Method for recovering cyclohexylamine from DCU and simultaneously producing 2-benzimidazolone as byproduct

Abstract

The invention discloses a method for recovering cyclohexylamine from DCU and simultaneously producing 2-benzimidazolone as a byproduct, and the method comprises the following steps: firstly weighing N, N '-dicyclohexylurea, o-phenylenediamine and ethylene glycol according to a preset proportion, adding into a reaction kettle, mixing, stirring, heating and reacting, after the reaction is completed, steaming out the generated cyclohexylamine and simultaneously obtaining 2-benzimidazolone; adding urea into the reaction kettle, continuously heating and reacting for 1 hour, converting excessive o-phenylenediamine into 2-benzimidazolone, cooling to 80 DEG C, adding a proper amount of water, and crystallizing 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 a reaction, cyclohexylamine is generated and evaporated out, 2-benzimidazolone is obtained at the same time, excessive o-phenylenediamine is converted into 2-benzimidazolone through urea, the purity of 2-benzimidazolone is improved, the whole recovery process is easy to operate, safe and low in cost, and the method is suitable for industrial production. And the 2-benzimidazolone with high purity can be obtained.

Description

Technical Field

[0001] The invention relates to the technical field of biological polypeptide condensation agent byproduct treatment, and 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, molecular weight 224.3425, is a white solid powder, which is generally a by-product of N,N'-dicyclohexylcarbodiimide (DCC) in industry. At the same time, a small amount of DCU is also produced in 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, but now with the improvement of DCC production technology, this method has no economic value.

[0003] The existing Chinese patent 201510895854.5 proposes a method of heating DCU and sodium hydroxide to 80-450°C to react and recover cyclohexylamine, which is a method of turning waste into treasure to a certain extent. However, this method uses a large amount of sodium hydroxide and requires high temperature, which will also cause great damage to the environment and the economic value generated is not high.

[0004] The above methods all have the problems of environmental pollution, high cost and low output value in the process of utilizing DCU, so it is urgent 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 and 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 and producing 2-benzimidazolone as a by-product, so as to solve the problem that the existing DCU recovery and treatment methods are relatively few, most of them are costly, polluting, and their safety cannot be guaranteed, and they 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 reaction kettle, 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, and 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 reaction kettle 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. The purity of 2-benzimidazolone purified by crystallization reaches more than 99.5%. It is an important intermediate for medicine, 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 and 2-benzimidazolone is generated, excess o-phenylenediamine is converted into 2-benzimidazolone by urea to improve the purity of 2-benzimidazolone, the whole recovery process is simple to operate, safe and low in cost, and high-purity 2-benzimidazolone can be obtained, so that the recovery method can 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 drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative work.

[0018] Figure 1 1. It is a schematic flow diagram of a method for recovering cyclohexylamine from DCU and producing 2-benzimidazolone as a by-product according to the present invention;

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

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

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Embodiment 1

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

[0024] Embodiment 2

[0025] See also Figure 1This embodiment provides a method for recovering cyclohexylamine from DCU and 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) therein, heating to an internal temperature of 150° C. with stirring for 1 hour, and starting to produce The liquid was recovered by a distillation device to obtain 19.7 g of cyclohexylamine (yield 99.5%, calculated according to DCU); then urea (1.50 g, 0.025 mol, 0.25 eq) was added to the reaction system and the temperature was maintained for reaction for 1 hour, then cooled to 80°C, 37.2 g of softened water was added thereto, cooled to room temperature for crystallization, filtered and dried to obtain 16.0 g of 2-benzimidazolone, with a yield of 99.3% (calculated according to o-phenylenediamine) and a purity of 99.6%.

[0026] Embodiment 3

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

[0028] Embodiment 4

[0029] See also Figure 1The present embodiment provides a method for recovering cyclohexylamine from DCU and 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) therein, heating to an internal temperature of 120° C. with stirring for 1 hour, and starting to produce 2-benzimidazolone. The raw liquid was recovered by a distillation device to obtain 19.8 g of cyclohexylamine (yield 100%, calculated according to DCU); then urea (3.30 g, 0.055 mol, 0.55 eq) was added to the reaction system and the temperature was maintained for reaction for 1 hour, then cooled to 80°C, 37.2 g of softened water was added thereto, cooled to room temperature for crystallization, filtered and dried to obtain 19.9 g of 2-benzimidazolone, with a yield of 99.0% (calculated according to o-phenylenediamine) and a purity of 99.5%.

[0030] Embodiment 5

[0031] See also Figure 1 The present embodiment provides a method for recovering cyclohexylamine from DCU and 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 to an internal temperature of 120° C. under stirring for 1 hour, and then starting to produce liquid, which is recovered by a distillation device to obtain 19.8 kg of cyclohexylamine (yield 100%, calculated based on DCU); then adding urea (72 kg, 12 mol, 0.12 eq) to the reaction system, continuing to maintain the temperature for 1 hour, cooling to 80° C., adding 37.2 kg of softened water thereto, cooling to room temperature for crystallization, centrifuging and drying 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 follows 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 principle of the present invention should be included in the protection scope 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 a preset temperature, and react for a preset time, and keep stirring the mixture during the reaction; Step 2: After a low-boiling-point liquid is produced in the reaction kettle, 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, and 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 while producing 2-benzimidazolone as a by-product according to claim 1, characterized in that: In the step 1, the mixture in the reaction kettle is heated to 110-200° C., and the reaction time is 5-8 hours.

3. A method for recovering cyclohexylamine from DCU while producing 2-benzimidazolone as a by-product according to claim 1, characterized in that: In the step 4, the crystallization solvent is water.

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