Method for preparing cyanuric acid through pyrolysis method
By screening and pretreating urea, and performing decomposition and pyrolysis reactions in the reactor, the problems of high reaction temperature, large energy consumption and low product purity in the urea pyrolysis method are solved, and the low energy consumption and high purity of cyanuric acid are achieved. Preparation, suitable for industrial production.
Patent Information
- Application Number
- CN202411543143.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-31
- Publication Date
- 2025-01-10
AI Technical Summary
The preparation of cyanuric acid by urea pyrolysis method has problems such as high reaction temperature, large energy consumption and low product purity, which affects production costs and product quality.
By screening and pretreating the urea, decomposition reaction is performed using a reactor with a stirring device and a temperature control system, and trimerization and pyrolysis reactions are carried out under the action of a catalyst, the reaction temperature and time are controlled, the reaction process is monitored, and finally, the reaction process is monitored. Cool and crush naturally to obtain a high purity cyanuric acid powder.
It achieves a reduction in reaction temperature, energy consumption and product purity, reduces production costs, simplifies operations, and is suitable for industrial production.
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Figure CN119285564A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of chemical industry, and in particular to a method for preparing cyanuric acid by pyrolysis. Background Art
[0002] Cyanuric acid is an important chemical raw material, widely used in synthetic resins, rubber, pesticides, medicines and other fields. At present, the preparation methods of cyanuric acid mainly include urea thermal decomposition method, melamine hydrolysis method, etc. Among them, urea thermal decomposition method is one of the most commonly used methods, but this method has problems such as high reaction temperature, high energy consumption and low product purity.
[0003] As an important chemical raw material, cyanuric acid has been widely used in many fields. It plays a key role in industries such as synthetic resins, rubber, pesticides and medicines. At present, the preparation methods of cyanuric acid mainly include urea thermal decomposition method and melamine hydrolysis method. Among these methods, urea thermal decomposition method has become the most commonly used one due to its simplicity and high efficiency. However, this method also has some significant problems, such as excessively high reaction temperature, high energy consumption and low product purity. These problems not only increase production costs, but may also affect the quality of the final product. Summary of the invention
[0004] The purpose of the present invention is to solve the above problems and to design a method for preparing cyanuric acid by thermal decomposition. The method has the advantages of low reaction temperature, low energy consumption and high product purity.
[0005] The present invention provides a method for preparing cyanuric acid by pyrolysis, and the method for preparing cyanuric acid by pyrolysis comprises the following steps:
[0006] Step 1: Screening the urea to remove impurities and agglomerates, and storing the screened urea in a dry environment;
[0007] Step 2: adding the pretreated urea into a reactor equipped with a stirring device and a temperature control system for decomposition reaction, and the ammonia generated during the reaction is discharged through a gas guide pipe;
[0008] Step 3: After the urea decomposition reaction is completed, slowly and evenly add a catalyst into the reactor. Under the action of the catalyst, isocyanic acid undergoes a trimerization reaction to generate cyanuric acid. The reaction progress is determined by monitoring the parameters of the reaction system.
[0009] Step 4: Transfer the generated cyanuric acid to a pyrolysis reactor for pyrolysis reaction. After the pyrolysis reaction is completed, allow the product to cool naturally to room temperature. The cooled product is cyanuric acid. The cyanuric acid is taken out of the reactor, crushed and sieved to obtain cyanuric acid powder with uniform particle size. The cyanuric acid powder is quality tested, and qualified cyanuric acid products are packaged and stored.
[0010] Optionally, in the first implementation of the present invention, the decomposition reaction of step 2 specifically includes the following process: the pretreated urea is slowly heated to 150-200°C in the reactor, the heating rate is controlled at 2-5°C per minute, the reaction is maintained within this temperature range for 1-2 hours, and a stirring device of the reactor is used, and the urea is gradually decomposed to generate isocyanic acid and ammonia during the decomposition reaction.
[0011] Optionally, in a second implementation of the present invention, the stirring speed of the stirring device of the reactor is 30-60 revolutions per minute.
[0012] Optionally, in a third implementation of the present invention, the catalyst in step three is one or more of aluminum oxide, silicon dioxide or activated carbon, and the amount of the catalyst used is 1-5% of the quality of the urea.
[0013] Optionally, in a fourth implementation of the present invention, in step three, under the action of a catalyst, isocyanic acid undergoes a trimerization reaction to generate cyanuric acid. During the reaction, the temperature is controlled at 150-200°C, while stirring is continued at a speed of 30-50 revolutions per minute, and the reaction time is 1-2 hours.
[0014] Optionally, in the fifth implementation of the present invention, during the monitoring of the reaction progress in step three, the pressure range of the reaction system is 0.1-0.3 MPa, and the temperature range is 150-200°C. When the pressure and temperature are stable in this range for 10-30 minutes and the concentration of isocyanic acid begins to decrease, and the concentration of cyanuric acid gradually increases, it can be judged that the trimerization reaction is proceeding smoothly.
[0015] Optionally, in a sixth implementation of the present invention, the pyrolysis reaction in step 4 specifically includes the following process: transferring the generated cyanuric acid to a pyrolysis reactor for pyrolysis reaction, heating the temperature to 300-400°C, controlling the heating rate at 3-6°C per minute, and pyrolysis time of 2-3 hours, and maintaining the atmosphere in the pyrolysis reactor stable by adding inert gas.
[0016] Optionally, in a seventh implementation of the present invention, the inert gas is nitrogen.
[0017] In the technical scheme provided by the present invention, urea is screened to remove impurities and agglomerates therein, and the screened urea is stored in a dry environment; the pretreated urea is added to a reactor with a stirring device and a temperature control system for decomposition reaction, and ammonia generated during the reaction is discharged through an air guide tube; after the urea decomposition reaction is completed, a catalyst is slowly and evenly added to the reactor, under the action of the catalyst, isocyanic acid undergoes trimerization reaction to generate cyanuric acid, and the reaction progress is judged by monitoring the parameters of the reaction system; the generated cyanuric acid is transferred to a pyrolysis reactor for pyrolysis reaction, after the pyrolysis reaction is completed, the product is allowed to cool naturally to room temperature, the cooled product is cyanuric acid, the cyanuric acid is taken out of the reactor, crushed and sieved to obtain cyanuric acid powder with uniform particle size, the cyanuric acid powder is quality tested, and the qualified cyanuric acid product is packaged and stored; the present invention adopts urea pyrolysis method to prepare cyanuric acid, the reaction temperature is low, the energy consumption is small, and the production cost is low; the catalyst is added during the urea pyrolysis process to improve the reaction rate and product purity; the preparation method of the present invention is simple, easy to operate, and suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the following detailed description of the preferred embodiment.The drawings are only for the purpose of illustrating the preferred embodiments and are not to be construed as limiting the invention.
[0019] Figure 1 A schematic flow chart of a method for preparing cyanuric acid by thermal decomposition provided in an embodiment of the present invention. DETAILED DESCRIPTION
[0020] The terms "first", "second", "third", "fourth", etc. (if any) in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "including" or "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, device, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.
[0021] The present invention will now be further described in conjunction with specific embodiments. The following embodiments are intended to illustrate the present invention rather than to further limit the present invention.
[0022] like Figure 1 As shown, a method for preparing cyanuric acid by thermal decomposition comprises the following steps:
[0023] Step 1: Screening the urea to remove impurities and agglomerates, and storing the screened urea in a dry environment;
[0024] Step 2: adding the pretreated urea into a reactor equipped with a stirring device and a temperature control system for decomposition reaction, and the ammonia generated during the reaction is discharged through a gas guide pipe;
[0025] Step 3: After the urea decomposition reaction is completed, slowly and evenly add a catalyst into the reactor. Under the action of the catalyst, isocyanic acid undergoes a trimerization reaction to generate cyanuric acid. The reaction progress is determined by monitoring the parameters of the reaction system.
[0026] Step 4: Transfer the generated cyanuric acid to a pyrolysis reactor for pyrolysis reaction. After the pyrolysis reaction is completed, allow the product to cool naturally to room temperature. The cooled product is cyanuric acid. The cyanuric acid is taken out of the reactor, crushed and sieved to obtain cyanuric acid powder with uniform particle size. The cyanuric acid powder is quality tested, and qualified cyanuric acid products are packaged and stored.
[0027] In this embodiment, the decomposition reaction of step 2 specifically includes the following process: the pretreated urea is slowly heated to 150-200°C in the reactor, the heating rate is controlled at 2-5°C per minute, the reaction is maintained within this temperature range for 1-2 hours, and a stirring device of the reactor is used. During the decomposition reaction, urea is gradually decomposed to generate isocyanic acid and ammonia, wherein the stirring speed of the stirring device of the reactor is 30-60 revolutions per minute.
[0028] In this embodiment, the catalyst in step three is one or more of aluminum oxide, silicon dioxide or activated carbon, and the amount of the catalyst used is 1-5% of the mass of urea.
[0029] In this embodiment, in step 3, under the action of a catalyst, isocyanic acid undergoes a trimerization reaction to generate cyanuric acid. During the reaction, the temperature is controlled at 150-200° C., while stirring is continued at a speed of 30-50 revolutions per minute, and the reaction time is 1-2 hours.
[0030] In this embodiment, during the monitoring of the reaction progress in step 3, the pressure range of the reaction system is 0.1-0.3 MPa, and the temperature range is 150-200°C. When the pressure and temperature are stable within this range for 10-30 minutes and the concentration of isocyanic acid begins to decrease, and the concentration of cyanuric acid gradually increases, it can be judged that the trimerization reaction is proceeding smoothly.
[0031] In this embodiment, the pyrolysis reaction in step 4 specifically includes the following process: transferring the generated cyanuric acid to a pyrolysis reactor for pyrolysis reaction, heating the temperature to 300-400°C, controlling the heating rate at 3-6°C per minute, and pyrolysis time for 2-3 hours, and maintaining the atmosphere in the pyrolysis reactor stable by adding an inert gas, wherein the inert gas is nitrogen.
[0032] Embodiment 1:
[0033] Embodiment 1:
[0034] Urea pretreatment: 100kg of urea is screened to remove impurities and agglomerates to ensure the purity and particle uniformity of the urea; the screened urea is stored in a dry environment to prevent it from absorbing moisture and affecting subsequent reactions.
[0035] Urea decomposition reaction: add the pretreated urea to a reactor equipped with a stirring device and a temperature control system. The stirring device adopts a paddle stirring paddle, which can be in the shape of a paddle, turbine or anchor type, etc. The stirring speed is set to 45 revolutions per minute to ensure that the urea can be fully mixed and heated evenly in the reactor; slowly heat up to 180°C at a heating rate of 3°C per minute to ensure that the temperature rises evenly and avoids local overheating; react at 180°C for 1.5 hours, stirring continuously during the reaction, during which the urea gradually decomposes to generate isocyanic acid and ammonia. The stirring device makes the reaction uniform and improves the reaction efficiency. By adding an appropriate amount of sodium bicarbonate, the pH of the reaction system is controlled at about 7.5, and the ammonia generated during the reaction is led out for collection and treatment; the pressure of the reaction system is maintained at 0.18MPa (absolute pressure) and the temperature is maintained at 180°C.
[0036] Trimerization reaction: After the urea decomposition reaction is completed, add 2kg of aluminum oxide as a catalyst into the reactor, slowly and evenly; under the action of the catalyst, isocyanic acid undergoes a trimerization reaction, the temperature is maintained at 180°C, the stirring speed is adjusted to 45 revolutions per minute, the reaction time is 1.5 hours, the pH of the reaction system is maintained at about 7.5, the pressure of the reaction system is stabilized at 0.22MPa (absolute pressure), and the temperature is maintained at 182°C.
[0037] Cyanuric acid pyrolysis: The generated cyanuric acid is transferred to a pyrolysis reactor, which should have good heating and temperature control functions, and the temperature is raised to 350°C at a rate of 4°C per minute; pyrolysis is carried out at 350°C for 2.5 hours, and nitrogen is introduced during the pyrolysis process to maintain a stable atmosphere. Through fine-tuning, the pH of the reaction system is controlled at about 6.5; the pressure in the pyrolysis reactor is 0.35MPa (absolute pressure) and the temperature is 350°C.
[0038] Product collection and processing: After the chemical reaction is completed, the cooling process converts the final product into cyanuric acid; next, the cyanuric acid needs to be taken out of the reactor for a series of subsequent treatments; first, the taken cyanuric acid is crushed to ensure that its particle size reaches the required uniformity. After crushing, the particle size consistency is further ensured through the screening process, so as to obtain cyanuric acid powder with uniform particle size; in order to ensure the quality of the cyanuric acid product, it needs to be subjected to detailed quality testing; the testing process includes the evaluation of purity, particle size distribution and other key indicators; these indicators can fully reflect the quality of cyanuric acid and ensure that it meets the established standards and requirements; if the test results show that the cyanuric acid product If the quality requirements are not met, further purification measures may be taken; the purification process may include recrystallization, filtration or other chemical treatment methods to remove impurities and improve the purity and overall quality of the product; through these steps, it can be ensured that the cyanuric acid product meets the required high quality standards; finally, for those qualified cyanuric acid products that pass the quality inspection, proper packaging and storage are required; the packaging process should ensure the sealing and protection of the product to prevent contamination or damage to the product by the external environment; the storage environment should be kept dry, well ventilated, and avoid direct sunlight to prevent cyanuric acid from decomposing or deteriorating; through these measures, the stability of cyanuric acid products and the reliability of long-term storage can be ensured.
[0039] Embodiment 2:
[0040] Urea pretreatment: 100kg of urea is screened to remove impurities and agglomerates to ensure the purity and particle uniformity of the urea; the screened urea is stored in a dry environment to prevent it from absorbing moisture and affecting subsequent reactions.
[0041] Urea decomposition reaction: add the pretreated urea to a reactor equipped with a stirring device and a temperature control system. The stirring device adopts a paddle stirring paddle, which can be in the shape of a paddle, turbine or anchor type, etc. The stirring speed is set to 50 revolutions per minute to ensure that the urea can be fully mixed and heated evenly in the reactor; slowly heat up to 160°C at a heating rate of 2.5°C per minute to ensure that the temperature rises evenly and avoids local overheating; react at 160°C for 2 hours, stirring continuously during the reaction, during which the urea gradually decomposes to generate isocyanic acid and ammonia. The stirring device makes the reaction uniform and improves the reaction efficiency. By adding an appropriate amount of sodium bicarbonate, the pH of the reaction system is controlled at about 7.8, and the ammonia generated during the reaction is led out for collection and treatment; the pressure of the reaction system is maintained at 0.12MPa (absolute pressure) and the temperature is maintained at 160°C.
[0042] Trimerization reaction: After the urea decomposition reaction is completed, add 3kg of aluminum oxide as a catalyst into the reactor, slowly and evenly; under the action of the catalyst, isocyanic acid undergoes a trimerization reaction, the temperature is maintained at 160°C, the stirring speed is adjusted to 40 revolutions per minute, the reaction time is 1.8 hours, the pH of the reaction system is maintained at about 7.8, the pressure of the reaction system is stabilized at 0.15MPa (absolute pressure), and the temperature is maintained at 161°C.
[0043] Cyanuric acid pyrolysis: The generated cyanuric acid is transferred to a pyrolysis reactor, which should have good heating and temperature control functions, and the temperature is raised to 320°C at a heating rate of 3.5°C per minute; pyrolysis is carried out at 350°C for 3 hours, and nitrogen is introduced during the pyrolysis process to maintain a stable atmosphere. Through fine-tuning, the pH of the reaction system is controlled at about 6.8; the pressure in the pyrolysis reactor is 0.25MPa (absolute pressure) and the temperature is 320°C.
[0044] Product collection and processing: After the chemical reaction is completed, the cooling process converts the final product into cyanuric acid; next, the cyanuric acid needs to be taken out of the reactor for a series of subsequent treatments; first, the taken cyanuric acid is crushed to ensure that its particle size reaches the required uniformity. After crushing, the particle size consistency is further ensured through the screening process, so as to obtain cyanuric acid powder with uniform particle size; in order to ensure the quality of the cyanuric acid product, it needs to be subjected to detailed quality testing; the testing process includes the evaluation of purity, particle size distribution and other key indicators; these indicators can fully reflect the quality of cyanuric acid and ensure that it meets the established standards and requirements; if the test results show that the cyanuric acid product If the quality requirements are not met, further purification measures may be taken; the purification process may include recrystallization, filtration or other chemical treatment methods to remove impurities and improve the purity and overall quality of the product; through these steps, it can be ensured that the cyanuric acid product meets the required high quality standards; finally, for those qualified cyanuric acid products that pass the quality inspection, proper packaging and storage are required; the packaging process should ensure the sealing and protection of the product to prevent contamination or damage to the product by the external environment; the storage environment should be kept dry, well ventilated, and avoid direct sunlight to prevent cyanuric acid from decomposing or deteriorating; through these measures, the stability of cyanuric acid products and the reliability of long-term storage can be ensured.
[0045] Embodiment 3:
[0046] Urea pretreatment: 100kg of urea is screened to remove impurities and agglomerates to ensure the purity and particle uniformity of the urea; the screened urea is stored in a dry environment to prevent it from absorbing moisture and affecting subsequent reactions.
[0047] Urea decomposition reaction: add the pretreated urea to a reactor equipped with a stirring device and a temperature control system. The stirring device adopts a paddle stirring paddle, which can be in the shape of a paddle, turbine or anchor type, etc. The stirring speed is set to 35 revolutions per minute to ensure that the urea can be fully mixed and heated evenly in the reactor; slowly heat up to 190°C at a heating rate of 4°C per minute to ensure that the temperature rises evenly and avoids local overheating; react at 190°C for 1 hour, stirring continuously during the reaction, during which the urea gradually decomposes to generate isocyanic acid and ammonia. The stirring device makes the reaction uniform and improves the reaction efficiency. By adding an appropriate amount of sodium bicarbonate, the pH of the reaction system is controlled at about 7.2, and the ammonia generated during the reaction is led out for collection and treatment; the pressure of the reaction system is maintained at 0.25MPa (absolute pressure) and the temperature is maintained at 190°C.
[0048] Trimerization reaction: After the urea decomposition reaction is completed, add 1 kg of aluminum oxide as a catalyst into the reactor, slowly and evenly; under the action of the catalyst, isocyanic acid undergoes a trimerization reaction, the temperature is maintained at 190°C, the stirring speed is adjusted to 50 revolutions per minute, the reaction time is 1.2 hours, the pH of the reaction system is maintained at about 7.2, the pressure of the reaction system is stabilized at 0.28 MPa (absolute pressure), and the temperature is maintained at 191°C.
[0049] Cyanuric acid pyrolysis: The generated cyanuric acid is transferred to a pyrolysis reactor, which should have good heating and temperature control functions, and the temperature is raised to 320°C at a rate of 5°C per minute; pyrolysis is carried out at 350°C for 2 hours, and nitrogen is introduced during the pyrolysis process to maintain a stable atmosphere. Through fine-tuning, the pH of the reaction system is controlled at about 6.2; the pressure in the pyrolysis reactor is 0.45MPa (absolute pressure) and the temperature is 380°C.
[0050] Product collection and processing: After the chemical reaction is completed, the cooling process converts the final product into cyanuric acid; next, the cyanuric acid needs to be taken out of the reactor for a series of subsequent treatments; first, the taken cyanuric acid is crushed to ensure that its particle size reaches the required uniformity. After crushing, the particle size consistency is further ensured through the screening process, so as to obtain cyanuric acid powder with uniform particle size; in order to ensure the quality of the cyanuric acid product, it needs to be subjected to detailed quality testing; the testing process includes the evaluation of purity, particle size distribution and other key indicators; these indicators can fully reflect the quality of cyanuric acid and ensure that it meets the established standards and requirements; if the test results show that the cyanuric acid product If the quality requirements are not met, further purification measures may be taken; the purification process may include recrystallization, filtration or other chemical treatment methods to remove impurities and improve the purity and overall quality of the product; through these steps, it can be ensured that the cyanuric acid product meets the required high quality standards; finally, for those qualified cyanuric acid products that pass the quality inspection, proper packaging and storage are required; the packaging process should ensure the sealing and protection of the product to prevent contamination or damage to the product by the external environment; the storage environment should be kept dry, well ventilated, and avoid direct sunlight to prevent cyanuric acid from decomposing or deteriorating; through these measures, the stability of cyanuric acid products and the reliability of long-term storage can be ensured.
[0051] Before conducting purity test on the cyanuric acid products prepared in the above three embodiments, it is necessary to prepare a series of necessary instruments and equipment, including high performance liquid chromatograph (HPLC), analytical balance, volumetric flask, pipette, etc. After the preparation work is completed, ensure that the laboratory environment meets the test requirements, including the stability of temperature and humidity, and ensure that there are no substances in the laboratory that may interfere with the test results. Only when these conditions are met can the purity test of the cyanuric acid product be carried out to ensure the accuracy and reliability of the test results.
[0052] Accurately weigh 0.1 g of sample from the cyanuric acid powder obtained in the three examples, dissolve the weighed sample in an appropriate amount of solvent, such as methanol or acetonitrile, etc., dilute to 100 ml in a volumetric flask, and shake well to obtain a sample solution; set the parameters of the high performance liquid chromatograph,
[0053] Set up HPLC parameters:
[0054] Mobile phase: methanol / water (or acetonitrile / water) volume ratio is 60:40.
[0055] Flow rate: 1.0ml / min.
[0056] Column temperature: 30℃.
[0057] Injection volume: 10 μl
[0058] Use a pipette to accurately draw 5 ml of a standard solution with a concentration of 1 mg / ml, inject it into a high performance liquid chromatograph, analyze it, and obtain the chromatogram and peak area of the standard; similarly, use a pipette to accurately draw 10 μl of a sample solution, inject it into a high performance liquid chromatograph, analyze it, and obtain the chromatogram and peak area of the sample.
[0059] A standard curve was established based on the concentration and peak area of the standard. The standard curve was plotted with the concentration of the standard as the horizontal axis and the peak area as the vertical axis to obtain a regression equation. The peak area of the sample was substituted into the regression equation to calculate the concentration of cyanuric acid in the sample.
[0060] Calculate the purity of the sample, purity = (mass of cyanuric acid in the sample / total mass of the sample) × 100%. Mass of cyanuric acid in the sample = sample solution concentration × sample solution volume × dilution multiple;
[0061] Particle size distribution detection: accurately weigh 5.00g of cyanuric acid powder sample and put it into the sample pool of the laser particle size analyzer. Set the dispersion medium of the laser particle size analyzer to deionized water and the dispersant to an appropriate amount of surfactant to improve the dispersibility of the sample. The amount of dispersant is 0.5% of the sample mass. Start the instrument, adjust the ultrasonic dispersion power to 200W, and the dispersion time to 5 minutes, so that the sample can be fully dispersed under specific conditions. The instrument adopts the principle of laser diffraction and emits a laser with a wavelength of 632.8nm to irradiate the sample. By measuring the scattered light intensity at different angles, it automatically records the number and distribution of particles in different particle size ranges, thereby obtaining a particle size distribution curve. According to the particle size distribution curve, analyze the particle size characteristics of the sample and evaluate the uniformity of the particle size distribution.
[0062] The cyanuric acid product obtained in Example 1 was detected by high performance liquid chromatography, and the product purity was 99.5%. The particle size distribution detected by laser particle size analyzer was uniform, which met the quality requirements; the cyanuric acid product obtained in Example 2 was detected by high performance liquid chromatography, and the product purity was 99.3%. The particle size distribution detected by laser particle size analyzer was uniform, which met the quality requirements; the cyanuric acid product obtained in Example 1 was detected by high performance liquid chromatography, and the product purity was 99.6%. The particle size distribution detected by laser particle size analyzer was uniform, which met the quality requirements.
[0063] Through the implementation of the above scheme, the present invention proposes a method for preparing cyanuric acid by pyrolysis, which can stably produce high-purity cyanuric acid products. In different embodiments, by accurately controlling the reaction conditions, such as stirring speed, heating rate, type and amount of catalyst, pH value of the reaction system, and key parameters such as pressure and temperature, cyanuric acid products that meet the quality requirements can be obtained; this method has the significant advantages of simple operation, easy control, high product purity, and suitability for industrial production. Specifically, by optimizing these reaction conditions, the yield and purity of cyanuric acid can be effectively improved, thereby ensuring the quality of the final product; in addition, the simple operation and easy control characteristics of the method make it highly practical and economical in large-scale production; therefore, the method for preparing cyanuric acid by pyrolysis of the present invention can not only meet the needs of industrial production, but also improve production efficiency and economic benefits while ensuring product quality.
[0064] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.
Claims
1. A method for preparing cyanuric acid by pyrolysis, characterized in that: The method for preparing cyanuric acid by pyrolysis comprises the following steps: Step 1: Screening the urea to remove impurities and agglomerates, and storing the screened urea in a dry environment; Step 2: adding the pretreated urea into a reactor equipped with a stirring device and a temperature control system for decomposition reaction, and the ammonia generated during the reaction is discharged through a gas guide pipe; Step 3: After the urea decomposition reaction is completed, slowly and evenly add a catalyst into the reactor. Under the action of the catalyst, isocyanic acid undergoes a trimerization reaction to generate cyanuric acid. The reaction progress is determined by monitoring the parameters of the reaction system. Step 4: Transfer the generated cyanuric acid to a pyrolysis reactor for pyrolysis reaction. After the pyrolysis reaction is completed, allow the product to cool naturally to room temperature. The cooled product is cyanuric acid. The cyanuric acid is taken out of the reactor, crushed and sieved to obtain cyanuric acid powder with uniform particle size. The cyanuric acid powder is quality tested, and qualified cyanuric acid products are packaged and stored.
2. The method for preparing cyanuric acid by thermal decomposition according to claim 1, characterized in that: The decomposition reaction of step 2 specifically includes the following process: the pretreated urea is slowly heated to 150-200°C in the reactor, the heating rate is controlled at 2-5°C per minute, the reaction is maintained within this temperature range for 1-2 hours, and a stirring device of the reactor is used. During the decomposition reaction, the urea is gradually decomposed to generate isocyanic acid and ammonia.
3. The method for preparing cyanuric acid by thermal decomposition as claimed in claim 2, characterized in that: The stirring speed of the stirring device of the reactor is 30-60 revolutions per minute.
4. The method for preparing cyanuric acid by thermal decomposition according to claim 1, characterized in that: In step 3, the catalyst is one or more of aluminum oxide, silicon dioxide or activated carbon, and the amount of the catalyst used is 1-5% of the quality of urea.
5. The method for preparing cyanuric acid by thermal decomposition according to claim 1, characterized in that: In step 3, under the action of a catalyst, isocyanic acid undergoes a trimerization reaction to generate cyanuric acid. During the reaction, the temperature is controlled at 150-200° C., while stirring is continued at a speed of 30-50 revolutions per minute, and the reaction time is 1-2 hours.
6. The method for preparing cyanuric acid by thermal decomposition according to claim 1, characterized in that: During the monitoring of the reaction progress in step 3, the pressure range of the reaction system is 0.1-0.3 MPa, and the temperature range is 150-200°C. When the pressure and temperature are stable in this range for 10-30 minutes and the concentration of isocyanic acid begins to decrease, and the concentration of cyanuric acid gradually increases, it can be judged that the trimerization reaction is proceeding smoothly.
7. The method for preparing cyanuric acid by thermal decomposition according to claim 1, characterized in that: The pyrolysis reaction in step 4 specifically includes the following process: transferring the generated cyanuric acid to a pyrolysis reactor for pyrolysis reaction, heating to 300-400°C, controlling the heating rate at 3-6°C per minute, and pyrolysis time of 2-3 hours, and maintaining the atmosphere in the pyrolysis reactor stable by adding inert gas.
8. The method for preparing cyanuric acid by thermal decomposition as claimed in claim 5, characterized in that: The inert gas is nitrogen.