CN107963995B

CN107963995B - Preparation method of melamine

Info

Publication number: CN107963995B
Application number: CN201810012116.5A
Authority: CN
Inventors: 严楠; 余潇兵; 邱静茹; 廖维林; 郭晓红
Original assignee: Jiangxi Normal University
Current assignee: Jiangxi Normal University
Priority date: 2018-01-05
Filing date: 2018-01-05
Publication date: 2020-01-10
Anticipated expiration: 2038-01-05
Also published as: CN107963995A

Abstract

The invention discloses a preparation method of melamine, which comprises the following steps of carrying out fluoro reaction on 1,3, 5-trichloro-s-triazine and tetrabutylammonium fluoride to obtain melamine and tetrabutylammonium chloride; the method does not need to use a catalyst, has high reaction selectivity, can achieve a yield of 95 percent, avoids the use of a high-risk fluorine reagent, namely hydrogen fluoride or a large amount of metal fluoride, and the addition of an expensive catalyst, has the advantages of simple operation, mild reaction conditions, low cost and the like, and is suitable for industrial production.

Description

Preparation method of melamine

Technical Field

The invention relates to a preparation method of melamine, in particular to a method for efficiently fluorinating 1,3, 5-trichloro-s-triazine to synthesize melamine by adopting tetrabutylammonium fluoride as a fluorinating reagent, belonging to the field of fine chemical engineering.

Background

Cyanuric fluoride is also known as 2,4, 6-trifluoro-1, 3, 5-triazine, cyanuric fluoride, english name: cyanicfluoride, 2,4, 6-trifloro-1, 3, 5-triazine (TFT). The molecular formula is as follows: c₃F₃N₃The structural formula:

cyanuric fluoride (TFT) is an important fluorinating agent that can be reacted with carboxylic acids to produce acyl fluoride compounds (J.Prakt. chem.2000,342,7, 711-714.). The cyanuric fluoride is an important intermediate for dye and medicine, and is a key intermediate for synthesizing fluoro-s-triazine reactive dye (EP Patent 1207186 and J supercritit Fluids 40: 477-484.). As the fluorine atom with high electronegativity replaces the chlorine atom, compared with the traditional chlorotriazine reactive dye, the fluoro-s-triazine reactive dye has the outstanding advantages of high fixation rate, low dyeing temperature, high dye stability and the like, and accords with the development direction of energy conservation and emission reduction of the current enterprises.

Although the fluorotriazine dye has the advantages of high color fixing rate and less pollution discharge, the melamine is not produced industrially in large batch all the time, and becomes the bottleneck of the production and application of the fluorotriazine dye in China. The preparation method of the cyanuric fluoride has been reported in the literature as early as the fifties of the last century, and mainly comprises two methods according to the difference of fluorinating agents: (1) the hydrogen fluoride method (Bayer company patents DE2643335, DE2643251, JP54014989 and Ciba Patents US4332939) uses hydrogen fluoride, which has strong corrosivity to equipment, high requirements on equipment, large hydrogen fluoride consumption and more recovery equipment. (2) The alkali metal fluoride (sodium fluoride, potassium fluoride) method is usually obtained by high temperature fluorination of cyanuric chloride and anhydrous potassium fluoride or sodium fluoride in sulfolane solvent (Bayer corporation patent DE3008923, J.Prakt. chem.2000,342,7,711-714.). The process has high reaction temperature, easy side reaction, low product yield, difficult recycling of sulfolane solvent, and hydrolysis of some non-substituted monofluoro dichlorotriazine and difluoro monochlorotriazine mixed in recycled sulfolane, thereby increasing the difficulty of waste salt treatment and causing serious corrosion of production equipment. Professor Sandford, university of duren, 2003, first reported a process for preparing cyanuric fluoride by catalytic nucleophilic fluorination of an ionic liquid under mild conditions in a yield of only 10% with the formation of monochlorodifluorotriazine and dichloromonofluorotriazine by-products (Journal of fluorine Chemistry,2003,123, 81-84.). In the report of Lu's and Wan's pioneer in China, PEG-600 is used as a catalyst, the dosage is 3.6 percent (relative to the amount of a solvent), xylene is used as the solvent, TCT and anhydrous potassium fluoride are stirred and refluxed for 16 hours, and a reaction solution is distilled to obtain a TFT; because the potassium fluoride is insoluble in dimethylbenzene and the reaction is heterogeneous, the industrial production is easy to agglomerate in a large quantity, and the energy consumption for recovering the PEG-600 with the high boiling point is large.

The intermediate of the melamine which is produced by adopting a fluoride salt method in small batch at home is adopted, but the price of the raw material of the fluorotriazine dye produced by the method is greatly higher than that of the traditional chlorotriazine dye due to high selling price, so that the development of the fluorotriazine dye is restricted. Therefore, a new process for synthesizing high-quality and low-cost cyanuric fluoride is needed to be developed to realize the large-scale application of the fluorotriazine dye in China.

Disclosure of Invention

Aiming at the defects of strong equipment corrosivity, high solvent recovery energy consumption, low product yield caused by side reaction easily generated under high temperature conditions, increased waste salt treatment difficulty and the like of the conventional method for preparing the melamine, the invention aims to provide the method for preparing the melamine, which has mild reaction conditions, strong selectivity and high yield, is low in cost, is green and environment-friendly and is beneficial to industrial production.

In order to achieve the technical purpose, the invention provides a preparation method of the melamine, which comprises the step of carrying out fluoro reaction on 1,3, 5-trichloro-s-triazine and tetrabutylammonium fluoride to obtain the melamine and tetrabutylammonium chloride.

In a preferred embodiment, the molar ratio of 1,3, 5-trichloro-s-triazine to tetrabutylammonium fluoride is 1: (3-5); more preferably 1: (3-4). The use of a suitable excess of tetrabutylammonium fluoride is beneficial for increasing the conversion of 1,3, 5-trichloro-s-triazine.

In a preferred embodiment, the conditions of the fluorination reaction are as follows: and (3) carrying out reaction under a protective atmosphere, wherein the reaction temperature is 30-70 ℃, and the reaction time is 3-8 hours. The protective atmosphere may be nitrogen, an inert gas, or a mixed atmosphere of nitrogen and an inert gas. In order to prevent the hydrolysis of the product, the drying of the reaction system should be ensured as much as possible, and the water content in the substrate raw material should be less than 1% by mass. The preferable reaction temperature is 40 to 60 ℃. The reaction time is preferably 5 to 7 hours.

Preferably, the fluorination reaction is carried out in a polar solvent. The reaction efficiency is relatively reduced by adopting a polar solvent and a solvent with weaker polarity or weaker polarity such as toluene, xylene and the like.

In a more preferred embodiment, the polar solvent includes at least one of dimethyl sulfoxide, dimethylacetamide, acetonitrile, tetrahydrofuran, N-methylpyrrolidone, and 1, 4-dioxane. Preferred solvents are dimethyl sulfoxide, dimethylacetamide or 1, 4-dioxane.

In a more preferable scheme, the dosage of the polar solvent is 3-7 times of the molar weight of 1,3, 5-trichloro-s-triazine; more preferably 4 to 6 times.

In a preferred scheme, the melamine is separated from the tetrabutylammonium chloride by reduced pressure distillation to obtain the melamine.

The preparation method of the invention comprises the following steps: the method comprises the following steps of placing a compound 1,3, 5-trichloro-s-triazine shown in a structural formula I and a compound tetrabutylammonium fluoride shown in a structural formula II in a polar organic solvent for reaction under the condition that a reaction system is kept dry to generate a compound cyanuric fluoride shown in a structural formula III and tetrabutylammonium chloride, collecting the obtained reaction mixture through simple reduced pressure distillation to obtain cyanuric fluoride (the pressure condition of the reduced pressure distillation is 0.010-0.015 MPa), and storing a cyanuric fluoride receiving container in a low-temperature environment (preferably storing in a low-temperature environment of-10-5 ℃).

The reaction formula is shown as:

compared with the prior art, the technical scheme of the invention has the following beneficial effects:

the prior art adopts the method for preparing the cyanuric fluoride by the hydrogen fluoride and the metal villiaumite, and has the defects of strong equipment corrosivity, large energy consumption for recovering the solvent, low product yield caused by side reaction easily generated under high temperature condition, increased difficulty in waste salt treatment and the like. In addition, the cost for preparing the melamine by adopting the prior process is higher, and the price of the raw material of the fluorotriazine dye produced by the process is greatly higher than that of the traditional chlorotriazine dye, so that the development of the fluorotriazine dye is restricted. The invention adopts tetrabutylammonium fluoride to replace hydrogen fluoride and metal fluoride salt in the traditional process as a reaction fluorine source for the first time, can obtain the cyanuric fluoride with the purity higher than 99.0 percent, has the yield of more than 95 percent, and almost has no by-products such as monochlorodifluorotriazine, dichloromonofluorotriazine and the like. In addition, the use of high-risk hydrogen fluoride or a large amount of metal fluoride and the like and the addition of expensive catalysts in the traditional method are avoided by adopting tetrabutylammonium fluoride as a fluorine source, and the method has the advantages of simple operation, mild reaction conditions, low cost and the like, and is suitable for industrial production. Compared with the traditional process, the method can greatly reduce the production cost of preparing the cyanuric fluoride and promote the development of the fluorotriazine dye.

Drawings

FIG. 1 is a nuclear magnetic resonance carbon spectrum of cyanuric fluoride.

FIG. 2 is the nuclear magnetic resonance fluorine spectrum of the cyanuric fluoride.

FIG. 3 is a gas chromatogram of melamine.

Detailed Description

The following examples are intended to further illustrate the present disclosure, but not to limit the scope of the claims.

Example 1

In a dry reaction vessel, 1,3, 5-trichloro-s-triazine (185g,1mol) and tetrabutylammonium fluoride (861g,3.3mol), anhydrous dimethyl sulfoxide (390g,5.0mol) were added. The reaction was stirred at 50 ℃ for 6 hours (TCL follow-up). The reaction device is changed into a distillation device, reduced pressure distillation is carried out, the reduced pressure is 0.012MPa, 124.2 g of colorless liquid with the boiling point of about 70 ℃ is collected, the content of the product is 99.2 percent by GC, and the yield is 92 percent. Under the condition of low temperature, the cyanuric fluoride is stored in a container made of polytetrafluoroethylene.

Comparative example 1

The other conditions were the same as in example 1, except that: potassium fluoride is used as a fluorine source instead of tetrabutylammonium fluoride, stirring reaction is carried out for 6 hours at 50 ℃, the reaction device is changed into a distillation device, reduced pressure distillation is carried out, the reduced pressure is 0.012MPa, 12.5 g of colorless liquid with the boiling point of about 70 ℃ is collected, the yield is 9.3%, and the content of the product is 98.0% by GC.

Example 2

1,3, 5-trichloro-s-triazine (370g,2mol) and tetrabutylammonium fluoride (1.722kg,6.6mol), anhydrous dimethylsulfoxide (780g,10.0mol) were charged in a dry reaction vessel, and the reaction was stirred at 60 ℃ for 6 hours. (TCL tracks the reaction). The reaction apparatus was changed to a distillation apparatus, and distillation was carried out under reduced pressure at 0.013MPa, 257 g of a colorless liquid having a boiling point of about 70 ℃ was collected, and the content of the product was 99.0% by GC, with a yield of 95%. Under the condition of low temperature, the cyanuric fluoride is stored in a container made of polytetrafluoroethylene.

Comparative example 2

The other conditions were the same as in example 2, except that: potassium fluoride was used as a fluorine source instead of tetrabutylammonium fluoride, and a PEG-600 (10%) catalyst was added, and the reaction was stirred at 60 ℃ for 6 hours, the reaction apparatus was changed to a distillation apparatus, and distillation was performed under reduced pressure at a reduced pressure of 0.013MPa, and 130 g of a colorless liquid having a boiling point of about 70 ℃ was collected, and the content of the product was 97.8% as determined by GC, and the yield was 48%.

Example 3

1,3, 5-trichloro-s-triazine (278g,1.5mol) and tetrabutylammonium fluoride (1.57kg,6.0mol), anhydrous dimethyl sulfoxide (702g,9.0mol) were charged into a dry reaction vessel, and the reaction was stirred at 60 ℃ for 6 hours. (TCL tracks the reaction). The reaction apparatus was changed to a distillation apparatus, and distillation was carried out under reduced pressure at 0.013MPa, and 188 g of a colorless liquid having a boiling point of about 70 ℃ was collected, and the content of the product was 99.0% by GC, and the yield was 93%. Under the condition of low temperature, the cyanuric fluoride is stored in a container made of polytetrafluoroethylene.

Example 4

1,3, 5-trichloro-s-triazine (278g,1.5mol) and tetrabutylammonium fluoride (1.57kg,6.0mol), anhydrous dimethyl sulfoxide (702g,9.0mol) were charged into a dry reaction vessel, and the reaction was stirred at 30 ℃ for 6 hours. (TCL tracks the reaction). The reaction apparatus was changed to a distillation apparatus, and distillation was carried out under reduced pressure at a reduced pressure of 0.013MPa, 142 g of a colorless liquid having a boiling point of about 70 ℃ was collected, and the content of the product was 98.5% by GC, with a yield of 70%. Under the condition of low temperature, the cyanuric fluoride is stored in a container made of polytetrafluoroethylene.

Example 5

In a dry reaction vessel, 1,3, 5-trichloro-s-triazine (185g,1mol) and tetrabutylammonium fluoride (861g,3.3mol), 1, 4-dioxane (440g,5.0mol) were added. The reaction was stirred at 50 ℃ for 6 hours (TCL follow-up). The reaction device was changed to a distillation device, and distillation was carried out under reduced pressure at 0.012MPa, and 119 g of a colorless liquid having a boiling point of about 70 ℃ was collected, and the content of the product was 99.0% as measured by GC, with a yield of 88%. Under the condition of low temperature, the cyanuric fluoride is stored in a container made of polytetrafluoroethylene.

Comparative example 3

In a dry reaction vessel, 1,3, 5-trichloro-s-triazine (185g,1mol) and tetrabutylammonium fluoride (861g,3.3mol), anhydrous dimethyl sulfoxide (390g,5.0mol) were added. The reaction was stirred at 50 ℃ for 2 hours (TCL follow-up). The reaction device was changed to a distillation device, and distillation was carried out under reduced pressure at 0.012MPa, 51.3 g of a colorless liquid having a boiling point of about 70 ℃ was collected, the content of the product was 97.8% by GC, and the yield was 38%. Under the condition of low temperature, the cyanuric fluoride is stored in a container made of polytetrafluoroethylene.

Example 6

1,3, 5-trichloro-s-triazine (37.0g,0.2mol) and tetrabutylammonium fluoride (172.3g,0.66 mol), anhydrous acetonitrile (41g,1.0mol) were added to a dry reaction vessel, and the reaction was stirred at 50 ℃ for 7 hours. (TCL tracks the reaction). The reaction apparatus was changed to a distillation apparatus, and distillation was carried out under reduced pressure at a reduced pressure of 0.013MPa, 19.4 g of a colorless liquid having a boiling point of about 70 ℃ was collected, and the content of the product was 97.5% by GC, with a yield of 72%. Under the condition of low temperature, the cyanuric fluoride is stored in a container made of polytetrafluoroethylene.

Comparative example 4

To a dry reaction vessel, 1,3, 5-trichloro-s-triazine (222g,1.2mol) and tetrabutylammonium fluoride (1.033kg,3.96mol), p-xylene (636g,6.0mol) were added. The reaction was stirred at 60 ℃ for 6 hours (TCL follow-up). The reaction device was changed to a distillation device, and distillation was carried out under reduced pressure at 0.012MPa, 56.7 g of a colorless liquid having a boiling point of about 70 ℃ was collected, the content of the product was 97.6% by GC, and the yield was 35%. Under the condition of low temperature, the cyanuric fluoride is stored in a container made of polytetrafluoroethylene.

Comparative example 5

In a dry reaction vessel, 1,3, 5-trichloro-s-triazine (185g,1mol) and tetrabutylammonium fluoride (861g,3.3mol), n-heptane (500g,5.0mol) were added. The reaction was stirred at 60 ℃ for 6 hours (TCL follow-up). The reaction apparatus was changed to a distillation apparatus, and distillation was carried out under reduced pressure at a reduced pressure of 0.013MPa, 29.7 g of a colorless liquid having a boiling point of about 70 ℃ was collected, and the content of the product was 98.0% as determined by GC, with a yield of 22%. Under the condition of low temperature, the cyanuric fluoride is stored in a container made of polytetrafluoroethylene.

Comparative example 6

1,3, 5-trichloro-s-triazine (37.0g,0.2mol) and tetrabutylammonium fluoride (172.3g,0.66 mol), anhydrous dimethyl sulfoxide (41g,1.0mol) were charged into a dry reaction vessel, and the reaction was stirred at 90 ℃ for 6 hours. (TCL tracks the reaction). The reaction apparatus was changed to a distillation apparatus, and distillation was carried out under reduced pressure at a reduced pressure of 0.013MPa, and 21.6 g of a colorless liquid having a boiling point of about 70 ℃ was collected, and the content of the product was 97% by GC, and the yield was 80%. Under the condition of low temperature, the cyanuric fluoride is stored in a container made of polytetrafluoroethylene.

Claims

1. A preparation method of the cyanuric fluoride is characterized in that: carrying out fluoro reaction on 1,3, 5-trichloro-s-triazine and tetrabutylammonium fluoride to obtain cyanuric fluoride and tetrabutylammonium chloride;

the conditions of the fluorination reaction are as follows: carrying out reaction under a protective atmosphere, wherein the reaction temperature is 30-70 ℃, and the reaction time is 3-8 hours;

the fluorination reaction is carried out in a polar solvent;

the polar solvent comprises at least one of dimethyl sulfoxide, dimethylacetamide, acetonitrile, tetrahydrofuran, N-methylpyrrolidone and 1, 4-dioxane.

2. The method of claim 1, wherein the first step comprises: the mol ratio of the 1,3, 5-trichloro-s-triazine to the tetrabutylammonium fluoride is 1: (3-5).

3. The method of claim 1, wherein the first step comprises: the dosage of the polar solvent is 3-7 times of the molar weight of the 1,3, 5-trichloro-s-triazine.

4. The method of claim 1, wherein the first step comprises: and separating the melamine and tetrabutylammonium chloride by reduced pressure distillation to obtain the melamine.