A green production method of an adc blowing agent

Abstract

This invention relates to the field of chemical production, specifically to a green production method for ADC foaming agent. The green production method for ADC foaming agent includes the following steps: mixing biuret, an acidic aqueous solution, and a catalyst to obtain a slurry; placing the slurry in a reactor for reaction; after the reaction, performing solid-liquid separation on the reaction product, collecting the solid phase, washing, and drying to obtain azodicarbonamide product; wherein, in step S2, the unreacted tail gas is discharged, and after adding an oxidizing gas, it is reintroduced into the reactor to participate in the reaction; the liquid mother liquor obtained in step S3 is adjusted to pH and then recycled entirely or partially back to step S1 for slurry preparation. The green production method for ADC foaming agent provided by this invention is environmentally friendly, achieving green production from the source, significantly improving production efficiency and economy, and producing excellent product quality.

Description

Technical Field

[0001] This invention relates to the field of chemical production, and more specifically, to a green production method for ADC foaming agent. Background Technology

[0002] Azodicarbonamide (ADC) is a general-purpose chemical foaming agent that is widely used in industries such as polyvinyl chloride, polyethylene, polypropylene, and rubber due to its high gas production, non-toxicity, odorlessness, and non-polluting properties.

[0003] Currently, the domestic industrial production of ADC foaming agents generally adopts a process route that uses urea to synthesize hydrazine hydrate as the starting material. This route mainly includes the following steps: First, urea reacts with sodium hypochlorite under alkaline conditions to generate a low-concentration hydrazine hydrate solution. This process has a low yield and produces a large amount of saline wastewater. Subsequently, the dilute hydrazine hydrate solution is desalted and purified, and then condensed with urea under acidic conditions (pH = 4-5) to generate the intermediate biuret (HDCA). Finally, biuret is oxidized using chlorine gas to obtain the final ADC product.

[0004] However, this traditional production process has the following prominent drawbacks:

[0005] The synthesis of hydrazine hydrate is inefficient and generates large amounts of wastewater: the yield of hydrazine hydrate produced by the reaction of urea and sodium hypochlorite is generally low, and the concentration of the resulting hydrazine hydrate solution is low. Subsequent concentration and desalination processes are energy-intensive and generate large amounts of difficult-to-treat wastewater. The condensation process is highly polluting: in the acid condensation process for producing biuret, ammonia and sodium carbonate are produced as byproducts, requiring neutralization with strong acids such as sulfuric acid. This step not only consumes additional chemical raw materials but also generates high-concentration ammonia nitrogen wastewater rich in ammonium sulfate and sodium sulfate, making treatment extremely difficult and costly. Overall, the energy consumption is high, failing to meet energy conservation and environmental protection requirements: the entire process from hydrazine hydrate synthesis to chlorine oxidation is lengthy, involving multiple concentration, separation, and neutralization reactions, resulting in enormous energy consumption and a heavy environmental burden.

[0006] Therefore, developing a new green production process for ADC foaming agents that can avoid or completely solve wastewater and waste salt problems at the source, while also having the advantages of high efficiency and low cost, has become a technical bottleneck that the industry urgently needs to overcome. Summary of the Invention

[0007] In view of this, the present invention aims to provide a green production method for ADC foaming agent, wherein the green production method for ADC foaming agent has mild, controllable and short reaction conditions and is environmentally friendly.

[0008] To solve the above-mentioned technical problems, this application is implemented as follows:

[0009] This invention provides a green production method for ADC foaming agent, comprising the following steps:

[0010] S1. Mix biuret, an acidic aqueous solution, and a catalyst to obtain a slurry;

[0011] S2. Place the slurry in a reactor and allow it to react.

[0012] S3. After the reaction is completed, the reaction product is subjected to solid-liquid separation. The solid phase is collected, washed, and dried to obtain the azodicarbonamide product.

[0013] In step S2, the unreacted tail gas is discharged, and after being replenished with oxidizing gas, it is reintroduced into the reactor to participate in the reaction.

[0014] The liquid mother liquor obtained in step S3 is adjusted by pH and then recycled in whole or in part back to step S1 for the preparation of slurry.

[0015] Preferably, in the above-mentioned green production method of an ADC foaming agent, the mass ratio of biuret to the acidic aqueous medium is 1:0.8~1.5;

[0016] The concentration of the acidic aqueous solution is 0.1wt% to 5wt%.

[0017] Preferably, in the above-mentioned green production method of an ADC foaming agent, the acidic medium in the acidic aqueous solution includes at least one of sulfuric acid, hydrogen chloride, and nitric acid.

[0018] Preferably, in the above-mentioned green production method of an ADC foaming agent, the catalyst includes a main catalyst and a co-catalyst;

[0019] The main catalyst includes vanadium-based compounds and / or manganese-based compounds;

[0020] The co-catalyst includes bromides.

[0021] Preferably, in the above-mentioned green production method of an ADC foaming agent, the vanadium-based compound includes ammonium metavanadate and / or vanadium oxysulfate;

[0022] The manganese-based compounds include manganese sulfate and / or manganese acetate;

[0023] The bromide includes at least one of sodium bromide, potassium bromide, and hydrobromic acid.

[0024] Preferably, in the above-mentioned green production method of an ADC foaming agent, the mass of the main catalyst is 0.01% to 0.5% of the mass of the biuret.

[0025] The mass of the co-catalyst is 0.1% to 2% of the mass of the biuret.

[0026] Preferably, in the above-mentioned green production method of ADC foaming agent, the reaction conditions are: temperature of 40-70°C, time of 4-8 hours, and atmosphere of inert atmosphere.

[0027] Preferably, in the above-mentioned green production method of ADC foaming agent, the specific method for solid-liquid separation is centrifugal separation;

[0028] During the centrifugal separation process, the resulting solid filter cake is washed online using a washing medium.

[0029] Preferably, in the above-mentioned green production method of ADC foaming agent, the washing medium is water, steam, or a dilute alkaline solution with a concentration of 0.01% to 0.5%; the alkali in the dilute alkaline solution is sodium carbonate or sodium bicarbonate.

[0030] The beneficial technical effects of the present invention through the above technical solution are as follows:

[0031] (1) The green production method of ADC foaming agent provided by the present invention adopts a composite system of main catalyst (vanadium / manganese compound) and co-catalyst, and generates a synergistic effect with the oxidizing property of oxygen. The present invention shortens the reaction time from about 7 hours to about 4.5 hours, and improves the equipment capacity and utilization rate.

[0032] (2) This invention uses a recyclable dilute acid medium. After the reaction, the mother liquor only needs to be adjusted at pH and can be reused. There is no wastewater discharge in the system. This fundamentally eliminates the high-concentration inorganic salt wastewater containing ammonium sulfate, sodium sulfate or sodium chloride produced by traditional chlorine oxidation or existing pure oxygen oxidation.

[0033] (3) The method of the present invention has mild, controllable and short reaction conditions, effectively suppresses excessive oxidation and side reactions, and the purity of the obtained ADC products is higher than 99%. Detailed Implementation

[0034] The present invention will be further described in detail below through examples. All raw materials used in the examples are commercially available.

[0035] Example 1

[0036] A green production method for ADC foaming agent includes the following steps:

[0037] (1) In a slurry preparation tank, add 1000g of biuret (HDCA), 1000g of 1% sulfuric acid solution, and a catalyst consisting of 0.5g of ammonium metavanadate (main catalyst) and 5g of sodium bromide (co-catalyst); stir mechanically until the mixture is uniform to obtain a slurry;

[0038] (2) The slurry is fed into the reactor, and the pressure of the reaction system is controlled at 0.2 MPa and the temperature at 60℃. At the same time, oxygen is introduced from the bottom of the reactor at a flow rate of 1.0 L / min for 4.5 h. The unreacted tail gas is discharged from the top, enters the gas recovery tank to replenish air, and then circulates back to the reaction system.

[0039] (3) The reaction product was sent to a centrifuge for solid-liquid separation. During centrifugation, a small amount of hot water was sprayed in an atomizing manner to wash the filter cake online. The resulting wet filter cake was dried at 80°C to obtain 985g of ADC product. The pH of the mother liquor obtained by centrifugation was approximately 2, and it was directly returned to step S1 for recycling.

[0040] The product yield was 98.5%, the purity was 99.2%, and the whiteness (L value) was 96.5.

[0041] Example 2

[0042] A green production method for ADC foaming agent includes the following steps:

[0043] (1) Slurry preparation: Take 1000g biuret, 1200g hydrochloric acid solution with a concentration of 0.5%, mix with 2g vanadium oxysulfate (main catalyst) and 10g hydrobromic acid (co-catalyst, pure) to prepare slurry.

[0044] (2) The slurry is fed into the reactor, the reaction pressure is controlled at 0.1 MPa, the temperature is 50℃, high-purity oxygen is introduced at a flow rate of 0.5 L / min, the reaction is carried out for 4.5 hours, the unreacted tail gas is discharged from the top, enters the gas recovery tank to replenish air, and then is recycled back to the reaction system.

[0045] (3) The reaction product was sent to a centrifuge for solid-liquid separation. During centrifugation, a small amount of hot water was sprayed in an atomizing manner to wash the filter cake online. The resulting wet filter cake was dried at 80°C to obtain 987g of ADC product. The pH of the mother liquor obtained by centrifugation was approximately 2, and it was directly returned to step S1 for recycling.

[0046] The product yield was 98.7%, the purity was 99.5%, and the whiteness (L value) was 97.0, according to the test results.

[0047] Example 3

[0048] A green production method for ADC foaming agent includes the following steps:

[0049] (1) In a slurry preparation tank, add 1000g of biuret (HDCA), 900g of 2% nitric acid solution, and a catalyst consisting of 1g of ammonium metavanadate (main catalyst) and 15g of sodium bromide (co-catalyst); mechanically stir until the mixture is uniform to obtain a slurry;

[0050] (2) The slurry is fed into the reactor, and the pressure of the reaction system is controlled at 0.4 MPa and the temperature at 65℃. At the same time, oxygen is introduced from the bottom of the reactor at a flow rate of 1.0 L / min and reacted for 4.5 h. The unreacted tail gas is discharged from the top, enters the gas recovery tank to replenish air, and then circulates back to the reaction system.

[0051] (3) The reaction product was sent to a centrifuge for solid-liquid separation. During centrifugation, a small amount of hot water was sprayed in an atomizing manner to wash the filter cake online. The resulting wet filter cake was dried at 80°C to obtain 991g of ADC product. The pH of the mother liquor obtained by centrifugation was approximately 2, and it was directly returned to step S1 for recycling.

[0052] The product yield was 99.1%, the purity was 99.4%, and the whiteness (L value) was 96.8.

[0053] Comparative Example 1

[0054] A green production method for ADC foaming agent differs from Example 1 in that: no main catalyst and co-catalyst are added, and the final product obtained is 520g of ADC product with a yield of only 52%, the product color is yellow, and the whiteness (L value) is only 85.3.

[0055] This demonstrates that the oxidation of biuret by oxygen is extremely inefficient in the absence of a catalyst.

[0056] Comparative Example 2

[0057] A green production method for ADC foaming agent includes the following steps:

[0058] In a reaction vessel, 1000g of biuret (HDCA), 1200g of 5% sulfuric acid solution, and 5g of sodium bromide as a catalyst were added and mechanically stirred to obtain a slurry.

[0059] (2) The temperature of the reactor was raised to 70°C. Chlorine gas was continuously introduced into the slurry at a flow rate of about 2.0 L / min under stirring. The reaction pressure was atmospheric pressure and the reaction time was about 7 hours. After the reaction was completed, the material was cooled to room temperature and then centrifuged. The filter cake was washed with water and the wet filter cake was dried at 80°C to obtain 952g of ADC product. The product yield was about 95.2% and the purity was 98.5%.

[0060] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A green production method for an ADC foaming agent, characterized in that, Includes the following steps: S1. Mix biuret, an acidic aqueous solution, and a catalyst to obtain a slurry; S2. Place the slurry in a reactor and allow it to react. S3. After the reaction is completed, the reaction product is subjected to solid-liquid separation. The solid phase is collected, washed, and dried to obtain the azodicarbonamide product. In step S2, the unreacted tail gas is discharged, and after being replenished with oxidizing gas, it is reintroduced into the reactor to participate in the reaction. The liquid mother liquor obtained in step S3 is adjusted by pH and then recycled in whole or in part back to step S1 for preparing slurry; the mass ratio of biuret to the acidic aqueous medium is 1:0.8~1.

5. The concentration of the acidic aqueous solution is 0.1 wt% to 5 wt%. The catalyst consists of a main catalyst and a co-catalyst; The main catalyst is a vanadium-based compound; The co-catalyst is a bromide.

2. The green production method of the ADC foaming agent according to claim 1, characterized in that, The acidic medium in the aqueous solution includes at least one of sulfuric acid, hydrogen chloride, and nitric acid.

3. The green production method of the ADC foaming agent according to claim 1, characterized in that, The vanadium-based compound is ammonium metavanadate and / or vanadium oxysulfate; The bromide is at least one of sodium bromide, potassium bromide, and hydrobromic acid.

4. The green production method of the ADC foaming agent according to claim 1, characterized in that, The mass of the main catalyst is 0.01% to 0.5% of the mass of the biuret. The mass of the co-catalyst is 0.1% to 2% of the mass of the biuret.

5. The green production method of the ADC foaming agent according to claim 1, characterized in that, The reaction conditions are: temperature 40-70℃, time 4-8h, and inert atmosphere.

6. The green production method of the ADC foaming agent according to claim 1, characterized in that, The specific method for solid-liquid separation is centrifugation. During the centrifugal separation process, the resulting solid filter cake is washed online using a washing medium.

7. The green production method of the ADC foaming agent according to claim 6, characterized in that, The washing medium is water, steam, or a dilute alkaline solution with a concentration of 0.01% to 0.5%; the alkali in the dilute alkaline solution is sodium carbonate or sodium bicarbonate.