CN109694321B - Method for preparing high-purity cyclohexanecarboxylic acid - Google Patents
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- CN109694321B CN109694321B CN201711002639.3A CN201711002639A CN109694321B CN 109694321 B CN109694321 B CN 109694321B CN 201711002639 A CN201711002639 A CN 201711002639A CN 109694321 B CN109694321 B CN 109694321B
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Abstract
The invention relates to a method for preparing high-purity cyclohexanecarboxylic acid, which takes CCA products produced by an industrial device as raw materials and adopts a static melt crystallization method to prepare the high-purity CCA. The method comprises the following steps: the method comprises the steps of firstly, melting and charging, namely adding CCA raw materials with the mass concentration of 97-99% into a crystallization tower in a heating and melting state; precooling and adding seed crystals, and adding the seed crystals into a crystallization tower to uniformly disperse the seed crystals in the tower; performing temperature reduction and crystallization in the third stage, introducing a cooling medium into the jacket of the crystallization tower for temperature reduction, and keeping the constant temperature for 15-30 minutes for crystallization after the temperature of the material is reduced to the crystallization end point temperature; fourthly, sweating and discharging: and (4) raising the temperature of the crystallization tower to the end temperature of 29-30 ℃ for perspiration collection of the CCA product. The method can prepare the high-purity CCA product with the purity of 99.9 percent, and the single-pass yield range is 25-55 percent. The method has the advantages of simple process, low cost, low energy consumption, no need of adding a solvent in the process and little pollution, and is an environment-friendly CCA preparation method.
Description
Technical Field
The application belongs to the technical field of chemicals, and relates to a method for preparing high-purity cyclohexanecarboxylic acid.
Background
Cyclohexanecarboxylic acids, also known as cyclohexanecarboxylic acids, and the like, are known by the english name: cyclohexane Carboxylic Acid (CCA), the structural formula is shown in figure 1, and the molecular formula is as follows: C7H12O2, molecular weight: 128.17, CAS: 98-89-5 deg.c, 28-31 deg.c, and is colorless flaky or columnar crystal dissolved in organic solvent.
CCA is an important chemical raw material and a drug intermediate, has very wide application value, is a good light curing agent, can be used as an intermediate of a drug for resisting pregnancy 392, a new schistosome drug praziquantel and a new drug for diabetes nateglinide, and can also be used as an efficient ultraviolet light curing initiator, a solubilizer for vulcanized rubber, a clarifying agent for petroleum, a drug intermediate and the like.
The main preparation methods of CCA include a Grignard reagent method, a benzoic acid hydrogen catalysis method, a cyclohexene carbon monoxide addition method, an addition method using cyclohexanone as a raw material and the like. In recent years, with the improvement of the CCA production method, the catalytic hydrogenation of benzoic acid is currently the mainstream production method of CCA, but differs in terms of reaction system, catalyst, yield, and the like.
CN201110158053.2 adopts a route of preparing caprolactam by a toluene method to prepare a byproduct CCA, adopts a normal hexane extraction mode to extract the CCA in a rearrangement reaction liquid, and the CCA concentration in an enrichment phase is 20-25 percent, which needs subsequent rectification separation. CN01130976.8 adopts fixed bed catalytic hydrogenation to prepare CCA, the reaction conversion rate is 90% at most, and the purity of the crude product is 99.1% at most after rectification and refining. CN201510018269.7 is based on the anhydrous and solvent-free preparation of CCA from benzoic acid by a one-step hydrogenation method, but the crude product needs to be purified by rectification with high energy consumption, but the purity of the CCA product is not reported.
The purity of CCA products obtained by the currently reported benzoic acid catalytic hydrogenation method is mostly not more than 98.5 percent and rarely reaches 99 percent, but the cost is high, the purity of the products still cannot meet the increasing requirement of high-end fields such as pharmacy on the purity of CCA, and the high-purity CCA has wide industrial application prospect. No literature report has been found on the technology dedicated to the purification of crude CCA.
Disclosure of Invention
The invention aims to provide a method for preparing high-purity cyclohexanecarboxylic acid, which optimizes the preparation and purification processes of CCA, improves the purity of CCA products and reduces environmental pollution.
The technical scheme of the invention is as follows: the method for preparing high-purity cyclohexanecarboxylic acid takes CCA products produced by an industrial device as raw materials, adopts a static melt crystallization method to prepare high-purity CCA, and comprises the following steps:
firstly, melting and charging: heating 99% CCA raw material with the mass concentration of 97% in a preheating tank to more than 35 ℃ to completely melt the CCA raw material into liquid; closing a valve at the bottom of the crystallization tower, and adding the molten CCA raw material in the preheating tank into the crystallization tower at one time;
precooling and adding seed crystals: introducing a cooling medium into a jacket of the crystallization tower to cool the raw material, keeping the temperature constant when the temperature of the CCA feed liquid reaches 30-26 ℃, and keeping the temperature constant for 30-60 min; adding seed crystals into the crystallization tower at a constant temperature stage, so that the seed crystals are uniformly dispersed in the crystallization tower;
step three, cooling and crystallizing: introducing a cooling medium into the jacket of the crystallization tower, and continuously cooling at a cooling rate within the range of 0.5-3 ℃/h; after the temperature of the materials in the crystallization tower is reduced to the crystallization end point temperature, keeping the constant temperature for 15-30 minutes, opening a valve at the bottom of the crystallization tower, discharging the residual non-crystallized mother liquor, and then closing the valve;
fourthly, sweating and discharging: keeping a valve at the bottom of the crystallization tower fully opened, and raising the temperature of the crystallization tower to 29-30 ℃ at a temperature raising rate of 0.5-3 ℃/h for perspiration; the perspiration mode adopts gravity flow or intermittent vacuum to perspire, and the constant temperature vacuum perspiration is carried out until no sweat drops; and closing a valve at the bottom of the crystallization tower, introducing a heating medium into a jacket of the crystallization tower to completely melt the crystals, and opening the valve at the bottom of the crystallization tower to collect the CCA.
The crystal seed is CCA fine solid with the mass concentration of 98.5-99.0% or a suspension prepared by dispersing the CCA fine solid in supercooling CCA molten liquid. The solid mass content of the seed crystal is 0.01-0.5% of the mass of the raw material CCA. When the mass concentration of the raw material is 97%, the temperature for adding the seed crystal is 26-27 ℃. When the mass concentration of the raw material is 98%, the temperature of adding the seed crystal is 27-29 ℃. When the mass concentration of the raw material is 99%, the temperature for adding the seed crystal is 28-30 ℃. When the perspiration mode is gravity flowing, the perspiration is discharged from the valve at the bottom of the crystallization tower only under the action of gravity. When the perspiration mode is intermittent vacuum perspiration, when the bottom part observes that sweat flows and is discharged automatically, the temperature is kept constant, the vacuum is opened to accelerate the perspiration, when no sweat is discharged, the vacuum is removed, the temperature is continuously raised to heat and perspire, and the process is repeated.
The process of the present invention involves melting the charge material, and the raw material must be heated to be completely melted before entering the crystallization tower, and cannot contain solids. And step three, taking a stage cooling crystallization process, wherein the cooling speed is slow firstly and then fast, the cooling speed is reduced to 26-29 ℃ at the speed of 0.5-1.5 ℃/h, and then the cooling speed is reduced to 25-27 ℃ at the speed of 1.5-3 ℃/h. And step four, in the sweating and discharging process in the stage, the temperature rise rate is first high and then low, the temperature rise rate is increased to 27-28.5 ℃ at the speed of 1.5-3 ℃/h, and the sweating end point temperature is 29-30 ℃. And step three, the cooling medium is water.
For the CCA raw material with the mass concentration of 97-99%, the high-purity CCA product with the concentration of 99.9% can be obtained through one-time static melting crystallization process by the method. When the concentration of the raw material is less than 97%, a plurality of static melt crystallization processes are required. Experiments show that the process yield of the refining process can be improved by classifying and recycling the crystallization mother liquor and the sweat as raw materials. According to the method, the CCA raw material with the mass concentration of 97-99% is subjected to static melt crystallization operation, so that a high-purity CCA product with the purity of 99.9% can be obtained, and the once-through yield range is 25-55%.
The CCA has low melting point (31 ℃), most impurities in the CCA are the bicyclohexane and the derivatives thereof, the melting point is lower, and the method is suitable for separation by a melt crystallization method. The invention utilizes a melting crystallization method to prepare the high-purity CCA product by taking the CCA crude product as a raw material, optimizes the preparation and refining processes of the CCA, can prepare the high-purity CCA product with the purity of 99.9 percent, and improves the product quality and the product yield. The method has the advantages of simple process, low energy consumption, low operation temperature, easy realization in industry, no need of adding solvent in the process, small pollution and low cost, and is a green CCA preparation method.
Drawings
FIG. 1 is a molecular structural formula of cyclohexanecarboxylic acid (CCA);
FIG. 2 is an XRD spectrum of a CCA crystal prepared by the method for preparing high-purity cyclohexanecarboxylic acid according to the invention;
FIG. 3 is a DSC spectrum of a CCA crystal prepared by the method of the present invention;
FIG. 4 is a microscope photograph of a CCA crystal prepared by the method of the present invention;
FIG. 5 is a gas chromatogram of a CCA prepared using the method of the present invention;
FIG. 6 is a gas chromatogram of CCA before purification.
Detailed Description
The present invention will be described in detail with reference to the following examples and drawings. The scope of protection of the invention is not limited to the embodiments, and any modification made by those skilled in the art within the scope defined by the claims also falls within the scope of protection of the invention.
Example 1
200g of CCA raw material produced by an industrial device with the mass concentration of 98.5 percent is weighed and placed in a crystallization tower at one time, and heated until the CCA raw material is completely melted. And introducing cooling water into a jacket of the crystallization tower to pre-cool the CCA raw material to 29 ℃, keeping the temperature constant, weighing 1g of 98.5 percent CCA solid powder as seed crystals, adding the seed crystals into the crystallization tower, and uniformly dispersing the seed crystals. Through the temperature and the flow of adjusting jacket cooling water, the crystallization of cooling begins again, and the cooling curve is: 0.5 ℃/h to 28 ℃, 2 ℃/h to 27 ℃. The temperature was maintained constant for 20 minutes.
The bottom valve of the crystallization column was opened and the uncrystallized mother liquor was drained with vacuum assistance. After the mother liquor is drained, the temperature rises to sweat, and the temperature rise curve is as follows: 2 ℃/h to 27.5 ℃, 0.5 ℃/h to 29.5 ℃. During the heating and sweating period, when sweat begins to drip from the valve at the bottom of the crystallization tower under the action of gravity, the vacuum is opened to accelerate sweating, when the sweat does not drip, the vacuum is removed, and the sweating is continuously heated at the heating speed, and the steps are repeated until the temperature reaches 29.5 ℃. And (3) keeping the temperature constant, opening the vacuum for perspiration until no sweat drips out, closing a valve at the bottom of the crystallization tower, introducing a heating medium into a jacket of the crystallization tower to completely melt crystals, and opening the valve at the bottom of the crystallization tower to collect a CCA product. The purity of the obtained CCA refined product is 99.93 percent, and the yield is 47 percent.
Example 2
200g of CCA raw material with the mass concentration of 99% is weighed, placed in a crystallization tower at one time and heated until the CCA raw material is completely melted. And (3) introducing cooling water into a jacket of the crystallization tower to pre-cool the CCA raw material to 28 ℃, keeping the temperature constant, weighing 0.04g of 99% CCA solid powder as seed crystals, adding the seed crystals into the crystallization tower, and uniformly dispersing. Through the temperature and the flow of adjusting jacket cooling water, the crystallization of cooling begins again, and the cooling curve is: 0.5 ℃/h to 27.5 ℃, 1 ℃/h to 27 ℃. The temperature was kept constant for 15 minutes.
The bottom valve of the crystallization column was opened and the uncrystallized mother liquor was drained with vacuum assistance. After the mother liquor is drained, the temperature rises to sweat, and the temperature rise curve is as follows: 1 ℃/h to 28.5 ℃, 0.5 ℃/h to 30 ℃. During the heating and sweating period, when sweat begins to drip from the valve at the bottom of the crystallization tower under the action of gravity, the vacuum is opened to accelerate sweating, when the sweat does not drip, the vacuum is removed, and the heating and sweating are continuously carried out at the heating speed, and the steps are repeated until the temperature reaches 30 ℃. And (3) keeping the temperature constant, opening the vacuum for perspiration until no sweat drips out, closing a valve at the bottom of the crystallization tower, introducing a heating medium into a jacket of the crystallization tower to completely melt crystals, and opening the valve at the bottom of the crystallization tower to collect a CCA product. The purity of the obtained CCA fine product is 99.94 percent, and the yield is 55 percent.
Example 3
200g of CCA raw material with the mass concentration of 97 percent is weighed, placed in a crystallization tower at one time and heated until the CCA raw material is completely melted. And (3) introducing cooling water into a jacket of the crystallization tower to pre-cool the CCA raw material to 26 ℃, keeping the temperature constant, weighing 0.06g of 98.5% CCA solid powder as seed crystal, adding the seed crystal into the crystallization tower, and uniformly dispersing. Through the temperature and the flow of adjusting jacket cooling water, the crystallization of cooling begins again, and the cooling curve is: 0.5 ℃/h to 25.5 ℃ and 3 ℃/h to 25 ℃. The temperature was kept constant for 30 minutes.
The bottom valve of the crystallization column was opened and the uncrystallized mother liquor was drained with vacuum assistance. After the mother liquor is drained, the temperature rises to sweat, and the temperature rise curve is as follows: 3 ℃/h to 28 ℃, 0.5 ℃/h to 29 ℃. During the heating and sweating period, when sweat begins to drip from the valve at the bottom of the crystallization tower under the action of gravity, the vacuum is opened to accelerate sweating, when the sweat does not drip, the vacuum is removed, and the sweating is continuously heated according to the heating speed, and the steps are repeated until the temperature reaches 29 ℃. And (3) keeping the temperature constant, opening the vacuum for perspiration until no sweat drips out, closing a valve at the bottom of the crystallization tower, introducing a heating medium into a jacket of the crystallization tower to completely melt crystals, and opening the valve at the bottom of the crystallization tower to collect a CCA product. The purity of the obtained CCA refined product is 99.90 percent, and the yield is 29 percent.
Example 4
200g of CCA raw material with the mass concentration of 98.5 percent is weighed and placed in a crystallization tower at one time, and the CCA raw material is heated until the CCA raw material is completely melted. And (3) introducing cooling water into a jacket of the crystallization tower to pre-cool the CCA raw material to 27 ℃, keeping the temperature constant, weighing 0.02g of 98.5% CCA solid powder as seed crystals, adding the seed crystals into the crystallization tower, and uniformly dispersing the seed crystals. Through the temperature and the flow of adjusting jacket cooling water, the crystallization of cooling begins again, and the cooling curve is: 0.5 ℃/h to 26.5 ℃ and 1 ℃/h to 26 ℃. The temperature was maintained constant for 20 minutes.
The bottom valve of the crystallization column was opened and the uncrystallized mother liquor was drained with vacuum assistance. After the mother liquor is drained, the temperature rises to sweat, and the temperature rise curve is as follows: 2 ℃/h to 27 ℃, 0.5 ℃/h to 29.5 ℃. During the heating and sweating period, when sweat begins to drip from the valve at the bottom of the crystallization tower under the action of gravity, the vacuum is opened to accelerate sweating, when the sweat does not drip, the vacuum is removed, and the sweating is continuously heated at the heating speed, and the steps are repeated until the temperature reaches 29.5 ℃. And (3) keeping the temperature constant, opening the vacuum for perspiration until no sweat drips out, closing a valve at the bottom of the crystallization tower, introducing a heating medium into a jacket of the crystallization tower to completely melt crystals, and opening the valve at the bottom of the crystallization tower to collect a CCA product. The purity of the obtained CCA refined product is 99.92 percent, and the yield is 51 percent.
Detecting the CCA of the product, wherein the result is as follows: figure 2 shows the XRD spectrum of CCA crystals; figure 3 shows a DSC spectrum of a CCA crystal; FIG. 4 shows a crystal photomicrograph of CCA; the gas chromatogram of the CCA shown in fig. 5. For comparison, fig. 6 shows a gas chromatogram of the raw material crude CCA.
Example 5
200g of CCA raw material with the mass concentration of 99% is weighed, placed in a crystallization tower at one time and heated until the CCA raw material is completely melted. And (3) introducing cooling water into a jacket of the crystallization tower to pre-cool the CCA raw material to 30 ℃, keeping the temperature constant, weighing 0.1g of 99% CCA solid powder as seed crystals, adding the seed crystals into the crystallization tower, and uniformly dispersing. Through the temperature and the flow of adjusting jacket cooling water, the crystallization of cooling begins again, and the cooling curve is: 0.5 ℃/h to 29 ℃, 1 ℃/h to 28 ℃. The temperature was kept constant for 15 minutes.
The bottom valve of the crystallization column was opened and the uncrystallized mother liquor was drained with vacuum assistance. After the mother liquor is drained, the temperature rises to sweat, and the temperature rise curve is as follows: 3 ℃/h to 29 ℃, 0.5 ℃/h to 30 ℃. During the heating and sweating period, when sweat begins to drip from the valve at the bottom of the crystallization tower under the action of gravity, the vacuum is opened to accelerate sweating, when the sweat does not drip, the vacuum is removed, and the heating and sweating are continuously carried out at the heating speed, and the steps are repeated until the temperature reaches 30 ℃. And (3) keeping the temperature constant, opening the vacuum for perspiration until no sweat drips out, closing a valve at the bottom of the crystallization tower, introducing a heating medium into a jacket of the crystallization tower to completely melt crystals, and opening the valve at the bottom of the crystallization tower to collect a CCA product. The purity of the obtained CCA refined product is 99.93 percent, and the yield is 53 percent.
Example 6
200g of CCA raw material with the mass concentration of 97 percent is weighed, placed in a crystallization tower at one time and heated until the CCA raw material is completely melted. And (3) introducing cooling water into a jacket of the crystallization tower to pre-cool the CCA raw material to 27 ℃, keeping the temperature constant, weighing 0.5g of 98.5% CCA solid powder as seed crystals, adding the seed crystals into the crystallization tower, and uniformly dispersing the seed crystals. Through the temperature and the flow of adjusting jacket cooling water, the crystallization of cooling begins again, and the cooling curve is: 0.5 ℃/h to 26.5 ℃ and 3 ℃/h to 26 ℃. The temperature was kept constant for 30 minutes.
The bottom valve of the crystallization column was opened and the uncrystallized mother liquor was drained with vacuum assistance. After the mother liquor is drained, the temperature rises to sweat, and the temperature rise curve is as follows: 3 ℃/h to 28 ℃, 0.5 ℃/h to 29.5 ℃. During the heating and sweating period, when sweat begins to drip from the valve at the bottom of the crystallization tower under the action of gravity, the vacuum is opened to accelerate sweating, when the sweat does not drip, the vacuum is removed, and the sweating is continuously heated at the heating speed, and the steps are repeated until the temperature reaches 29.5 ℃. And (3) keeping the temperature constant, opening the vacuum for perspiration until no sweat drips out, closing a valve at the bottom of the crystallization tower, introducing a heating medium into a jacket of the crystallization tower to completely melt crystals, and opening the valve at the bottom of the crystallization tower to collect a CCA product. The purity of the obtained CCA refined product is 99.91 percent, and the yield is 25 percent.
The method for preparing high-purity cyclohexanecarboxylic acid disclosed and proposed by the invention can be used for experiments by persons skilled in the art by appropriately changing raw materials, process parameters and other links by referring to the contents in the text. While the methods and products of the present invention have been described in terms of preferred embodiments, it will be apparent to those of ordinary skill in the art that variations and modifications in the methods and products described herein may be made and equivalents employed to implement the techniques of the present invention without departing from the spirit and scope of the invention. It is expressly intended that all such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and content of the invention.
Claims (2)
1. A method for preparing high-purity cyclohexanecarboxylic acid, which takes CCA products produced by an industrial device as raw materials and adopts a static melt crystallization method to prepare the high-purity CCA, comprises the following steps:
firstly, melting and charging: heating CCA raw materials with the mass concentration of 98.5-99% in a preheating tank to over 35 ℃ to completely melt the CCA raw materials into liquid; closing a valve at the bottom of the crystallization tower, and adding the molten CCA raw material in the preheating tank into the crystallization tower at one time;
precooling and adding seed crystals: introducing a cooling medium into a jacket of the crystallization tower to cool the raw material, keeping the temperature constant when the temperature of the CCA feed liquid reaches 30-27 ℃, and keeping the temperature constant for 30-60 min; adding seed crystals into the crystallization tower at a constant temperature stage, so that the seed crystals are uniformly dispersed in the crystallization tower; the seed crystal is CCA fine solid with the mass concentration of 98.5-99.0% or suspension prepared by dispersing the CCA fine solid in supercooling CCA molten liquid; the solid mass content of the seed crystal is 0.01-0.5% of the mass of the raw material CCA;
step three, cooling and crystallizing: introducing a cooling medium into the jacket of the crystallization tower, and continuously cooling at a cooling rate of 0.5-2 ℃/h; after the temperature of the materials in the crystallization tower is reduced to the crystallization end point temperature, keeping the constant temperature for 15-20 minutes, opening a valve at the bottom of the crystallization tower, discharging the residual non-crystallized mother liquor, and then closing the valve;
fourthly, sweating and discharging: keeping a valve at the bottom of the crystallization tower fully opened, and raising the temperature of the crystallization tower to 29-30 ℃ at a temperature raising rate of 0.5-3 ℃/h for perspiration; the perspiration mode adopts gravity flow or intermittent vacuum to perspire, and the constant temperature vacuum perspiration is carried out until no sweat drops; and closing a valve at the bottom of the crystallization tower, introducing a heating medium into a jacket of the crystallization tower to completely melt the crystals, and opening the valve at the bottom of the crystallization tower to collect the CCA.
2. The process for producing a highly pure cyclohexanecarboxylic acid as claimed in claim 1, wherein: when the mass concentration of the raw material is 98%, the temperature of adding the seed crystal is 27-29 ℃; when the mass concentration of the raw material is 99%, the temperature of adding the seed crystal is 28-30 ℃.
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