KR102157615B1 - Method of preparing urea using amine compound and carbon dioxide - Google Patents

Abstract

Disclosed is a production method of urea using an amine compound and carbon dioxide. The production method of urea includes a step of producing urea by using the amine compound and a 2-pyrrolidone derivative as a solvent and reacting with the carbon dioxide, thereby producing high yield cyclic urea under mild reaction conditions and no catalyst conditions.

Description

Manufacturing method of urea using amine compound and carbon dioxide {METHOD OF PREPARING UREA USING AMINE COMPOUND AND CARBON DIOXIDE}

The present invention relates to a method for producing urea using an amine compound and carbon dioxide, and more particularly, to prepare a cyclic or linear urea by reacting an amine compound and carbon dioxide under a catalytic condition using a 2-pyrrolidone derivative as a solvent. It's about how to do it.

Direct carboxylation of amine compounds to produce urea is believed to be one of the most promising pathways for converting carbon dioxide into valuable chemicals. In particular, ethylene urea (imidazolidin-2-one), a cyclic urea among various ureas, is used as an organic intermediate in various chemical industries.

Cyclic urea has been industrially produced by reacting urea and diamine under severe conditions of about 250°C, and then quenching the resulting melt with water to prepare an aqueous solution containing desired cyclic urea and NH ₃ . However, the urea process has disadvantages such as formation of a large amount of water-insoluble by-products and corrosion of equipment due to the treatment of aqueous ammonia.

Catalytic carboxylation processes using carbon dioxide as a source of carbonyl have also been intensively studied. However, most of the catalysts reported to date require further improvements in terms of activity, stability and/or recyclability in practical applications.

Non-catalytic carboxylation methods have also been tried, but severe reaction conditions including high pressure as well as high temperatures of about 250° C. are required to obtain a suitable cyclic urea yield.

Therefore, there is a need for a process capable of producing high yield urea, particularly cyclic urea, under mild reaction conditions and no catalyst conditions.

An object of the present invention is to provide a method for producing urea capable of producing urea in high yield under mild reaction conditions and no catalyst conditions using an amine compound and carbon dioxide.

According to an aspect of the present invention, in Reaction Scheme 1 or 2 below, the amine compound represented by Structural Formula 1, the amine compound represented by Structural Formula 3, and the amine compound represented by Structural Formula 4 are each used as a solvent. Using and reacting with carbon dioxide to prepare urea represented by Structural Formula 2 and Structural Formula 5, respectively, there is provided a method for producing urea including.

[Scheme 1]

[Scheme 2]

In Scheme 1 above,

n is any one of an integer of 1 to 4,

R ¹ and R ² are the same as or different from each other, and each independently a hydrogen atom or a C1 to C3 alkyl group,

In Scheme 2 above,

R ³ and R ⁴ are the same as or different from each other, and each independently a C1 to C9 alkyl group or a C5 to C7 cycloalkyl group,

q is 1 or 2,

R ⁵ to R ⁷ are the same as or different from each other, and each independently a hydrogen atom or a C1 to C3 alkyl group.

In addition, n is 1 or 2, R ¹ is a hydrogen atom or a C1 to C3 alkyl group, R ² is a hydrogen atom, R ³ and R ⁴ are the same as or different from each other, and each independently a C3 to C6 alkyl group, or It is a C5 or C6 cycloalkyl group, q is 1, and R ⁵ to R ⁷ may be a hydrogen atom.

In addition, n may be 1 and R ¹ may be a methyl group.

In addition, n may be 2 and R ¹ may be a hydrogen atom.

In addition, the amine compound represented by the above structural formula 1 is ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, 1,2-butane Diamine (1,2-butanediamine), 1,3-butanediamine (1,3-butanediamine), 1,4-butanediamine (1,4-butanediamine), 2,3-butanediamine (2,3-butanediamine) , 1,2-pentanediamine (1,2-pentanediamnie), 1,3-pentanediamine (1,3-pentanediamine), 1,4-pentanediamine (1,4-pentanediamine), 1,5-pentanediamine ( 1,5-pentanediamine) and 2,3-pentanediamine (2,3-pentanediamine) may contain at least one selected from the group consisting of.

In addition, the amine compound represented by Structural Formula 3 and the amine compound represented by Structural Formula 4 may each include at least one selected from the group consisting of n-butylamine and cyclohexylamine. .

In addition, the solvent may be 250 to 500 parts by weight based on 100 parts by weight of the amine compound.

In addition, the reaction may be carried out at a temperature of 150 to 250 ℃.

In addition, the reaction may be carried out at a pressure of 1 to 20 MPa.

In addition, the reaction may be carried out under catalyst-free conditions.

In addition, the reaction may further include a catalyst.

In addition, the catalyst may include at least one selected from the group consisting of Na ₂ CO ₃ , K ₂ CO ₃ and Cs ₂ CO ₃ .

In addition, the molar ratio (mol/mol) of the amine compound and the catalyst may be 50 to 150.

According to another aspect of the present invention, there is provided urea prepared according to the method for producing urea.

In the method for producing urea of the present invention, by using a 2-pyrrolidone derivative as a solvent, a high yield of urea can be prepared under mild reaction conditions and no catalyst conditions.

Since these drawings are for reference only to explain exemplary embodiments of the present invention, the technical idea of the present invention should not be limited to the accompanying drawings.
1 is a flow chart showing a method of manufacturing urea according to an embodiment of the present invention.
Figure 2 shows the carbon dioxide absorption behavior of the diamine compound in 2-pyrrolidone and N-methyl-2-pyrrolidone.
FIG. 3A shows the results of gas chromatography-mass spectrometry (GC-Mass) analysis of 2-pyrrolidone (2-PY).
FIG. 3B shows the results of gas chromatography-mass spectrometry (GC-Mass) analysis of deuterated 2-pyrrolidone (2-PY-d ₁ ).
3C shows the results of gas chromatography-mass spectrometry (GC-Mass) analysis of ethylenediamine (EDA).
Figure 3d shows the gas chromatography-mass spectrometry (GC-Mass) analysis results of deuterated ethylenediamine (EDA-d _x , x = 1 ~ 4).
Figure 4 shows (a) reaction intermediate, (b) 2-pyrrolidone, (c) 2-pyrrolidone containing 20% by weight reaction intermediate, (d) N-methyl-2-pyrrolidone and (e ) It shows the result of FT-IR analysis of N-methyl-2-pyrrolidone containing 20% by weight of the reaction intermediate.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art may easily implement the present invention.

However, the following description is not intended to limit the present invention to a specific embodiment, and in describing the present invention, when it is determined that a detailed description of a related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted. .

The terms used herein are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, terms such as "comprise" or "have" are intended to designate the presence of features, numbers, steps, actions, elements, or combinations thereof described in the specification, but one or more other features or It is to be understood that the possibility of addition or presence of numbers, steps, actions, components, or combinations thereof is not preliminarily excluded.

In addition, terms including ordinal numbers such as first and second to be used hereinafter may be used to describe various elements, but the elements are not limited by the terms. These terms are used only for the purpose of distinguishing one component from another component. For example, without departing from the scope of the present invention, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element.

In addition, when a component is referred to as being "formed" or "stacked" on another component, it may be formed or stacked by being directly attached to the front surface or one surface on the surface of the other component. It should be understood that there may be more other components in the.

Hereinafter, a method for producing urea using the amine compound and carbon dioxide of the present invention will be described in detail. However, this is presented as an example, and the present invention is not limited thereby, and the present invention is only defined by the scope of the claims to be described later.

1 is a flow chart showing a method of manufacturing urea according to an embodiment of the present invention.

Referring to FIG. 1, in the following scheme 1 or 2, the amine compound represented by Structural Formula 1, the amine compound represented by Structural Formula 3, and the amine compound represented by Structural Formula 4 were used as a solvent. And reacting with carbon dioxide to prepare urea represented by Structural Formula 2 and Structural Formula 5, respectively.

[Scheme 1]

[Scheme 2]

In Scheme 1 above,

n is any one of an integer of 1 to 4,

R ¹ and R ² are the same as or different from each other, and each independently a hydrogen atom or a C1 to C3 alkyl group,

In Scheme 2 above,

R ³ and R ⁴ are the same as or different from each other, and each independently a C1 to C9 alkyl group or a C5 to C7 cycloalkyl group,

q is 1 or 2,

R ⁵ to R ⁷ are the same as or different from each other, and each independently a hydrogen atom or a C1 to C3 alkyl group.

In addition, n is 1 or 2, R ¹ is a hydrogen atom or a C1 to C3 alkyl group, R ² is a hydrogen atom, R ³ and R ⁴ are the same as or different from each other, and each independently a C3 to C6 alkyl group, or It is a C5 or C6 cycloalkyl group, q is 1, and R ⁵ to R ⁷ may be a hydrogen atom.

In addition, n may be 1 and R ¹ may be a methyl group.

In addition, n may be 2 and R ¹ may be a hydrogen atom.

In addition, the amine compound represented by the above structural formula 1 is ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, 1,2-butane Diamine (1,2-butanediamine), 1,3-butanediamine (1,3-butanediamine), 1,4-butanediamine (1,4-butanediamine), 2,3-butanediamine (2,3-butanediamine) , 1,2-pentanediamine (1,2-pentanediamnie), 1,3-pentanediamine (1,3-pentanediamine), 1,4-pentanediamine (1,4-pentanediamine), 1,5-pentanediamine ( 1,5-pentanediamine) and 2,3-pentanediamine (2,3-pentanediamine) may include one or more selected from the group consisting of, preferably ethylenediamine (ethylenediamine), 1,2-propanediamine ( 1,2-propanediamine) and 1,3-propanediamine (1,3-propanediamine) may include at least one selected from the group consisting of, more preferably, may include ethylenediamine (ethylenediamine).

In addition, the amine compound represented by Structural Formula 3 and the amine compound represented by Structural Formula 4 may each include at least one selected from the group consisting of n-butylamine and cyclohexylamine. .

In addition, the solvent may be 250 to 500 parts by weight based on 100 parts by weight of the amine compound, preferably 300 to 450 parts by weight, more preferably 350 to 400 parts by weight.

In addition, the reaction may be carried out at a temperature of 150 to 250°C, preferably 170 to 220°C, and even more preferably at 190 to 210°C. When the reaction is performed at a temperature of less than 150° C., the yield of urea is low, which is not preferable, and when it exceeds 250° C., the generation rate of by-products may increase, which is not preferable.

In addition, the reaction may be carried out at a pressure of 1 to 20 MPa, preferably 2 to 10 MPa, more preferably at a pressure of 3 to 7 MPa. When the reaction is carried out at a pressure of less than 1 MPa, the yield of urea is low, which is not preferable, and when it exceeds 20 MPa, it is unnecessary because the yield cannot be improved any more.

In addition, the reaction may be carried out under catalyst-free conditions.

In addition, the reaction may further include a catalyst.

In addition, the catalyst may include at least one selected from the group consisting of Na ₂ CO ₃ , K ₂ CO ₃ and Cs ₂ CO ₃ , and preferably selected from the group consisting of K ₂ CO ₃ and Cs ₂ CO ₃ . It may include one or more, and more preferably may include Cs ₂ CO ₃ .

The molar ratio (mol/mol) of the amine compound and the catalyst may be 50 to 150, more preferably 70 to 120, and even more preferably 90 to 110.

The present invention provides urea prepared according to the method for producing urea.

[Example]

Hereinafter, a preferred embodiment of the present invention will be described. However, this is for illustrative purposes, and the scope of the present invention is not limited thereby.

Urea Produce

Example One

To 100 mL of a high-pressure stainless steel reactor equipped with a thermocouple and electric heater, 100 mmol of ethylenediamine (Aldrich Chemical) and 20 mL of 2-pyrrolidone (Aldrich Chemical) as a solvent were added, and then carbon dioxide (CO ₂ , Sin Yang Gas) was washed three times.

The reactor was heated to 200° C. under a carbon dioxide pressure of 1.0 MPa. At 200° C. the carbon dioxide pressure was further increased to 5.0 MPa and maintained throughout the reaction through a carbon dioxide reservoir equipped with a high pressure regulator and pressure transducer. The reaction was carried out for 2 hours, after which the reactor was cooled to room temperature and then reduced pressure to prepare urea.

The reaction of Example 1 is as shown in Scheme 3 below.

[Scheme 3]

Example 2

Urea was prepared in the same manner as in Example 1, except that 1 mmol of K ₂ CO ₃ was additionally used as a catalyst.

Example 3

Urea was prepared in the same manner as in Example 1, except that 1 mmol of Cs ₂ CO ₃ was additionally used as a catalyst.

Example 4

Urea was prepared in the same manner as in Example 1, except that 1,2-propanediamine (1,2-propanediamnine, Aldrich Chemical) was used instead of using ethylenediamine (Aldrich Chemical).

The reaction of Example 4 is as shown in Scheme 4 below.

[Scheme 4]

Example 5

Urea was prepared in the same manner as in Example 1, except that 1,3-propanediamine (1,3-propanediamnine, Aldrich Chemical) was used instead of using ethylenediamine (Aldrich Chemical).

The reaction of Example 5 is as shown in Scheme 5 below.

[Scheme 5]

Example 6

Urea was prepared in the same manner as in Example 1, except that the reaction temperature was performed at 150°C instead of at 200°C.

Example 7

Urea was prepared in the same manner as in Example 1, except that the reaction temperature was performed at 160°C instead of 200°C.

Example 8

Urea was prepared in the same manner as in Example 1, except that the reaction temperature was performed at 170°C instead of 200°C.

Example 9

Urea was prepared in the same manner as in Example 1, except that the reaction temperature was performed at 180°C instead of at 200°C.

Example 10

Urea was prepared in the same manner as in Example 1, except that the reaction temperature was performed at 190°C instead of 200°C.

Example 11

Urea was prepared in the same manner as in Example 1, except that the reaction temperature was performed at 210°C instead of 200°C.

Example 12

Urea was prepared in the same manner as in Example 1, except that the reaction temperature was performed at 220°C instead of 200°C.

Example 13

Urea was prepared in the same manner as in Example 1, except that the reaction pressure was performed at 2.0 MPa instead of 5.0 MPa.

Example 14

Urea was prepared in the same manner as in Example 1, except that the reaction pressure was performed at 7.0 MPa instead of 5.0 MPa.

Example 15

Urea was prepared in the same manner as in Example 1, except that the reaction pressure was performed at 10.0 MPa instead of 5.0 MPa.

Example 16

Instead of using ethylenediamine (Aldrich Chemical), n-butylamine (Aldrich Chemical) was used, and the reaction was carried out at 170°C for 4 hours instead of 200°C for 2 hours. Except for that, urea was prepared in the same manner as in Example 1.

The reaction of Example 16 is as shown in Scheme 6 below.

[Scheme 6]

Example 17

Except that instead of using ethylenediamine (Aldrich Chemical), cyclohexylamine (Aldrich Chemical) was used, and the reaction was carried out at 170°C for 4 hours instead of 200°C for 2 hours. Was prepared in the same manner as in Example 1.

The reaction of Example 17 is as shown in Scheme 7 below.

[Scheme 7]

Comparative example One

Except for the use of N-methyl-2-pyrrolidone (NMP, Aldrich Chemical) instead of using 2-pyrrolidone (Aldrich Chemical) as a solvent Urea was prepared in the same manner as in Example 1.

Comparative example 2

Instead of using 2-pyrrolidone (Aldrich Chemical) as a solvent, N-methyl-2-pyrrolidone (N-methyl-2-pyrrolidone, NMP, Aldrich Chemical) was used as a catalyst, and K Urea was prepared in the same manner as in Example 1, except that 1 mmol of ₂ CO ₃ was additionally used.

Comparative example 3

Instead of using 2-pyrrolidone (Aldrich Chemical) as a solvent, N-methyl-2-pyrrolidone (N-methyl-2-pyrrolidone, NMP, Aldrich Chemical) was used as a catalyst, and Cs Urea was prepared in the same manner as in Example 1, except that 1 mmol of ₂ CO ₃ was additionally used.

Comparative example 4

Instead of using 2-pyrrolidone (Aldrich Chemical) as a solvent, N-methyl-2-pyrrolidone (N-methyl-2-pyrrolidone, NMP, Aldrich Chemical) was used, and ethylenediamine ( Urea was prepared in the same manner as in Example 1, except that 1,2-propanediamine (1,2-propanediamnine, Aldrich Chemical) was used instead of using ethylenediamine, Aldrich Chemical).

Comparative example 5

Instead of using 2-pyrrolidone (Aldrich Chemical) as a solvent, N-methyl-2-pyrrolidone (N-methyl-2-pyrrolidone, NMP, Aldrich Chemical) was used, and ethylenediamine ( Urea was prepared in the same manner as in Example 1, except that 1,3-propanediamine (1,3-propanediamnine, Aldrich Chemical) was used instead of using ethylenediamine, Aldrich Chemical).

Comparative example 6

Except for using methanol (methanol, CH ₃ OH, Aldrich Chemical) instead of using 2-pyrrolidone (Aldrich Chemical) as a solvent, and additionally using 1 mmol of K ₂ CO ₃ as a catalyst. Urea was prepared in the same manner as in Example 1.

Comparative example 7

Instead of using 2-pyrrolidone (Aldrich Chemical) as a solvent, methanol (methanol, CH ₃ OH, Aldrich Chemical) was used, and instead of using ethylenediamine (Aldrich Chemical) 1, Urea was prepared in the same manner as in Example 1, except that 2-propanediamine (1,2-propanediamnine, Aldrich Chemical) was used, and 1 mmol of K ₂ CO ₃ was additionally used as a catalyst.

Comparative example 8

Instead of using 2-pyrrolidone (Aldrich Chemical) as a solvent, N-methyl-2-pyrrolidone (N-methyl-2-pyrrolidone, NMP, Aldrich Chemical) was used, and ethylenediamine ( Except that n-butylamine (Aldrich Chemical) was used instead of ethylenediamine, Aldrich Chemical), and the reaction was carried out at 170°C for 4 hours instead of 200°C for 2 hours. Urea was prepared in the same manner as in Example 1.

Comparative example 9

Instead of using 2-pyrrolidone (Aldrich Chemical) as a solvent, N-methyl-2-pyrrolidone (N-methyl-2-pyrrolidone, NMP, Aldrich Chemical) was used, and ethylenediamine ( Examples except that cyclohexylamine (Aldrich Chemical) was used instead of ethylenediamine, Aldrich Chemical), and the reaction was carried out at 170° C. for 4 hours instead of 2 hours at 200° C. Urea was prepared in the same manner as in 1.

Table 1 below summarizes the reaction conditions of urea prepared according to Examples 1 to 17 and Comparative Examples 1 to 9.

division Amine compounds menstruum catalyst Reaction temperature
(℃) Reaction pressure
(MPa) Reaction time
(h) Example 1 Ethylenediamine 2-pyrrolidone - 200 5 2 Example 2 Ethylenediamine 2-pyrrolidone K ₂ CO ₃ 200 5 2 Example 3 Ethylenediamine 2-pyrrolidone Cs ₂ CO ₃ 200 5 2 Example 4 1,2-propanediamine 2-pyrrolidone - 200 5 2 Example 5 1,3-propanediamine 2-pyrrolidone - 200 5 2 Example 6 Ethylenediamine 2-pyrrolidone - 150 5 2 Example 7 Ethylenediamine 2-pyrrolidone - 160 5 2 Example 8 Ethylenediamine 2-pyrrolidone - 170 5 2 Example 9 Ethylenediamine 2-pyrrolidone - 180 5 2 Example 10 Ethylenediamine 2-pyrrolidone - 190 5 2 Example 11 Ethylenediamine 2-pyrrolidone - 210 5 2 Example 12 Ethylenediamine 2-pyrrolidone - 220 5 2 Example 13 Ethylenediamine 2-pyrrolidone - 200 2 2 Example 14 Ethylenediamine 2-pyrrolidone - 200 7 2 Example 15 Ethylenediamine 2-pyrrolidone - 200 10 2 Example 16 n-butylamine 2-pyrrolidone - 170 5 4 Example 17 Cyclohexylamine 2-pyrrolidone - 170 5 4 Comparative Example 1 Ethylenediamine NMP - 200 5 2 Comparative Example 2 Ethylenediamine NMP K ₂ CO ₃ 200 5 2 Comparative Example 3 Ethylenediamine NMP Cs ₂ CO ₃ 200 5 2 Comparative Example 4 1,2-propanediamine NMP - 200 5 2 Comparative Example 5 1,3-propanediamine NMP - 200 5 2 Comparative Example 6 Ethylenediamine CH ₃ OH K ₂ CO ₃ 200 5 2 Comparative Example 7 1,2-propanediamine CH ₃ OH K ₂ CO ₃ 200 5 2 Comparative Example 8 n-butylamine 2-pyrrolidone - 170 5 4 Comparative Example 9 Cyclohexylamine 2-pyrrolidone - 170 5 4

[Test Example]

Test example 1: depending on the solvent Diamine Carbon dioxide absorption capacity analysis

Figure 2 shows the carbon dioxide absorption behavior of the diamine compound in 2-pyrrolidone and N-methyl-2-pyrrolidone. Specifically, in order to understand the excellent promoting effect of 2-pyrrolidone on the carboxylation of diamines, 1, at 313K temperature and 30 kPa of carbon dioxide pressure and 2-pyrrolidone and N-methyl-2-pyrrolidone It shows the carbon dioxide absorption behavior of 2-propanediamine.

Referring to Figure 2, it can be seen that the carbon dioxide absorption rate of 1,2-propanediamine is faster than that of N-methyl-2-pyrrolidone in 2-pyrrolidone, and the carbon dioxide absorption capacity is also N- It can be seen that it is higher than methyl-2-pyrrolidone. In addition, 1,2-propanediamine solution using 2-pyrrolidone as a solvent transforms into a homogeneous and viscous solution upon absorption of carbon dioxide, while 1,2- It can be seen that the propanediamine solution becomes turbid immediately after contact with carbon dioxide to form an insoluble gel.

The only structural difference between 2-pyrrolidone and N-methyl-2-pyrrolidone is that 2-pyrrolidone has a proton hydrogen atom attached to a nitrogen atom, whereas N-methyl-2-pyrrolidone has a nitrogen atom. It has a methyl group bonded to. Therefore, it can be seen that when 2-pyrrolidone is used as a solvent due to the NH hydrogen atom of 2-pyrrolidone, a higher carbon dioxide absorption rate and capacity are displayed than when using N-methyl-2-pyrrolidone as a solvent. .

Test example 2: 2 - Pyrrolidone Proton mobility analysis of N-H hydrogen atom

Figure 3a shows the result of gas chromatography-mass spectrometry (GC-Mass) analysis of 2-pyrrolidone (2-PY), and Figure 3b is a deuterated 2-pyrrolidone (2-PY). -d ₁ ) shows the results of gas chromatography-mass spectrometry (GC-Mass) analysis. Figure 3c shows the results of gas chromatography-mass spectrometry (GC-Mass) analysis of ethylenediamine (EDA), Figure 3d is deuterated ethylenediamine (EDA-d _x , x = 1 to 4) It shows the results of gas chromatography-mass spectrometry (GC-Mass) analysis.

3A to 3D, mixing of deuterium into ethylenediamine was clearly observed after 2-PY-d ₁ interacted with ethylenediamine. It was found that this hydrogen-deuterium exchange (HD exchange) takes place for the interaction between EDA-d _x and 2-pyrrolidone.

Hydrogen-deuterium exchange (HD exchange) studies using deuterated 2-pyrrolidone and ethylenediamine using mass spectrometry show that 2-pyrrolidone can form a hydrogen bond network through a peptide group, This may be advantageous for the carboxylation reaction of ethylenediamine. As expected, no deuterium bonds were observed when D ₂ O interacted with N-methyl-2-pyrrolidone which does not have a proton hydrogen atom.

Therefore, it can be confirmed that the presence of the proton N-H hydrogen atom of 2-pyrrolidone contributes to the acceleration of carboxylation of the amine.

Test example 3: 2 - With pyrrolidone Analysis of hydrogen bond interaction of reaction intermediates

Figure 4 shows (a) reaction intermediate, (b) 2-pyrrolidone, (c) 2-pyrrolidone containing 20% by weight reaction intermediate, (d) N-methyl-2-pyrrolidone and (e ) It shows the result of FT-IR analysis of N-methyl-2-pyrrolidone containing 20% by weight of the reaction intermediate.

Referring to FIG. 4, the absorption peaks at 1560cm ^-1 of the reaction intermediate (a) and 1675cm ^-1 of 2-pyrrolidone (b) are frequencies due to the carbonyl stretching vibration of the reaction intermediate and 2-pyrrolidone, respectively. Appears to be When 20% by weight of the reaction intermediate was dissolved in 2-pyrrolidone, it can be seen that the carbonyl peak of the reaction intermediate shifted to a higher frequency of 1595cm ^-1 by 35cm ^-1 . 2-carbonyl peak of pyrrolidone can also be confirmed that, go to a higher frequency 1687cm ^-1 by 12cm ^-1. Thus, it can be confirmed that there is a strong interaction between the reaction intermediate and 2-pyrrolidone.

In addition, a similar phenomenon was observed in the NH absorption peak of the reaction intermediate and 2-pyrrolidone. It can be seen that at 3296cm ^-1 , the frequency due to the NH expansion and contraction vibration of the reaction intermediate moves to a higher frequency of 3307cm ^-1 . These results indicate that a number of hydrogen bonding interactions exist between the ammonium group of the reaction intermediate and the carbonyl group of 2-pyrrolidone as well as the carbonyl group of the reaction intermediate and the NH group of 2-pyrrolidone. This suggests that the presence of the CO ₂ adduct of a diamine, such as a reaction intermediate, may aid the transfer of hydrogen atoms from NH to the carbonyl group of 2-pyrrolidone. In other words, the keto-enol transformation of 2-pyrrolidone can proceed through interaction with the reaction intermediate.

Referring to (e) of FIG. 4, it can be seen that the carbonyl peak of the reaction intermediate moves to a higher frequency at 1567cm ^-1 when the reaction intermediate is dissolved in N-methyl-2-pyrrolidone. However, when compared to that obtained from 2-pyrrolidone, the degree of shift of the peak was 7 cm ^-1 as expected from the significantly lower yield of urea in N-methyl-2-pyrrolidone, which is 2-pyrrolidone. It is about a fifth of the observed value when interacting with.

Test example 4: Urea Yield analysis

Urea prepared according to Examples 1 to 17 and Comparative Examples 1 to 9 used 1,4-dioxane as an internal standard to quantify the yield. The yield of urea was calculated based on the following equation 1.

[Equation 1]

Solvent influence

Table 2 below summarizes the yield according to the type of solvent when preparing urea.

division Amine compounds menstruum catalyst Urea yield
(%) Example 1 Ethylenediamine 2-pyrrolidone - 83.0 Example 2 Ethylenediamine 2-pyrrolidone K ₂ CO ₃ 98.1 Example 3 Ethylenediamine 2-pyrrolidone Cs ₂ CO ₃ 99.0 Example 4 1,2-propanediamine 2-pyrrolidone - 93.3 Example 5 1,3-propanediamine 2-pyrrolidone - 95.1 Example 16 n-butylamine 2-pyrrolidone - 37.0 Example 17 Cyclohexylamine 2-pyrrolidone - 16.0 Comparative Example 1 Ethylenediamine NMP - 21.1 Comparative Example 2 Ethylenediamine NMP K ₂ CO ₃ 48.2 Comparative Example 3 Ethylenediamine NMP Cs ₂ CO ₃ 73.4 Comparative Example 4 1,2-propanediamine NMP - 33.5 Comparative Example 5 1,3-propanediamine NMP - 34.1 Comparative Example 6 Ethylenediamine CH ₃ OH K ₂ CO ₃ 5.8 Comparative Example 7 1,2-propanediamine CH ₃ OH K ₂ CO ₃ 6.7 Comparative Example 8 n-butylamine NMP - 8.8 Comparative Example 9 Cyclohexylamine NMP - 2.5

According to Table 2, the yield of Example 1 using 2-pyrrolidone as a solvent in a catalyst-free condition was 83.0%, and Example 2 and Example using K ₂ CO ₃ or Cs ₂ CO ₃ as a catalyst. It can be seen that the yield of 3 is 98.1% and 99.0%, respectively. Therefore, when 2-pyrrolidone is used as a solvent, urea can be prepared in excellent yield even under a catalyst-free condition, but it can be confirmed that urea can be produced in a higher yield when a catalyst is additionally used.

In addition, the yield of urea in Example 1 using 2-pyrrolidone as a solvent in a catalyst-free condition was higher than that of urea in Comparative Example 1 in which the solvent was used as NMP under the same conditions, and the solvent was used as NMP. , It can be seen that the yield was higher than that of Comparative Example 2 and Comparative Example ₃ using the catalyst and Comparative Example 6 using the solvent as CH ₃ OH and the catalyst.

In addition, in the case of using 2-pyrrolidone as a solvent, when preparing urea from 1,2-propanediamine, 1,3-propanediamine, n-butylamine and cyclohexylamine as well as ethylenediamine, NMP or It can be seen that urea is prepared in a better yield than when using CH ₃ OH.

Influence of reaction temperature

Table 3 shows the yield according to the reaction temperature when preparing urea.

division Reaction temperature
(℃) Urea yield
(%) Example 1 200 83.0 Example 6 150 2.8 Example 7 160 9.5 Example 8 170 22.0 Example 9 180 48.1 Example 10 190 73.6 Example 11 210 79.7 Example 12 220 77.4

According to Table 3, it can be seen that the yield of urea increases rapidly as the reaction temperature increases under the same conditions, and the yield of urea slightly decreases when it exceeds 200°C. Therefore, it is preferable that the reaction temperature is 200°C, and when it exceeds 220°C, it can be seen that the yield decreases as by-products are generated.

Reaction pressure effect

Table 4 below summarizes the yield according to the reaction pressure during urea production.

division Reaction pressure
(MPa) Urea yield
(%) Example 1 5 83.0 Example 13 2 80.4 Example 14 7 83.8 Example 15 10 84.3

According to Table 4, it can be seen that as the reaction pressure increased from 2 MPa to 10 MPa, the urea yield increased only 3.9% from 80.4% to 84.3%. Therefore, it can be seen that the yield of urea does not change significantly according to the reaction pressure change under the same conditions.

The scope of the present invention is indicated by the claims to be described later rather than the detailed description, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention. do.

Claims (14)

In Reaction Scheme 1 or 2 below, the amine compound represented by Structural Formula 1, the amine compound represented by Structural Formula 3, and the amine compound represented by Structural Formula 4 were each used as a solvent and reacted with carbon dioxide. And the step of preparing urea (urea) each represented by Structural Formula 5; Method for producing urea comprising:
[Scheme 1]

[Scheme 2]

In Scheme 1 above,
n is any one of an integer of 1 to 4,
R ¹ and R ² are the same as or different from each other, and each independently a hydrogen atom or a C1 to C3 alkyl group,
In Scheme 2 above,
R ³ and R ⁴ are the same as or different from each other, and each independently a C1 to C9 alkyl group or a C5 to C7 cycloalkyl group,
q is 1 or 2,
R ⁵ to R ⁷ are the same as or different from each other, and each independently a hydrogen atom or a C1 to C3 alkyl group. The method of claim 1,
n is 1 or 2,
R ¹ is a hydrogen atom or a C1 to C3 alkyl group,
R ² is a hydrogen atom,
R ³ and R ⁴ are the same as or different from each other, and each independently a C3 to C6 alkyl group, or a C5 or C6 cycloalkyl group,
q is 1,
R ⁵ to R ⁷ is a method for producing urea, characterized in that a hydrogen atom. The method of claim 2,
n is 1,
A method for producing urea, characterized in that R ¹ is a methyl group. The method of claim 2,
n is 2,
A method for producing urea, characterized in that R ¹ is a hydrogen atom. The method of claim 1,
The amine compound represented by the structural formula 1 is ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, 1,3-propanediamine, 1,2-butanediamine ( 1,2-butanediamine), 1,3-butanediamine, 1,4-butanediamine, 2,3-butanediamine, 1 ,2-pentanediamine (1,2-pentanediamnie), 1,3-pentanediamine (1,3-pentanediamine), 1,4-pentanediamine (1,4-pentanediamine), 1,5-pentanediamine (1, 5-pentanediamine) and 2,3-pentanediamine (2,3-pentanediamine) method for producing urea comprising at least one selected from the group consisting of. The method of claim 1,
The amine compound represented by Structural Formula 3 and the amine compound represented by Structural Formula 4 each contain at least one selected from the group consisting of n-butylamine and cyclohexylamine. Method for producing urea. The method of claim 1,
The method for producing urea, wherein the solvent is 250 to 500 parts by weight based on 100 parts by weight of the amine compound. The method of claim 1,
The method for producing urea, characterized in that the reaction is carried out at a temperature of 150 to 250 ℃. The method of claim 1,
The method for producing urea, characterized in that the reaction is carried out at a pressure of 1 to 20 MPa. The method of claim 1,
The method for producing urea, characterized in that the reaction is carried out under no catalyst conditions. The method of claim 1,
The method for producing urea, characterized in that the reaction further comprises a catalyst. The method of claim 11,
The method for producing urea, characterized in that the catalyst comprises at least one selected from the group consisting of Na ₂ CO ₃ , K ₂ CO ₃ and Cs ₂ CO ₃ . The method of claim 11,
The method for producing urea, characterized in that the molar ratio (mol/mol) of the amine compound and the catalyst is 50 to 150. delete

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