A process for the preparation of 1,2-cyclohexanediamine

Abstract

The present application relates to a kind of methods for preparing 1,2-cyclohexanediamine, the method includes the following steps in turn: (1) the byproduct of hexanediamine is carried out in the heavy removal tower, and the first separation product is collected from the top of the heavy removal tower, the byproduct of hexanediamine includes 1,2-cyclohexanediamine, hexanediamine, 2-methylpentanediamine, hexamethyleneimine, N1-ethylhexane-1,6-diamine and water;(2) the first separation product is carried out in the light removal tower, and 1,2-cyclohexanediamine is collected from the bottom of the light removal tower.

Description

Technical Field

[0001] This invention belongs to the field of separation and purification, and specifically relates to a method for preparing 1,2-cyclohexanediamine. Background Technology

[0002] During the production of hexamethylenediamine, the reactive properties of amines inevitably lead to cyclization, forming 1,2-cyclohexanediamine. As a byproduct of hexamethylenediamine production, 1,2-cyclohexanediamine is generally treated as mixed hazardous waste, generating large amounts of ammonia nitrogen pollutants during incineration, resulting in waste. Purified 1,2-cyclohexanediamine is used in the production of specialty polyamides, specialty polyurethanes, and other polymer materials, finding wide applications in epoxy resin curing agents, pharmaceutical intermediates, and agricultural and pesticide chemicals. Currently, the 1,2-cyclohexanediamine produced by hexamethylenediamine plants is of low purity, and most is identified as hazardous waste or mixed with polyamines, requiring disposal costs or being sold at extremely low prices, resulting in the underutilization of the intrinsic value of 1,2-cyclohexanediamine. Summary of the Invention

[0003] To obtain 1,2-cyclohexanediamine with high purity and high yield, the present invention provides a method for preparing 1,2-cyclohexanediamine, the method comprising the following steps performed sequentially:

[0004] (1) The hexamethylenediamine byproduct is deweighted in a deweighting tower, and the first separated product is collected from the top of the deweighting tower. The hexamethylenediamine byproduct includes 1,2-cyclohexanediamine, hexamethylenediamine, 2-methylpentanediamine, hexamethyleneimine, N1-ethylhexane-1,6-diamine and water.

[0005] (2) The first separation product is subjected to light removal in a light removal tower, and 1,2-cyclohexanediamine is collected from the bottom of the light removal tower.

[0006] Considering that existing hexamethylenediamine byproducts contain not only 1,2-cyclohexanediamine (boiling point 190℃, molecular weight 114.2), but also hexamethylenediamine (boiling point 204℃, molecular weight 116.2), 2-methylpentanediamine (boiling point 193℃, molecular weight 116.2), hexamethyleneimine (or cyclohexaneimine, molecular weight 99.17, boiling point 138℃), N1-ethylhexane-1,6-diamine (boiling point 216.7℃, molecular weight 144.26), and water (boiling point 100℃, molecular weight 18), among which 1,2-cyclohexanediamine and 2-methylpentanediamine have very similar boiling points and molecular weights, this poses a great challenge to the separation and purification of 1,2-cyclohexanediamine. This invention employs a method of first removing heavy components and then removing light components. The heavy component removal process removes hexamethylenediamine, N1-ethylhexane-1,6-diamine, and 2-methylpentanediamine, while the light component removal process removes hexamethyleneimine and water, ultimately yielding 1,2-cyclohexanediamine with high purity and high yield.

[0007] Preferably, the content of 1,2-cyclohexanediamine in the hexamethylenediamine byproduct is 55-75 wt%.

[0008] And / or, the content of hexamethylenediamine in the hexamethylenediamine byproduct is 10-30 wt%;

[0009] And / or, the content of 2-methylpentanediamine in the hexamethylenediamine byproduct is 5-15 wt%;

[0010] And / or, the content of N1-ethylhexane-1,6-diamine in the hexamethylenediamine byproduct is 5-15 wt%;

[0011] And / or, the content of hexamethyleneimine in the hexamethylenediamine byproduct is 1-5 wt%;

[0012] And / or, the water content in the hexamethylenediamine byproduct is <0.5 wt%.

[0013] Preferably, in step (1), the theoretical number of plates in the deweighting tower is ≥40, the tower top operating pressure is 1~5KPa, preferably 1~3KPa, and the tower top operating temperature is 110~150℃, preferably 110~130℃.

[0014] Preferably, in step (2), the theoretical number of plates in the light-light removal tower is ≥45, the operating pressure at the top of the tower is 1~5 KPa, preferably 1~3 KPa, and the operating temperature at the bottom of the tower is 110~160℃, preferably 130~150℃.

[0015] Preferably, in step (1), the feed inlet of the hexamethylenediamine byproduct is located at the 20th to 30th plate from bottom to top of the deweighting tower, and the feed inlet of the hexamethylenediamine byproduct is located at 500 to 600 mm, preferably 550 mm, of the height of the deweighting tower; preferably, the reflux ratio of the deweighting tower is 10 to 20.

[0016] Preferably, in step (2), the inlet of the first separated product is located at the 25th to 35th plate from bottom to top of the light-light removal tower, and the inlet of the first separated product is located at 550 to 650 mm, preferably 600 mm, of the height of the light-light removal tower; preferably, the reflux ratio of the light-light removal tower is 20 to 50.

[0017] Preferably, in step (1), after deweighting, hexamethylenediamine, N1-ethylhexane-1,6-diamine, and 2-methylpentanediamine are collected at the bottom of the deweighting tower and preferably incinerated. The present invention preferably uses incineration to remove the substances obtained at the bottom of the deweighting tower.

[0018] Preferably, in step (2), after the removal of light components, hexamethyleneimine and water are collected from the top of the light component removal tower and preferably incinerated. The present invention preferably uses incineration to remove the material from the top of the light component removal tower.

[0019] Preferably, in step (2), the purity of the obtained 1,2-cyclohexanediamine is ≥99.90%, and the recovery rate is ≥90.0%, preferably ≥95.0%.

[0020] The beneficial effects of this invention are:

[0021] This invention employs a method of first removing heavy components and then removing light components to achieve the separation and purification of high-purity and high-yield 1,2-cyclohexanediamine, thus solving the technical problem of producing high-purity 1,2-cyclohexanediamine using hexanediamine byproducts. Attached Figure Description

[0022] Figure 1 This is a process flow diagram of a method for preparing 1,2-cyclohexanediamine according to an embodiment of the present invention. Detailed Implementation

[0023] The present invention will be further illustrated by the following embodiments, but this is not intended to limit the present invention. Those skilled in the art can make modifications or improvements based on the basic idea of ​​the invention, but as long as they do not depart from the basic idea of ​​the present invention, they are all within the scope of the present invention.

[0024] Examples 1-12

[0025] (1) The hexamethylenediamine byproducts (containing 68.2 wt% 1,2-cyclohexamethylenediamine, 13.4 wt% hexamethylenediamine, 7.3 wt% 2-methylpentanediamine, 9.3 wt% N1-ethylhexane-1,6-diamine, 1.6 wt% hexamethyleneimine, and 0.2 wt% water) were deweighted in a deweighting tower (see Table 1), and the first separated product was collected from the top of the deweighting tower.

[0026] (2) The first separation product was subjected to light removal in a light removal tower (see Table 1), and 1,2-cyclohexanediamine was collected from the bottom of the light removal tower.

[0027] Comparative Example 1

[0028] (1) The hexamethylenediamine byproducts (containing 68.2 wt% 1,2-cyclohexamethylenediamine, 13.4 wt% hexamethylenediamine, 7.3 wt% 2-methylpentanediamine, 9.3 wt% N1-ethylhexane-1,6-diamine, 1.6 wt% hexamethyleneimine, and 0.2 wt% water) were de-lighted in a light-light removal tower (see Table 1), and the first separated product was collected from the bottom of the light-light removal tower.

[0029] (2) The first separation product was deweighted in a deweighting tower (see Table 1), and 1,2-cyclohexanediamine was collected from the top of the deweighting tower.

[0030] Table 1 shows the process parameters for the preparation of 1,2-cyclohexanediamine in Examples 1-12 and Comparative Example 1:

[0031]

[0032] Performance testing:

[0033] The purity of the obtained 1,2-cyclohexanediamine was determined by gas chromatography.

[0034] The yield of 1,2-cyclohexanediamine was defined as the ratio of the actual mass of 1,2-cyclohexanediamine obtained to the theoretical mass of 1,2-cyclohexanediamine in the hexanediamine byproduct.

[0035] Table 2 shows the purity and yield of 1,2-cyclohexanediamine obtained in Examples 1-12 and Comparative Example 1:

[0036]

[0037] Combining Table 1 and Table 2, we can see that:

[0038] Comparing Examples 10, 1, 2, and 3, it can be seen that the purity and yield of 1,2-cyclohexanediamine obtained in Examples 1-3, where the top operating temperature of the deweighting column was between 110 and 130°C, were significantly improved. However, in Example 10, where the deweighting column operated at a higher temperature, at least one of the purity and yield of 1,2-cyclohexanediamine was reduced.

[0039] Comparing Examples 4, 2, and 5, it can be seen that the purity and yield of the 1,2-cyclohexanediamine obtained in Examples 4, 2, and 5 are significantly improved when the operating pressure at the top of the deweighting column is 1~5 kPa.

[0040] Comparing Examples 11, 8, 2, 9, and 12, it can be seen that in Examples 8, 2, and 9, the reboiler operating temperature in the light-light removal column was between 130 and 150°C, resulting in significantly improved purity and yield of 1,2-cyclohexanediamine. However, in Example 11, with a lower reboiler operating temperature, and in Example 12, with a higher reboiler operating temperature, at least one of the resulting 1,2-cyclohexanediamines showed a decrease in purity and yield.

[0041] Comparing Examples 16, 2, and 7, it can be seen that the purity and yield of 1,2-cyclohexanediamine obtained by operating at the top of the column in Examples 6, 2, and 7 at a pressure of 1-5 kPa is significantly improved.

[0042] Comparing Example 2 and Comparative Example 1, in Comparative Example 1, only the order of light and heavy removal was adjusted, while the relevant process parameters remained unchanged. The purity and yield of the obtained 1,2-cyclohexanediamine both decreased.

Claims

1. A method for preparing 1,2-cyclohexanediamine, characterized in that, The method includes the following steps performed sequentially: (1) The hexamethylenediamine byproduct is deweighted in a deweighting tower, and the first separated product is collected from the top of the deweighting tower. The hexamethylenediamine byproduct includes 1,2-cyclohexanediamine, hexamethylenediamine, 2-methylpentanediamine, hexamethyleneimine, N1-ethylhexane-1,6-diamine and water. (2) The first separation product is subjected to light removal in a light removal tower, and 1,2-cyclohexanediamine is collected from the bottom of the light removal tower.

2. The method according to claim 1, characterized in that, The content of 1,2-cyclohexanediamine in the hexamethylenediamine byproduct is 55-75 wt%. And / or, the content of hexamethylenediamine in the hexamethylenediamine byproduct is 10-30 wt%; And / or, the content of 2-methylpentanediamine in the hexamethylenediamine byproduct is 5-15 wt%; And / or, the content of N1-ethylhexane-1,6-diamine in the hexamethylenediamine byproduct is 5-15 wt%; And / or, the content of hexamethyleneimine in the hexamethylenediamine byproduct is 1-5 wt%; And / or, the water content in the hexamethylenediamine byproduct is <0.5 wt%.

3. The method according to claim 1 or 2, characterized in that, In step (1), the theoretical number of plates in the deweighting tower is ≥40, the operating pressure at the top of the tower is 1~5 KPa, preferably 1~3 KPa, 110~150℃, preferably 110~130℃.

4. The method according to claim 1 or 2, characterized in that, In step (2), the theoretical number of plates in the light-light removal tower is ≥45, the operating pressure at the top of the tower is 1~5 KPa, preferably 1~3 KPa, and the operating temperature at the bottom of the tower is 110~160℃, preferably 130~150℃.

5. The method according to claim 1 or 2, characterized in that, In step (1), the feed inlet of the hexamethylenediamine byproduct is located at the 20th to 30th plate from bottom to top of the deweighting tower. The feed inlet of the hexamethylenediamine byproduct is located at 500 to 600 mm, preferably 550 mm, of the height of the deweighting tower. Preferably, the reflux ratio of the deweighting tower is 10 to 20.

6. The method according to claim 1 or 2, characterized in that, In step (2), the feed inlet of the first separated product is located at the 25th to 35th plate from bottom to top of the light-light removal tower, and the feed inlet of the first separated product is located at 550 to 650 mm, preferably 600 mm, of the height of the light-light removal tower; preferably, the reflux ratio of the light-light removal tower is 10 to 30.

7. The method according to claim 1 or 2, characterized in that, In step (1), after deweighting, hexamethylenediamine, N1-ethylhexane-1,6-diamine, and 2-methylpentanediamine are collected at the bottom of the deweighting tower and preferably incinerated.

8. The method according to claim 1 or 2, characterized in that, In step (2), after light removal, hexamethyleneimine and water are collected from the top of the light removal tower and preferably incinerated.

9. The method according to claim 1 or 2, characterized in that, In step (2), the purity of the obtained 1,2-cyclohexanediamine is ≥99.90%, the recovery rate is ≥90.0%, and preferably ≥95.0%.

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