CN111087342A - Recovery method of 2-methylpyridine in preparation process of 2-cyanopyridine - Google Patents
Recovery method of 2-methylpyridine in preparation process of 2-cyanopyridine Download PDFInfo
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- CN111087342A CN111087342A CN201911417102.2A CN201911417102A CN111087342A CN 111087342 A CN111087342 A CN 111087342A CN 201911417102 A CN201911417102 A CN 201911417102A CN 111087342 A CN111087342 A CN 111087342A
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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) and (3) distillation: carrying out azeotropic distillation on wastewater generated in a 2-cyanopyridine preparation process to obtain an aqueous solution containing 27-40% of pyridine and 13-20% of 2-methylpyridine; (2) and (3) dehydrating: adding 30-48% of alkali liquor into the aqueous solution of the 2-methylpyridine obtained in the step (1), mixing and layering, wherein the upper layer is a 2-methylpyridine mixed solution, the lower layer is an alkali solution, and separating the solution to obtain a 2-methylpyridine mixed solution; (3) and (3) rectification: and (3) rectifying the solution obtained in the step (2), controlling the reflux ratio to be 1-3:1, and obtaining 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 tower top. By adopting the method, the recovery rate of the 2-methylpyridine in the 2-cyanopyridine production wastewater reaches more than 95 percent, 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, and particularly relates to a recovery method of 2-methylpyridine.
Background
2-methylpyridine
English name: 2-Methylpyridine
Molecular formula and molecular weight: c6H7N＝93.13
Physical and chemical properties:
appearance: colorless oily liquid with unpleasant odor
Melting Point (. degree. C.): -70
Boiling point (. degree.C., atmospheric pressure): 128-129
Flash point (. degree. C.): 39
Relative density (water ═ 1): 0.95
Solubility: dissolving in water, alcohol, ether, and most organic solvents.
2-methylpyridine is an important chemical intermediate and also an important raw material for fine chemical engineering. The 2-methylpyridine can be used for producing long-acting sulfanilamide, anti-allergic medicine chlorpheniramine, pesticide intermediates, feeds and feed intermediates and other fields, and can also be used for weedicide paraquat and weedicide.
The 2-methylpyridine can also be used for synthesizing special resin vinylpyridine and a 2-vinylpyridine intermediate, the latter is used for producing the pyridine styrene butadiene latex, the pyridine styrene butadiene latex is an adhesive for nylon cord fabrics in radial tires, the butadiene styrene latex in China at present mainly depends on import, according to introduction of relevant information, the yield of gum dipping cord fabrics in China at present is more than 20 ten thousand tons, about 1500 tons of 2-vinylpyridine is needed, and the dosage of 2-methylpyridine is increased by about 25% at home every year, so the market potential of the 2-methylpyridine in China is very large.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is to provide a method for recovering 2-methylpyridine from a 2-cyanopyridine absorption liquid, which effectively reduces the raw material waste and the production cost of the 2-cyanopyridine.
The technical scheme of the invention is that the recovery method of 2-methylpyridine in the preparation process of 2-cyanopyridine comprises the following steps:
(1) and (3) distillation: carrying out azeotropic distillation on wastewater generated in a 2-cyanopyridine preparation process to obtain an aqueous solution containing 27-40% of pyridine and 13-20% of 2-methylpyridine;
(2) and (3) dehydrating: adding 30-48% of alkali liquor into the aqueous solution of the 2-methylpyridine obtained in the step (1), mixing and layering, wherein the upper layer is a 2-methylpyridine mixed solution, the lower layer is an alkali solution, and separating the solution to obtain a 2-methylpyridine mixed solution;
(3) and (3) rectification: and (3) rectifying the solution obtained in the step (2), controlling the reflux ratio to be 1-3:1, and obtaining 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 tower top.
In the step (2), the 2-methylpyridine and the alkali liquor are not mutually soluble, and layering can occur.
The technological process of the present invention includes the first step of eliminating salt through azeotropic distillation, the second step of eliminating azeotropic equilibrium through alkali dewatering, and the third step of rectifying, separating and purifying 2-methylpyridine and pyridine.
According to the method for recovering 2-methylpyridine in the 2-cyanopyridine preparation process, the wastewater generated in the 2-cyanopyridine preparation process in the step (1) preferably contains 5-10% of 2-methylpyridine 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 preferred that the azeotropic distillation in the step (1) is carried out at a still temperature of 90 to 105 ℃.
According to the method for recovering 2-methylpyridine in the preparation process of 2-cyanopyridine, the water solution in the step (1) preferably contains 40-60 wt% of water.
According to the method for recovering 2-methylpyridine in the preparation process of 2-cyanopyridine, the alkali in the step (2) is preferably 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 method for recovering 2-methylpyridine in the preparation process of 2-cyanopyridine, the upper layer of 2-methylpyridine 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 ratio of 2-methylpyridine in water: the mass ratio of the alkali liquor is 1: 0.1-2.
Preferably, in the step (3) rectification, the temperature of the kettle is 100-.
More preferably, in the step (3) rectification, the kettle temperature is 110-.
The invention has the beneficial effects that:
the method provided by the invention can be used for recovering the 2-methylpyridine in the wastewater generated in the 2-cyanopyridine preparation process, and fills a technical blank for recovering the 2-methylpyridine in the wastewater generated in the 2-cyanopyridine preparation process. After the method is adopted, the recovery rate of the 2-methylpyridine reaches more than 95 percent, the byproduct pyridine with the content of more than or equal to 99.9 percent 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 the method for recovering 2-methylpyridine in the preparation process of 2-cyanopyridine provided by the present invention.
Example 1
Putting 2-cyanopyridine wastewater containing 5% of 2-methylpyridine and 15% of pyridine into a distillation kettle, carrying out azeotropic distillation through the azeotropic action of the 2-methylpyridine, the pyridine and the water, continuously extracting a mixed solution of the 2-methylpyridine and the pyridine containing 45% of water from the top of the distillation kettle at the temperature of 90-105 ℃, adding a potassium hydroxide aqueous solution with the concentration of 40% into the solution, controlling the mass ratio of the extracted solution to the alkali solution to be 1:1.2, controlling the water content of the dehydrated pyridine and 2-methylpyridine mixed solution to be 5%, rectifying, controlling the reflux ratio to be 2:1 at the temperature of 110 ℃ and 140 ℃, and sequentially obtaining the pyridine with the content of 99.9% and the 2-methylpyridine with the content of 99.5% from the top of the distillation kettle, wherein the recovery rate of the 2-methylpyridine is 95%.
Example 2
Putting 2-cyanopyridine wastewater containing 8% of 2-methylpyridine and 18% of pyridine into a distillation kettle, carrying out azeotropic distillation through the azeotropic action of the 2-methylpyridine, the pyridine and the water, continuously extracting a mixed solution of the 2-methylpyridine and the pyridine containing 35% of water from the top of the distillation kettle at the temperature of 90-105 ℃, adding a sodium hydroxide aqueous solution with the concentration of 48% into the aqueous solution, controlling the mass ratio of the extracted solution to the alkali solution to be 1:0.5, controlling the water content of the dehydrated mixed solution of the pyridine and the 2-methylpyridine to be 2%, rectifying at the temperature of 110 ℃ and 140 ℃, controlling the reflux ratio to be 3:1, and sequentially obtaining the pyridine with the content of 99.91% and the 2-methylpyridine with the content of 99.6% from the top of the distillation kettle, wherein the recovery rate of the 2-methylpyridine is 97.
Example 3
Putting 2-cyanopyridine wastewater containing 10% of 2-methylpyridine and 20% of pyridine into a distillation kettle, carrying out azeotropic distillation through the azeotropic action of the 2-methylpyridine, the pyridine and the water, continuously extracting a 2-methylpyridine and pyridine mixed solution containing 55% of water 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 the alkali solution to be 1:0.5, controlling the water content of the dehydrated pyridine and 2-methylpyridine mixed solution to be 3%, rectifying, controlling the reflux ratio to be 2:1 at the kettle temperature of 110 ℃ and 140 ℃, and sequentially obtaining pyridine with the content of 99.93% and 2-methylpyridine with the content of 99.6% from the top of the distillation kettle, wherein the recovery rate of the 2-methylpyridine is 95.5%.
Example 4
Putting 2-cyanopyridine wastewater containing 6% of 2-methylpyridine and 16% of pyridine into a distillation kettle, carrying out azeotropic distillation through the azeotropic action of the 2-methylpyridine, the pyridine and the water, continuously extracting a mixed solution of the 2-methylpyridine and the pyridine containing 60% of water 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 the alkali solution to be 1:0.8, controlling the water content of the dehydrated mixed solution of the pyridine and the 2-methylpyridine to be 2%, rectifying at the temperature of 110 ℃ and 140 ℃, controlling the reflux ratio to be 3:1, and sequentially obtaining the pyridine with the content of 99.95% and the 2-methylpyridine with the content of 99.8% from the top of the distillation kettle, wherein the recovery rate of the 2-methylpyridine is 97%.
Example 5
Putting 2-cyanopyridine wastewater containing 10% of 2-methylpyridine and 15% of pyridine into a distillation kettle, carrying out azeotropic distillation through the azeotropic action of the 2-methylpyridine, the pyridine and the water, continuously extracting a mixed solution of the 2-methylpyridine and the pyridine containing 45% of water 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 the alkali solution to be 1:1.75, controlling the water content of the dehydrated mixed solution of the pyridine and the 2-methylpyridine to be 3%, rectifying, controlling the reflux ratio to be 1:1 at the kettle temperature of 110 ℃ and 140 ℃, and sequentially obtaining the pyridine containing 99.93% of the pyridine and the 2-methylpyridine containing 99.7% of the pyridine from the top of the distillation kettle, wherein the recovery rate of the 2-methylpyridine is 95%.
The method recovers the 2-methylpyridine in the wastewater generated by the preparation process of the 2-cyanopyridine, the recovery rate of the 2-methylpyridine reaches more than 95 percent, the byproduct pyridine with the content of more than or equal to 99.9 percent is obtained, the consumption of raw materials is reduced, and the cost is reduced.
Claims (10)
1. A method for recovering 2-methylpyridine in a 2-cyanopyridine preparation process is characterized by comprising the following steps: the method comprises the following steps:
(1) and (3) distillation: carrying out azeotropic distillation on wastewater generated in a 2-cyanopyridine preparation process to obtain an aqueous solution containing 27-40% of pyridine and 13-20% of 2-methylpyridine;
(2) and (3) dehydrating: adding 30-48% of alkali liquor into the aqueous solution of the 2-methylpyridine obtained in the step (1), mixing and layering, wherein the upper layer is a 2-methylpyridine mixed solution, the lower layer is an alkali solution, and separating the solution to obtain a 2-methylpyridine mixed solution;
(3) and (3) rectification: and (3) rectifying the solution obtained in the step (2), controlling the reflux ratio to be 1-3:1, and obtaining 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 tower top.
2. The method for recovering 2-methylpyridine in the process for preparing 2-cyanopyridine according to claim 1, wherein: the wastewater generated in the 2-cyanopyridine preparation process in the step (1) contains 5-10% of 2-methylpyridine and 15-20% of pyridine.
3. The method for recovering 2-methylpyridine in the process for preparing 2-cyanopyridine according to claim 1, wherein: in the azeotropic distillation in the step (1), the temperature of a distillation kettle is 90-105 ℃.
4. The method for recovering 2-methylpyridine in the process for preparing 2-cyanopyridine according to claim 1, wherein: the water solution in the step (1) contains 40-60 wt% of water.
5. The method for recovering 2-methylpyridine in the process for preparing 2-cyanopyridine according to claim 1, wherein: in the step (2), the alkali is selected from one of potassium hydroxide and sodium hydroxide.
6. The method for recovering 2-methylpyridine in the process for preparing 2-cyanopyridine according to claim 1, wherein: the mass concentration of the alkali liquor in the step (2) is 35-45%.
7. The method for recovering 2-methylpyridine in the process for preparing 2-cyanopyridine according to claim 1, wherein: the 2-methylpyridine mixed solution on the upper layer 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.
8. The method for recovering 2-methylpyridine in the process for preparing 2-cyanopyridine according to claim 1, wherein: in the step (2), the aqueous solution of 2-methylpyridine: the mass ratio of the alkali liquor is 1: 0.1-2.
9. The method for recovering 2-methylpyridine in the process for preparing 2-cyanopyridine according to claim 1, wherein: in the step (3) of rectification, the temperature of the kettle is 100-.
10. The method for recovering 2-methylpyridine in the process for preparing 2-cyanopyridine according to claim 9, wherein: in the step (3) of rectification, the kettle temperature is 110-.
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