 55 wt% per mole of sodium diethyl hypophosphite was added dropwise every hour for 25 min. After the addition was complete, the mixture was reacted for 1.2 hours to obtain a white precipitate, which was cooled to below 50° C., filtered, and the filter cake was washed with distilled water and then heated and dried under vacuum to obtain a white powdery solid, i.e., 126.98 g of diethyl aluminum hypophosphite. The solid product yield was 98.66% (the solid product yield was calculated in the same manner as in Example 1). According to PNMR analysis, the purity of the diethyl aluminum hypophosphite was 99.76%.

[0079] Example 6

[0080] A method for preparing diethyl aluminum hypophosphite comprises the following steps:

[0081] (1) adding soluble potassium hypophosphite, water and dimethylformamide to a reactor and mixing and stirring to obtain a soluble potassium hypophosphite solution with a concentration of 30 wt %, wherein the mass ratio of water to dimethylformamide is 4:6; replacing the air in the reactor with nitrogen, maintaining the reactor pressure at 0.6 MPa, replacing three times, and heating to 30° C.;

[0082] (2) introducing ethylene into the soluble potassium hypophosphite solution in the reactor at a rate of 15 g per hour per mole of soluble potassium hypophosphite in the reaction solution, maintaining the pressure in the reactor at 0.6 MPa and the temperature of the reaction solution at 30° C.;

[0083] (3) After exhausting the nitrogen in the kettle, 0.15 mol / L potassium persulfate, 0.15 mol / L potassium bisulfite and a nitrogen-doped carbon quantum dot aqueous solution accounting for 1.5 wt% of the mass ratio of soluble potassium hypophosphite are dripped into the reactor, wherein the total mass of the initiator system is 0.5% of the mass of the soluble sodium hypophosphite, and the reaction is maintained at 30° C. for 2 h to obtain an intermediate product, and distilled water is added to the solution to dilute the reaction solution to 35% of the original concentration and then heated to 85° C. to obtain a diethyl potassium hypophosphite solution;

[0084] (4) After adjusting the pH value of the potassium diethyl hypophosphite solution to 2 with sulfuric acid, 200 g of an Al2(SO4)3·18H2O aqueous solution with a concentration of 50 wt% per mole of potassium diethyl hypophosphite was added dropwise every hour for 20 min. After the addition was completed, the mixture was reacted for 1.5 hours to obtain a white precipitate, which was cooled to below 50° C., filtered, and the filter cake was washed with distilled water and then heated and dried under vacuum to obtain a white powdery solid, i.e., diethyl aluminum hypophosphite. The solid product yield was 99.32% (the solid product yield was calculated in the same manner as in Example 1). According to PNMR analysis, the purity of the diethyl aluminum hypophosphite was 99.63%.

[0085] Example 7

[0086] A method for preparing diethyl aluminum hypophosphite comprises the following steps:

[0087] (1) adding soluble sodium hypophosphite, water and acetonitrile to a reactor and mixing and stirring to obtain a soluble sodium hypophosphite solution with a concentration of 40 wt %, wherein the mass ratio of water to acetonitrile is 5:5; replacing the air in the reactor with nitrogen, maintaining the reactor pressure at 0.9 MPa, replacing three times, and heating to 30° C.;

[0088] (2) ethylene is introduced into the soluble sodium hypophosphite solution in the reactor at a rate of 25 g per hour per mole of soluble sodium hypophosphite in the reaction solution, the pressure in the reactor is maintained at 0.9 MPa, and the temperature of the reaction solution is maintained at 30° C.;

[0089] (3) After exhausting the nitrogen in the kettle, 1.2 mol / L sodium persulfate, 1.2 mol / L sodium bisulfite and a nitrogen-doped carbon quantum dot aqueous solution accounting for 1 wt% of the mass ratio of soluble sodium hypophosphite are dripped into the reactor, wherein the total mass of the initiator system is 0.8% of the mass of the soluble sodium hypophosphite, and the reaction is maintained at 50° C. for 1 hour to obtain an intermediate product, and distilled water is added to the solution to dilute the reaction solution to 20% of the original concentration and then heated to 80° C. to obtain a diethyl sodium hypophosphite solution;

[0090] (4) After adjusting the pH value of the sodium diethyl hypophosphite solution to 2 with sulfuric acid, 200 g of an Al2(SO4)3·18H2O aqueous solution with a concentration of 45 wt% per mole of sodium diethyl hypophosphite was added dropwise every hour for 25 min. After the addition was completed, the mixture was reacted for 1 hour to obtain a white precipitate, which was cooled to below 50° C., filtered, and the filter cake was washed with distilled water and then heated and dried under vacuum to obtain a white powdery solid, i.e., diethyl aluminum hypophosphite. The solid product yield was 99.36% (the solid product yield was calculated in the same manner as in Example 1). According to PNMR analysis, the purity of the diethyl aluminum hypophosphite was 99.48%.

[0091] Example 8

[0092] A method for preparing diethyl aluminum hypophosphite comprises the following steps:

[0093] (1) adding soluble sodium hypophosphite, water, acetonitrile and dimethylformamide into a reactor and mixing and stirring to obtain a soluble sodium hypophosphite solution with a concentration of 30 wt %, wherein the mass ratio of water, acetonitrile and dimethylformamide is 4:3:3; replacing the air in the reactor with nitrogen, maintaining the pressure of the reactor at 0.8 MPa, replacing three times, and heating to 40° C.;

[0094] (2) introducing ethylene into the soluble sodium hypophosphite solution in the reactor at a rate of 20 g per hour per mole of soluble sodium hypophosphite in the reaction solution, maintaining the pressure in the reactor at 0.8 MPa and the temperature of the reaction solution at 40° C.;

[0095] (3) After exhausting the nitrogen in the kettle, 1.5 mol / L sodium persulfate, 1.5 mol / L sodium bisulfite and a nitrogen-doped carbon quantum dot aqueous solution accounting for 1 wt% of the mass ratio of soluble sodium hypophosphite are dripped into the reactor, wherein the total mass of the initiator system is 0.6% of the mass of sodium hypophosphite, and the reaction is maintained at 40° C. for 1 hour to obtain an intermediate product, and distilled water is added to the solution to dilute the reaction solution to 30% of the original concentration and then heated to 75° C. to obtain a diethyl sodium hypophosphite solution;

[0096] (4) After adjusting the pH value of the sodium diethyl hypophosphite solution to 2 with sulfuric acid, 100 g of an Al2(SO4)3·18H2O aqueous solution with a concentration of 45 wt% per mole of sodium diethyl hypophosphite was added dropwise every hour for 50 min. After the addition was completed, the mixture was reacted for 1 hour to obtain a white precipitate. The mixture was cooled to below 50° C., filtered, and the filter cake was washed with distilled water and then heated and dried under vacuum to obtain a white powdery solid, i.e., diethyl aluminum hypophosphite. The solid product yield was 99.17% (the solid product yield was calculated in the same manner as in Example 1). The purity of the diethyl aluminum hypophosphite was 99.48% as determined by PNMR analysis.

[0097] Comparative Example 1

[0098] The difference between Comparative Example 1 and Example 1 is that in step (3) of Comparative Example 1, no nitrogen-doped carbon quantum dot aqueous solution is added, and the rest is the same as in Example 1, to obtain a solid product, i.e., diethyl aluminum hypophosphite, with a solid product yield of 98.21% (the calculation method of the solid product yield is the same as in Example 1). According to PNMR analysis, the purity of diethyl aluminum hypophosphite is 31.03%.

[0099] Comparative Example 2

[0100] The difference between Comparative Example 2 and Example 1 is that in Comparative Example 2, the initiator system of step (3) does not contain an aqueous sodium bisulfate solution, but only contains an aqueous sodium persulfate solution with a concentration of 1 mol / L. The other conditions are the same as those of Example 1. After 1 hour, it is found that the ethylene consumption is substantially zero, indicating that the reaction has not been initiated.

[0101] In summary, the present invention uses nitrogen-doped carbon quantum dots as catalysts, and under the action of a redox free radical initiation system composed of an oxidant and a reductant, the reaction temperature can be effectively reduced to 25-50°C, the reaction efficiency can be improved, and the prepared diethylaluminum hypophosphite has high purity and high yield; in addition, energy consumption can be reduced, production costs can be reduced, and environmental pollution can be reduced. In addition, the present invention uses a gaseous organic solvent miscible with water as a reaction solvent, which can increase the concentration of ethylene in the reaction solution, while maintaining the solubility of soluble hypophosphite in the reaction solution, which not only simplifies the reaction steps, but also improves the efficiency and stability of the reaction system.

[0102] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing diethyl aluminum hypophosphite, characterized in that: The following steps are involved: (1) mixing a soluble hypophosphite with a first solvent in a reactor to obtain a soluble hypophosphite solution; (2) replacing the air in the reactor with nitrogen and raising the temperature; (3) introducing ethylene into the soluble hypophosphite solution in the reactor to obtain a reaction solution, and then mixing an initiator, a catalyst and the reaction solution to react to obtain a diethyl hypophosphite solution; and then adding a second solvent to the diethyl hypophosphite solution to obtain a diluted diethyl hypophosphite solution; (4) adjusting the pH of the diluted diethyl hypophosphite solution obtained in step (3) to acidic, adding an aqueous solution of aluminum sulfate, reacting, and obtaining the diethyl aluminum hypophosphite; The initiator includes an oxidizing agent and a reducing agent.

2. The preparation method according to claim 1, characterized in that: The oxidant includes at least one of ammonium persulfate, potassium persulfate, sodium persulfate, potassium monopersulfate, sodium monopersulfate and ammonium monopersulfate; the reducing agent includes at least one of sodium sulfite, sodium bisulfite, potassium sulfite and potassium bisulfite; and / or the mass ratio of the initiator to the soluble hypophosphite is (0.27-1.1):

100.

3. The preparation method according to claim 1, characterized in that: In step (1), the soluble hypophosphite includes at least one of sodium hypophosphite, potassium hypophosphite and ammonium hypophosphite; and / or the first solvent includes water and an organic solvent.

4. The preparation method according to claim 3, characterized in that: The concentration of the soluble hypophosphite solution is 27-55wt%; and / or the organic solvent includes at least one of dioxane, dimethyl sulfoxide, acetonitrile, dimethylformamide, tetrahydrofuran, and acetone; and / or, in the first solvent, the mass proportion of water is 1-99%.

5. The preparation method according to claim 1, characterized in that: In step (2), during the replacement, the pressure in the reactor is maintained at 0.45-1.1 MPa; and / or the heating temperature is 22-50°C.

6. The preparation method according to claim 1, characterized in that: In step (3), the mass of ethylene introduced per hour is 13-60 g per mole of soluble hypophosphite in the reaction solution; and / or, after the ethylene is introduced, the pressure in the reactor is maintained at 0.45-1.1 MPa and the temperature of the reaction solution is maintained at 22-50°C.

7. The preparation method according to claim 1, characterized in that: In step (3), the catalyst comprises nitrogen-doped carbon quantum dots; And / or, the mass ratio of the catalyst to the soluble hypophosphite is (0.09-2.2):100; And / or, the reaction temperature is 22-50°C, and the reaction time is 0.9-2.5h; and / or, the second solvent comprises water; and / or, after adding the second solvent, the concentration of the diethyl hypophosphite solution is 18-55% of the original concentration; And / or, after adding the second solvent, heating is performed to obtain a diethyl hypophosphite solution, and the heating temperature is 70-95°C.

8. The preparation method according to claim 1, characterized in that: In step (4), after adjusting the pH to acidic, an aqueous solution of aluminum sulfate is added dropwise to obtain a mixed solution, which is then reacted, and the precipitate is taken and dried to obtain the diethyl aluminum hypophosphite.

9. The preparation method according to claim 8, characterized in that: The aluminum sulfate aqueous solution is a 22-60wt% Al2(SO4)3·18H2O aqueous solution; and / or, relative to each mole of diethyl hypophosphite in the mixed solution, the mass of the Al2(SO4)3·18H2O aqueous solution added dropwise per hour is 60-380g; and / or, the dropping time is 14-65min; and / or, the reaction time is 1.0-2.0h.

10. Application of the preparation method according to any one of claims 1 to 9 in the field of flame retardancy.