Kettle residue recovery process of methyl carbamate

Abstract

The invention relates to a kettle residue recovery process of methyl carbamate, and belongs to the technical field of chemical engineering, the kettle residue recovery process of methyl carbamate comprises the following steps: adding the kettle residue of methyl carbamate into water, stirring for dissolving, adding chloroform, extracting, standing for layering, taking an oil phase dissolved with methyl carbamate at the lower layer, cooling to room temperature, filtering, washing, and drying to obtain the methyl carbamate. Drying to constant weight to obtain recycled methyl carbamate; and adjusting the pH value of an upper water phase composed of impurities such as urea, biuret and triuret to 7.5-8 by using a pH regulator, introducing into a sealed reaction tank filled with a modified mesoporous molecular sieve, adsorbing at normal temperature and normal pressure, filtering, and treating the filtrate at 60-80 DEG C to obtain the recycled and treated urea. The whole preparation process is simple and controllable, and the methyl carbamate and the urea in the kettle residues of the methyl carbamate are recycled.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry, and in particular relates to a process for recovering the kettle residue of methyl carbamate. Background Art

[0002] Methyl carbamate is an important fine chemical that can be widely used as a variety of additives, and can also be widely used as an organic synthesis intermediate in the fields of pesticides, medicines, etc. Nowadays, methyl carbamate is generally synthesized into carbamate by one-step alcoholysis using urea and alcohols as reaction raw materials. In the production process, after the reactor liquid is subjected to vacuum distillation and the methyl carbamate product is separated, a reactor residue accounting for about 30% of the reactor liquid is produced. If it is not recycled and processed, it will cause a large amount of resource waste and the discharge of waste residue will cause serious environmental pollution. In order to solve this problem and thoroughly realize green production, it is necessary to study the treatment of the reactor residue.

[0003] The main components of methyl carbamate still residue are unproposed methyl carbamate, urea, biuret, triuret, etc. There are few reports on the recovery methods of methyl carbamate still residue in the prior art. The treatment methods of general chemical still residue include: incineration and landfill, chemical treatment, biodegradation, etc. Among them, chemical treatment is widely used in the treatment of still residue due to its characteristics of efficient recovery of useful substances, reduction of environmental pollution, strong adaptability, mature and reliable technology, etc.

[0004] The document "Study on Treatment and Utilization of Methyl Carbamate Production Residues" achieves the regeneration of methyl carbamate by reacting methyl carbamate residues with methanol in one step, and prepares crude methyl carbamate with a purity of 99.25%. However, the procedures for recovering methyl carbamate still residues in the document and the prior art are relatively complicated, and the utilization rate of effective substances in the methyl carbamate still residues is low. Summary of the invention

[0005] In order to solve the problems in the prior art of recovering methyl carbamate still residue that the procedure is relatively complicated and the utilization rate of effective substances in the methyl carbamate still residue is low, the present invention provides a process for recovering methyl carbamate still residue.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A process for recovering the residual product of methyl carbamate comprises the following steps:

[0008] The kettle residue of methyl carbamate is put into water, stirred to dissolve, and then chloroform is added, and extraction is carried out at 50°C for 40 minutes. After static stratification, the lower oil phase containing methyl carbamate is taken, and the temperature is naturally reduced to room temperature for 20 minutes. After drying at 45°C to constant weight, the recovered methyl carbamate is obtained; and the upper aqueous phase composed of impurities such as urea, biuret, triuret, etc. is adjusted to a pH of 7.5-8 by a pH regulator, and passed into a sealed reaction tank filled with a modified mesoporous molecular sieve, and adsorbed at room temperature and pressure for 40-60 minutes, and then filtered, and the filtrate is dried at 60-80°C to constant weight to obtain recovered urea.

[0009] The usage ratio of the kettle residue of methyl carbamate, water and chloroform is 19.5Kg:40L:50L; the mass ratio of the water phase to the modified mesoporous molecular sieve is 10:0.5-0.6.

[0010] Furthermore, the still residue of methyl carbamate contains 40 wt% of urea, 20 wt% of methyl carbamate, 10 wt% of biuret, and the rest are impurities.

[0011] Furthermore, the pH adjuster is a sodium hydroxide solution or a potassium hydroxide solution, and the concentration of the pH adjuster is 0.1-0.4 mol / L.

[0012] Furthermore, the preparation steps of the modified mesoporous molecular sieve are:

[0013] Step S1: adding tetraethoxysilane and dodecylamine into deionized water, stirring evenly, then adding anhydrous ethanol solvent, and then starting stirring reaction. After the reaction is completed, cooling to room temperature, then washing 4-6 times, and vacuum drying after washing to obtain a mesoporous molecular sieve;

[0014] The dosage ratio of tetraethoxysilane, dodecylamine, deionized water and anhydrous ethanol is 2.08Kg: 0.185-0.925Kg: 7.2-10.8L: 4.5-11.5L; the stirring reaction temperature is 40-50°C and the reaction time is 12-36h.

[0015] Step S2: adding the mesoporous molecular sieve into deionized water, and then adding 0.4 mol / L copper sulfate solution, and then starting to stir. After the stirring is completed, filtering is performed, and the filter cake is vacuum dried to obtain the modified mesoporous molecular sieve;

[0016] The dosage ratio of the mesoporous molecular sieve, deionized water and copper sulfate solution is 10Kg:200L:20L-28L; the stirring reaction temperature is 35-45°C, and the stirring reaction time is 0.5-2h.

[0017] Beneficial effects of the present invention:

[0018] 1. The present invention uses chloroform as an extractant to separate methyl carbamate and impurities such as urea, biuret, triuret, etc. in the kettle residue of methyl carbamate into an oil phase and an aqueous phase, dries the oil phase to obtain recycled methyl carbamate, and filters the aqueous phase through a modified mesoporous molecular sieve to obtain recycled urea, thereby achieving effective separation of methyl carbamate and impurities such as urea, biuret, triuret, etc., and improving the recovery efficiency and purity of methyl carbamate and urea.

[0019] 2. The present invention uses a sealed reaction tank filled with a modified mesoporous molecular sieve for filtration, and the mesoporous molecular sieve is impregnated with a copper sulfate solution, which can enrich the active sites on the surface of the molecular sieve and optimize the spatial distribution of the active sites, thereby improving the adsorption capacity of the prepared modified mesoporous molecular sieve adsorbent, and can effectively adsorb impurities such as biuret and triuret; further, impurities such as urea, biuret, and triuret are adjusted by a pH regulator to be in an alkaline environment. In an alkaline environment, copper ions form stable coordination bonds with nitrogen atoms, oxygen atoms, etc. in biuret molecules, and this coordination effect is stronger than the interaction between urea and copper ions, so that biuret is retained in the internal voids of the molecular sieve, which significantly improves the purity of urea.

[0020] 3. The whole preparation process of the present invention has a mild reaction temperature, a simple and controllable reaction process, and realizes the recycling of methyl carbamate and urea in the kettle residue of methyl carbamate, thereby reducing and avoiding the pollution of the environment by organic matter. DETAILED DESCRIPTION

[0021] The following will be combined with 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] The kettle residue of methyl carbamate of the present invention contains 40 wt% of urea, 20 wt% of methyl carbamate, 10 wt% of biuret, and the rest are impurities.

[0023] Example 1

[0024] The preparation steps of the modified mesoporous molecular sieve of this embodiment are:

[0025] Step S1: 2.08 kg of tetraethoxysilane and 0.185 kg of dodecylamine were added to 7.2 L of deionized water, and then 4.5 L of anhydrous ethanol solvent was added after stirring evenly, and then stirred at 40° C. for 12 h. After the reaction was completed, it was cooled to room temperature, and then washed 4 times. After washing, it was vacuum dried to obtain a mesoporous molecular sieve;

[0026] Step S2: add 10 kg of mesoporous molecular sieve into 200 L of deionized water, then add 20 L of 0.4 mol / L copper sulfate solution, and then stir at 35° C. for 0.5 h. After stirring, filter and vacuum dry the filter cake to obtain the modified mesoporous molecular sieve.

[0027] Example 2

[0028] The preparation steps of the modified mesoporous molecular sieve of this embodiment are:

[0029] Step S1: 2.08 kg of tetraethoxysilane and 0.6 kg of dodecylamine were added to 8.5 L of deionized water, stirred evenly, and then 8.5 L of anhydrous ethanol solvent was added, followed by stirring and reacting at 45 ° C for 24 hours. After the reaction was completed, it was cooled to room temperature, then washed 4 times, and then vacuum dried to obtain a mesoporous molecular sieve;

[0030] Step S2: add 10 kg of mesoporous molecular sieve into 200 L of deionized water, then add 25 L of 0.4 mol / L copper sulfate solution, and then stir at 40° C. for 1.5 h. After stirring, filter and vacuum dry the filter cake to obtain the modified mesoporous molecular sieve.

[0031] Example 3

[0032] The preparation steps of the modified mesoporous molecular sieve of this embodiment are:

[0033] Step S1: 2.08 kg of tetraethoxysilane and 0.925 kg of dodecylamine were added to 10.8 L of deionized water, and then 11.5 L of anhydrous ethanol solvent was added after stirring evenly, and then stirred at 50° C. for 36 hours. After the reaction was completed, it was cooled to room temperature, and then washed 4 times. After washing, it was vacuum dried to obtain a mesoporous molecular sieve;

[0034] Step S2: add 10 kg of mesoporous molecular sieve into 200 L of deionized water, then add 28 L of 0.4 mol / L copper sulfate solution, and then stir at 45° C. for 2 h. After stirring, filter and vacuum dry the filter cake to obtain the modified mesoporous molecular sieve.

[0035] Comparative Example 1

[0036] The preparation steps of the modified mesoporous molecular sieve of this comparative example are:

[0037] 2.08 kg of tetraethoxysilane and 0.185 kg of dodecylamine were added into 7.2 L of deionized water, stirred evenly, and then 4.5 L of anhydrous ethanol solvent was added. Then, stirring reaction was started at 40 °C for 12 h. After the reaction was completed, it was cooled to room temperature and then washed 4 times. After washing, it was vacuum dried to obtain the mesoporous molecular sieve.

[0038] Example 4

[0039] This embodiment provides a process for recovering the residual product of methyl carbamate, comprising the following steps:

[0040] 19.5 kg of the kettle residue of methyl carbamate was put into 40 L of water, stirred to dissolve, then 50 L of chloroform was added, and the mixture was extracted at 50°C for 40 min. After static stratification, the lower oil phase containing methyl carbamate was taken out, and the mixture was naturally cooled to room temperature for 20 min, and dried at 45°C to constant weight to obtain the recovered methyl carbamate; and the upper aqueous phase composed of impurities such as urea, biuret, and triuret was adjusted to pH 7.5 with 0.1 mol / L sodium hydroxide solution, and passed into a sealed reaction tank filled with a modified mesoporous molecular sieve, wherein the mass ratio of the aqueous phase to the modified mesoporous molecular sieve was 10:0.5. After adsorption at room temperature and pressure for 40 min, the mixture was filtered, and the filtrate was dried at 60°C to constant weight to obtain the recovered urea.

[0041] The preparation steps of the modified mesoporous molecular sieve are the same as those in Example 1.

[0042] Example 5

[0043] This embodiment provides a process for recovering the residual product of methyl carbamate, comprising the following steps:

[0044] 19.5 kg of the kettle residue of methyl carbamate was put into 40 L of water, stirred to dissolve, then 50 L of chloroform was added, and the mixture was extracted at 50 ° C for 40 min. After static stratification, the lower oil phase containing methyl carbamate was taken, and the mixture was naturally cooled to room temperature for 20 min, and dried at 45 ° C to constant weight to obtain the recovered methyl carbamate; and the upper aqueous phase composed of impurities such as urea, biuret, triuret, etc. was adjusted to pH 7.8 with 0.3 mol / L sodium hydroxide solution, and passed into a sealed reaction tank filled with a modified mesoporous molecular sieve, wherein the mass ratio of the aqueous phase to the modified mesoporous molecular sieve was 10:0.55, and the mixture was adsorbed at room temperature and pressure for 50 min and then filtered. The filtrate was dried at 70 ° C to constant weight to obtain the recovered urea.

[0045] The preparation steps of the modified mesoporous molecular sieve are the same as those in Example 2.

[0046] Example 6

[0047] This embodiment provides a process for recovering the residual product of methyl carbamate, comprising the following steps:

[0048] 19.5 kg of the kettle residue of methyl carbamate was put into 40 L of water, stirred to dissolve, then 50 L of chloroform was added, and the mixture was extracted at 50°C for 40 min. After static stratification, the lower oil phase containing methyl carbamate was taken out, and the mixture was naturally cooled to room temperature for 20 min, and dried at 45°C to constant weight to obtain the recovered methyl carbamate. The upper aqueous phase composed of impurities such as urea, biuret, and triuret was adjusted to pH 8 with 0.4 mol / L potassium hydroxide solution, and passed into a sealed reaction tank filled with a modified mesoporous molecular sieve, wherein the mass ratio of the aqueous phase to the modified mesoporous molecular sieve was 10:0.6. After adsorption at room temperature and pressure for 60 min, the mixture was filtered, and the filtrate was dried at 80°C to constant weight to obtain the recovered urea.

[0049] The preparation steps of the modified mesoporous molecular sieve are the same as those in Example 3.

[0050] Comparative Example 2

[0051] This comparative example provides a process for recovering the residual product of methyl carbamate. The remaining steps and raw materials are the same as those of Example 4, except that the modified mesoporous molecular sieve is replaced by the product prepared in Comparative Example 1.

[0052] Examples 4 to 6 and Comparative Example 2 were tested, and the items were as follows:

[0053] 1. The purity and recovery rate of methyl carbamate were determined by gas chromatography. Recovery rate = content of methyl carbamate recovered / content of methyl carbamate in methyl carbamate kettle residue × 100%. The test results are shown in Table 1.

[0054] 2. The biuret content in the recovered urea was determined by using "Determination of Biuret Content in Urea - Spectrophotometric Method" GB / T2443-91. The test results are shown in Table 2.

[0055] 3. The triuret content in the recovered urea was detected by high performance liquid chromatography. The test results are shown in Table 3.

[0056] Table 1

[0057] project purity(%) Recovery rate (%) Example 4 99.35 98.71 Example 5 99.46 98.83 Example 6 99.58 99.12 Comparative Example 2 99.34 98.69

[0058] It can be observed from Table 1 that the purity and recovery rate of methyl carbamate obtained in Examples 4 to 6 and Comparative Example 2 are relatively high, indicating that the use of chloroform as an extractant can effectively achieve the recovery of methyl carbamate in the kettle residue.

[0059] Table 2

[0060] project Biuret(%) Example 4 0.06 Example 5 0.05 Example 6 0.03 Comparative Example 2 0.12

[0061] As can be seen from Table 2, the content of biuret in the urea recovered and treated in Examples 4 to 6 is lower than the content of biuret in Comparative Example 2.

[0062] Table 3

[0063] project Triuret(%) Example 4 Not detected Example 5 Not detected Example 6 Not detected Comparative Example 2 0.03

[0064] As can be seen from Table 2, the content of triuret in the urea recovered and treated in Examples 4 to 6 is lower than the content of triuret in Comparative Example 2.

[0065] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0066] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for recovering the residual product of methyl carbamate, characterized in that: The following steps are involved: The kettle residue of methyl carbamate is put into water, stirred to dissolve, and then chloroform is added, and extraction is carried out at 50°C for 40 minutes. After static stratification, the lower oil phase containing methyl carbamate is taken out, cooled to room temperature for recrystallization for 20 minutes, and dried at 45°C to constant weight to obtain the recovered methyl carbamate; and the upper aqueous phase composed of impurities such as urea, biuret, triuret, etc. is adjusted to pH 7.5-8 by a pH regulator, passed into a sealed reaction tank filled with a modified mesoporous molecular sieve, adsorbed at room temperature and pressure for 40-60 minutes, and then filtered, and the filtrate is treated at 60-80°C for 40-50 minutes to obtain the recovered urea.

2. A process for recovering methyl carbamate residue according to claim 1, characterized in that: The usage ratio of the kettle residue of methyl carbamate, water and chloroform is 19.5Kg:40L:50L.

3. A process for recovering methyl carbamate residue according to claim 1, characterized in that: The mass ratio of the water phase to the modified mesoporous molecular sieve is 10:0.5-0.

6.

4. A process for recovering methyl carbamate residue according to claim 1, characterized in that: The pH adjuster is a sodium hydroxide solution or a potassium hydroxide solution, and the concentration of the pH adjuster is 0.1-0.4 mol / L.

5. A process for recovering methyl carbamate residue according to claim 1, characterized in that: The still residue of methyl carbamate contains 40 wt% urea, 20 wt% methyl carbamate, 10 wt% biuret, and the rest are impurities.

6. A process for recovering methyl carbamate residue according to claim 1, characterized in that: The preparation steps of modified mesoporous molecular sieve are: Step S1: adding tetraethoxysilane and dodecylamine into deionized water, stirring evenly, then adding anhydrous ethanol, and then starting the stirring reaction. After the reaction is completed, cooling to room temperature, then washing 4-6 times, and vacuum drying to obtain a mesoporous molecular sieve; Step S2: adding the mesoporous molecular sieve into deionized water, and then adding 0.4 mol / L copper sulfate solution, and then starting to stir. After the stirring is completed, filtering is performed, and the filter cake is vacuum dried to obtain the modified mesoporous molecular sieve.

7. A process for recovering methyl carbamate residue according to claim 6, characterized in that: In step S1, the usage ratio of tetraethoxysilane, dodecylamine, deionized water and anhydrous ethanol is 2.08Kg: 0.185-0.925Kg: 7.2-10.8L: 4.5-11.5L.

8. A process for recovering methyl carbamate residue according to claim 6, characterized in that: In step S1, the stirring reaction temperature is 40-50°C and the time is 12-36h.

9. A process for recovering methyl carbamate residue according to claim 6, characterized in that: In step S2, the usage ratio of the mesoporous molecular sieve, deionized water, and copper sulfate solution is 10Kg:200L:20L-28L.

10. A process for recovering methyl carbamate residue according to claim 6, characterized in that: In step S2, the stirring reaction temperature is 35-45° C., and the stirring reaction time is 0.5-2 h.