A method for recycling 2-methylpyridine waste solvent

Abstract

The present invention relates to the technical field of solvent recovery and reuse, and discloses a method for recovering and reusing 2-methylpyridine waste solvent, comprising the following steps: step S1. adding 2-methylpyridine waste solvent to a salting-out reactor, continuing to add a salting-out agent, precipitating solid salt, and obtaining a solid-liquid mixture; step S2. centrifuging the solid-liquid mixture to obtain a centrifuge; step S3. transporting the centrifuge to a distillation tower, and adding water to the distillation tower for azeotropic distillation of water vapor, and the top steam enters a pervaporation membrane for dehydration; step S4. transporting the solvent treated in step S3 to a distillation tower for distillation, and the solvent extracted from the side line of the distillation tower is industrial-grade 2-methylpyridine. The recovery and reuse method provided by the present invention has the characteristics of high yield, low energy consumption, simple production process, and stable operation method, and the purified salting-out agent can also be recycled, which is energy-saving and environmentally friendly and suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of solvent recovery and reuse, in particular to a method for recovering and reusing 2-methylpyridine waste solvent. Background Art

[0002] 2-Methylpyridine is a colorless oily liquid with a strong unpleasant pyridine odor. It is used as a raw material for the synthesis of medicines, dyes, and resins. It can be used to make fertilizer enhancers, herbicides, livestock anthelmintics, rubber accelerators, dye intermediates, etc.

[0003] 2-Methylpyridine is an important chemical intermediate and an important raw material for fine chemicals. It can be used to produce long-acting sulfonamides, antiallergic drug chlorpheniramine, pesticide intermediates, feed and feed intermediates and other fields. It can also be used in herbicides paraquat and chlorquat. 2-Methylpyridine can also be used to synthesize special resins such as polyvinylpyridine and 2-vinylpyridine intermediates. The latter is used to produce styrene-butadiene latex, which is a binder for nylon cord fabrics in radial tires.

[0004] Especially with the development of organic synthesis technology and pesticide active molecule design skills and the demand for new pesticides in agricultural production, 2-methylpyridine pesticides have been widely used in many pesticides such as fungicides, herbicides, plant growth regulators, etc. In the process of pesticide production, a large amount of 2-methylpyridine waste solvent containing impurities such as salts and water will be generated. The existing technology generally forms a minimum azeotrope by azeotroping 2-methylpyridine waste solvent with water, but conventional distillation methods cannot fully separate 2-methylpyridine from water. If it is directly discharged, it will cause great pollution to the environment and great waste of resources. Summary of the invention

[0005] In view of this, the present invention provides a method for recycling 2-methylpyridine waste solvent to solve the problem of environmental pollution and resource waste caused by direct discharge of existing 2-methylpyridine waste solvent.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A method for recycling 2-methylpyridine waste solvent comprises the following steps:

[0008] Step S1. Adding 2-methylpyridine waste solvent into a salting-out reactor, and continuing to add a salting-out agent to precipitate solid salt to obtain a solid-liquid mixture;

[0009] Step S2. centrifuging the solid-liquid mixture to obtain a centrifuge;

[0010] Step S3. The centrifuged liquid is transported to a distillation tower, and water is added to the distillation tower for azeotropic distillation of water vapor, and the top steam enters a pervaporation membrane for dehydration;

[0011] Step S4. The solvent treated in step S3 is transported to a distillation tower for distillation, and the solvent extracted from the side line of the distillation tower is industrial-grade 2-methylpyridine.

[0012] Preferably, in the above-mentioned method for recycling and reusing 2-methylpyridine waste solvent, the 2-methylpyridine waste solvent in step S1 includes sulfonate, sodium chloride and 2-methylpyridine.

[0013] Preferably, in the above-mentioned method for recycling and reusing 2-methylpyridine waste solvent, the salting-out agent in step S1 includes methanol, ethanol, isopropanol, and acetonitrile.

[0014] Preferably, in the above-mentioned method for recycling 2-methylpyridine waste solvent, the feed rate of the waste solvent in step S1 is 0.1-5m 3 / h, the feed rate of the salting-out agent is 0.5-6m 3 / h.

[0015] Preferably, in the above-mentioned method for recycling and reusing 2-methylpyridine waste solvent, the centrifugation step in step S2 is: centrifuging the solid-liquid mixture at 0.1-10 m 3 / h and added into a fully automatic centrifuge for centrifugal separation of solid salt and 2-methylpyridine.

[0016] Preferably, in the above-mentioned method for recycling and reusing 2-methylpyridine waste solvent, step S3 also includes: detecting the water content of the solvent after being treated by the pervaporation membrane, and judging whether the water content reaches a preset water content, if it reaches the preset water content, proceeding to step S4, otherwise, refluxing to the distillation tower to continue the cycle of azeotropic distillation and pervaporation membrane dehydration.

[0017] Preferably, in the above-mentioned method for recycling and reusing 2-methylpyridine waste solvent, the preset water content is that the water content of the solvent after being treated by the pervaporation membrane is less than 1%.

[0018] Preferably, in the above-mentioned method for recycling and reusing 2-methylpyridine waste solvent, the rate at which the overhead steam enters the pervaporation membrane in step S3 is 0.5-3 m / s. 3 / h.

[0019] Preferably, in the above-mentioned method for recycling and reusing 2-methylpyridine waste solvent, the operating pressure of the distillation tower in step S4 is atmospheric pressure operation, the top temperature is 90-105°C, the bottom temperature is 125-135°C, and the reflux ratio is 0.5-10.

[0020] Preferably, in the above-mentioned method for recycling and reusing 2-methylpyridine waste solvent, the number of plates of the distillation tower in step S4 is 18-28, the feed inlet is the 6th to 12th plate, and the side line outlet is arranged at the 13th to 21st plate.

[0021] Preferably, in the above-mentioned method for recycling 2-methylpyridine waste solvent, the extraction rate of 2-methylpyridine in step S4 is 0.2-2m 3 / h.

[0022] The present invention provides a method for recycling 2-methylpyridine waste solvent. Compared with the prior art, the method has the following beneficial effects:

[0023] The present invention uses salting out, centrifugation, distillation, pervaporation membrane, and rectification integrated coupling technology to recycle the solvent, and the overall energy consumption of the process is low. The waste liquid containing 3-methylpyridine with a purity of only 50-70% (wt) is purified to industrial-grade 2-methylpyridine with a purity greater than 98.5% (wt), and the recovery rate is greater than 98%. The water content of 2-methylpyridine is significantly reduced, and the dehydration performance is significant. The present invention realizes the recycling and reuse of 2-methylpyridine waste solvent, reduces the degree of environmental pollution caused by waste solvents in the production of the agrochemical industry, and saves production costs;

[0024] The recycling method provided by the present invention also has the characteristics of high yield, low energy consumption, simple production process and stable operation method, and the purified salting-out agent can also be recycled, which is energy-saving and environmentally friendly and suitable for large-scale industrial production. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

[0026] Example 1

[0027] This embodiment discloses a method for recycling 2-methylpyridine waste solvent, comprising the following steps:

[0028] Step S1. Waste solvent containing 55% 2-methylpyridine was heated to 2 m 3 / h was added into the salting out reactor and continued at 3m 3 Methanol is added at a rate of / h to precipitate solid salt and obtain a solid-liquid mixture;

[0029] Step S2. The solid-liquid mixture is heated to 5 m 3 / h into a fully automatic centrifuge, and centrifuge to separate sulfonate, sodium chloride and 2-methylpyridine. The obtained centrifuge liquid is the crude 2-methylpyridine;

[0030] Step S3: The centrifugal liquid is transported to a distillation tower, and water is added to the distillation tower for azeotropic distillation. The top steam of the tower is 1.8 m 3 / h rate into the pervaporation membrane for dehydration; the water content of the solvent after the pervaporation membrane treatment was detected to be 1.5%, the solvent was refluxed to the distillation tower to continue azeotropic distillation and pervaporation membrane dehydration, and the water content of the solvent was detected to be 0.8%;

[0031] Step S4. The solvent treated in step S3 is transported to a distillation tower with a total of 20 plates for atmospheric distillation. The feed inlet is the 8th plate, the top temperature is 100°C, the bottom temperature is 130°C, the reflux ratio is 5, and the 15th plate of the distillation tower is 1m 3 The solvent extracted at a rate of / h is industrial grade 2-methylpyridine.

[0032] Example 2

[0033] This embodiment discloses a method for recycling 2-methylpyridine waste solvent, comprising the following steps:

[0034] Step S1. Waste solvent containing 60% 2-methylpyridine was heated to 3 m 3 / h was added into the salting out reactor and continued at 4m 3 Ethanol is added at a rate of / h to precipitate solid salt and obtain a solid-liquid mixture;

[0035] Step S2. The solid-liquid mixture is heated to 8 m 3 / h into a fully automatic centrifuge, and centrifuge to separate sulfonate, sodium chloride and 2-methylpyridine. The obtained centrifuge liquid is the crude 2-methylpyridine;

[0036] Step S3: The centrifugal liquid is transported to a distillation tower, and water is added to the distillation tower for azeotropic distillation. The top steam of the tower is 0.5 m 3 / h rate into the pervaporation membrane for dehydration; the water content of the solvent after the pervaporation membrane treatment was detected to be 1%;

[0037] Step S4. The solvent treated in step S3 is transported to a distillation tower with a total of 18 plates for atmospheric distillation. The feed inlet is the 6th plate, the top temperature is 105°C, the bottom temperature is 135°C, the reflux ratio is 8, and the 1.5m 3 The solvent extracted at a rate of / h is industrial grade 2-methylpyridine.

[0038] Example 3

[0039] This embodiment discloses a method for recycling 2-methylpyridine waste solvent, comprising the following steps:

[0040] Step S1. Waste solvent containing 70% 2-methylpyridine was heated to 5 m 3 / h was added into the salting out reactor and continued at 6m 3 Isopropanol was added at a rate of / h to precipitate solid salt and obtain a solid-liquid mixture;

[0041] Step S2. The solid-liquid mixture is heated to 10 m 3 / h into a fully automatic centrifuge, and centrifuge to separate sulfonate, sodium chloride and 2-methylpyridine. The obtained centrifuge liquid is the crude 2-methylpyridine;

[0042] Step S3: The centrifugal liquid is transported to a distillation tower, and water is added to the distillation tower for azeotropic distillation. The top steam of the tower is 3m 3 / h rate into the pervaporation membrane for dehydration; the water content of the solvent after the pervaporation membrane treatment was detected to be 0.9%;

[0043] Step S4. The solvent treated in step S3 is transported to a distillation tower with a total of 28 plates for atmospheric distillation. The feed inlet is the 12th plate, the tower top temperature is 90°C, the tower bottom temperature is 125°C, the reflux ratio is 0.5, and the solvent is distilled from the 21st plate of the distillation tower side line at 2m 3 The solvent extracted at a rate of / h is industrial grade 2-methylpyridine.

[0044] Example 4

[0045] This embodiment discloses a method for recycling 2-methylpyridine waste solvent, comprising the following steps:

[0046] Step S1. Waste solvent containing 40% 2-methylpyridine was diluted with 0.1 m 3 / h was added into the salting out reactor and continued at 0.5m 3 / h to add acetonitrile to precipitate a solid salt and obtain a solid-liquid mixture;

[0047] Step S2. The solid-liquid mixture is heated to 1 m 3 / h into a fully automatic centrifuge, and centrifuge to separate sulfonate, sodium chloride and 2-methylpyridine. The obtained centrifuge liquid is the crude 2-methylpyridine;

[0048] Step S3: The centrifugal liquid is transported to a distillation tower, and water is added to the distillation tower for azeotropic distillation. The top steam of the tower is 1m 3 / h rate into the pervaporation membrane for dehydration; the water content of the solvent after the pervaporation membrane treatment was detected to be 2.2%, the solvent was refluxed to the distillation tower to continue azeotropic distillation, and the water content of the solvent after the top steam entered the pervaporation membrane for dehydration was 0.6%;

[0049] Step S4. The solvent treated in step S3 is transported to a distillation tower with a total of 22 plates for atmospheric distillation. The feed inlet is the 10th plate, the tower top temperature is 95°C, the tower bottom temperature is 130°C, the reflux ratio is 10, and the 17th plate of the distillation tower is 0.2 m 3 The solvent extracted at a rate of / h is industrial grade 2-methylpyridine.

[0050] Example 5

[0051] This embodiment discloses a method for recycling 2-methylpyridine waste solvent, comprising the following steps:

[0052] Step S1. Waste solvent containing 30% 2-methylpyridine was added at 1 m 3 / h was added into the salting out reactor and continued at 2m 3 Methanol is added at a rate of / h to precipitate solid salt and obtain a solid-liquid mixture;

[0053] Step S2. The solid-liquid mixture is heated to 0.1 m 3 / h into a fully automatic centrifuge, and centrifuge to separate sulfonate, sodium chloride and 2-methylpyridine. The obtained centrifuge liquid is the crude 2-methylpyridine;

[0054] Step S3: The centrifugal liquid is transported to a distillation tower, and water is added to the distillation tower for azeotropic distillation. The top steam of the tower is 2.5 m 3 / h rate into the pervaporation membrane for dehydration; the water content of the solvent after the pervaporation membrane treatment was detected to be 0.9%;

[0055] Step S4. The solvent treated in step S3 is transported to a distillation tower with a total of 24 plates for atmospheric distillation. The feed inlet is the 10th plate, the tower top temperature is 90°C, the tower bottom temperature is 130°C, the reflux ratio is 3, and the 19th plate of the distillation tower is 0.8 m 3 The solvent extracted at a rate of / h is industrial grade 2-methylpyridine.

[0056] Comparative Example 1

[0057] This comparative example discloses a method for recycling 2-methylpyridine waste solvent, comprising the following steps:

[0058] Step S1. Waste solvent containing 55% 2-methylpyridine was heated to 2 m 3 / h was added into the salting out reactor and continued at 3m 3 Methanol is added at a rate of / h to precipitate solid salt and obtain a solid-liquid mixture;

[0059] Step S2. The solid-liquid mixture is heated to 5 m 3 / h into a fully automatic centrifuge, and centrifuge to separate sulfonate, sodium chloride and 2-methylpyridine. The obtained centrifuge liquid is the crude 2-methylpyridine;

[0060] Step S3: The centrifugal liquid is transported to a distillation tower, and water is added to the distillation tower for azeotropic distillation. The top steam of the tower is 1.8 m 3 / h rate into the pervaporation membrane for dehydration;

[0061] Step S4. The solvent treated in step S3 is transported to a distillation tower with a total of 20 plates for atmospheric distillation. The feed inlet is the 8th plate, the top temperature is 100°C, the bottom temperature is 130°C, the reflux ratio is 5, and the 15th plate of the distillation tower is 1m 3 The solvent extracted at a rate of / h is industrial grade 2-methylpyridine.

[0062] Comparative Example 2

[0063] This comparative example discloses a method for recycling 2-methylpyridine waste solvent, comprising the following steps:

[0064] Step S1. Waste solvent containing 55% 2-methylpyridine was heated to 2 m 3 / h was added into the salting out reactor and continued at 3m 3 Methanol is added at a rate of / h to precipitate solid salt and obtain a solid-liquid mixture;

[0065] Step S2. The solid-liquid mixture is heated to 5 m 3 / h into a fully automatic centrifuge, and centrifuge to separate sulfonate, sodium chloride and 2-methylpyridine. The obtained centrifuge liquid is the crude 2-methylpyridine;

[0066] Step S3: The centrifugal liquid is transported to a distillation tower, and water is added to the distillation tower for azeotropic distillation. The top steam of the tower is 1.8 m 3 / h rate into the pervaporation membrane for dehydration; the water content of the solvent after the pervaporation membrane treatment was detected to be 1.5%, the solvent was refluxed to the distillation tower to continue azeotropic distillation and pervaporation membrane dehydration, and the water content of the solvent was detected to be 0.8%;

[0067] Step S4. The solvent treated in step S3 is transported to a distillation tower with a total of 50 plates for atmospheric distillation. The feed inlet is the 20th plate, the tower top temperature is 100°C, the tower bottom temperature is 130°C, the reflux ratio is 5, and the 35th plate of the distillation tower is 1m 3 The solvent extracted at a rate of / h is industrial grade 2-methylpyridine.

[0068] Comparative Example 3

[0069] This comparative example discloses a method for recycling 3-methylpyridine waste solvent, comprising the following steps:

[0070] Step S1. Waste solvent containing 55% 3-methylpyridine was heated to 2 m 3 / h was added into the salting out reactor and continued at 3m 3 Methanol is added at a rate of / h to precipitate solid salt and obtain a solid-liquid mixture;

[0071] Step S2. The solid-liquid mixture is heated to 5 m 3 / h is added into a fully automatic centrifuge, and sulfonate, sodium chloride and 3-methylpyridine are separated by centrifugation. The obtained centrifuge liquid is the crude 3-methylpyridine;

[0072] Step S3: The centrifugal liquid is transported to a distillation tower, and water is added to the distillation tower for azeotropic distillation. The top steam of the tower is 1.8 m 3 / h rate into the pervaporation membrane for dehydration; the water content of the solvent after the pervaporation membrane treatment was detected to be 1.5%, the solvent was refluxed to the distillation tower to continue azeotropic distillation and pervaporation membrane dehydration, and the water content of the solvent was detected to be 0.8%;

[0073] Step S4. The solvent treated in step S3 is transported to a distillation tower with a total of 20 plates for atmospheric distillation. The feed inlet is the 8th plate, the top temperature is 100°C, the bottom temperature is 130°C, the reflux ratio is 5, and the 15th plate of the distillation tower is 1m 3 The solvent extracted at a rate of / h is industrial grade 3-methylpyridine.

[0074] The present invention measures the technical indicators such as purity, recovery rate, water content, etc. of 2-methylpyridine recovered in Examples 1-5 and Comparative Examples 1-2 and 3-methylpyridine recovered in Comparative Example 3. The measurement results are shown in Table 1-2.

[0075] Table 1 Determination results of 2-methylpyridine after recovery in Examples 1-5 and Comparative Examples 1-2

[0076]

[0077] Table 2 Comparative Example 3 Determination results of 3-picoline after recovery

[0078] name Purity (wt%) Water content (wt%) Pyridine (wt%) Recovery rate (%) Mixing experiment with water Industrial grade standards ≥98.5 ≤0.2 ≤1.0 -- Through experiments Comparative Example 3 96.3 0.13 0.5 79.2 Through experiments

[0079] As can be seen from Table 1-2, the present invention obtains industrial-grade 2-methylpyridine by controlling the water content of the solvent entering the distillation tower and limiting the number of distillation tower plates, the position of the feed port, and the position of the production port, and a higher recovery rate of 2-methylpyridine is obtained using the method of the present invention; in addition, the method of the present invention has a specific effect on 2-methylpyridine, and is not suitable for the treatment of other types of pyridine waste solvents.

[0080] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the scheme disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0081] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for recycling 2-methylpyridine waste solvent, characterized in that: The following steps are involved: Step S1. Adding 2-methylpyridine waste solvent into a salting-out reactor, and continuing to add a salting-out agent to precipitate solid salt to obtain a solid-liquid mixture; Step S2. centrifuging the solid-liquid mixture to obtain a centrifuge; Step S3. The centrifuged liquid is transported to a distillation tower, and water is added to the distillation tower for azeotropic distillation of water vapor, and the top steam enters a pervaporation membrane for dehydration; Step S4. The solvent treated in step S3 is transported to a distillation tower for distillation, and the solvent extracted from the side line of the distillation tower is industrial-grade 2-methylpyridine; The 2-methylpyridine waste solvent in step S1 includes sulfonate, sodium chloride and 2-methylpyridine; The salting-out agent in step S1 includes methanol, ethanol, isopropanol, and acetonitrile; The feed rate of the waste solvent in step S1 is 0.1-5 m 3 / h, the feed rate of the salting-out agent is 0.5-6m 3 / h; The rate at which the tower top steam enters the pervaporation membrane in step S3 is 0.5-3 m / s. 3 / h; The operating pressure of the distillation tower in step S4 is atmospheric pressure, the tower top temperature is 90-105°C, the tower bottom temperature is 125-135°C, and the reflux ratio is 0.5-10; The extraction rate of 2-methylpyridine in step S4 is 0.2-2m 3 / h.

2. The method for recycling 2-methylpyridine waste solvent according to claim 1, characterized in that: Step S3 also includes: detecting the water content of the solvent after being treated by the pervaporation membrane, and determining whether the water content reaches a preset water content. If so, proceeding to step S4; otherwise, refluxing to the distillation tower to continue the cycle of azeotropic distillation and pervaporation membrane dehydration.

3. The method for recycling 2-methylpyridine waste solvent according to claim 2, characterized in that: The preset water content is that the water content of the solvent after being treated by the pervaporation membrane is less than 1%.

4. The method for recycling 2-methylpyridine waste solvent according to claim 1, characterized in that: The number of plates of the distillation tower in step S4 is 18-28, the feed inlet is at the 6th to 12th plate, and the side line outlet is arranged at the 13th to 21st plate.

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