CN112661670A - Method for preparing 1,6-hexamethylene dicarbamate in non-catalytic mode - Google Patents
Method for preparing 1,6-hexamethylene dicarbamate in non-catalytic mode Download PDFInfo
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Abstract
The invention relates to a method for preparing 1,6-hexamethylene dicarbamate without catalysis, which takes dialkyl carbonate and hexamethylene diamine as raw materials and adds a specific solvent, so that the preparation process has higher conversion efficiency without adding a catalyst; the preparation method has mild reaction conditions, high reaction efficiency and high yield of the target product 1,6-hexamethylene dicarbamate, and the preparation method can complete the preparation process within the temperature range of 25-100 ℃ within 2-10h, and the yield of the 1,6-hexamethylene dicarbamate in the product can reach more than 90%.
Description
Technical Field
The invention belongs to the technical field of organic chemical industry, and relates to a method for preparing 1,6-hexamethylene dicarbamate in a non-catalytic manner.
Background
1,6-hexamethylene diisocyanate (1,6-hexamethylene diisocyanate, HDI) is aliphatic isocyanate with the largest demand amount in the current polyurethane industry, and compared with aromatic diphenylmethane diisocyanate, phenylisocyanate and the like, the polyurethane derivative has the advantages of bright color, moderate hardness, oil resistance, wear resistance, no yellowing, chalking resistance, outdoor solarization resistance, gloss retention, color retention and the like due to the saturated straight-chain alkane structure, and is widely applied to the aspects of automobile and airplane OEM coatings, refinishing paints, high-grade wood furniture paints, anticorrosive coatings, adhesives with good light stability and the like.
Currently, the phosgene method is mainly used for producing 1,6-hexamethylene diisocyanate industrially. The method adopts the highly toxic phosgene as the raw material, and has the advantages of long synthesis process route, complex technology, expensive raw material cost, high equipment cost, heavy environmental pollution, extremely harsh production conditions, and great environmental pollution and ecological safety risk caused by easy leakage. Therefore, the non-phosgene method has been a focus of attention of researchers. In the method for preparing HDI without phosgene which is reported at present, the pyrolysis method of carbamate obtains wide attention due to the advantages of mild reaction conditions, recyclable by-products and the like. Thus, the preparation of the pyrolytic precursor 1,6-hexamethylene dicarbamate is a key step of the technology.
For the synthesis of 1,6-hexamethylene dicarbamate, a catalyzed reaction of hexamethylene diamine with a carbonate is generally employed.
CN1727330A discloses a method for synthesizing hexamethylene-1, 6-diamino methyl formate, which comprises the steps of adding hexamethylene diamine into dimethyl carbonate, adding a certain amount of lead compound, reacting under magnetic stirring after the addition is finished, continuously separating out a byproduct methanol in the reaction process, filtering out a catalyst after the reaction is finished, recycling the catalyst, distilling under reduced pressure to remove a solvent, and crystallizing to obtain a white solid hexamethylene-1, 6-diamino methyl formate.
CN101337189A discloses an application of a solid acid catalyst in the synthesis of 1,6-hexamethylene diisocyanate, wherein the catalyst is SO4 2-/TiO2-ZnO-ZrO2-Al2O3Synthesis of 1,6-hexamethylene diisocyanate from hexamethylene diamine and carbonDimethyl formate is used as a raw material to prepare hexamethylene dicarbamate at the temperature of 50-90 ℃, and then 1,6-hexamethylene diisocyanate is obtained through pyrolysis.
CN105126804A discloses a preparation method for synthesizing 1,6-hexamethylene dicarbamate, wherein the catalyst adopted in the preparation process comprises X/SiO2Wherein X is a metal salt, and the supported metal salt comprises NaOCH3、NaOAc、Pb(OAc)2、Sc(OTf)3、NaCF3SO3Or Na2C2O4Yield of 1,6-hexamethylene dicarbamate in the preparation process thereof<70 percent, complex catalyst preparation process and high industrial application cost.
Therefore, the development of a preparation method of 1,6-hexamethylene dicarbamate which has low cost, no pollution, simple operation and high product yield is still of great significance.
Disclosure of Invention
The invention aims to provide a method for preparing 1,6-hexamethylene dicarbamate in a non-catalytic manner, which takes dialkyl carbonate and hexamethylene diamine as raw materials and adds a specific solvent, so that the preparation process has higher conversion efficiency without adding a catalyst; the preparation method has mild reaction conditions, high reaction efficiency and high yield of the target product 1,6-hexamethylene dicarbamate, and the preparation method can complete the preparation process within the temperature range of 25-100 ℃ within 2-10h, and the yield of the 1,6-hexamethylene dicarbamate in the product can reach more than 90%.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a non-catalytic method for preparing 1,6-hexamethylene dicarbamate, which comprises the steps of mixing dialkyl carbonate, hexamethylene diamine and a solvent, and reacting to obtain the 1,6-hexamethylene dicarbamate, wherein the solvent comprises any one or the combination of at least two of methanol, ethanol, water or tetrahydrofuran; the molar ratio of the solvent to hexamethylenediamine is (4-8):1, for example 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1 or 7.5:1, etc.
The traditional method for preparing 1,6-hexamethylene dicarbamate usually needs to add a catalyst in the process, the process is divided into homogeneous catalysis and heterogeneous catalysis according to different catalyst forms, the homogeneous catalyst is difficult to separate and recycle in the homogeneous catalysis process, the 1,6-hexamethylene dicarbamate has low yield, and the product is difficult to separate, while the heterogeneous catalysis generally has the problem of low yield; in the process of preparing the 1,6-hexamethylene dicarbamate by the method, dialkyl carbonate and hexamethylene diamine are used as raw materials, a specific solvent is added for reaction, the 1,6-hexamethylene dicarbamate is prepared, the temperature required in the preparation process is low, the preparation process can be completed within the temperature range of 25-100 ℃ for 2-10 hours, and the yield of the 1,6-hexamethylene dicarbamate in the product can reach more than 90%.
In the preparation process, the adding amount of the solvent is controlled to ensure that the molar ratio of the solvent to the hexamethylene diamine is (4-8) to 1, which is beneficial to improving the efficiency of catalytic reaction and shortening the time required by the reaction; when the molar ratio of solvent to hexamethylenediamine is < 4:1, the hexamethylenediamine conversion is too low (< 20%).
Preferably, the reaction is accompanied by stirring.
Preferably, the reaction is carried out with the exclusion of lower alcohols.
The lower alcohol in the present invention refers to any one of ethanol, propanol or butanol or a combination of at least two thereof, and the combination illustratively includes a combination of ethanol and propanol, a combination of butanol and ethanol, or a combination of propanol and butanol, and the like.
Preferably, the method for removing the lower alcohol comprises nitrogen introduction and/or reduced pressure distillation.
Preferably, the dialkyl carbonate is selected from any one of diethyl carbonate, dipropyl carbonate, or dibutyl carbonate, or a combination of at least two thereof, which illustratively includes a combination of diethyl carbonate and dipropyl carbonate, a mixture of diethyl carbonate and dibutyl carbonate, or a mixture of dipropyl carbonate and dibutyl carbonate, or the like.
Preferably, the molar ratio of dialkyl carbonate to hexamethylenediamine is (2-10):1, such as 3:1, 5:1, 7:1 or 10:1, etc.
Preferably, the molar ratio of the solvent, dialkyl carbonate and hexamethylenediamine is (4-8): 2-10):1, e.g. 5:9:1, 6:7:1 or 7:3:1, etc.
Preferably, the temperature of the reaction is 25-100 ℃, such as 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃ or 90 ℃, preferably 40-80 ℃.
In the preparation process, the reaction temperature is controlled to be 25-100 ℃, and when the reaction temperature is lower than 25 ℃, the reaction speed is very low under the influence of thermodynamics; thermodynamic equilibrium is reached when the reaction temperature is > 100 ℃.
Preferably, the reaction time is 2-10h, such as 3h, 4h, 5h, 6h, 7h, 8h or 9h, etc., preferably 3-8 h.
The reaction time is controlled to be 2-10h in the preparation process, and when the reaction time is less than 2h, the reaction efficiency is lower; when the reaction time is more than 10h, the reaction reaches the equilibrium, and the conversion rate of the reaction yield is not changed any more
As a preferred technical scheme of the invention, the method comprises the following steps:
(1) stirring and mixing dialkyl carbonate, hexamethylene diamine and a solvent, wherein the molar ratio of the solvent to the dialkyl carbonate to the hexamethylene diamine is (4-8) to (2-10) to 1; the dialkyl carbonate is selected from any one or a combination of at least two of diethyl carbonate, dipropyl carbonate or dibutyl carbonate;
the dialkyl carbonate is selected from any one or a combination of at least two of diethyl carbonate, dipropyl carbonate or dibutyl carbonate;
(2) reacting the mixed solution obtained in the step (1) at the temperature of 25-100 ℃ for 2-10h to obtain the 1,6-hexamethylene dicarbamate, wherein stirring is carried out in the reaction process, and low carbon alcohol is removed in the reaction process by adopting a nitrogen introducing and/or reduced pressure distillation mode.
Compared with the prior art, the invention has the following beneficial effects:
(1) the specific solvent is added in the preparation process of the method, so that the process of preparing the 1,6-hexamethylene dicarbamate can be rapidly carried out without adding a catalyst, the reaction condition is mild, the conversion rate of hexamethylene diamine is high, and the yield of the product 1,6-hexamethylene dicarbamate is high;
(2) according to the method, a catalyst is not required to be added in the preparation process, so that the catalyst is not required to be separated after the reaction is finished, the energy consumption in the preparation process is reduced, and the method has a good industrial prospect;
(3) the preparation process of the method is pollution-free, the operation process is simple and convenient, and the potential safety hazard is small.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
Non-catalytic preparation method of 1,6-hexamethylene dicarbamate:
(1) stirring and mixing diethyl carbonate, hexamethylene diamine and water, wherein the molar ratio of the water to the diethyl carbonate to the hexamethylene diamine is 4:2: 1;
(2) and (2) reacting the mixed solution obtained in the step (1) at the temperature of 40 ℃ for 10 hours to obtain the 1,6-hexamethylene dicarbamate, wherein stirring is carried out in the reaction process, and low-carbon alcohol is removed in a reduced pressure distillation mode in the reaction process.
After the reaction is finished, a sample is taken for gas chromatography analysis, and the conversion rate of the hexamethylene diamine and the yield of the 1,6-hexamethylene dicarbamate are determined.
Example 2
This example differs from example 1 in that the molar ratio of water to diethyl carbonate to hexamethylenediamine was changed to 7:6:1, and the other conditions were exactly the same as in example 1.
Example 3
This example differs from example 1 in that the molar ratio of water to diethyl carbonate to hexamethylenediamine was replaced by 8:10:1, and the other conditions were exactly the same as in example 1.
Example 4
Non-catalytic preparation method of 1,6-hexamethylene dicarbamate:
(1) stirring and mixing diethyl carbonate, hexamethylene diamine and ethanol, wherein the molar ratio of the ethanol to the diethyl carbonate to the hexamethylene diamine is 4:2: 1;
(2) and (2) reacting the mixed solution obtained in the step (1) at the temperature of 90 ℃ for 3 hours to obtain the 1,6-hexamethylene dicarbamate, wherein stirring is carried out in the reaction process, and low-carbon alcohol is removed in a reduced pressure distillation mode in the reaction process.
After the reaction is finished, a sample is taken for gas chromatography analysis, and the conversion rate of the hexamethylene diamine and the yield of the 1,6-hexamethylene dicarbamate are determined.
Example 5
The difference between this example and example 4 is that the molar ratio of ethanol, diethyl carbonate and hexamethylene diamine was changed to 8:6:1, and the other conditions were exactly the same as in example 4.
Example 6
The difference between this example and example 4 is that the molar ratio of ethanol, diethyl carbonate and hexamethylene diamine was changed to 8:10:1, and the other conditions were exactly the same as in example 4.
Example 7
Non-catalytic preparation method of 1,6-hexamethylene dicarbamate:
(1) stirring and mixing dipropyl carbonate, hexamethylene diamine and a mixed solvent (marked as tetrahydrofuran/water) of tetrahydrofuran and water, wherein the molar ratio of tetrahydrofuran to water is 1:1, and the molar ratio of the mixed solvent, dipropyl carbonate and hexamethylene diamine is 4:2: 1;
(2) and (2) reacting the mixed solution obtained in the step (1) at the temperature of 45 ℃ for 8 hours to obtain the 1,6-hexamethylene dicarbamate, wherein stirring is carried out in the reaction process, and low-carbon alcohol is removed in a reduced pressure distillation mode in the reaction process.
After the reaction is finished, a sample is taken for gas chromatography analysis, and the conversion rate of the hexamethylene diamine and the yield of the 1,6-hexamethylene dicarbamate are determined.
Example 8
The difference between the present example and example 7 is that the molar ratio of tetrahydrofuran to water mixed solvent, dipropyl carbonate and hexamethylene diamine was changed to 8:6:1, and the other conditions were completely the same as those in example 7.
Example 9
The difference between the present example and example 7 is that the molar ratio of tetrahydrofuran to water mixed solvent, dipropyl carbonate and hexamethylene diamine was changed to 8:10:1, and the other conditions were completely the same as those in example 7.
Example 10
Non-catalytic preparation method of 1,6-hexamethylene dicarbamate:
(1) stirring and mixing diethyl carbonate, hexamethylene diamine and methanol, wherein the molar ratio of the methanol to the diethyl carbonate to the hexamethylene diamine is 4:3: 1;
(2) reacting the mixed solution obtained in the step (1) at the temperature of 80 ℃ for 6h to obtain the 1,6-hexamethylene dicarbamate, wherein stirring is carried out in the reaction process, and low-carbon alcohol is removed in a reduced pressure distillation mode in the reaction process.
After the reaction is finished, a sample is taken for gas chromatography analysis, and the conversion rate of the hexamethylene diamine and the yield of the 1,6-hexamethylene dicarbamate are determined.
Example 11
The difference between this example and example 10 is that the molar ratio of methanol to diethyl carbonate to hexamethylenediamine was changed to 8:5:1, and the other conditions were exactly the same as in example 10.
Example 12
The difference between this example and example 10 is that the molar ratio of methanol to diethyl carbonate to hexamethylenediamine was changed to 10:9:1, and the other conditions were exactly the same as in example 10.
Comparative example 1
A method for preparing 1,6-hexamethylene dicarbamate:
(1) stirring and mixing diethyl carbonate and hexamethylene diamine, wherein the molar ratio of the diethyl carbonate to the hexamethylene diamine is 10: 1;
(2) and (2) reacting the mixed solution obtained in the step (1) at the temperature of 80 ℃ for 5 hours to obtain the 1,6-hexamethylene dicarbamate, wherein stirring is carried out in the reaction process, and low-carbon alcohol is removed in a reduced pressure distillation mode in the reaction process.
The conditions of the preparation processes described in examples 1 to 12 of the present invention and comparative example 1, the conversion of hexamethylenediamine after the preparation process is completed, and the yield of 1,6-hexamethylene dicarbamate are shown in table 1:
TABLE 1
As can be seen from the above table, the method of the invention adds a certain amount of specific solvent into the raw materials of dialkyl carbonate and hexamethylene diamine, so that the conversion rate of hexamethylene diamine as a reactant and the yield of 1,6-hexamethylene dicarbamate as a product in the preparation process are obviously improved.
As can be seen from examples 1 to 12, in the above-mentioned preparation processes of the examples of the present invention, the conversion rate of hexamethylenediamine in the preparation process can be up to 100%, and the yield of 1,6-hexamethylene dicarbamate can be up to 93%, thus demonstrating that the present invention adds a specific amount of a specific solvent in the preparation process, so that a method for preparing 1,6-hexamethylene dicarbamate from dialkyl carbonate and hexamethylenediamine as raw materials is feasible and has significant economic benefits.
The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.
Claims (10)
1. A non-catalytic method for preparing 1,6-hexamethylene dicarbamate is characterized in that the method comprises the steps of mixing dialkyl carbonate, hexamethylene diamine and a solvent, and carrying out reaction to obtain the 1,6-hexamethylene dicarbamate, wherein the solvent comprises any one or the combination of at least two of methanol, ethanol, water or tetrahydrofuran; the molar ratio of the solvent to the hexamethylene diamine is (4-8) to 1.
2. The method of claim 1, wherein the reaction is accompanied by agitation.
3. The method of claim 1 or 2, wherein the reaction is accompanied by the exclusion of lower alcohols.
4. The method of claim 3, wherein the method of removing the lower alcohol comprises introducing nitrogen and/or distilling under reduced pressure.
5. The method of any one of claims 1 to 4, wherein the dialkyl carbonate is selected from any one of diethyl carbonate, dipropyl carbonate, or dibutyl carbonate, or a combination of at least two thereof.
6. The method of any of claims 1-5, wherein the molar ratio of dialkyl carbonate to hexamethylenediamine is (2-10): 1.
7. The method of any of claims 1-6, wherein the molar ratio of the solvent, dialkyl carbonate, and hexamethylenediamine is (4-8): (2-10): 1.
8. The process according to any one of claims 1 to 7, wherein the temperature of the reaction is from 25 to 100 ℃, preferably from 40 to 80 ℃.
9. The process according to any one of claims 1 to 8, wherein the reaction time is from 2 to 10h, preferably from 3 to 8 h.
10. The method according to any one of claims 1 to 9, characterized in that it comprises the steps of:
(1) stirring and mixing dialkyl carbonate, hexamethylene diamine and a solvent, wherein the molar ratio of the solvent to the dialkyl carbonate to the hexamethylene diamine is (4-8) to (2-10) to 1; the dialkyl carbonate is selected from any one or a combination of at least two of diethyl carbonate, dipropyl carbonate or dibutyl carbonate;
(2) reacting the mixed solution obtained in the step (1) at the temperature of 25-100 ℃ for 2-10h to obtain the 1,6-hexamethylene dicarbamate, wherein stirring is carried out in the reaction process, and low carbon alcohol is removed in the reaction process by adopting a nitrogen introducing and/or reduced pressure distillation mode.
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| CN115073325A (en) * | 2022-07-05 | 2022-09-20 | 中国科学院过程工程研究所 | Synthetic method for preparing pentamethylene dicarbamate by adopting dimethyl carbonate |
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Application publication date: 20210416 |