Method for preparing cyanuric acid from urea
By heating urea in a preheater and using zirconium oxide and stainless steel as filler materials in the reactor, the problems of low yield and purity of cyanuric acid were solved, achieving efficient and simple preparation of cyanuric acid and reducing process costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA ENERGY LONGYUAN ENVIRONMENTAL PROTECTION CO LTD
- Filing Date
- 2025-12-26
- Publication Date
- 2026-05-15
AI Technical Summary
In existing technologies, the yield and purity of cyanuric acid are low, the process is complex, and there are many by-products. In particular, the urea pyrolysis method has parallel side reactions, resulting in low product selectivity.
Urea is heated by a preheater and hot air is blown in to volatilize it. It is then reacted in a reactor filled with packing material. Solid products are separated by a drum screen. Zirconia and/or stainless steel are used as packing materials. The reaction temperature and time are controlled to avoid wall adhesion in conventional tunnel kilns and simplify the process.
It improved the conversion rate and purity of cyanuric acid to 98.5%, simplified the process flow, reduced process costs, and reduced the generation of by-products.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of chemical technology, specifically to a method for preparing cyanuric acid from urea. Background Technology
[0002] Cyanuric acid, also known as cyanuric acid, has the chemical formula C3H3N3O3. It exists in two isomers: the ketone form and the enol form, and usually exists as a mixture of the two isomers. Cyanuric acid is a white crystalline solid at room temperature, with a slightly bitter taste. It is essentially non-toxic, soluble in hot water, slightly soluble in cold water, and its aqueous solution is acidic. It is insoluble in cold alcohols, ethers, and organic solvents such as benzene.
[0003] Cyanuric acid is a very important chemical synthesis raw material, mainly used in the manufacture of sodium dichloroisocyanurate, trichloroisocyanuric acid, tris(β-hydroxyethyl) isocyanurate, triallyl ester, cyanuric acid-formaldehyde resin, epoxy resin, antioxidants, coatings, adhesives, and halogenated trihydroxyazine drugs in medicine. Currently, more than 500 series of products using cyanuric acid have been developed domestically and internationally, of which more than 200 are commercially available. These products are high-value-added, widely used, highly competitive, and urgently needed fine chemical products in the market.
[0004] Existing methods for synthesizing cyanuric acid mainly include urea pyrolysis, phosgene-ammonia reaction synthesis, cyanate trimerization, hydrogen cyanide oxidation, and cyanuric chloride hydrolysis. Currently, the most mainstream process is urea pyrolysis. However, this method suffers from multiple parallel side reactions, resulting in low selectivity for the target product and numerous impurities, primarily biuret and cyanuric acid monoamide. Reliable data indicates that the commonly used rotary kiln urea pyrolysis method, due to its slow heating process, produces a large number of byproducts, requiring further purification. Summary of the Invention
[0005] The purpose of this invention is to overcome the problems of low yield and purity of cyanuric acid prepared by existing methods and the complexity of the process flow, and to provide a method for preparing cyanuric acid from urea. The cyanuric acid prepared according to the method of this invention has high conversion rate and purity, and the operation process is simple and the process cost is low.
[0006] To achieve the above objectives, the present invention provides a method for preparing cyanuric acid from urea. The method includes: heating urea in a preheater, then blowing in hot air to volatilize the urea, and conveying the volatilized urea to a reactor containing a packing material for reaction, then conveying the packing material with attached solid products to a drum screen, and separating the solid products from the packing material with attached solid products.
[0007] Preferably, the heating process is carried out by electric heating and / or hot flue gas.
[0008] Preferably, the heating temperature is 150-170°C.
[0009] Preferably, the temperature of the hot air is 150-170°C.
[0010] Preferably, the mass-to-volume ratio of the urea and the hot air is 1 kg: 5-10 m³. 3 .
[0011] Preferably, the reaction conditions include a temperature of 270-300℃ and a time of 10-20 min.
[0012] Preferably, the filler material is zirconium oxide and / or stainless steel.
[0013] The volume of the filling material accounts for 90-95% of the internal volume of the reactor.
[0014] Preferably, the filling material is spherical and / or ellipsoidal in shape.
[0015] Preferably, the diameter of the filler material is 0.5-2 cm.
[0016] Preferably, the rotational speed of the drum screen is 30-50 r / min.
[0017] Preferably, the method further includes: collecting the gaseous products in the reactor and separating the ammonia component for recycling.
[0018] According to the method for preparing cyanuric acid from urea as described in this invention, urea is first heated to a volatile state in a first reactor, and then the volatile urea is transferred to a second reactor for reaction using negative pressure. This process can avoid the wall adhesion problem in conventional tunnel kilns, greatly shortens the volume of the reaction equipment for the same output, and the purity of the cyanuric acid produced by this process can reach up to 98.5%. At the same time, it eliminates the acid washing step in conventional processes, greatly reducing process costs. Attached Figure Description
[0019] Figure 1 This is a process flow diagram for preparing cyanuric acid from urea according to the present invention.
[0020] Figure Labels 1. First reactor; 2. Second reactor; 3. Rotary drum screen. Detailed Implementation
[0021] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.
[0022] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0023] like Figure 1 As shown, the apparatus for the method of preparing cyanuric acid from urea according to the present invention includes: a preheater 1, a reactor 2, and a drum screen 3.
[0024] The method for preparing cyanuric acid from urea according to the present invention includes: heating urea in a preheater 1, then blowing in hot air to volatilize the urea, and conveying the volatilized urea to a reactor 2 containing a packing material for reaction, then conveying the packing material with attached solid products to a drum screen 3, and separating the solid products from the packing material with attached solid products.
[0025] In the method described in this invention, the heating process can be carried out by electric heating and / or hot flue gas. In the most preferred embodiment, the heating process can be carried out by electric heating. The heating temperature can be 150-170℃, preferably 160-165℃. The heating process can suppress the generation of byproducts such as biuret and improve the conversion rate of cyanuric acid.
[0026] In the method described in this invention, the temperature of the hot air can be 150-170°C, preferably 155-165°C.
[0027] In the method described in this invention, the mass-to-volume ratio of urea and hot air can be 1 kg: 5-10 m³. 3 Preferably, 1kg: 6-8m 3 .
[0028] In the method described in this invention, the reaction conditions may include: a temperature of 270-300°C and a time of 10-20 min. Preferably, the reaction conditions include: a temperature of 280-290°C and a time of 12-18 min. In a specific embodiment, after the volatile urea comes into contact with the filler material, it adheres to the surface and reacts to generate melamine. The filler material with melamine adhering to its surface is then conveyed to the drum screen 3 to separate the melamine. The separated filler material is then returned to the reactor 2 for reuse.
[0029] In the method described in this invention, the filler material can be zirconium oxide and / or stainless steel. In the most preferred embodiment, the filler material is zirconium oxide.
[0030] In the method described in this invention, the volume percentage of the filling material in the inner cavity of the reactor 2 can be 90-95%, preferably 92-94%. The shape of the filling material can be spherical and / or ellipsoidal. In the most preferred embodiment, the filling material is spherical. The diameter of the filling material can be 0.5-2 cm, preferably 1-1.5 cm. A wire mesh is provided at the inlet of the reactor 2 to prevent the filling material in the reactor 2 from entering the pipe.
[0031] In the method described in this invention, the rotational speed of the drum screen 3 can be 30-50 r / min, preferably 35-45 r / min. The drum screen 3 can be any conventional drum screen in the art.
[0032] In the method described in this invention, preferably, the method further includes: collecting the gaseous products in the reactor (2) and separating the ammonia component for recycling.
[0033] The following examples further illustrate the method for preparing cyanuric acid from urea according to the present invention. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.
[0034] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available.
[0035] The purity of the cyanuric acid prepared in this embodiment was determined according to standard HG / T 4818-2015.
[0036] Example 1 The apparatus used in the method for preparing cyanuric acid from urea in this embodiment includes: a preheater 1, a reactor 2, and a drum screen 3.
[0037] Urea is fed into preheater 1 and heated electrically to a temperature of 155°C. Then, hot air is blown in at 155°C to volatilize the urea. The mass-to-volume ratio of urea to hot air is 1 kg: 7 m³ / kg. 3The volatile urea is fed into reactor 2 containing zirconia spheres for reaction. The reaction conditions include: a temperature of 285℃, a reaction time of 15 min, a volume of zirconia spheres occupying 94% of the internal volume of reactor 2, and a diameter of 1 cm for the zirconia spheres. After the reaction is complete, the zirconia spheres with attached solid products are fed into a drum screen at a rotation speed of 40 r / min. The solid product, cyanuric acid A1, is separated from the zirconia spheres with attached solid products, and the gaseous product containing ammonia, B1, is collected from reactor 2.
[0038] After testing and calculation, the purity of cyanuric acid A1 was 98.94%, and the yield was 89.6%; the concentration of ammonia in the gaseous product B1 was 13.9%.
[0039] Example 2 The apparatus used in the method for preparing cyanuric acid from urea in this embodiment includes: a preheater 1, a reactor 2, and a drum screen 3.
[0040] Urea is fed into preheater 1 and heated electrically to a temperature of 165°C. Then, hot air is blown in at 165°C to volatilize the urea. The mass-to-volume ratio of urea to hot air is 1 kg: 10 m³ / kg. 3 The volatile urea is fed into reactor 2 containing zirconia spheres for reaction. The reaction conditions include: temperature 280℃, time 10 min, the volume of the zirconia spheres occupying 90% of the internal volume of reactor 2, and the diameter of the zirconia spheres being 1 cm. After the reaction is complete, the zirconia spheres with attached solid products are fed into a drum screen at a rotation speed of 40 r / min. The solid product, cyanuric acid A2, is separated from the zirconia spheres with attached solid products, and the gaseous product containing ammonia, B2, is collected from reactor 2.
[0041] After testing and calculation, the purity of cyanuric acid A2 was 98.78%, and the yield was 87.3%; the concentration of ammonia in the gaseous product B2 was 7.2%.
[0042] Example 3 The apparatus used in the method for preparing cyanuric acid from urea in this embodiment includes: a preheater 1, a reactor 2, and a drum screen 3.
[0043] Urea is fed into preheater 1 and heated electrically to a temperature of 160°C. Then, hot air is blown in at 160°C to volatilize the urea. The mass-to-volume ratio of urea to hot air is 1 kg: 5 m³ / kg. 3The volatile urea is fed into reactor 2 containing zirconia spheres for reaction. The reaction conditions include: temperature 275℃, time 10 min, the volume of the zirconia spheres occupying 95% of the internal volume of reactor 2, and the diameter of the zirconia spheres being 1 cm. After the reaction is complete, the zirconia spheres with attached solid products are fed into a drum screen at a rotation speed of 50 r / min. The solid product, cyanuric acid A3, is separated from the zirconia spheres with attached solid products, and the gaseous product containing ammonia, B3, is collected from reactor 2.
[0044] After testing and calculation, the purity of cyanuric acid A3 was 98.31%, and the yield was 86.2%; the concentration of ammonia in the gaseous product B3 was 11.8%.
[0045] Example 4 Following the method of Example 1, cyanuric acid was obtained, except that the heating temperature of preheater 1 was adjusted to 135°C, resulting in cyanuric acid A4 and gaseous product B4.
[0046] After testing and calculation, the purity of cyanuric acid A4 was 96.60%, and the yield was 71.3%; the concentration of ammonia in the gaseous product B4 was 9.8%.
[0047] Example 5 Following the method of Example 1, except that the temperature of the blown-in hot air was adjusted to 180°C, cyanuric acid A5 and gaseous product B5 were obtained.
[0048] After testing and calculation, the purity of cyanuric acid A5 was 98.22%, and the yield was 65.3%; the concentration of ammonia in the gaseous product B5 was 8.3%.
[0049] Example 6 The method of cyanuric acid is the same as in Example 1, except that the mass-to-volume ratio of urea and hot air is adjusted to 1 kg: 3 m³. 3 The resulting product is cyanuric acid A6 and gaseous product B6.
[0050] After testing and calculation, the purity of cyanuric acid A6 was 97.91%, and the yield was 66.9%; the concentration of ammonia in the gaseous product B6 was 15.8%.
[0051] Example 7 Following the method of Example 1, except that the temperature of the urea reaction was adjusted to 260°C, cyanuric acid A7 and gaseous product B7 were obtained.
[0052] After testing and calculation, the purity of cyanuric acid A7 was 92.34%, and the yield was 87.2%; the concentration of ammonia in the gaseous product B7 was 14.4%.
[0053] The purity and yield of the cyanuric acid prepared in the above examples are shown in Table 1 below.
[0054] Table 1
[0055] The concentrations of ammonia in the gaseous products collected in the above embodiments are shown in Table 2 below.
[0056] Table 2
[0057] As can be seen from the results in Table 1, the cyanuric acid prepared according to the method of the present invention has high purity and yield, and the process is simple.
[0058] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A method for preparing cyanuric acid from urea, characterized in that, The method includes: heating urea in a preheater (1), then blowing in hot air to volatilize the urea, and conveying the volatilized urea to a reactor (2) containing packing material for reaction, then conveying the packing material with attached solid products to a drum screen (3), and separating the solid products from the packing material with attached solid products.
2. The method according to claim 1, characterized in that, The heating process is achieved by electric heating and / or heating with hot flue gas; Preferably, the heating temperature is 150-170°C.
3. The method according to claim 1 or 2, characterized in that, The temperature of the hot air is 150-170℃.
4. The method according to any one of claims 1-3, characterized in that, The mass-to-volume ratio of the urea and the hot air is 1 kg: 5-10 m³. 3 .
5. The method according to any one of claims 1-4, characterized in that, The reaction conditions include a temperature of 270-300℃ and a time of 10-20 min.
6. The method according to any one of claims 1-5, characterized in that, The filler material is zirconium oxide and / or stainless steel.
7. The method according to any one of claims 1-6, characterized in that, The volume of the filling material accounts for 90-95% of the internal volume of the reactor (2).
8. The method according to any one of claims 1-7, characterized in that, The filling material is spherical and / or ellipsoidal in shape; Preferably, the diameter of the filler material is 0.5-2 cm.
9. The method according to any one of claims 1-8, characterized in that, The rotational speed of the drum screen (3) is 30-50 r / min.
10. The method according to any one of claims 1-9, characterized in that, The method further includes: collecting the gaseous products in the reactor (2) and separating the ammonia component for recycling.