A method for recovering cyclohexylamine from DCU while producing 2-benzimidazolone as a by-product

Abstract

The invention discloses a method for recovering cyclohexylamine from DCU and simultaneously producing 2-benzimidazolone as a by-product. The method comprises the following steps: firstly, N,N'-dicyclohexylurea, o-phenylenediamine and ethylene glycol are weighed according to a preset ratio, added into a reactor, mixed, stirred and heated for reaction, after the reaction is completed, the generated cyclohexylamine is distilled off and the 2-benzimidazolone is obtained, then, urea is added into the reactor, the heating reaction is continued for 1 hour, excess o-phenylenediamine is converted into 2-benzimidazolone, and the mixture is cooled to 80°C and a suitable amount of water is added for crystallization to obtain high-purity 2-benzimidazolone. According to the method, N,N'-dicyclohexylurea, o-phenylenediamine and ethylene glycol are mixed in proportion and heated for reaction to generate and distill off cyclohexylamine and simultaneously obtain 2-benzimidazolone, and excess o-phenylenediamine is converted into 2-benzimidazolone using urea to improve the purity of the 2-benzimidazolone. The entire recovery process is simple to operate, safe and low in cost, and can obtain high-purity 2-benzimidazolone.

Description

Technical Field

[0001] The present invention relates to the technical field of biological polypeptide condensation agent byproduct treatment, in particular to a method for recovering cyclohexylamine from DCU and simultaneously producing 2-benzimidazolone as a byproduct. Background Art

[0002] N,N'-dicyclohexylurea (DCU), chemical formula C 13 H 24 N2O, with a molecular weight of 224.3425, is a white solid powder. It is generally a by-product of N,N'-dicyclohexylcarbodiimide (DCC) in industry. At the same time, a small amount of DCU is also produced during the production process of DCC. These by-products of DCU have long been treated as hazardous waste. This treatment process not only consumes a lot of manpower and material resources, but also causes great damage to the environment. In the early days, The Journal of Organic Chemistry. 1967, 32: 2895 and Chemical Reagents, 1992, 14 (1): 54, a method of using DCU to produce DCC was proposed. However, with the improvement of DCC production technology, this method has no economic value.

[0003] Existing Chinese patent 201510895854.5 proposes a method for recovering cyclohexylamine by heating DCU with sodium hydroxide to 80-450°C. This method, to some extent, transforms waste into treasure. However, this method uses large amounts of sodium hydroxide and requires high temperatures, which also causes significant environmental damage and has low economic value.

[0004] The above methods all have problems such as environmental pollution, high cost and low output value in the process of utilizing DCU. Therefore, there is an urgent need to develop an environmentally friendly, safe and high-output DCU comprehensive utilization method. Therefore, the present invention proposes a method for recovering cyclohexylamine from DCU while producing 2-benzimidazolone as a by-product to solve the problems existing in the prior art. Summary of the Invention

[0005] In view of the above problems, the purpose of the present invention is to propose a method for recovering cyclohexylamine from DCU while producing 2-benzimidazolone as a by-product, so as to solve the problem that existing DCU recovery and treatment methods are relatively few, most of which are costly, highly polluting, and unsafe, and cannot be applied to large-scale production and preparation.

[0006] In order to achieve the purpose of the present invention, the present invention is implemented by the following technical scheme: a method for recovering cyclohexylamine from DCU while producing 2-benzimidazolone as a by-product, comprising the following steps:

[0007] Step 1: Add N,N'-dicyclohexylurea, o-phenylenediamine and ethylene glycol into a reaction kettle at a mass ratio of 1:1-1.5:2-5, stir, heat to a preset temperature, and react for a preset time, and keep stirring the mixture during the reaction;

[0008] Step 2: After a low-boiling-point liquid is produced in the reactor, it is evaporated and the obtained reaction product is cyclohexylamine, which is recovered;

[0009] Step 3: After the cyclohexylamine is recovered, urea is added to the reactor, and the mass ratio of N,N'-dicyclohexylurea, o-phenylenediamine, ethylene glycol and urea is 1:1-1.5:2-5:0.1-0.6. The heating reaction is continued for 1 hour to convert the excess o-phenylenediamine into 2-benzimidazolone;

[0010] Step 4: Cool the reaction system to 80° C., add water and ethanol thereto, cool and crystallize, and then centrifuge to obtain a high-purity byproduct 2-benzimidazolone.

[0011] A further improvement is that in the step 1, the mixture in the reactor is heated to 110-200° C., and the reaction time is 5-8 hours.

[0012] A further improvement is that in step 4, the crystallization solvent is water.

[0013] The heating reaction route of N,N'-dicyclohexylurea and o-phenylenediamine in ethylene glycol in the present invention is as follows:

[0014]

[0015] As the reaction proceeds, the distilled liquid is cyclohexylamine, which can be used to synthesize N,N'-dicyclohexylcarbodiimide (DCU). Urea is then added to convert the excess o-phenylenediamine into 2-benzimidazolone. After crystallization and purification, the purity of 2-benzimidazolone reaches over 99.5%. It is an important intermediate for medicines, pigments and dyes. Its nitration and reduction product, 5,6-diaminobenzimidazolone, is a special intermediate for high-grade organic pigments.

[0016] The beneficial effects of the present invention are as follows: N,N'-dicyclohexylurea, o-phenylenediamine and ethylene glycol are mixed in proportion and heated for reaction, cyclohexylamine is evaporated to generate 2-benzimidazolone, and excess o-phenylenediamine is converted into 2-benzimidazolone using urea to improve the purity of 2-benzimidazolone. The entire recovery process is simple, safe and low in cost, and high-purity 2-benzimidazolone can be obtained, thereby enabling the recovery method to be applied to large-scale production and preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0018] Figure 1 This is a schematic flow diagram of a method for recovering cyclohexylamine from DCU while producing 2-benzimidazolone as a by-product;

[0019] Figure 2 This is a liquid phase spectrum of the high-purity 2-benzimidazolone obtained by the present invention;

[0020] Figure 3 The graph is the nuclear magnetic hydrogen spectrum of the high-purity 2-benzimidazolone obtained by the present invention. DETAILED DESCRIPTION

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0022] Example 1

[0023] See also Figure 1 This embodiment provides a method for recovering cyclohexylamine from DCU and simultaneously producing 2-benzimidazolone as a by-product, comprising the following steps: taking a 100 mL three-necked flask, installing a thermometer and a distillation apparatus, adding DCU (22.4 g, 0.10 mol), o-phenylenediamine (11.9 g, 0.11 mol, 1.1 eq) and ethylene glycol (18.6 g, 0.30 mol, 3.0 eq) thereto, heating to an internal temperature of 120° C. with stirring and reacting for 1 hour, and then starting to produce The liquid was recovered by distillation to obtain 19.5 g of cyclohexylamine (yield 98.5%, calculated based on DCU); urea (0.72 g, 0.012 mol, 0.12 eq) was then added to the reaction system, and the temperature was maintained for reaction for 1 h. The reaction was then cooled to 80°C, and 37.2 g of softened water was added thereto. The mixture was cooled to room temperature for crystallization, filtered, and dried to obtain 14.6 g of 2-benzimidazolone with a yield of 98.6% (calculated based on o-phenylenediamine) and a purity of 99.5%.

[0024] Example 2

[0025] See also Figure 1This embodiment provides a method for recovering cyclohexylamine from DCU and simultaneously producing 2-benzimidazolone as a by-product, comprising the following steps: taking a 100 mL three-necked flask, installing a thermometer and a distillation apparatus, adding DCU (22.4 g, 0.10 mol), o-phenylenediamine (13.0 g, 0.12 mol, 1.2 eq) and ethylene glycol (18.6 g, 0.30 mol, 3.0 eq) thereto, heating to an internal temperature of 150° C. with stirring for 1 hour, and starting to produce The liquid was recovered by distillation to obtain 19.7 g of cyclohexylamine (yield 99.5%, calculated based on DCU); urea (1.50 g, 0.025 mol, 0.25 eq) was then added to the reaction system, and the reaction temperature was maintained for 1 h. The reaction was then cooled to 80°C, 37.2 g of softened water was added thereto, and the mixture was cooled to room temperature for crystallization. The mixture was filtered and dried to obtain 16.0 g of 2-benzimidazolone with a yield of 99.3% (calculated based on o-phenylenediamine) and a purity of 99.6%.

[0026] Example 3

[0027] See also Figure 1 This embodiment provides a method for recovering cyclohexylamine from DCU and simultaneously producing 2-benzimidazolone as a by-product, comprising the following steps: taking a 100 mL three-necked flask, installing a thermometer and a distillation apparatus, adding DCU (22.4 g, 0.10 mol), o-phenylenediamine (11.9 g, 0.11 mol, 1.1 eq) and ethylene glycol (31.0 g, 0.50 mol, 5.0 eq) thereto, heating to an internal temperature of 120° C. under stirring for 1 hour, and starting to produce The liquid was recovered by distillation to obtain 19.4 g of cyclohexylamine (yield 98.0%, calculated based on DCU); urea (0.72 g, 0.012 mol, 0.12 eq) was then added to the reaction system, and the temperature was maintained for reaction for 1 hour. The reaction was then cooled to 80°C, and 62.0 g of softened water was added thereto. The mixture was cooled to room temperature for crystallization, filtered, and dried to obtain 14.4 g of 2-benzimidazolone with a yield of 97.3% (calculated based on o-phenylenediamine) and a purity of 99.9%.

[0028] Example 4

[0029] See also Figure 1This embodiment provides a method for recovering cyclohexylamine from DCU and simultaneously producing 2-benzimidazolone as a by-product, comprising the following steps: taking a 100 mL three-necked flask, installing a thermometer and a distillation apparatus, adding DCU (22.4 g, 0.10 mol), o-phenylenediamine (16.2 g, 0.15 mol, 1.5 eq) and ethylene glycol (31.0 g, 0.50 mol, 5.0 eq) thereto, heating to an internal temperature of 120° C. with stirring for 1 hour, and starting to produce cyclohexylamine. The raw liquid was recovered by distillation to obtain 19.8 g of cyclohexylamine (yield 100%, calculated based on DCU); urea (3.30 g, 0.055 mol, 0.55 eq) was then added to the reaction system, and the reaction temperature was maintained for 1 hour. The system was then cooled to 80°C, 37.2 g of softened water was added, and the system was cooled to room temperature for crystallization. The product was filtered and dried to obtain 19.9 g of 2-benzimidazolone with a yield of 99.0% (calculated based on o-phenylenediamine) and a purity of 99.5%.

[0030] Example 5

[0031] See also Figure 1 This embodiment provides a method for recovering cyclohexylamine from DCU while simultaneously producing 2-benzimidazolone as a by-product, comprising the following steps: adding DCU (22.4 kg, 100 mol), o-phenylenediamine (11.9 kg, 110 mol, 1.1 eq), and ethylene glycol (18.6 kg, 300 mol, 3.0 eq) to a 100-L reactor; heating the reaction mixture to an internal temperature of 120° C. with stirring for 1 hour, during which liquid begins to be produced, and recovering 19.8 kg of cyclohexylamine (yield 100%, calculated based on DCU) through a distillation apparatus; then adding urea (72 kg, 12 mol, 0.12 eq) to the reaction system, maintaining the temperature for 1 hour, and cooling the reaction mixture to 80° C., adding 37.2 kg of demineralized water, cooling the reaction mixture to room temperature for crystallization, centrifuging, and drying the reaction mixture to obtain 14.7 kg of 2-benzimidazolone with a yield of 99.3% (calculated based on o-phenylenediamine) and a purity of 99.5%.

[0032] The liquid phase spectrum of 2-benzimidazolone in the present invention is as follows Figure 2 As shown, the 2-benzimidazolone of 2-benzimidazolone is as shown Figure 3 shown.

[0033] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for recovering cyclohexylamine from DCU and producing 2-benzimidazolone as a by-product, characterized in that: The following steps are involved: Step 1: Add N,N'-dicyclohexylurea, o-phenylenediamine and ethylene glycol into a reaction kettle at a mass ratio of 1:1-1.5:2-5, stir, heat to 110-200°C, and react for 5-8 hours, while stirring the mixture during the reaction; Step 2: After a low-boiling-point liquid is produced in the reactor, it is evaporated and the obtained reaction product is cyclohexylamine, which is recovered; Step 3: After the cyclohexylamine is recovered, urea is added to the reactor, and the mass ratio of N,N'-dicyclohexylurea, o-phenylenediamine, ethylene glycol and urea is 1:1-1.5:2-5:0.1-0.

6. The heating reaction is continued for 1 hour to convert the excess o-phenylenediamine into 2-benzimidazolone; Step 4: Cool the reaction system to 80° C., add water and ethanol thereto, cool and crystallize, and then centrifuge to obtain a high-purity byproduct 2-benzimidazolone.

2. A method for recovering cyclohexylamine from DCU with the simultaneous by-production of 2-benzimidazolone according to claim 1, characterized in that: In the step 4, the crystallization solvent is water.

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