Process for the preparation of an azodicarbonamide

Abstract

The application provides a preparation method of azodicarbonamide, comprising the following steps: S1, uniformly mixing hydrogen peroxide solution with a stabilizer and a cocatalyst to obtain a first reaction solution; S2, mixing biurea, water and a catalyst to obtain a second reaction suspension; S3, dropwise adding the preheated first reaction solution into the second reaction suspension to perform an oxidation reaction, and obtaining azodicarbonamide after the reaction is completed; the stabilizer in the step S1 is one or more of 1,3-diamino-2-hydroxypropane-N,N,N',N'-tetraacetic acid, 8-hydroxyquinoline, sodium dihydrogen pyrophosphate and nitrilotrimethylene phosphoric acid. In the application, the selection of the hydrogen peroxide stabilizer and the cocatalyst can reduce the decomposition speed of hydrogen peroxide and improve the utilization rate of hydrogen peroxide, so that the loss of raw materials is reduced, the cost of raw materials is reduced, and the production profit is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fine chemical industry, in particular to a preparation method of azodicarbonamide. BACKGROUND

[0002] Azodicarbonamide (ADC foaming agent for short) has the molecular formula (H2NOCN=NCONH2) and is a light yellow powder. ADC foaming agent is non-toxic, odorless, non-polluting, non-discoloring and non-flammable. It is soluble in dimethyl sulfoxide, dimethylformamide and alkaline solution, and insoluble in acid, alcohol, ketone, benzene, gasoline and water. The decomposition temperature range is short, the reaction is sensitive, and the gas is not easy to lose during use. The decomposition gas is composed of nitrogen, carbon monoxide, carbon dioxide and a small amount of ammonia, and the gas generation amount is ≥200ml / g, which is a good foaming agent. ADC foaming agent is the most widely used high-efficiency foaming agent, which can be used as a foaming agent for polyvinyl chloride, polyethylene, polypropylene, polyamide 11, neoprene, acetonitrile rubber, butyl rubber, butadiene styrene rubber and silicone rubber, and can be used for normal pressure foaming and pressurized foaming.

[0003] At present, the industrial ADC foaming agent is generally produced by the chlorination method. This method has low cost, but the reaction is violent, and it is difficult to control the end point. When the chlorine is excessive, the decomposition of ADC foaming agent is often caused, and the actual yield of the product is reduced. At the same time, 3t of hydrochloric acid (14%-17%) is generated for the preparation of 1t of ADC foaming agent, which is harsh for the requirements of equipment and environmental protection.

[0004] The preparation of ADC foaming agent by hydrogen peroxide method is to oxidize biurea under the action of a catalyst using hydrogen peroxide, and the yield of ADC foaming agent can reach 96%. However, an excessive amount of hydrogen peroxide is generally used, which is usually 105%-110% of the reaction equivalent. The utilization rate of hydrogen peroxide is only 88%-92%, and a large amount of hydrogen peroxide is wasted.

[0005] How to improve the utilization rate of hydrogen peroxide in the synthesis reaction of ADC foaming agent has become a problem to be solved. SUMMARY

[0006] Therefore, the present application aims to provide a preparation method of azodicarbonamide to overcome the problem of low utilization rate of hydrogen peroxide in the prior art.

[0007] To achieve the above-mentioned purpose, the technical scheme of the present application is as follows:

[0008] A preparation method of azodicarbonamide, comprising the following steps:

[0009] S1, uniformly mixing hydrogen peroxide solution, stabilizer and catalyst to obtain a first reaction liquid;

[0010] S2, mixing biurea, water and catalyst to obtain a second reaction suspension;

[0011] S3, adding the preheated first reaction solution drop by drop into the second reaction suspension to perform oxidation reaction, and obtaining azodicarbonamide after the reaction is completed.

[0012] The stabilizer in step S1 is one or more of 1,3-diamino-2-hydroxypropane-N,N,N',N'-tetraacetic acid, 8-hydroxyquinoline, sodium pyrophosphate, nitrilotrimethylene phosphoric acid.

[0013] Preferably, the stabilizer is one or more of 1,3-diamino-2-hydroxypropane-N,N,N',N'-tetraacetic acid, 8-hydroxyquinoline, sodium pyrophosphate, nitrilotrimethylene phosphoric acid.

[0014] Preferably, the stabilizer is one or both of 1,3-diamino-2-hydroxypropane-N,N,N',N'-tetraacetic acid and nitrilotrimethylene phosphoric acid.

[0015] Preferably, the stabilizer is nitrilotrimethylene phosphoric acid.

[0016] Preferably, the mass concentration of the hydrogen peroxide solution is 10% to 70%; preferably, the mass concentration of the hydrogen peroxide solution is 45% to 55%; and in actual industry, a hydrogen peroxide solution with a concentration of 50% is generally selected.

[0017] Preferably, in step S1, the mass of the stabilizer added in the first reaction solution is 0.01% to 0.5% of the mass of the hydrogen peroxide solution.

[0018] Preferably, in step S1, the co-catalyst is one or more of 2,6-dichloro-benzoquinone and tetrachlorobenzoquinone.

[0019] Preferably, in step S1, the mass of the co-catalyst added in the first reaction solution is 0.01% to 0.05% of the mass of the hydrogen peroxide solution.

[0020] Preferably, in step S2, the mass ratio of biurea to water in the second reaction suspension is 1:1 to 1:3, and the molar ratio of biurea to hydrogen peroxide is 0.95:1 to 1.05:1; preferably, the molar ratio of biurea to hydrogen peroxide is 1:1.

[0021] Preferably, in step S3, the temperature of the oxidation reaction is 50°C to 100°C, and the reaction time is 2h to 10h.

[0022] Preferably, in step S2, the catalyst is one or more of potassium iodide, sodium iodide and hydrogen iodide; preferably, the catalyst is hydrogen iodide.

[0023] Preferably, the mass of the catalyst is 0.01%-0.05% of the total mass of the reaction materials, which is the sum of the masses of the biurea, water, hydrogen peroxide, catalyst, co-catalyst and stabilizer.

[0024] In actual production, hydrogen peroxide as a raw material cannot be recycled, and hydrogen peroxide not involved in the synthesis of ADC foaming agent during the reaction will be decomposed, which will cause loss of raw materials, resulting in rising of raw material cost and falling of profit.

[0025] In the preparation method of azodicarbonamide provided by the present application, the stabilizer can chelate impurity metal ions in the reaction, so that hydrogen peroxide is not catalytically decomposed into water and oxygen by the impurity metal ions; the co-catalyst can make hydrogen peroxide rapidly generate hydroxyl radicals, react with iodine ions to generate iodine element, and then continue to participate in the reaction to oxidize biurea. Under the joint action of the stabilizer and the co-catalyst, on the one hand, the decomposition rate of hydrogen peroxide itself is reduced, and on the other hand, the participation rate of hydrogen peroxide in the main reaction is increased, so that the ineffective decomposition of hydrogen peroxide is reduced, and the utilization rate of hydrogen peroxide is improved.

[0026] Compared with the prior art, the preparation method of azodicarbonamide provided by the present application has the following advantages:

[0027] The preparation method of azodicarbonamide provided by the present application optimizes the selection of hydrogen peroxide stabilizer and co-catalyst, which can reduce the decomposition rate of hydrogen peroxide, accelerate the participation rate of hydrogen peroxide in the main reaction, reduce the risk of explosion caused by excessive oxygen generated by decomposition, and at the same time, improve the reaction rate of hydrogen peroxide in the reaction system, so that more hydrogen peroxide participates in the synthesis reaction of ADC foaming agent, the utilization rate of hydrogen peroxide is improved, thereby reducing the loss of raw materials, reducing the cost of raw materials, and improving the production profit; the examples of the present application show that the utilization rate of hydrogen peroxide can reach more than 95%. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0029] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0030] The present application will be described in detail below with reference to the embodiments.

[0031] The reactions in the following examples were all carried out in a tank reactor, and different reactors can also be selected by those skilled in the art according to the circumstances.

[0032] The percentages described below are all mass fractions; the yield of the ADC foaming agent is calculated based on the amount of hydrazine diurea fed: ADC foaming agent yield = ADC foaming agent output amount / hydrazine diurea fed amount; in the process of synthesizing the ADC foaming agent, processes such as the invalid decomposition of hydrogen peroxide, side reactions involving hydrogen peroxide, etc. occur, in order to measure the effective utilization rate of hydrogen peroxide, the utilization rate of hydrogen peroxide can be calculated by the formula: hydrogen peroxide utilization rate = hydrogen peroxide consumption amount participating in the main reaction / hydrogen peroxide fed amount.

[0033] Example 1

[0034] S1: 28.81 g of hydrogen peroxide solution (50%) was mixed with 0.0864 g of 1,3-diamino-2-hydroxypropane-N,N,N',N'-tetraacetic acid and 0.0086 g of chloranil to obtain a first reaction solution;

[0035] S2: 50 g of hydrazine diurea and 100 g of water were uniformly mixed to obtain a second reaction suspension;

[0036] S3: The first reaction solution was preheated to 80°C, and then the second reaction suspension was loaded into a tank reactor with a condenser, a thermometer and stirring, and the preheated first solution was added dropwise into the tank reactor, the dropwise addition time was 3 h, the reaction pressure was normal pressure, and the reaction time was 5 h; after the reaction was completed, the product was collected to obtain the ADC foaming agent.

[0037] The reaction results are shown in Table 1.

[0038] The reaction processes of Examples 2-22 were the same as those of Example 1. The reaction conditions and reaction results are shown in Table 1 and Table 2.

[0039] The reaction processes of Comparative Examples 1-15 were the same as those of Example 1. The reaction conditions and reaction results are shown in Table 3 and Table 4.

[0040] Table 1

[0041]

[0042]

[0043]

[0044] Table 2

[0045]

[0046]

[0047]

[0048] Table 3

[0049]

[0050]

[0051]

[0052] Table 4

[0053]

[0054]

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions described in the foregoing embodiments can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the claims and the description of the present application.

[0056] The above only describes the preferred embodiments of the present application, and is not intended to limit the present application, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A process for the preparation of azodicarbonamide, characterized in that, The method comprises the following steps: S1, mixing hydrogen peroxide solution, stabilizer and catalyst to obtain a first reaction solution; S2, mixing biurea, water and catalyst to obtain a second reaction suspension; S3, adding the preheated first reaction solution drop by drop into the second reaction suspension to perform oxidation reaction, and obtaining azodicarbonamide after the reaction is completed; The stabilizer in step S1 is one or more of 1,3-diamino-2-hydroxypropane-N,N,N',N'-tetraacetic acid, 8-hydroxyquinoline, sodium dihydrogen pyrophosphate and nitrilotrimethylene phosphoric acid; In step S1, the mass of the stabilizer added in the first reaction solution is 0.01%-0.5% of the mass of the hydrogen peroxide solution; In step S1, the catalyst is one or more of potassium iodide, sodium iodide and hydrogen iodide; The mass of the catalyst is 0.01%-0.05% of the mass of the total reaction material, and the total reaction material is the sum of the masses of biurea, water, hydrogen peroxide, catalyst, catalyst and stabilizer. The stabilizer is nitrilotrimethylene phosphoric acid. The mass concentration of the hydrogen peroxide solution is 10%-70%.

2. The process for the preparation of azodicarbonamide according to claim 1, characterized in that: The mass concentration of the hydrogen peroxide solution is 45%-55%.

3. The process for the preparation of azodicarbonamide according to claim 1, characterized in that: The mass concentration of the hydrogen peroxide solution is 50%.

4. The process for the preparation of azodicarbonamide according to claim 3, characterized in that: In step S2, the mass ratio of biurea to water in the second reaction suspension is 1:1-1:3, and the molar ratio of biurea to hydrogen peroxide is 0.95:1-1.05:

1.

5. The process for the preparation of azodicarbonamide according to claim 4, characterized in that: In step S2, the molar ratio of biurea to hydrogen peroxide in the second reaction suspension is 1:

1.

6. The process for the preparation of azodicarbonamide according to claim 1, characterized in that: In step S3, the temperature of the oxidation reaction is 50°C-100°C, and the reaction time is 2h-10h.

7. The process for the preparation of azodicarbonamide according to claim 6, characterized in that: In step S2, the catalyst is hydrogen iodide.

8. The process for the preparation of azodicarbonamide according to claim 1, characterized in that: ​ 9. The process for the preparation of azodicarbonamide according to claim 1, characterized in that: ​

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