CN114057637A - Method for purifying 4-cyanopyridine by recrystallization - Google Patents
Method for purifying 4-cyanopyridine by recrystallization Download PDFInfo
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- CN114057637A CN114057637A CN202010788779.3A CN202010788779A CN114057637A CN 114057637 A CN114057637 A CN 114057637A CN 202010788779 A CN202010788779 A CN 202010788779A CN 114057637 A CN114057637 A CN 114057637A
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- 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
- C07D213/60—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 with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
- C07D213/78—Carbon atoms having three bonds to hetero atoms, with at the most one bond to halogen, e.g. ester or nitrile radicals
- C07D213/84—Nitriles
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Abstract
The patent discloses a method for purifying 4-cyanopyridine by recrystallization, wherein a crude product of the 4-cyanopyridine is melted at 75-80 ℃ under normal pressure; adding water into the molten crude 4-cyanopyridine, and preserving heat at 55-65 ℃; slowly cooling to 8-12 ℃ while stirring to obtain 4-cyanopyridine slurry; centrifuging and filtering to obtain filtrate and filter residue; adding water into the filter residue, and stirring to obtain slurry; filtering to obtain filtrate and filter residue; and drying filter residues to obtain a finished product of 4-cyanopyridine. The method provided by the invention realizes separation and purification of 4-cyanopyridine, improves the purity of 4-cyanopyridine, and can purify and utilize the by-product 4-cyanopyridine crude product in the process of producing 3-cyanopyridine.
Description
Technical Field
The invention relates to the field of industrial chemistry, in particular to a method for purifying 4-cyanopyridine by recrystallization, and more particularly relates to a method for purifying a by-product 4-cyanopyridine produced in the process of producing 3-cyanopyridine by carrying out ammoxidation reaction on 3-methylpyridine serving as a raw material.
Background
At present, a chemical solvent recrystallization and physical separation method is used for purifying a 4-cyanopyridine crude product, a large amount of chemical reagents are introduced into the chemical solvent recrystallization method, the treatment difficulty of the generated waste liquid is high, the requirement on the material of a reaction container is high, and the purity is low; the purity obtained by the physical separation method is low, and the energy consumption is large.
Chinese patent 201610847788.9 discloses a method for purifying 4-cyanopyridine by combining chemical recrystallization and physical separation, comprising the steps of: chemical recrystallization: dissolving the crude 4-cyanopyridine product in a mixed solvent of petroleum ether and n-butanol, cooling, separating out solids, filtering, washing and drying the solids to obtain the 4-cyanopyridine with the purity of more than 99 percent; recovering the solvent from the liquid part under reduced pressure to obtain a residue; step two: physical separation: heating the remainder obtained in the first step to 50-70 ℃, naturally cooling to 30-45 ℃ after the system is transparent, preserving the temperature for 1-3 hours, separating out solids, and filtering to obtain solids; the solid is 4-cyanopyridine with purity of 78-85%; step three: and (3) repeating the operation of the first step on the solid obtained in the second step once to obtain the 4-cyanopyridine with the purity of more than 99%, wherein the purity of the 4-cyanopyridine recovered according to the published embodiment is 99.2-99.6%, and the total extraction rate is 92-99%. However, this method requires the introduction of chemical reagents and requires high requirements for the reaction equipment.
Chinese patent 201911094086.8 discloses a method for purifying 4-cyanopyridine by volatilization and recrystallization, which comprises (1) melting 4-cyanopyridine: adding the crude 4-cyanopyridine product into a reactor under normal pressure, controlling the temperature of the reactor, and melting crystals; (2) and (3) volatilization: controlling the temperature of the reactor to be stable, and volatilizing 4-cyanopyridine by utilizing the difference between the saturated vapor pressure of the 4-cyanopyridine and impurities; (3) and (3) recrystallization: 4-cyanopyridine vapor formed by volatilization enters a crystallizer, the temperature of the wall of the crystallizer is controlled, 4-cyanopyridine crystals are formed on the wall of the crystallizer, the purity of the 4-cyanopyridine recovered according to the published embodiment is 98.56-99.93%, and the yield is lower than 70%. The invention has the problems of low yield, low recovery purity and the like.
Chinese patent 201910706748.6 discloses a method for purifying 4-cyanopyridine by melt crystallization, which comprises (1) melting 4-cyanopyridine: adding 4-cyanopyridine crystals into a reactor under normal pressure, controlling the temperature of the reactor to be 80-90 ℃, and melting the 4-cyanopyridine crystals; (2) cooling: controlling the temperature of the reactor, and reducing the temperature of the molten 4-cyanopyridine to 71.5-73.5 ℃ according to a certain cooling speed; (3) and (3) crystallization: maintaining the temperature at 71.5-73.5 ℃ for crystallization; (4) separation and extraction: discharging the base solution without crystal formation, raising the temperature of the reactor to 80-90 ℃, melting the crystal to obtain a 4-cyanopyridine finished product, wherein the recovery purity of the 4-cyanopyridine is 97.66-99.42% according to data published by the embodiment. However, the primary yield is 35.1-40.5% according to the embodiment, although the comprehensive yield is more than 90%, the method is not substantially described.
Chinese patent 201810673365.9 discloses a method for separating 4-cyanopyridine by solvent cooling crystallization, which comprises (1) decolorizing a mixed cyanopyridine raw material containing 3-cyanopyridine and 4-cyanopyridine at high temperature; (2) dissolving the decolored mixed cyanopyridine raw material in a dominant solvent (methanol) in a crystallizer to prepare a supersaturated solution; (3) and (2) cooling the supersaturated solution to the termination temperature at a certain cooling rate to separate out 4-cyanopyridine, discharging the 4-cyanopyridine and the mixed cyanopyridine mother liquor out of the crystallizer in a form of slurry to enter a filter, separating the 4-cyanopyridine and the mixed cyanopyridine in the filter, and drying to obtain a high-purity 4-cyanopyridine product, wherein the recovery purity of the 4-cyanopyridine is 99.2-99.7% according to data published by an embodiment. This method also requires the introduction of chemical reagents and yields are unknown.
In conclusion, the existing method for purifying 4-cyanopyridine needs to introduce other chemical reagents, the treatment difficulty of the generated waste liquid is high, the requirement on the material of a reaction vessel is high, the purity of the obtained 4-cyanopyridine finished product is not high, and the like.
Disclosure of Invention
The purpose of the patent is to make up for the defects of the prior art, and provide a method for purifying 4-cyanopyridine by recrystallization, so that the separation and purification of 4-cyanopyridine are realized, the purity of 4-cyanopyridine is improved, and a by-product 4-cyanopyridine crude product in the process of producing 3-cyanopyridine can be purified and utilized.
In order to achieve the purpose, the invention adopts the technical scheme that:
a method for purifying 4-cyanopyridine by recrystallization specifically comprises the following steps:
(1) 4-cyanopyridine melting: melting the crude product of 4-cyanopyridine at 75-80 ℃ under normal pressure;
(2) adding water: adding water into the molten crude 4-cyanopyridine, and preserving heat at 55-65 ℃;
(3) and (3) recrystallization: slowly cooling to 8-12 ℃ while stirring to obtain 4-cyanopyridine slurry;
(4) separation: centrifuging and filtering the 4-cyanopyridine slurry obtained in the step (3) to obtain filtrate and filter residue;
(5) washing with water: adding water into the filter residue obtained in the step (4), and stirring to obtain slurry;
(6) separation: centrifuging and filtering the slurry obtained in the step (5) to obtain filtrate and filter residue;
(7) and (3) drying: and (4) drying the filter residue obtained in the step (6) to obtain a finished product of 4-cyanopyridine.
In some embodiments, the crude 4-cyanopyridine is in solution during the incubation of step (2).
In some embodiments, the mass of water added in step (2) is 2-5 times the mass of the crude 4-cyanopyridine; in some preferred embodiments, 2-3 times; when the amount of water added is lower than this range, the amount of residual impurities increases, the purity of the finished product decreases, and when the amount of water is higher than this range, the requirement for the volume of the vessel increases, which leads to an increase in cost.
In some embodiments, the slow cooling rate in step (3) is 0.3-0.5 ℃/min, and too fast cooling may result in too fast crystal growth, increased impurity residue, and too slow cooling may increase reaction time and decrease efficiency.
In some embodiments, the mass of the water added in the step (4) is 2-5 times of the mass of the filter residue; in some preferred embodiments, 2-3 times; this step can further remove the adhering impurities, and when the amount of water added is lower than this range, the impurity residue increases, the purity of the finished product is low, and when the amount of water is higher than this range, the water consumption increases, resulting in an increase in cost.
In some embodiments, the stirring speed in step (3) is 55-65 rpm.
In some embodiments, step (3) is slowly cooled to 10 ℃ while stirring.
In some embodiments, the stirring speed in step (5) is 55-65 rpm.
The invention has the beneficial effects that:
(1) the method solves the problem that other chemical substances are introduced in the purification process of the 4-cyanopyridine, utilizes the characteristic that the solubility of the 4-cyanopyridine in water is not high, utilizes water as a solvent for recrystallization, does not introduce other substances, reduces the treatment difficulty of the generated waste liquid, has low requirement on the material of a reactor, and has less steps, higher overall yield and purity, the yield can reach more than 89 percent and the purity can reach more than 99.8 percent because other substances are not introduced.
(2) Stirring is carried out in the recrystallization process, external force is generated to crystallize the crystals, the crystals have good crystal forms and agglomeration is avoided, and thus, a finished product with good phase is obtained.
(3) The water solution produced by the method can be used as process water for producing 3-cyanopyridine, does not produce waste liquid, and is more environment-friendly.
Drawings
FIG. 1 is a gas chromatogram of crude 4-cyanopyridine of example 1;
FIG. 2 is a gas chromatogram of the finished 4-cyanopyridine of example 1;
FIG. 3 is a gas chromatogram of the crude 4-cyanopyridine of example 2;
FIG. 4 is a gas chromatogram of the finished 4-cyanopyridine of example 2;
FIG. 5 is a gas chromatogram of the crude 4-cyanopyridine of example 3;
FIG. 6 is a gas chromatogram of the finished 4-cyanopyridine of example 3;
FIG. 7 is a gas chromatogram of the finished 4-cyanopyridine of example 4;
FIG. 8 is a gas chromatogram of the finished 4-cyanopyridine of example 5.
Detailed Description
The following examples are given to facilitate a better understanding of the invention, but do not limit the invention. The experimental procedures in the following examples are conventional unless otherwise specified. The test materials used in the following examples were purchased from a conventional biochemical reagent store unless otherwise specified.
Example 1
(1) 4-cyanopyridine melting: under normal pressure, adding 0.99kg of crude 4-cyanopyridine into a reactor, controlling the temperature of the reactor to be 75-80 ℃, and melting crystals;
(2) adding water: adding 2.0kg of water into the reactor, controlling the temperature of the reactor, and keeping the temperature at 60 ℃;
(3) and (3) recrystallization: starting a stirring device, stirring at the rotating speed of 60rpm, controlling the temperature of the reactor, and slowly cooling from 60 ℃ to 10 ℃ at the speed of 0.3 ℃/min to obtain 4-cyanopyridine slurry;
(4) separation: centrifuging and filtering the 4-cyanopyridine slurry to obtain 1.85kg of filtrate and 1.12kg of filter residue;
(5) washing with water: adding 2.25kg of water into the filter residue, and fully stirring at the rotating speed of 60rpm to obtain slurry;
(6) separation: centrifuging and filtering the slurry to obtain 2.35kg of filtrate and filter residue;
(7) and (3) drying: and drying the filter residue to obtain 0.85kg of finished 4-cyanopyridine product.
The 4-cyanopyridine was purified by the method of example 1 using crude 4-cyanopyridine of 96.02% purity and giving a finished 4-cyanopyridine of 89.27% yield and a finished 4-cyanopyridine of 99.82% purity, the gas chromatogram of the crude product being shown in FIG. 1 and the gas chromatogram of the finished product being shown in FIG. 2.
Example 2
(1) 4-cyanopyridine melting: under normal pressure, adding 1.00kg of crude 4-cyanopyridine into a reactor, controlling the temperature of the reactor to be 75-80 ℃, and melting crystals;
(2) adding water: adding 2.0kg of water into the reactor, controlling the temperature of the reactor, and keeping the temperature at 60 ℃;
(3) and (3) recrystallization: starting a stirring device, stirring at the rotating speed of 60rpm, controlling the temperature of the reactor, and slowly cooling from 60 ℃ to 10 ℃ at the speed of 0.5 ℃/min to obtain 4-cyanopyridine slurry;
(4) separation: centrifuging and filtering the 4-cyanopyridine slurry to obtain 1.82kg of filtrate and 1.09kg of filter residue;
(5) washing with water: adding 2.20kg of water into the filter residue, and fully stirring at the rotating speed of 60rpm to obtain slurry;
(6) separation: centrifuging and filtering the slurry to obtain 2.31kg of filtrate and filter residue;
(7) and (3) drying: and drying the filter residue to obtain 0.89kg of finished 4-cyanopyridine product.
The 4-cyanopyridine was purified by the method of example 2 using crude 4-cyanopyridine of 97.18% purity, yielding 91.47% of the final 4-cyanopyridine product and 99.88% of the final 4-cyanopyridine product, the gas chromatogram of the crude product being shown in FIG. 3 and the gas chromatogram of the final product being shown in FIG. 4.
Example 3
(1) 4-cyanopyridine melting: under normal pressure, adding 1.00kg of crude 4-cyanopyridine into a reactor, controlling the temperature of the reactor to be 75-80 ℃, and melting crystals;
(2) adding water: adding 2.0kg of water into the reactor, controlling the temperature of the reactor, and keeping the temperature at 60 ℃;
(3) and (3) recrystallization: starting a stirring device, stirring at the rotating speed of 60rpm, controlling the temperature of the reactor, and slowly cooling from 60 ℃ to 10 ℃ at the speed of 0.4 ℃/min to obtain 4-cyanopyridine slurry;
(4) separation: centrifuging and filtering the 4-cyanopyridine slurry to obtain 1.78kg of filtrate and 1.10kg of filter residue;
(5) washing with water: adding 2.20kg of water into the filter residue, and fully stirring at the rotating speed of 60rpm to obtain slurry;
(6) separation: centrifuging and filtering the slurry to obtain 2.29kg of filtrate and filter residue;
(7) and (3) drying: and drying the filter residue to obtain 0.87kg of finished 4-cyanopyridine product.
The 4-cyanopyridine was purified by the method of example 3 using crude 4-cyanopyridine of 97.26% purity and giving a finished 4-cyanopyridine product of 89.36% yield and a finished 4-cyanopyridine of 99.90% purity, the gas chromatogram of the crude product being shown in FIG. 5 and the gas chromatogram of the finished product being shown in FIG. 6.
Example 4
(1) 4-cyanopyridine melting: under normal pressure, adding 1.00kg of crude 4-cyanopyridine into a reactor, controlling the temperature of the reactor to be 75-80 ℃, and melting crystals;
(2) adding water: adding 1.0kg of water into the reactor, controlling the temperature of the reactor, and keeping the temperature at 60 ℃;
(3) and (3) recrystallization: starting a stirring device, stirring at the rotating speed of 60rpm, controlling the temperature of the reactor, and slowly cooling from 60 ℃ to 10 ℃ at the speed of 0.4 ℃/min to obtain 4-cyanopyridine slurry;
(4) separation: centrifuging and filtering the 4-cyanopyridine slurry to obtain 0.87kg of filtrate and 1.10kg of filter residue;
(5) washing with water: adding 2.05kg of water into the filter residue, and fully stirring at the rotating speed of 60rpm to obtain slurry;
(6) separation: centrifuging and filtering the slurry to obtain 2.11kg of filtrate and filter residue;
(7) and (3) drying: and drying the filter residue to obtain 0.87kg of finished 4-cyanopyridine product.
The 4-cyanopyridine was purified by the method of example 4 using the crude 4-cyanopyridine of 97.26% purity from the same batch of material of example 3, giving a finished 4-cyanopyridine yield of 89.22% and a finished 4-cyanopyridine purity of 99.75%, the crude product having a gas chromatogram as shown in FIG. 5 and the finished product having a gas chromatogram as shown in FIG. 7. Compared with the example 3, the water amount in the step (2) is reduced, so that more impurities remain, and the purity of the final product is lower.
Example 5
(1) 4-cyanopyridine melting: under normal pressure, adding 1.03kg of crude 4-cyanopyridine into a reactor, controlling the temperature of the reactor to be 75-80 ℃, and melting crystals;
(2) adding water: adding 2.05kg of water into the reactor, controlling the temperature of the reactor, and keeping the temperature at 60 ℃;
(3) and (3) recrystallization: starting a stirring device, stirring at the rotating speed of 60rpm, controlling the temperature of the reactor, and slowly cooling from 60 ℃ to 10 ℃ at the speed of 0.4 ℃/min to obtain 4-cyanopyridine slurry;
(4) separation: centrifuging and filtering the 4-cyanopyridine slurry to obtain 1.89kg of filtrate and 1.11kg of filter residue;
(5) washing with water: adding 1.01kg of water into the filter residue, and fully stirring at the rotating speed of 60rpm to obtain slurry;
(6) separation: centrifuging and filtering the slurry to obtain 1.08kg of filtrate and filter residue;
(7) and (3) drying: and drying the filter residue to obtain 0.88kg of finished 4-cyanopyridine product.
The 4-cyanopyridine was purified by the method of example 5 using the crude 4-cyanopyridine of 97.26% purity from the same batch of example 3, yielding 87.70% yield of the final 4-cyanopyridine product with a purity of 99.84% for the final 4-cyanopyridine product, the gas chromatogram of the crude product being shown in FIG. 5 and the gas chromatogram of the final product being shown in FIG. 8. Compared with the example 3, the water amount in the step (5) is reduced, and impurities on the surface of the crystal are more remained, so that the purity of the final product is slightly lower.
Claims (10)
1. The method for purifying 4-cyanopyridine by recrystallization is characterized by comprising the following steps:
(1) 4-cyanopyridine melting: melting the crude product of 4-cyanopyridine at 75-80 ℃ under normal pressure;
(2) adding water: adding water into the molten crude 4-cyanopyridine, and preserving heat at 55-65 ℃;
(3) and (3) recrystallization: slowly cooling to 8-12 ℃ while stirring to obtain 4-cyanopyridine slurry;
(4) separation: centrifuging and filtering the 4-cyanopyridine slurry obtained in the step (3) to obtain filtrate and filter residue;
(5) washing with water: adding water into the filter residue obtained in the step (4), and stirring to obtain slurry;
(6) separation: centrifuging and filtering the slurry obtained in the step (5) to obtain filtrate and filter residue;
(7) and (3) drying: and (4) drying the filter residue obtained in the step (6) to obtain a finished product of 4-cyanopyridine.
2. The method for purifying 4-cyanopyridine by recrystallization according to claim 1, wherein the crude 4-cyanopyridine product is dissolved during the step (2) of incubating.
3. The method for purifying 4-cyanopyridine by recrystallization according to claim 1, wherein the amount of water added in step (2) is 2 to 5 times the amount of crude 4-cyanopyridine.
4. The method for purifying 4-cyanopyridine by recrystallization according to claim 3, wherein the amount of water added in step (2) is 2 to 3 times the amount of crude 4-cyanopyridine.
5. The method for purifying 4-cyanopyridine by recrystallization according to claim 1, wherein the slow cooling rate in step (3) is 0.3-0.5 ℃/min.
6. The method for purifying 4-cyanopyridine by recrystallization according to claim 1, wherein the mass of water added in the step (4) is 2 to 5 times the mass of the residue.
7. The method for purifying 4-cyanopyridine by recrystallization according to claim 6, wherein the mass of water added in the step (4) is 2 to 3 times the mass of the residue.
8. The method for purifying 4-cyanopyridine by recrystallization according to claim 1, wherein the stirring speed in step (3) is 55-65 rpm.
9. The method for purifying 4-cyanopyridine by recrystallization according to claim 1, wherein the temperature in step (3) is slowly decreased to 10 ℃ while stirring.
10. The method for purifying 4-cyanopyridine by recrystallization according to claim 1, wherein the stirring speed in step (5) is 55-65 rpm.
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Application publication date: 20220218 |