CN111087342B - Recovery method of 2-picoline in preparation process of 2-cyanopyridine - Google Patents
Recovery method of 2-picoline in preparation process of 2-cyanopyridine Download PDFInfo
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- CN111087342B CN111087342B CN201911417102.2A CN201911417102A CN111087342B CN 111087342 B CN111087342 B CN 111087342B CN 201911417102 A CN201911417102 A CN 201911417102A CN 111087342 B CN111087342 B CN 111087342B
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- methylpyridine
- cyanopyridine
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07D—HETEROCYCLIC COMPOUNDS
- C07D213/00—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members
- C07D213/02—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members
- C07D213/04—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom
- C07D213/06—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom containing only hydrogen and carbon atoms in addition to the ring nitrogen atom
- C07D213/16—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom containing only hydrogen and carbon atoms in addition to the ring nitrogen atom containing only one pyridine ring
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Abstract
The invention discloses a method for recovering 2-methylpyridine in a 2-cyanopyridine preparation process, which comprises the following steps: (1) distillation: carrying out azeotropic distillation on the wastewater generated by the preparation process of the 2-cyanopyridine to obtain an aqueous solution containing 27-40% of pyridine and 13-20% of 2-picoline; (2) dehydration: adding 30% -48% alkali solution into the 2-methylpyridine aqueous solution obtained in the step (1), mixing, layering, wherein the upper layer is the 2-methylpyridine mixed solution, the lower layer is the alkali solution, and separating the 2-methylpyridine mixed solution after separating; (3) rectifying: rectifying the solution obtained in the step (2), and controlling the reflux ratio to be 1-3:1, wherein the 2-picoline with the content of more than or equal to 99.5% and the pyridine with the content of more than or equal to 99.9% are obtained at the top of the tower. By adopting the method, the recovery rate of the 2-picoline in the 2-cyanopyridine production wastewater reaches more than 95%, the raw material consumption is reduced, and the production cost of the 2-cyanopyridine is reduced.
Description
Technical Field
The invention relates to the field of pyridine preparation, in particular to a recovery method of 2-methylpyridine.
Background
2-methylpyridine
English name: 2-Methylpyridine
Molecular formula and molecular weight: c (C) 6 H 7 N＝93.13
Physical and chemical properties:
appearance: colorless oily liquid having unpleasant smell
Melting point (. Degree. C.): -70
Boiling point (c, normal pressure): 128-129
Flash point (c): 39
Relative density (water=1): 0.95
Solubility: is soluble in water, alcohol, ether, and most organic solvents.
2-methylpyridine is an important chemical intermediate and is also an important raw material for fine chemical engineering. The 2-picoline can be used for producing long-acting sulfanilamide, antiallergic chlorphenamine, pesticide intermediates, feeds and feed intermediates and other fields, and can also be used for herbicide paraquat and paraquat.
The 2-methyl pyridine can also be used for synthesizing special resin vinyl pyridine and a 2-vinyl pyridine intermediate, the latter is used for producing styrene-butadiene pyridine latex, the styrene-butadiene pyridine latex is an adhesive of nylon cord fabrics in radial tires, the current domestic styrene-butadiene pyridine latex mainly depends on import, according to related data, the current annual gum dipping cord fabric yield in China exceeds 20 ten thousand tons, the 2-vinyl pyridine is required to be about 1500 tons, the using amount of the 2-methyl pyridine is increased at about 25% per year in China, and therefore, the 2-methyl pyridine has great domestic market potential.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is to provide the recovery method of the 2-picoline in the 2-cyanopyridine absorption liquid, so that the waste of raw materials is effectively reduced, and the production cost of the 2-cyanopyridine is reduced.
The technical scheme of the invention is that the recovery method of the 2-methylpyridine in the preparation process of the 2-cyanopyridine comprises the following steps:
(1) And (3) distilling: carrying out azeotropic distillation on the wastewater generated by the preparation process of the 2-cyanopyridine to obtain an aqueous solution containing 27-40% of pyridine and 13-20% of 2-picoline;
(2) Dehydrating: adding 30% -48% alkali solution into the 2-methylpyridine aqueous solution obtained in the step (1), mixing, layering, wherein the upper layer is the 2-methylpyridine mixed solution, the lower layer is the alkali solution, and separating the 2-methylpyridine mixed solution after separating;
(3) And (3) rectifying: rectifying the solution obtained in the step (2), and controlling the reflux ratio to be 1-3:1, wherein the 2-picoline with the content of more than or equal to 99.5% and the pyridine with the content of more than or equal to 99.9% are obtained at the top of the tower.
In the step (2), the 2-methylpyridine is not mutually dissolved with alkali liquor, and layering can occur.
The technological process of the present invention includes azeotropic distillation to eliminate salt, alkali dewatering to eliminate azeotropic balance, and rectifying to separate and purify 2-methylpyridine and pyridine.
According to the recovery method of 2-picoline in the 2-cyanopyridine preparation process of the present invention, it is preferable that the wastewater generated in the 2-cyanopyridine preparation process of the step (1) contains 5-10% of 2-picoline and 15-20% of pyridine.
According to the method for recovering 2-methylpyridine in the process for producing 2-cyanopyridine of the present invention, it is preferable that the distillation still temperature is 90 to 105℃in the azeotropic distillation in the step (1).
According to the method for recovering 2-methylpyridine in the process for producing 2-cyanopyridine of the present invention, it is preferable that the aqueous solution of step (1) contains 40 to 60% by weight of water.
According to the method for recovering 2-methylpyridine in the process for producing 2-cyanopyridine of the present invention, it is preferable that the base in the step (2) is one selected from potassium hydroxide and sodium hydroxide.
Preferably, the mass concentration of the alkali liquor in the step (2) is 35-45%.
According to the recovery method of 2-picoline in the preparation process of 2-cyanopyridine, the upper layer 2-picoline mixed solution in the step (2) preferably comprises the following components in percentage by weight: 65-75% of pyridine, 20-30% of 2-methylpyridine and 2-5% of water.
Preferably, in step (2), the aqueous solution of 2-methylpyridine: alkali liquor mass ratio=1:0.1-2.
Preferably, in the rectification in the step (3), the kettle temperature is 100-140 ℃.
More preferably, in the rectification in the step (3), the kettle temperature is 110-140 ℃.
The beneficial effects of the invention are as follows:
the invention recovers the 2-picoline in the wastewater generated by the 2-cyanopyridine preparation process, and fills the technical blank of recovering the 2-picoline in the wastewater generated by the 2-cyanopyridine preparation process. After the method is adopted, the recovery rate of the 2-methylpyridine reaches more than 95%, the byproduct pyridine with the content more than or equal to 99.9% is obtained, the consumption of raw materials is reduced, and the cost is reduced.
Drawings
Fig. 1 is a process flow diagram of the present invention.
Detailed Description
The following provides a specific embodiment of a method for recovering 2-methylpyridine in a 2-cyanopyridine preparation process.
Example 1
Adding 2-cyanopyridine wastewater containing 5% of 2-methylpyridine and 15% of pyridine into a distillation kettle, performing azeotropic distillation under the azeotropic action of 2-methylpyridine, pyridine and water, continuously extracting a mixed solution containing 45% of 2-methylpyridine and pyridine from the top of the distillation kettle at the temperature of 90-105 ℃, adding a 40% potassium hydroxide aqueous solution into the solution, controlling the mass ratio of the extracted solution to an alkaline solution to be 1:1.2, controlling the water content in the dehydrated mixed solution of pyridine and 2-methylpyridine to be 5%, rectifying, controlling the kettle temperature to be 110-140 ℃ and controlling the reflux ratio to be 2:1, and sequentially obtaining pyridine with the content of 99.9% and 2-methylpyridine with the recovery rate of 99.5% from the top of the distillation kettle to be 95%.
Example 2
Adding 2-cyanopyridine wastewater containing 8% of 2-picoline and 18% of pyridine into a distillation kettle, performing azeotropic distillation under the azeotropic action of 2-picoline, pyridine and water, continuously extracting a mixed solution containing 35% of 2-picoline and pyridine from the top of the distillation kettle at the temperature of 90-105 ℃, adding a 48% sodium hydroxide aqueous solution into the aqueous solution, controlling the mass ratio of the extracted solution to an alkaline solution to be 1:0.5, controlling the water content of the dehydrated mixed solution of pyridine and 2-picoline to be 2%, rectifying, controlling the reflux ratio at the temperature of 110-140 ℃ at the temperature of 3:1, and sequentially obtaining pyridine with the content of 99.91% and 2-picoline with the recovery rate of 97% from the top of the distillation kettle.
Example 3
Adding 2-cyanopyridine wastewater containing 10% of 2-methylpyridine and 20% of pyridine into a distillation kettle, performing azeotropic distillation under the azeotropic action of 2-methylpyridine, pyridine and water, continuously extracting a mixed solution containing 55% of 2-methylpyridine and pyridine from the top of the distillation kettle at the temperature of 90-105 ℃, adding a sodium hydroxide aqueous solution with the concentration of 45% into the solution, controlling the mass ratio of the extracted solution to an alkaline solution to be 1:0.5, controlling the water content of the dehydrated mixed solution of pyridine and 2-methylpyridine to be 3%, rectifying, controlling the reflux ratio at the temperature of 110-140 ℃ to be 2:1, and sequentially obtaining pyridine with the content of 99.93% and 2-methylpyridine with the recovery rate of 99.6% from the top of the distillation kettle to be 95.5%.
Example 4
Adding 2-cyanopyridine wastewater containing 6% of 2-methylpyridine and 16% of pyridine into a distillation kettle, performing azeotropic distillation under the azeotropic action of 2-methylpyridine, pyridine and water, continuously extracting a mixed solution containing 60% of 2-methylpyridine and pyridine from the top of the distillation kettle at the temperature of 90-105 ℃, adding a potassium hydroxide aqueous solution with the concentration of 48% into the solution, controlling the mass ratio of the extracted solution to an alkaline solution to be 1:0.8, controlling the water content of the dehydrated mixed solution of pyridine and 2-methylpyridine to be 2%, rectifying, controlling the reflux ratio to be 3:1 at the temperature of 110-140 ℃, and sequentially obtaining pyridine with the content of 99.95% and 2-methylpyridine with the recovery rate of 97% from the top of the distillation kettle.
Example 5
Adding 2-cyanopyridine wastewater containing 10% of 2-methylpyridine and 15% of pyridine into a distillation kettle, performing azeotropic distillation under the azeotropic action of 2-methylpyridine, pyridine and water, continuously extracting a mixed solution containing 45% of 2-methylpyridine and pyridine from the top of the distillation kettle at the temperature of 90-105 ℃, adding a 30% potassium hydroxide aqueous solution into the solution, controlling the mass ratio of the extracted solution to an alkaline solution to be 1:1.75, controlling the water content of the dehydrated mixed solution of pyridine and 2-methylpyridine to be 3%, rectifying, controlling the reflux ratio at the temperature of 110-140 ℃ at the temperature of 1:1, and sequentially obtaining pyridine with the content of 99.93% and 2-methylpyridine with the recovery rate of 95% from the top of the distillation kettle.
According to the invention, the 2-picoline in the wastewater generated by the preparation process of the 2-cyanopyridine is recovered, the recovery rate of the 2-picoline reaches more than 95%, the byproduct pyridine with the content more than or equal to 99.9% is obtained, the raw material consumption is reduced, and the cost is reduced.
Claims (8)
1. A method for recovering 2-picoline in a 2-cyanopyridine preparation process is characterized in that: comprising the following steps:
(1) And (3) distilling: carrying out azeotropic distillation on the wastewater generated by the preparation process of the 2-cyanopyridine to obtain an aqueous solution containing 27-40% of pyridine and 13-20% of 2-picoline; the waste water generated by the preparation process of the 2-cyanopyridine contains 5-10% of 2-methylpyridine and 15-20% of pyridine;
(2) Dehydrating: adding 30% -48% alkali solution into the water solution containing 27% -40% pyridine and 13% -20% 2-methylpyridine, mixing, layering, wherein the upper layer is a 2-methylpyridine mixed solution, the lower layer is an alkali solution, and separating the 2-methylpyridine mixed solution after separating; the alkali in the alkali liquor is selected from one of potassium hydroxide and sodium hydroxide;
(3) And (3) rectifying: rectifying the 2-methylpyridine mixed solution obtained in the step (2), and controlling the reflux ratio to be 1-3:1 to obtain 2-methylpyridine with the content of more than or equal to 99.5% and pyridine with the content of more than or equal to 99.9% at the top of the tower.
2. The method for recovering 2-picoline in a 2-cyanopyridine preparation process according to claim 1, wherein: in the azeotropic distillation in the step (1), the temperature of a distillation kettle is 90-105 ℃.
3. The method for recovering 2-picoline in a 2-cyanopyridine preparation process according to claim 1, wherein: the water solution containing 27-40% of pyridine and 13-20% of 2-methylpyridine in the step (1) contains 40-60% of water by weight.
4. The method for recovering 2-picoline in a 2-cyanopyridine preparation process according to claim 1, wherein: the mass concentration of the alkali liquor in the step (2) is 35-45%.
5. The method for recovering 2-picoline in a 2-cyanopyridine preparation process according to claim 1, wherein: the upper layer 2-methylpyridine mixed solution in the step (2) comprises the following components in percentage by weight: 65-75% of pyridine, 20-30% of 2-methylpyridine and 2-5% of water.
6. The method for recovering 2-picoline in a 2-cyanopyridine preparation process according to claim 1, wherein: in the step (2), an aqueous solution containing 27-40% of pyridine and 13-20% of 2-methylpyridine: alkali liquor mass ratio=1:0.1-2.
7. The method for recovering 2-picoline in a 2-cyanopyridine preparation process according to claim 1, wherein: in the rectification in the step (3), the kettle temperature is 100-140 ℃.
8. The method for recovering 2-picoline in a 2-cyanopyridine preparation process according to claim 7, wherein: in the rectification in the step (3), the kettle temperature is 110-140 ℃.
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