CN115181070A - Method for producing melamine - Google Patents
Method for producing melamine Download PDFInfo
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- CN115181070A CN115181070A CN202210958951.4A CN202210958951A CN115181070A CN 115181070 A CN115181070 A CN 115181070A CN 202210958951 A CN202210958951 A CN 202210958951A CN 115181070 A CN115181070 A CN 115181070A
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- catalyst
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D251/00—Heterocyclic compounds containing 1,3,5-triazine rings
- C07D251/02—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings
- C07D251/12—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings having three double bonds between ring members or between ring members and non-ring members
- C07D251/26—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings having three double bonds between ring members or between ring members and non-ring members with only hetero atoms directly attached to ring carbon atoms
- C07D251/40—Nitrogen atoms
- C07D251/54—Three nitrogen atoms
- C07D251/56—Preparation of melamine
- C07D251/60—Preparation of melamine from urea or from carbon dioxide and ammonia
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/14—Phosphorus; Compounds thereof
- B01J27/16—Phosphorus; Compounds thereof containing oxygen, i.e. acids, anhydrides and their derivates with N, S, B or halogens without carriers or on carriers based on C, Si, Al or Zr; also salts of Si, Al and Zr
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D251/00—Heterocyclic compounds containing 1,3,5-triazine rings
- C07D251/02—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings
- C07D251/12—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings having three double bonds between ring members or between ring members and non-ring members
- C07D251/26—Heterocyclic compounds containing 1,3,5-triazine rings not condensed with other rings having three double bonds between ring members or between ring members and non-ring members with only hetero atoms directly attached to ring carbon atoms
- C07D251/40—Nitrogen atoms
- C07D251/54—Three nitrogen atoms
- C07D251/62—Purification of melamine
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/141—Feedstock
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Catalysts (AREA)
Abstract
The invention relates to the technical field of chemical industry, in particular to a method for producing melamine, which comprises the steps of adding urea and a catalyst into a reactor, introducing ammonia gas, heating to 418-455 ℃, and reacting under the condition of keeping the partial pressure of the ammonia gas at 0.15-0.4 MPa; carrying out centrifugal separation on the mixed liquid containing the solid obtained by the reaction to obtain a crude melamine product and purifying the crude melamine product; the catalyst is obtained by the following preparation method: (1) Mixing pseudo-boehmite, phosphorus pentoxide and water, adding sulfuric acid to adjust the pH value, and then introducing carbon dioxide gas to stir to prepare modified alumina gel; (2) Adding silica gel, activated carbon and a filler into the aluminum gel, uniformly mixing, and performing extrusion forming to obtain a catalyst precursor; (3) Roasting the catalyst precursor at 400-485 ℃ for 6-14h, and then cooling in carbon dioxide gas flow to obtain the catalyst. The method has the advantages of high melamine yield, few byproducts, reduced consumption of the catalyst and urea, reduced replacement frequency of the catalyst and more stable operation.
Description
Technical Field
The invention relates to the technical field of chemical industry, in particular to a method for producing melamine.
Background
Melamine is an important nitrogen heterocyclic ring organic chemical intermediate product, is mainly used for producing melamine-formaldehyde resin, and is widely applied to the fields of wood processing, coating, papermaking, textile, leather processing and the like. In recent years, the application field and range of melamine are more and more extensive, the consumption is rapidly increased, and in order to improve the productivity and the product quality and reduce the production cost, enterprises continuously seek a melamine production method capable of further improving the productivity and optimizing the product quality.
The urea method is mostly adopted in China for producing melamine, and the method is divided into a high-pressure process, a low-pressure process and a normal-pressure process according to the characteristics of the production process, wherein the normal-pressure process and the low-pressure process are adopted more at present, but the normal-pressure and low-pressure production processes have very strict requirements on catalysts and have the advantages of high strength, high activity, large load, low price and the like.
Therefore, the performance of the catalyst has a crucial influence on the whole melamine production process, so that continuous research on various excellent catalysts is extremely necessary and beneficial for enterprises to optimize the production process so as to improve the productivity and reduce the cost, and more selectivity can be provided for the enterprises, thereby being beneficial to the benign competition and development in the industry.
In view of the above, the present invention is particularly proposed.
Disclosure of Invention
In order to solve the technical problems, the invention provides a method for producing melamine, the catalyst adopted by the method has high activity and good selectivity, the method has the advantages of high melamine yield, few byproducts, good product quality, reduced consumption of the catalyst and urea, reduced replacement frequency of the catalyst, more stable operation and more optimized overall process.
The basic concept of the technical scheme of the invention is as follows:
a method for producing melamine, said method comprises adding urea and catalyst into reactor, inject ammonia, heat to 418-455 duC, keep the ammonia partial pressure under the condition of 0.15-0.4 MPa, react; carrying out centrifugal separation on the mixed liquid containing the solid obtained by the reaction to obtain a crude melamine product and purifying the crude melamine product;
the catalyst is obtained by the following preparation method:
(1) Mixing pseudo-boehmite, phosphorus pentoxide and water, adding sulfuric acid to adjust the pH value, and then introducing carbon dioxide gas to stir to prepare modified alumina gel;
(2) Adding silica gel, activated carbon and a filler into the aluminum gel, uniformly mixing, and performing extrusion forming to obtain a catalyst precursor;
(3) Roasting the catalyst precursor at 400-485 ℃ for 6-14h, and then cooling in carbon dioxide gas flow to obtain the catalyst.
As one example, in the step (1), carbon dioxide gas is introduced for stirring for 3 to 5 hours.
As one example, the weight ratio of pseudo-boehmite, phosphorus pentoxide and water is 1: 0.1-0.3: 30-65, and the amount of sulfuric acid is added to bring the pH of the material to 8-9.5.
In one example, the weight ratio of silica gel to activated carbon to filler is 3: 0.05-0.2: 4-6.
As one example, the filler is a mixture of sesbania powder, activated clay, zeolite powder, diatomite and calcium carbonate in a weight ratio of 2:2 to (0.5-1) to 2 to (0.1-0.5).
As one example, the filler is a mixture of sesbania powder, activated clay, zeolite powder, diatomite and calcium carbonate in a weight ratio of 2:0.7:2:0.3.
In one case, the catalyst is spherical and has an average particle size in the range of 85 to 100. Mu.m.
As one example, in the step (3), the temperature is increased to 400 ℃ at a temperature rising speed of 10 ℃/mmin, and the mixture is roasted for 2 hours; then the temperature is raised to 485 ℃ at the temperature rise speed of 20 ℃/mmin, and then the roasting is continued for 4 hours at the temperature.
As one example, the method comprises the steps of adding urea and a catalyst into a reactor, introducing ammonia gas, heating to 435 ℃, and keeping the partial pressure of the ammonia gas at 0.35MPa for reaction.
As an example, the purification process of crude melamine comprises the following steps:
adding the crude melamine and acid clay into a dissolving tank according to the weight ratio of 100:4, mixing the crude melamine and the acid clay with the circulating mother liquor after heat exchange to 62 ℃, introducing hydrogen chloride gas to adjust the pH to 7.2, and stirring to obtain a suspension system;
heating the suspension system to 122 ℃ to dissolve the suspension system to form a saturated 7.1% concentrated solution, and filtering to remove impurities;
decoloring the filtered liquid, exchanging heat with circulating mother liquor to recover energy and reduce the temperature, then entering the middle part of a circulating crystallizer, and crystallizing at the temperature of 48 ℃ to form magma supernatant and magma concentrated solution;
and extracting the crystal slurry concentrated solution, performing centrifugal separation to obtain a filter cake and filtrate, and drying the filter cake to obtain the purified melamine.
Compared with the prior art, the invention has the following advantages:
1. the method adopts a new catalyst, the catalyst has high activity and good selectivity, enriches the selection processes for enterprises, and is favorable for promoting the benign competitive situation of hundreds of flowers in the industry.
2. The method has the advantages of high melamine yield and few byproducts, and can reduce the difficulty of subsequent product treatment.
3. The method of the invention has the advantages of reduced consumption of catalyst and urea, reduced replacement frequency of the catalyst and more stable operation.
4. In the catalyst used in the invention, phosphorus pentoxide, active carbon and the like are uniformly dispersed in the catalyst system, so that the active sites are increased, the catalytic activity is high, and the catalyst is not easy to inactivate.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention are clearly and completely described below. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention without any inventive step, are within the scope of protection of the invention.
As a specific example, the urea charge loading of the following examples and comparative examples was uniformly 220 g/kg-h-1 catalyst.
But it should not be construed as unduly limiting the technical aspects of the invention.
Example 1
A method for producing melamine, add urea and catalyst into reactor, inject ammonia, heat to 435 ℃, keep the ammonia partial pressure under the condition of 0.35MPa, react; carrying out centrifugal separation on the mixed liquid containing the solid obtained by the reaction to obtain a crude melamine product and purifying the crude melamine product;
the purification process comprises the following steps: adding the crude melamine product and acid clay into a dissolving tank according to the weight ratio of 100:4, mixing the crude melamine product and the acid clay with the circulating mother liquor after heat exchange to 62 ℃, introducing hydrogen chloride gas to adjust the pH value to 7.2, and stirring to obtain a suspension system;
heating the suspension system to 122 ℃ to dissolve the suspension system to form a saturated 7.1% concentrated solution, and filtering to remove impurities;
decoloring the filtered liquid, exchanging heat with circulating mother liquor to recover energy and reduce the temperature, then entering the middle part of a circulating crystallizer, and crystallizing at the temperature of 48 ℃ to form magma supernatant and magma concentrated solution;
and extracting the crystal slurry concentrated solution, performing centrifugal separation to obtain a filter cake and filtrate, and drying the filter cake to obtain the purified melamine.
The catalyst is obtained by the following preparation method:
(1) Mixing pseudo-boehmite, phosphorus pentoxide and water in a weight ratio of 1: 0.3: 65, adding sulfuric acid to adjust the pH =8, then introducing carbon dioxide gas and stirring for 3-5 h to prepare modified aluminum glue;
(2) Adding silica gel, activated carbon and a filler in a weight ratio of 3: 0.15: 4 into the aluminum gel, uniformly mixing, and performing extrusion forming to obtain a catalyst precursor;
the filler is a mixture of sesbania powder, activated clay, zeolite powder, diatomite and calcium carbonate in a weight ratio of 2:0.7:2: 0.3;
(3) Heating the catalyst precursor to 400 ℃ at a heating rate of 10 ℃/min, and roasting for 2h; then raising the temperature to 485 ℃ at the temperature rise speed of 20 ℃/min, then continuing roasting for 4h at the temperature, and then cooling in carbon dioxide gas flow to obtain the catalyst.
The catalyst is spherical and has an average particle size of 85-100 μm.
Example 2
The only difference from example 1 is that the weight ratio of pseudoboehmite, phosphorus pentoxide and water was 1: 0.1: 30.
Example 3
The only difference from example 1 is that the weight ratio of pseudo-boehmite, phosphorus pentoxide and water was 1: 0.2: 55.
Example 4
The only difference from example 1 is that the weight ratio of silica gel, activated carbon and filler was 3: 0.2: 6.
Example 5
The only difference from example 1 is that the weight ratio of silica gel, activated carbon and filler was 3: 0.05: 5.
Example 6
The only difference from example 1 is that the filler is a mixture of sesbania powder, activated clay, zeolite powder, diatomaceous earth and calcium carbonate in a weight ratio of 2: 0.5: 2: 0.5.
Example 7
The only difference from example 1 is that the filler is a mixture of sesbania powder, activated clay, zeolite powder, diatomaceous earth and calcium carbonate in a weight ratio of 2: 1: 2: 0.1.
Example 8
The only difference from example 1 is that the catalyst was obtained by calcining the catalyst precursor at 485 c for 6.25h and then cooling it in a carbon dioxide gas stream.
Comparative example 1
The only difference from example 1 is that no phosphorus pentoxide is added in step (1).
Comparative example 2
The only difference from example 1 is that no activated carbon was added in step (2).
Comparative example 3
The only difference from example 1 is that in step (3) the catalyst precursor was calcined at 490 c for 6.25h and then allowed to cool naturally in atmospheric conditions.
Comparative example 4
The only difference from example 1 is that the reaction was carried out by introducing ammonia gas, heating to 410 ℃ and maintaining the partial pressure of ammonia gas at 0.35 MPa.
Comparative example 5
The only difference from example 1 is that the reaction was carried out by introducing ammonia gas, heating to 460 ℃ and maintaining the partial pressure of ammonia gas at 0.35 MPa.
Comparative example 6
The only difference from example 1 is that the reaction was carried out by introducing ammonia gas, heating to 435 ℃ and maintaining the partial pressure of ammonia gas at 0.5 MPa.
The effects of examples 1 to 8 and comparative examples 1 to 6 are shown in the following table.
TABLE 1
From the effect data of the above table it can be derived:
the catalyst formulation of comparative example 1 or 2 is different from the technical idea of the present invention in that the yield of melamine is remarkably reduced and the consumption of urea and catalyst is increased, and the stability of the whole production process is lowered due to the shortened operation period of the catalyst.
The calcination process in the catalyst preparation method of comparative example 3 does not adopt the technical concept of the present invention, the yield of melamine is also reduced, the consumption of urine and catalyst is also increased, the operation period is shorter than that of the technical scheme of the present invention, and there is a great improvement and promotion space.
Comparative examples 4-6 the reaction parameters of urea, catalyst and ammonia in the process for producing melamine are not in the technical idea of the present invention, and are not favorable for exerting the superiority of the catalyst to the utmost extent, it can be seen that the conditions of heating to 418-455 ℃ and maintaining the partial pressure of ammonia at 0.15-0.4 MPa defined in the present invention are particularly matched with the catalyst prepared in the present invention to form the excellent process for producing melamine of the present invention.
Although the embodiments of the present invention have been described above, the above description is only for the purpose of understanding the present invention, and is not intended to limit the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A method for producing melamine is characterized in that urea and a catalyst are added into a reactor, ammonia gas is introduced, the temperature is heated to 418-455 ℃, and the ammonia gas partial pressure is kept at 0.15-0.4 MPa for reaction; carrying out centrifugal separation on the mixed liquid containing solids obtained by the reaction to obtain a crude melamine product and purifying the crude melamine product;
the catalyst is prepared by the following preparation method:
(1) Mixing pseudo-boehmite, phosphorus pentoxide and water, adding sulfuric acid to adjust the pH value, and then introducing carbon dioxide gas to stir to prepare modified alumina gel;
(2) Adding silica gel, activated carbon and a filler into the aluminum gel, uniformly mixing, and performing extrusion forming to obtain a catalyst precursor;
(3) And roasting the catalyst precursor at 400-485 ℃ for 6-14h, and then cooling in carbon dioxide gas flow to obtain the catalyst.
2. The method for producing melamine according to claim 1, wherein in step (1), the carbon dioxide gas is introduced and stirred for 3 to 5 hours.
3. A process for producing melamine as claimed in claim 1, wherein the weight ratio of the pseudoboehmite, the phosphorus pentoxide and the water is 1 (0.1-0.3) to (30-65), and the amount of sulfuric acid added is such that the pH of the material is 8-9.5.
4. The method for producing melamine according to claim 1, wherein the weight ratio of the colloidal silica, the activated carbon and the filler is 3 (0.05-0.2) to (4-6).
5. Process for the production of melamine according to claim 4, characterized in that said filler is a mixture of sesbania powder, activated clay, zeolite powder, diatomaceous earth and calcium carbonate in a weight ratio of 2:2: (0.5 to 1): 2: (0.1-0.5).
6. Process for the production of melamine according to claim 5, characterized in that said filler is a mixture of sesbania powder, activated clay, zeolite powder, diatomaceous earth and calcium carbonate in a weight ratio of 2:2:0.7:2:0.3.
7. process for the production of melamine according to claim 1, characterized in that said catalyst is of spherical type with an average particle size ranging from 85 to 100 μm.
8. The method for producing melamine according to claim 1, wherein in step (3), the temperature is raised to 400 ℃ at a temperature raising rate of 10 ℃/min, and the mixture is baked for 2h; then the temperature is increased to 485 ℃ at the temperature rising speed of 20 ℃/min, and then the roasting is continued for 4h at the temperature.
9. Process for the production of melamine according to any one of claims 1 to 8, wherein urea and a catalyst are introduced into the reactor and the reaction is carried out with introduction of ammonia, heating to 435 ℃ and maintaining the partial pressure of ammonia at 0.35 MPa.
10. Process for the production of melamine according to any one of claims 1 to 8, characterized in that the purification process of the crude melamine comprises the following steps:
mixing the crude melamine product and acid clay according to the ratio of 100:4, adding the mixture into a dissolving tank in a weight ratio of 62 ℃, mixing the mixture with the circulating mother liquor after heat exchange, introducing hydrogen chloride gas to adjust the pH to 7.2, and stirring to obtain a suspension system;
heating the suspension system to 122 ℃ to dissolve the suspension system to form a saturated 7.1% concentrated solution, and filtering to remove impurities;
decoloring the filtered liquid, exchanging heat with circulating mother liquor to recover energy and reduce the temperature, then entering the middle part of a circulating crystallizer, and crystallizing at the temperature of 48 ℃ to form magma supernatant and magma concentrated solution;
and extracting the crystal slurry concentrated solution, performing centrifugal separation to obtain a filter cake and filtrate, and drying the filter cake to obtain the purified melamine.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210958951.4A CN115181070A (en) | 2022-08-10 | 2022-08-10 | Method for producing melamine |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210958951.4A CN115181070A (en) | 2022-08-10 | 2022-08-10 | Method for producing melamine |
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| CN115181070A true CN115181070A (en) | 2022-10-14 |
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| CN202210958951.4A Pending CN115181070A (en) | 2022-08-10 | 2022-08-10 | Method for producing melamine |
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Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3332947A (en) * | 1965-09-14 | 1967-07-25 | American Cyanamid Co | Production of melamine |
| WO1995006042A1 (en) * | 1993-08-23 | 1995-03-02 | Conser S.P.A. | Process for the production of high purity melamine |
| US20030083496A1 (en) * | 1998-12-31 | 2003-05-01 | Hans Vrijenhoef | High-pressure process for the preparation of melamine from urea |
| CN1455774A (en) * | 2000-09-13 | 2003-11-12 | 卡萨尔化学股份有限公司 | Process for production of high purity melamine from urea |
| DE502004003874D1 (en) * | 2004-01-17 | 2007-07-05 | Casale Chemicals Sa | Process for the gentle cooling and crystallization of melamine from a melamine melt or from the gas phase |
| CN102558079A (en) * | 2011-12-30 | 2012-07-11 | 南通紫鑫实业有限公司 | Process for producing melamine |
| CN104788394A (en) * | 2015-04-14 | 2015-07-22 | 四川金象赛瑞化工股份有限公司 | Melamine refining method |
| CN113694911A (en) * | 2021-09-16 | 2021-11-26 | 四川金象赛瑞化工股份有限公司 | Catalyst for synthesizing melamine and preparation method thereof |
-
2022
- 2022-08-10 CN CN202210958951.4A patent/CN115181070A/en active Pending
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3332947A (en) * | 1965-09-14 | 1967-07-25 | American Cyanamid Co | Production of melamine |
| WO1995006042A1 (en) * | 1993-08-23 | 1995-03-02 | Conser S.P.A. | Process for the production of high purity melamine |
| US20030083496A1 (en) * | 1998-12-31 | 2003-05-01 | Hans Vrijenhoef | High-pressure process for the preparation of melamine from urea |
| CN1455774A (en) * | 2000-09-13 | 2003-11-12 | 卡萨尔化学股份有限公司 | Process for production of high purity melamine from urea |
| US20040010144A1 (en) * | 2000-09-13 | 2004-01-15 | Willi Ripperger | Process for the production of high purity melamine from urea |
| DE502004003874D1 (en) * | 2004-01-17 | 2007-07-05 | Casale Chemicals Sa | Process for the gentle cooling and crystallization of melamine from a melamine melt or from the gas phase |
| CN102558079A (en) * | 2011-12-30 | 2012-07-11 | 南通紫鑫实业有限公司 | Process for producing melamine |
| CN104788394A (en) * | 2015-04-14 | 2015-07-22 | 四川金象赛瑞化工股份有限公司 | Melamine refining method |
| CN113694911A (en) * | 2021-09-16 | 2021-11-26 | 四川金象赛瑞化工股份有限公司 | Catalyst for synthesizing melamine and preparation method thereof |
Non-Patent Citations (2)
| Title |
|---|
| 王建民: "三聚氰胺生产技术现状及发展趋势", 《氮肥技术》, vol. 39, no. 4, pages 31 - 34 * |
| 陈文: "三聚氰胺生产中新型催化剂的应用研究", 《化工进展》, no. 10, pages 39 - 41 * |
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