WO2021081743A1

WO2021081743A1 - Method for recovering catechol from o-ethoxyphenol reaction liquid

Info

Publication number: WO2021081743A1
Application number: PCT/CN2019/113938
Authority: WO
Inventors: 毛海舫; 刘吉波; 章平毅; 姚跃良; 王洪朝; 王朝阳; 靳苗苗; 孟涛; 张驰原; 李箫磊
Original assignee: 上海应用技术大学
Priority date: 2019-10-29
Filing date: 2019-10-29
Publication date: 2021-05-06
Also published as: CN110944968A

Abstract

A method for recovering catechol from an o-ethoxyphenol reaction liquid, which comprises the steps of: mixing catechol with ethanol for reaction to form a reaction liquid; rectifying the reaction liquid to remove water and excessive ethanol in the reaction liquid to obtain a column sump liquid; cooling and crystallizing the column sump liquid while stirring, and keeping the temperature for a certain period of time to separate out a catechol-containing crystallized mixture from the column sump liquid; carrying out solid-liquid separation on the crystallized mixture to obtain an o-ethoxyphenol-containing crystallized mother liquid and a catechol crude product solid; and purifying the catechol crude product solid to obtain a purified mother liquid and a catechol finished product.

Description

Method for recovering catechol from o-ethoxyphenol reaction solution

Technical field

The invention relates to the technical field of synthetic chemistry, in particular to a method for recovering catechol from a reaction solution of o-ethoxyphenol.

Background technique

O-ethoxy phenol, also known as o-hydroxy phenyl ethyl ether, 2-ethoxy phenol, 2-hydroxy phenyl ethyl ether, is a colorless to light yellow transparent liquid, which can be used to synthesize ethyl vanillin. Ethyl vanillin can not only be used as a fragrance in the food and cosmetic industries, but also an important raw material for medicine. As an important supplement to vanillin, the global demand for ethyl vanillin is increasing, so the demand for o-ethoxyphenol is also increasing. In 2005, the consumption of o-ethoxyphenol in my country was 335 tons. In the following ten years, it has been increasing by an annual average rate of 6.3%. At present, the domestic production has reached more than 2500 tons.

At present, there are four main methods for synthesizing o-ethoxyphenol: ethanol monoethylation method, ethyl chloride monoethylation method, o-nitrophenol method, and o-aminophenethyl ether method. Among them, the ethyl chloride monoethylation method has a short reaction step but produces a large amount of corrosive gas hydrogen chloride; the o-nitrophenol method and the o-aminophenethyl ether method have long process routes, and require harsh process conditions such as diazotization. The treatment process is cumbersome and the environment is polluted. However, the ethanol monoethylation method has a short process route, less environmental pollution, and has a very large reaction advantage. The conversion rate of ethanol monoethylation to produce o-ethoxyphenol is about 10%-40%. In the reaction system, there will be a large amount of residual catechol that does not participate in the reaction that needs to be recovered, and a small amount of di-etherification will be generated. Therefore, the purity of the recovered catechol is only about 92%. Catechol is reused as a raw material to participate in the production of o-ethoxy phenol. Since the main purpose of o-ethoxy phenol is to produce ethyl vanillin, the purity of catechol is a product of ethyl vanillin. The quality impact is very important. In the existing production process, the reaction liquid needs to be rectified to recover the excess solvent ethanol and the produced by-product water, and then o-ethoxyphenol is obtained through rectification, and the bottom liquid of the o-ethoxy phenol rectification tower is rectified again. Catechol. Of course, the separation of o-ethoxyphenol, catechol and impurities can be achieved through rectification, but the boiling point of o-ethoxyphenol is 236℃, and the boiling point of catechol is 245℃-246℃. The difference between the boiling points is less than 10℃, and there are many impurities such as phthalic diethyl ether, 2-methoxy-6-methylguaiacol, and the boiling points of impurities are between the boiling points of o-ethoxyphenol and phthalic diethyl ether. The difference in boiling point between phenols is small. Therefore, the difficulty of separating o-ethoxyphenol and catechol by rectification is obviously increased, the efficiency is very low, and the energy consumption is high.

Summary of the invention

According to the defects of the prior art, the main purpose of the present invention is to disclose a method for recovering catechol from the o-ethoxyphenol reaction solution. The recovery method is achieved by dynamic crystallization method, which is under stirring conditions. Once the crystal nucleus is formed, the crystal nucleus can grow around the crystal nucleus. Therefore, it has the advantages of fast crystal growth, short crystallization time, uniform crystal particles of materials, simple operation and easy separation of crystal materials.

Another object of the present invention is to disclose a method for recovering catechol from the o-ethoxyphenol reaction solution. The reaction solution obtained after the reaction of catechol and ethanol is rectified, stirred and cooled, and solid-liquid High-purity catechol is recovered through steps such as separation and heating and sweating.

Another object of the present invention is to disclose a method for recovering catechol from the o-ethoxyphenol reaction solution. The reaction solution obtained after the reaction of catechol and ethanol undergoes rectification, stirring and cooling, and solid-liquid separation. And solvent washing treatment and other steps to recover high-purity catechol.

Another object of the present invention is to disclose a method for recovering catechol from the o-ethoxyphenol reaction solution, using the characteristic that catechol has a large difference in melting point from other compositions. The melting point of catechol is 105°C. At room temperature, o-ethoxyphenol and impurities are non-crystallized liquids. The catechol and o-ethoxyphenol can be separated and purified by cooling and crystallization, which has simple separation, convenient operation, low energy consumption, etc. Advantage.

According to the above objective, the present invention discloses a method for recovering catechol from a reaction solution of o-ethoxyphenol. The steps include: mixing and reacting catechol with ethanol to form a reaction solution, and rectifying and removing the reaction solution. The water and excess ethanol in the reaction liquid are used to obtain the tower still liquid. The tower still liquid is cooled and crystallized under stirring, and kept for a certain period of time, so that the catechol-containing crystalline mixture is precipitated from the tower still liquid. Solid-liquid separation is carried out to obtain a crystallization mother liquor containing o-ethoxyphenol, a crude catechol solid and a crude catechol solid to be purified to obtain a purified mother liquor and a catechol product.

In a more preferred embodiment of the present invention, the tower bottom liquid contains catechol, o-ethoxyphenol, residual ethanol and other impurities.

In a more preferred embodiment of the present invention, the cooling rate of stirring, cooling and crystallization of the tower kettle liquid is controlled at 5°C/h-50°C/h.

In a more preferred embodiment of the present invention, the certain time for keeping the pyrocatechol crystals precipitated is 0.5 hour to 2 hours.

In a more preferred embodiment of the present invention, the crystallization end temperature for cooling and crystallization of the tower bottom liquid is 0°C-50°C.

In a more preferred embodiment of the present invention, the content of catechol in the bottom of the tower liquid is not less than 50%, the content of o-ethoxyphenol is 10%-45%, and the total content of residual ethanol and impurities is not more than 20%. .

In a more preferred embodiment of the present invention, the solid-liquid separation is achieved by vacuum filtration or centrifugation.

In a more preferred embodiment of the present invention, the purification treatment is achieved by warming up sweating, wherein the warming up sweating can be a programmed temperature increase, a gradient temperature increase, or a direct temperature increase.

In a more preferred embodiment of the present invention, the step of warming up sweating further includes: heating and keeping the crude catechol solid for sweating and keeping it for a certain period of time to remove the purified mother liquor, and the crude catechol from which the purified mother liquor has been removed. The solid undergoes solid-liquid separation to obtain a finished product of catechol.

In a more preferred embodiment of the present invention, the temperature for warming up and sweating is 90°C to 98°C.

In a more preferred embodiment of the present invention, the certain time of heat preservation is 0.5 hour to 2.0 hours.

In a more preferred embodiment of the present invention, when the content of catechol in the purified mother liquor is less than 50%, the steps further include: mixing the purified mother liquor and the crystallization mother liquor to obtain a finished product of o-ethoxyphenol through rectification, and The catechol is collected and crystallized to recover the catechol.

In a more preferred embodiment of the present invention, when the content of catechol in the mother liquor of the product is between 50% and 90%, the steps further include: combining catechol as the crystallization raw material with the tower bottom liquid to perform the process again Crystallization to obtain catechol crude solids, catechol crude solids for solid-liquid separation to obtain crystallization mother liquor and catechol crude solids, and catechol crude solids for purification treatment to obtain purified mother liquor and ortho-catechol crude solids. Hydroquinone finished product.

In a more preferred embodiment of the present invention, when the content of catechol in the purified mother liquor is ≥90%, then catechol is the finished catechol.

In a more preferred embodiment of the present invention, the ortho-purification treatment is achieved by solvent washing.

In a more preferred embodiment of the present invention, the solvent used in the solvent washing can be ethanol, methanol, toluene or butyl acetate.

In a more preferred embodiment of the present invention, the solvent washing step further includes: providing a solvent, washing the crude catechol solids with the solvent, and performing solid-liquid separation on the washed crude catechol to remove the solvent. The finished product of catechol is recovered and the washing mother liquor is obtained.

In a more preferred embodiment of the present invention, the solvent washing step further includes: when the solvent is ethanol, mixing the washing mother liquor with the reaction liquid, crystallizing the reaction liquid with the washing mother liquor to recover ethanol and obtain o-benzene Diphenol and ethyl guaiacol.

In a more preferred embodiment of the present invention, when the solvent is ethanol and the concentration is greater than 50%, the steps further include: directly mixing the washing mother liquor with the reaction solution, rectifying the mixed reaction solution to recover the ethanol and The rectified reaction liquid and the rectified reaction liquid are crystallized to recover the o-phthalone and obtain ethyl guaiacol.

In a more preferred embodiment of the present invention, the temperature of the solvent washing does not exceed the crystallization end temperature, wherein the crystallization end temperature is 0°C-50°C.

In a more preferred embodiment of the present invention, the content of the recovered product of catechol obtained by purifying the crude catechol is not less than 98%, the content of o-ethoxyphenol is not more than 1% and other impurities The content of a single impurity in it is not higher than 0.2%.

Description of the drawings

FIG. 1 is a flow chart showing an embodiment of a method for recovering catechol from a reaction solution of o-ethoxyphenol according to the technology disclosed in the present invention.

Fig. 2 is a schematic diagram showing the steps of purifying crude catechol solids by warming up sweating according to the technology disclosed in the present invention.

Fig. 3 is a schematic diagram showing the processing steps when the content of catechol in the purified mother liquor is different according to the technology disclosed in the present invention.

Fig. 4 is a schematic diagram showing the steps of washing crude catechol solids with a solvent according to the technology disclosed in the present invention.

Detailed ways

In order to make the purpose, technical features, and advantages of the present invention better known to those in the relevant technical field and able to implement the present invention, the technical features and implementation modes of the present invention are illustrated in detail in conjunction with the accompanying drawings and listed here. The preferred embodiment is further explained. The drawings to be compared in the following text are schematic representations related to the features of the present invention, and are not and need not be drawn completely based on actual situations. The description of the implementation of this case involves technical content familiar to those skilled in the art, and will not be described again.

Please refer to Figure 1 first. Fig. 1 shows a flowchart of an embodiment of a method for recovering catechol from a reaction solution of o-ethoxyphenol according to the present invention. In Figure 1, step S1: catechol and ethanol are mixed and reacted to form a reaction liquid. In this step, catechol is used as a raw material and undergoes a gas phase catalytic reaction with ethanol to form a reaction liquid, wherein the reaction liquid is an o-ethoxyphenol reaction liquid. Step S2: rectifying the reaction liquid to remove low-boiling substances such as water and excess ethanol in the reaction liquid to obtain a tower bottom liquid. In this step, the reaction solution with o-ethoxyphenol is used to recover ethanol in the reaction solution by means of reduced pressure rectification, the recovered ethanol is separated from the reaction solution, and the by-products produced during the reaction in step S1 are removed ,water. Therefore, after the reaction liquid is rectified under reduced pressure, a rectified tower still liquid can be obtained, wherein the tower still liquid contains o-ethoxyphenol, catechol and other impurities. In the present invention, the content of o-ethoxyphenol in the tower bottom liquid is not less than 50%, the content of o-ethoxyphenol is in the range of 10%-45%, and the residual content can be obtained by means of gas-phase or liquid-phase analysis. The total content of ethanol and impurities is not more than 20%.

Next, in step S3: cooling and crystallization of the tower kettle liquid under stirring, and keeping it for a certain period of time, so that catechol-containing crystals are precipitated from the tower kettle liquid. In this step, the tower still liquid formed in step S2 is transferred to the crystallizer, and the tower still liquid is cooled and crystallized under stirring under agitation, and the cooling rate is controlled at 5℃/h-50℃ /h, and according to this cooling rate to reach the crystallization end temperature, the crystallization end temperature is the target temperature. It should be noted that the crystallization end temperature is different according to the initial content of catechol as the reactant. When the initial content of catechol as the reactant is higher, the crystallization end temperature is Relatively high; on the contrary, when the initial content of catechol as the reactant is low, the crystallization end temperature is also low. Generally speaking, the crystallization end temperature is controlled at 0℃-50℃.

Step S4: performing solid-liquid separation on the crystallization mixture to obtain a crystallization mother liquor and a crude catechol solid. In this step, solid-liquid separation can be achieved by conventional methods such as vacuum filtration or centrifugation.

Step S5: Purifying the crude catechol solid to obtain a purified mother liquor and finished catechol. In this step, the purification treatment can be achieved by warming up sweating or solvent washing. The following is a further description of warming up sweating and solvent washing.

Please refer to Figure 2 and Figure 3 at the same time. Figure 2 shows a schematic diagram of the steps of purifying crude catechol solids by warming up sweating, and Figure 3 shows a schematic diagram of the processing steps when the content of catechol in the purified mother liquor is different. In FIG. 2, steps S1-S4 are the same as those disclosed in FIG. 1, with the difference that the purification process is further described. In step S510: the crude catechol solid is heated to sweat and kept for a certain period of time to remove the purified mother liquor (sweat mother liquor). In this step, heating and sweating can be programmed heating, gradient heating or direct heating, and the temperature is 90°C to 98°C, and the temperature is maintained for at least 0.5 hour to 2.0 hours. The processing method of the purified mother liquor (sweating mother liquor) obtained in step S510 after the content analysis of the gas phase or the liquid phase is shown in FIG. 3. In step S51012: when the content of catechol in the purified mother liquor is less than 50%, proceed to step S51014: mix the purified mother liquor and the crystallization mother liquor to obtain an o-ethoxyphenol product through rectification. Next, step S51016: Catechol is collected and crystallized to recover the catechol. In step S51016, the step of collecting the catechol and recrystallizing is the same as the aforementioned step S3, that is, after the catechol is collected, a cooling crystallization step is performed under stirring to precipitate catechol-containing crystals.

In addition, in step S51022: when the content of catechol in the purified mother liquor is between 50% and 90%, proceed to step S51024: catechol is used as the crystallization raw material and the tower bottom liquid is combined for recrystallization to obtain Crude catechol solid. In this step, the purified mother liquor with a content of 50%-90% of catechol is combined with the tower bottom liquor obtained in the aforementioned step S2, and the aforementioned steps S3-step S5 are repeated again to obtain the purified mother liquor and The finished product of catechol. That is to say, when the content of catechol in the product mother liquor is between 50% and 90% by gas or liquid phase analysis, the purified mother liquor can be combined with the aforementioned tower still liquid, and the stirring and step S3 can be repeated. Cooling crystallization, solid-liquid separation in step S4 and purification treatment in step S5, until the crude catechol solid in the purified mother liquor is completely precipitated.

In addition, in step S51032: when the content of catechol in the purified mother liquor is ≥90%, then catechol is a finished product of catechol.

Therefore, after the crude catechol solids are precipitated in the above steps S51014 and S51024, step S512 of Figure 2 is performed: the crystallization mother liquor containing o-ethoxyphenol and the purified mother liquor are mixed and then rectified to obtain o-ethyl The finished product of oxyphenol. In this step, the o-ethoxyphenol-containing crystallization mother liquor obtained through solid-liquid separation in the foregoing step S4 is combined with a purified mother liquor with a lower content, and the o-ethoxyphenol product is obtained through rectification again.

Then, step S514: performing solid-liquid separation on the crude catechol solid from which the purified mother liquor has been removed to obtain the catechol product. The solid-liquid separation in this step is also achieved by conventional methods such as vacuum filtration or centrifugation.

Therefore, the crude solid content of catechol obtained by warming up sweating is not less than 98%, the content of o-ethoxyphenol is not more than 1%, and the single impurity in other impurities is not more than 0.2%, so The recovered crude catechol solids can be reused as raw materials for the re-synthesis of o-ethoxyphenol, so as to save the cost of raw materials.

In addition, please refer to Figure 4. Figure 4 shows a schematic flow diagram of the steps of washing crude catechol solids with a solvent. In Fig. 4, steps S1 to S4 are the same as those described in Fig. 1, with the difference that the purification process is further described. In step S520: provide a solvent. The solvent provided in this step can be ethanol, methanol, toluene or butyl acetate, and these solvents can be used as organic solvents for dissolving ethyl guaiacol. Then step S522: washing the crude catechol solids with a solvent. In this step, the temperature of the solvent during the washing of the crude catechol solids does not exceed the crystallization end temperature of the cooling crystallization, that is, the temperature of the solvent does not exceed 0°C-50°C. Then, step S524: performing solid-liquid separation on the washed crude catechol to remove the solvent to recover the catechol product and obtain the washing mother liquor. In this step, solid-liquid separation can be achieved by conventional methods such as vacuum filtration or centrifugation as disclosed above.

Furthermore, if the washing mother liquor is ethanol, step S526 to step S528 are performed. Step S526: When the washing mother liquor is ethanol, the washing mother liquor is directly mixed with the reaction liquid. The condition in this step is that when the washing solvent provided in the foregoing step S520 is ethanol, the washing mother liquor after washing the crude catechol solids with ethanol contains ethanol, and the reaction liquid in the foregoing step S1 is made of o-benzene. Diphenol reacts with ethanol to form, so the washing mother liquor is mixed with the reaction liquid again. Then in step S528: rectify the mixed reaction liquid to recover ethanol and recover catechol through crystallization and obtain the product ethylguaiacol.

It should be noted that when the solvent used in step S520 is ethanol and the concentration of ethanol is controlled above 50%, the obtained washing mother liquor can be directly mixed with the reaction solution, and the catechol is directly recovered by crystallization after the ethanol is recovered. And the product ethyl guaiacol is obtained.

Next, the following examples are respectively proposed for the method of recovering catechol from the o-ethoxyphenol reaction liquid disclosed in the present invention. Among them, Examples 1 to 6 show the recovery of catechol by means of warming up sweating. Phenol, Example 7-Example 11 are washing solvents to recover catechol.

Example 1:

Add 3800 g of the o-ethoxyphenol reaction solution to a rectification kettle equipped with a rectification column filled with glass threaded fillers to perform vacuum rectification, which collects 1832 g of a mixture of ethanol and water. A total of 1938 g of tower kettle liquid was obtained, in which 2% of ethanol remained, the content of catechol was 79.6%, and the content of o-ethoxyphenol was 16.2% by gas chromatography analysis.

Transfer the tower kettle liquid to a 2L crystallizer, and start cooling and crystallization under stirring conditions. Under stirring conditions, the jacket of the crystallizer was cooled with cooling water to an internal temperature of about 92°C, added a small amount of catechol seed crystals to start crystallization, and then continued to use cooling water for about 3 hours to slowly cool down to an internal temperature of 40°C. Keep the temperature for 1.5 hours.

The bottom valve of the crystallizer was opened, and 432 g of the crystallization mother liquor was separated by filtration under reduced pressure. After analysis, the content of catechol in the crystallization mother liquor was 33.2%.

Until no more liquid drips, start to heat up sweating treatment. Directly inject hot water at 65±1℃ into the jacket of the crystallizer. After 1 hour of heat preservation, it is suction filtered until there is almost no dripping. The first sweating mother liquor is about 132g, which contains 46.2% catechol; crystallinity Directly inject hot water at 85±1℃ into the jacket of the device and keep it warm for 1 hour, and then suction and filter until there is almost no dripping. The second sweating mother liquor is about 102g, which contains 73.3% catechol; crystals Directly inject hot water at 95±1℃ into the jacket of the device, and keep it warm for 1 hour, and then suction and filter until there is almost no dripping. The third sweating mother liquor 3 is about 79g, and it contains 95.2% catechol; Finally, 1190 g of the finished product of catechol was taken out, the content was 99.2%, and the recovery rate of catechol was 77.0%.

The content of catechol in the crystallization mother liquor and the first sweating mother liquor is less than 50%, and can be combined as a rectification raw material to obtain o-ethoxyphenol products; the second sweating mother liquor has a catechol content of 73.3%, which can be Combined with the next batch of tower kettle liquid, it is directly used for crystallization and recovery of catechol; the third sweating mother liquor can be directly used for sweating to obtain the finished catechol.

Example 2:

3700 g of the reaction liquid was added to a rectification vessel equipped with a rectification column filled with glass threaded filler to perform vacuum rectification, which collected 1808 g of a mixture of ethanol and water. A total of 1894 g of tower kettle liquid was obtained, in which 0.9% of ethanol remained, the content of catechol was 76.5%, and the content of o-ethoxyphenol was 20.3% by gas chromatography analysis.

Transfer the tower kettle liquid to a 2L crystallizer, and start cooling and crystallization under stirring conditions. Under stirring conditions, cooling water is passed into the mold jacket for cooling. The starting temperature of the cooling water is 95℃, and the cooling water is programmed at a rate of 50±0.5℃/hour. When the cooling water temperature drops to 30℃, the cooling is stopped and maintained. The cooling water temperature is kept at 30±0.1℃ for half an hour to crystallize.

The bottom valve of the crystallizer was opened, and 332 g of the crystallization mother liquor was separated by filtration under reduced pressure. The content of catechol in the crystallization mother liquor was analyzed by gas chromatography to be 28.6%.

Start to heat up and sweat until no more liquid drips. The mold jacket is heated with hot water, and the water temperature is increased at a rate of 40±0.5°C/hour, and 97°C is used as the end of the temperature rise. When the temperature was raised to 50℃, suction filtration once yielded about 187g of the mother liquor for the first sweating, which was tested to contain 41.2% catechol; when the temperature was raised to 75℃, suction filtration once yielded about 192g of the second sweating mother liquor, which was tested to contain catechol. Hydroquinone 58.2%; when the temperature is raised to 97°C, the third sweating mother liquor is about 143g obtained by suction filtration once, and it is tested that it contains 95.5% of catechol; finally, 1035g of catechol is taken out, with a content of 98.5%, catechol The recovery rate of phenol is 71.3%.

The content of catechol in the crystallization mother liquor and the first sweating mother liquor is less than 50%, which is used as the raw material for obtaining o-ethoxyphenol by rectification; the second sweating mother liquor can be combined with the next batch of tower kettle liquid and used directly Catechol is recovered from the crystallization; the third sweating mother liquor can be directly used for sweating to obtain the finished product of catechol.

Example 3:

3700 g of the reaction liquid was added to a rectification vessel equipped with a rectification column filled with glass threaded filler to perform vacuum rectification, which collected 1812 g of a mixture of ethanol and water. A total of 1888 g of tower kettle liquid was obtained, in which 1.2% of ethanol remained, the content of catechol was 71.2%, and the content of o-ethoxyphenol was 25.7% by gas chromatography analysis.

Transfer the tower kettle liquid to a 2L crystallizer, and start cooling and crystallization under stirring conditions. Under stirring conditions, cooling water is passed into the mold jacket for cooling. The starting temperature of the cooling water is 95℃, and the cooling water is programmed at a rate of 30±0.5℃/hour. When the cooling water temperature drops to 22℃, the cooling will stop and keep warm. Hours, the crystallization process is over.

The bottom valve of the crystallizer was opened, and 329 g of the crystallization mother liquor was separated by filtration under reduced pressure. After analysis, the catechol content in the crystallization mother liquor was 24.9%.

Until no more liquid drips, start to heat up sweating treatment. The jacket of the crystallizer is heated with hot water, and the water temperature is increased at a rate of 30±0.5°C/hour, and 96°C is used as the end of the temperature rise. When the temperature is raised to 55°C, suction filtration once obtains about 233g of the first sweating mother liquor, which is tested to contain 38.2% catechol; when the temperature is raised to 75°C, suction filtration once obtains about 168g of the second sweating mother liquor, which is tested Contains 54.8% catechol; when the temperature is raised to 97°C, suction filtration once obtains about 108g of the second sweating mother liquor, which is tested to contain 92.9% catechol; finally, 1017g of catechol is taken out, with a content of 99.1%. The recovery rate of catechol is 75.5%.

Example 4:

3700 g of the reaction liquid was added to a rectification vessel equipped with a rectification column filled with glass threaded fillers to perform vacuum rectification, and 1822 g of a mixture of ethanol and water was collected. A total of 1882 g of tower kettle liquid was obtained, in which 0.8% of ethanol remained, the content of catechol was 67.2%, and the content of o-ethoxyphenol was 28.5% by gas chromatography analysis.

Transfer the tower kettle liquid to a 2L crystallizer, and start cooling and crystallization under stirring conditions. Under stirring conditions, cooling water is introduced into the mold jacket for cooling. The starting temperature of the cooling water is 95°C, and the temperature is lowered by a program at a rate of 20±0.5°C/hour. When the cooling water temperature drops to 12°C, the cooling stops and keeps warm. 2 Hours, the crystallization process is over.

The bottom valve of the crystallizer was opened, and 452 g of the crystallization mother liquor was separated by filtration under reduced pressure. After analysis, the catechol content in the crystallization mother liquor was 16.3%.

Until no more liquid drips, start to heat up sweating treatment. The jacket of the crystallizer is heated with hot water, and the water temperature is increased at a rate of 20±0.5°C/hour, and 96°C is used as the end of the temperature rise. When the temperature is raised to 65°C, suction filtration once obtains about 273g of the first sweating mother liquor, which is detected to contain 42.5% of catechol; when the temperature is raised to 80°C, suction filtration once obtains about 135g of the second sweating mother liquor. It contains 60.8% catechol; when the temperature is increased to 96°C, about 88g of the third sweating mother liquor is obtained by suction filtration once, and the test contains 94.7% of catechol. Finally, 932g of catechol is taken out, with a content of 98.6%. The recovery rate of catechol was 72.6%.

Example 5:

3800 g of the reaction liquid was added to a rectification vessel equipped with a rectification column filled with glass threaded fillers to perform vacuum rectification, and 1889 g of a mixture of ethanol and water was collected. A total of 1894 g of tower kettle liquid was obtained, in which 0.6% of ethanol remained, the content of catechol was 62.1%, and the content of o-ethoxyphenol was 34.6% by gas chromatography analysis.

Transfer the tower kettle liquid to a 2L crystallizer, and start cooling and crystallization under stirring conditions. Under stirring conditions, cooling water is passed into the mold jacket for cooling. The starting temperature of the cooling water is 95°C, and the temperature is reduced by a program at a rate of 10±0.5°C/hour. When the temperature of the cooling water drops to 10°C, the cooling is stopped and the temperature is kept 1.5. Hours, the crystallization process is over.

The bottom valve of the crystallizer was opened, and 552 g of the crystallization mother liquor was separated by filtration under reduced pressure. After analysis, the catechol content in the crystallization mother liquor was 16.2%.

Start to heat up and sweat until no more liquid drips. The mold jacket is heated with hot water, and the water temperature is increased at a rate of 15±0.5°C/h, and 95°C is used as the end of the temperature rise. When the temperature is raised to 60°C, the temperature is kept for 0.5 hours, and the first sweating mother liquor is obtained by suction filtration once, about 258g, which contains 38.5% of catechol; the water temperature is then increased to 80°C at a rate of 15±0.5°C/hour , Heat preservation for 0.5 hours, suction filtration once to obtain about 124g of the second sweating mother liquor, which is tested to contain 55.2% catechol; when the water temperature is programmed to rise to 95°C at a rate of 15±0.5°C/hour, hold for 0.5 hours and pump After filtering once, about 81g of the third sweating mother liquor was obtained, which was tested to contain 95.7% of catechol; finally, 852g of catechol was taken out, the content was 98.9%, and the recovery rate of catechol was 71.6%.

The content of catechol in the crystal mother liquor and the first sweating mother liquor is less than 50%, which is used as the raw material for obtaining o-ethoxyphenol by rectification; the second sweating mother liquor can be combined with the next batch of tower kettle liquid and used directly Catechol is recovered from the crystallization; the third sweating mother liquor can be directly used for sweating to obtain the finished product of catechol.

Example 6:

3800 g of the reaction liquid was added to a rectification vessel equipped with a rectification column filled with glass threaded fillers to perform vacuum distillation, which collected 1797 g of a mixture of ethanol and water. A total of 1986 g of the tower kettle liquid was obtained, in which the residual ethanol was 2.2%, the content of catechol was 52.9%, and the content of o-ethoxyphenol was 39.1% by gas chromatography.

Transfer the tower kettle liquid to a 2L crystallizer, and start cooling and crystallization under stirring conditions. Under stirring conditions, cooling water is passed into the mold jacket for cooling. The starting temperature of the cooling water is 93°C, and the temperature is programmed at a rate of 45±0.5°C/hour. When the temperature of the cooling water drops to 1°C, the cooling will stop and keep warm Hours, the crystallization process is over.

The bottom valve of the crystallizer was opened, and 648 g of the crystallization mother liquor was separated by filtration under reduced pressure. After analysis, the catechol content in the crystallization mother liquor was 17.2%.

When there is basically no more liquid dripping, start to heat up and sweat. The jacket of the crystallizer is heated with hot water, and the water temperature is increased at a rate of 25±0.5°C/h, and 95°C is used as the end of the temperature rise. When the temperature is increased to 40°C, the temperature is kept for 0.5 hours, and the first perspiration mother liquor is about 440g obtained by suction filtration once, which is tested to contain 22.5% of catechol; the water temperature is then increased to 75°C at a rate of 25±0.5°C/hour , Heat preservation for 0.5 hours, suction filtration once to obtain about 76g of the second sweating mother liquor, which is determined to contain 48.2% catechol; when the water temperature is programmed to rise to 95°C at a rate of 25±0.5°C/hour, hold for 0.5 hours and pump After filtering once, about 41g of the second sweating mother liquor was obtained, which was tested to contain 94.7% of catechol; finally, 761.1g of finished catechol was taken out, the content was 99.1%, and the recovery rate of catechol was 72.3%.

The content of catechol in the crystallization mother liquor, the first sweating mother liquid and the second sweating mother liquid is less than 50%, which is used as the raw material for obtaining o-ethoxyphenol by distillation; the third sweating mother liquid can be directly processed The finished product of catechol is obtained through sweating operation.

Example 7:

Add 3800g of the o-ethoxyphenol reaction solution to a distillation still equipped with a rectification column filled with glass threaded filler to carry out vacuum distillation, which collects 1835g of a mixture of ethanol and water; a total of 1938g of column liquid is obtained, which is analyzed by gas chromatography Among them, the residual ethanol is 2%, the content of catechol is 79.6%, and the content of o-ethoxyphenol is 16.2%.

Transfer the tower kettle liquid to a 2L crystallizer, and start cooling and crystallization under stirring conditions. Under stirring conditions, the jacket of the crystallizer was cooled by cooling water to an internal temperature of about 92°C, added a small amount of catechol seed crystals to start crystallization, and then continued to use cooling water for about 3 hours to slowly cool down to an internal temperature of 38°C and keep it for 1.5 hours .

Open the bottom valve of the crystallizer and filter under reduced pressure to separate 426 g of the crystallization mother liquor. After analysis, the catechol content in the crystallization mother liquor is 28.6%.

Until no more liquid drips, the washing process is started. The crude crystalline product was washed once with 75 g of ethanol, and 247 g of the washing mother liquor was separated by filtration to obtain 1270 g of the recovered catechol product. After analysis, the content of catechol in the washing mother liquor was 48.1%, the content of recovered catechol finished product was 98.5%, and the content of ethanol was 0.3%, and the recovery rate of catechol reached 84.2%.

The crystallization mother liquor was subjected to vacuum distillation to obtain 234g of ethyl guaiacol finished product, with a purity of 99.4%; at the same time, 137g of an enriched catechol fraction with a catechol content of 87% was obtained. This part of the fraction is compared with the next batch of towers. The kettle liquid is mixed to recover catechol through crystallization.

The washing mother liquor is directly mixed with the next batch of reaction liquid, and after the ethanol is recovered, the catechol and the ethyl guaiacol are obtained.

Example 8:

3420 g of the reaction liquid was added to a rectification kettle equipped with a rectification column filled with glass threaded filler to perform vacuum distillation, which collected 1665 g of a mixture of ethanol and water to obtain a total of 1757 g of column liquid. The column still liquid is added to the rectification operation step of Example 7) 137g of the catechol fraction obtained by the rectification, and the total is 1894g after mixing. According to gas chromatography analysis, the ethanol residue is 0.9%, the catechol content is 76.5%, and the o-ethoxylate The base phenol content is 20.3%.

Transfer the tower kettle liquid to a 2L crystallizer, and start cooling and crystallization under stirring conditions. Under stirring conditions, cooling water is passed into the mold jacket for cooling. The starting temperature of the cooling water is 95°C, and the cooling water is programmed at a rate of 50±0.5°C/hour. When the cooling water temperature drops to 30°C, the cooling is stopped and maintained. The cooling water temperature is kept at 30±0.1℃ for half an hour to crystallize.

The bottom valve of the crystallizer was opened, and 397 g of the crystallization mother liquor was separated by filtration under reduced pressure. The catechol content in the crystallization mother liquor was analyzed by gas chromatography to be 21.1%.

Until no more liquid drips, the washing process is started. The crude crystalline product was washed once with 50g of ethanol with a concentration of 90%, and the washing mother liquor was separated by filtration; washing and filtration with 50g of ethanol with a concentration of 90% were repeated twice, a total of 339g of washing mother liquor was obtained, and the recovered phthalate was obtained. 1256g of phenol product. After analysis, the catechol content of the washing mother liquor was 25.5%, the content of the recovered catechol finished product was 99.3%, and the ethanol content was 0.2%, and the catechol recovery rate reached 86.1%.

The crystallization mother liquor was subjected to vacuum distillation to obtain 295 g of ethyl guaiacol finished product, with a purity of 99.5%; at the same time, 76 g of an enriched catechol fraction with a catechol content of 85% was obtained. This part of the fraction is compared with the next batch of towers. The kettle liquid is mixed to recover catechol through crystallization.

Example 9:

Add 3,500 g of the reaction liquid to a rectification kettle equipped with a rectification column filled with glass threaded filler, add 339 g of the washing mother liquor obtained in Example 8, and perform vacuum distillation after mixing, which collects 1922 g of a mixture of ethanol and water; to obtain a tower kettle The total amount of liquid was 1888g, and the tower bottom liquid was analyzed by gas chromatography, which contained 1.2% of ethanol, 71.2% of catechol, and 25.7% of o-ethoxyphenol.

The bottom valve of the crystallizer was opened, and 549 g of the crystallization mother liquor was separated by filtration under reduced pressure. After analysis, the catechol content in the crystallization mother liquor was 24.4%.

Until no more liquid drips, the washing process is started. The crude crystalline product was washed once with 80 g of ethanol with a concentration of 70%, and the washing mother liquor was separated by filtration; the washing and filtration with 50 g of ethanol with a concentration of 70% were repeated twice, a total of 458 g of the washing mother liquor was obtained, and the recovered phthalate was obtained. 1073g of phenol product. After analysis, the catechol content of the washing mother liquor was 25.2%, the content of the recovered catechol product was 99.3%, and the ethanol content was 0.2%, and the catechol recovery rate reached 79.8%.

The crystallization mother liquor was subjected to vacuum distillation to obtain 379 g of ethyl guaiacol finished product, with a purity of 99.6%, and the first separation yield of ethyl guaiacol was 78.1%; at the same time, 123 g of enriched catechol fraction and catechol were obtained. The phenol content is 83%, and this fraction is mixed with the next batch of tower still liquid to recover catechol through crystallization.

Example 10:

3700 g of the reaction liquid was added to a rectification kettle equipped with a rectification column filled with glass threaded fillers to perform vacuum distillation, which collected 1822 g of a mixture of ethanol and water to obtain a total of 1885 g of column liquid. The tower kettle liquid was analyzed by gas chromatography, in which 0.8% ethanol remained, the content of catechol was 67.2%, and the content of o-ethoxyphenol was 28.5%.

The bottom valve of the crystallizer was opened, and 703 g of the crystallization mother liquor was separated by filtration under reduced pressure. After analysis, the content of catechol in the mother liquor was 26.3%.

When there is almost no dripping, the washing process is started. The first crystallization product is washed once with ethanol with a temperature of 15°C, 50g and a concentration of 60%, and the washing mother liquor is separated by filtration; and then washed and filtered twice with ethanol with a temperature of 15°C, 50g and a concentration of 60%. A total of 312 g of washing mother liquor was obtained, and 1003 g of recovered catechol product was obtained. After analysis, the washing mother liquor catechol content was 25.5%, the recovered catechol product content was 99.5%, and the ethanol content was 0.2%, and the catechol recovery rate reached 79.1%.

The crystallization mother liquor was subjected to vacuum distillation to obtain 428g of ethyl guaiacol finished product, with a purity of 99.7%, and the first separation yield of ethyl guaiacol was 79.7%; at the same time, 243g of enriched catechol fraction and o-benzene were obtained. The diphenol content is 76%, and this fraction is mixed with the next batch of column liquid to recover catechol through crystallization.

Example 11:

3800 g of the reaction liquid was added to a rectification kettle equipped with a rectification column filled with glass threaded fillers to perform vacuum rectification, which collected 1889 g of a mixture of ethanol and water to obtain a total of 1894 g of column liquid. The tower kettle liquid was analyzed by gas chromatography, which contained 0.6% of ethanol, 62.1% of catechol, and 34.6% of o-ethoxyphenol.

The bottom valve of the crystallizer was opened, and 752 g of the crystallization mother liquor was separated by filtration under reduced pressure. After analysis, the content of catechol in the crystallization mother liquor was 24.2%.

When there is almost no dripping, the washing process is started. The initial crystallization product was washed once with 45 g of toluene, and the washing mother liquor was separated by filtration; and then washed and filtered once with 45 g of toluene, a total of 368 g of washing mother liquor was obtained, and 855 g of recovered catechol product was obtained. After analysis, the catechol content of the washing mother liquor was 37.1%, the content of recovered catechol finished product was 99.6%, and the content of toluene was 0.2%, and the recovery rate of catechol reached 72.7%.

The crystallization mother liquor was subjected to vacuum distillation to obtain 548 g of ethyl guaiacol finished product, with a purity of 99.5%, and the yield of ethyl guaiacol was 83.7%. At the same time, 185 g of enriched catechol fraction and catechol were obtained. The phenol content is 87%, and this fraction is mixed with the next batch of tower still liquid to recover catechol through crystallization.

Toluene is recovered from the washing mother liquor under reduced pressure, and the tower still liquid is directly mixed with the next batch of reaction liquid, and after the ethanol is recovered, catechol and ethylguaiacol are obtained.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the scope of rights of the present invention. At the same time, the above descriptions should be understood and implemented by those skilled in the relevant technical fields, so the others do not deviate from what is disclosed in the present invention. All equivalent changes or modifications made in the spirit should be included in the scope of the patent application.

Claims

A method for recovering catechol, which is characterized in that it comprises:

Mixing and reacting catechol and ethanol to form a reaction liquid;

Rectifying the reaction liquid to remove the water and excess ethanol in the reaction liquid to obtain tower bottom liquid;

Stirring, cooling and crystallization of the tower still liquid, and holding it for a certain period of time, so that the catechol-containing crystal mixture is precipitated from the tower still liquid;

Performing solid-liquid separation on the tower bottom liquid and the catechol-containing crystals to obtain a crystallization mother liquor containing o-ethoxyphenol and a crude catechol solid; and

Purification treatment is performed on the crude catechol solid to obtain a purified mother liquor and a catechol product.
The method for recovering catechol according to claim 1, wherein the tower bottom liquid comprises the catechol, o-ethoxyphenol, residual ethanol and other impurities.
The method for recovering catechol according to claim 1, characterized in that the cooling rate of stirring, cooling and crystallization of the tower bottom liquid is controlled at 5°C/h-50°C/h.
The method for recovering catechol according to claim 1, characterized in that the certain period of time during which the tower bottom liquid is stirred, cooled and crystallized, and kept warm is 0.5 hour to 2 hours.
The method for recovering catechol according to claim 1, wherein the crystallization end temperature of the cooling crystallization of the tower bottom liquid is 0°C-50°C.
The method for recovering catechol according to any one of claim 2, wherein the content of catechol in the tower bottom liquid is not less than 50%, and the o-ethoxyphenol The content is 10%-45%, and the total content of the residual ethanol and the impurities is not more than 20%.
The method for recovering catechol according to claim 1, wherein the solid-liquid separation is achieved by vacuum filtration or centrifugation.
The method for recovering catechol according to claim 1, wherein the purification treatment is achieved by warming up sweating, wherein the warming up sweating can be programmed temperature increase, gradient temperature increase or direct temperature increase.
The method for recovering catechol according to claim 8, wherein the step of warming up and sweating further comprises:

Performing the heating and sweating on the crude catechol solid and keeping it warm for a certain period of time to remove the purified mother liquor;

Mixing the crystallization mother liquor containing the o-ethoxyphenol with the purified mother liquor and then performing rectification to obtain a finished o-ethoxyphenol product; and

Solid-liquid separation is performed on the crude catechol solid from which the purified mother liquor has been removed to obtain the finished catechol.
The method for recovering catechol according to claim 8 or 9, characterized in that the temperature of the elevated sweating is 90°C-98°C.
The method for recovering catechol according to claim 10, wherein the certain time of the heat preservation is 0.5 hour to 2.0 hours.
The method for recovering catechol according to claim 1 or 9, characterized in that, when the content of the catechol in the purified mother liquor is less than 50%, the step further comprises:

Mixing the purified mother liquor and the crystallization mother liquor to obtain a finished product of o-ethoxyphenol through rectification; and

The catechol is collected and crystallized to recover the catechol.
The method for recovering catechol according to claim 1 or 9, characterized in that, when the content of catechol in the purified mother liquor is between 50% and 90%, the step further comprises:

Combining the catechol as a crystallization raw material with the tower bottom liquid for recrystallization to obtain the crude catechol solid;

Performing the solid-liquid separation on the crude catechol solid to obtain the crystallization mother liquor and the crude catechol solid; and

The purification treatment is performed on the crude catechol solid to obtain the purified mother liquor and the finished catechol product.
The method for recovering catechol according to claim 1 or 9, characterized in that, when the content of catechol in the purified mother liquor is ≥90%, then the catechol is The finished product of catechol.
The method for recovering catechol according to claim 1, wherein the ortho-purification treatment is achieved by solvent washing.
The method for recovering catechol according to claim 15, wherein the solvent used in the solvent washing can be ethanol, methanol, toluene or butyl acetate.
The method for recovering catechol according to claim 15, wherein the solvent washing step further comprises:

Provide solvent;

Washing the crude catechol solid by using the solvent; and

Solid-liquid separation is performed on the washed crude catechol to remove the solvent to recover the catechol product and obtain a washing mother liquor.
The method for recovering catechol according to claim 17, wherein the solvent washing step further comprises:

When the solvent is ethanol, mixing the washing mother liquor with the reaction liquid; and

The reaction liquid with the washing mother liquor is crystallized to recover the ethanol and obtain the catechol and ethylguaiacol.
The method for recovering catechol according to claim 17, wherein when the solvent is ethanol and the concentration is greater than 50%, the step further comprises:

Mixing the washing mother liquor directly with the reaction liquid;

Rectifying the mixed reaction liquid to recover the ethanol and the rectified reaction liquid; and

The reaction liquid after the rectification is crystallized to recover the catechol and obtain ethyl guaiacol.
The method for recovering catechol according to any one of claims 16-19, wherein the temperature of the solvent washing does not exceed the crystallization end temperature.
The method for recovering catechol according to claim 20, wherein the end temperature of the crystallization is 0°C-50°C.
The method for recovering catechol according to claim 1, characterized in that the content of the finished catechol product obtained by performing the purification treatment on the crude catechol solid is not less than 98%, The content of the o-ethoxyphenol is not more than 1% and the content of a single impurity in the other impurities is not more than 0.2%.