2, 5-dihydroxy terephthalic acid and synthesis method thereof

Abstract

The invention provides 2, 5-dihydroxyterephthalic acid and a synthetic method thereof, and the synthetic method comprises the following steps: obtaining raw materials including potassium formate, hydroquinone and potassium carbonate, adding the potassium formate into a reaction kettle, heating to a preset temperature range, and stirring for melting; after the potassium formate is completely molten, adding the hydroquinone and potassium carbonate, and controlling the molar ratio of the hydroquinone to the potassium carbonate to be within a preset range; continuously heating and stirring to enable the reaction temperature to reach a preset temperature, starting to introduce CO2 gas, and controlling the introduction flow of CO2 to be within a preset range; judging whether the reaction is finished or not according to the curing degree of the feed liquid on the wall of the reaction kettle, and controlling the reaction time within a preset range; adding water, stirring and dissolving the condensate, adjusting the pH to a preset range by using an acid solution, separating out a solid, and filtering to obtain a crude product; adjusting the pH value of the filtrate to a preset range by using an acid solution, separating out a solid, filtering to obtain a filter cake, and repeating the alkali dissolution and acid precipitation step for preset times.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical industry, in particular to a method for synthesizing 2,5-dihydroxyterephthalic acid. Background Art

[0002] The synthesis of 2,5-dihydroxyterephthalic acid (2,5-dihydroxyterephthalic acid) presents a key technical challenge. When the reactor temperature reaches 200°C and CO2 gas is introduced, the viscosity of the reaction system increases dramatically, resulting in a decrease in stirring efficiency. This not only affects the dispersion and dissolution of the CO2 but can also cause local overheating and trigger side reactions. Furthermore, since the degree of solidification of the liquid on the reactor walls is difficult to accurately determine, determining the reaction endpoint is uncertain, potentially leading to incomplete or overreaction. Furthermore, the subsequent purification process requires multiple repetitions of the alkaline dissolution and acid precipitation steps, increasing production costs and extending the production cycle. Controlling the amount and contact time of activated carbon in the activated carbon decolorization process to avoid adsorption losses is also a challenging issue. Finally, in the drying process, improving drying efficiency and reducing energy consumption while ensuring product quality are also pressing technical challenges. Addressing these issues is crucial for improving the purity and yield of 2,5-dihydroxyterephthalic acid. Summary of the Invention

[0003] The present invention provides a method for synthesizing 2,5-dihydroxyterephthalic acid, which mainly comprises:

[0004] Obtaining raw materials including potassium formate, hydroquinone and potassium carbonate, adding the potassium formate into a reaction kettle and heating the kettle to a predetermined temperature range and stirring to melt;

[0005] After the potassium formate is completely melted, adding the hydroquinone and potassium carbonate, and controlling the molar ratio of the hydroquinone to potassium carbonate to be within a preset range;

[0006] By continuing to heat and stir, the reaction temperature reaches a predetermined temperature, and CO2 gas is introduced, and the flow rate of CO2 is controlled within a preset range;

[0007] According to the solidification degree of the liquid on the wall of the reactor, the reaction is judged to be complete and the reaction time is controlled within the preset range;

[0008] The solid was dissolved by adding water and stirring, and then the pH was adjusted to a preset range with an acid solution, and the solid was precipitated and filtered to obtain a crude product;

[0009] dissolving the crude product by adjusting the pH to a preset range with an alkaline solution, adding activated carbon for decolorization, and filtering afterward, wherein the alkaline solution is at least one of aqueous ammonia, aqueous sodium carbonate, or aqueous sodium sulfite solution;

[0010] The filtrate is adjusted to a preset pH range with an acid solution to precipitate solids and filter to obtain a filter cake, and the alkaline dissolution and acid precipitation steps are repeated for a preset number of times;

[0011] The filter cake is treated by vacuum drying or low-temperature drying to obtain a 2,5-dihydroxyterephthalic acid product with a purity not lower than a preset value and a yield not lower than a preset value.

[0012] The technical solution provided by the embodiment of the present invention may have the following beneficial effects:

[0013] The present invention discloses an efficient synthesis method for 2,5-dihydroxyterephthalic acid. The method achieves high purity and high yield of the product by precisely controlling the reaction conditions, including temperature, raw material ratio and CO2 flow rate. During the reaction process, the present invention innovatively uses the solidification degree of the liquid on the wall of the reactor to judge the reaction endpoint, effectively avoiding the problem of insufficient or excessive reaction. In the subsequent purification process, the method of alternating acid and alkali to adjust the pH value is combined with activated carbon decolorization to further improve the purity of the product. Finally, vacuum drying or low-temperature drying treatment is used to ensure the quality of the final product. This method not only simplifies the synthesis process, but also significantly improves the production efficiency and quality of 2,5-dihydroxyterephthalic acid, providing a cost-effective and practical preparation technology for related industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The present invention is a flow chart of a method for synthesizing 2,5-dihydroxyterephthalic acid. DETAILED DESCRIPTION

[0015] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0016] like Figure 1 The synthesis method of 2,5-dihydroxyterephthalic acid in this embodiment may specifically include:

[0017] Step S101: obtaining raw materials including potassium formate, hydroquinone and potassium carbonate, adding the potassium formate into a reactor and heating the reactor to a predetermined temperature range and stirring to melt the reactor.

[0018] Obtain raw materials including potassium formate, hydroquinone, and potassium carbonate, and record their quality and status information. Add potassium formate to a reactor, set the temperature of the heating device to 165-168°C, and start the stirring device. Determine whether the potassium formate is completely melted. If so, add hydroquinone and potassium carbonate. Adjust the temperature of the heating device to 200°C, start the carbon dioxide gas supply, and set the flow rate to 10 L / min. Monitor the state of the materials in the reactor to determine whether the materials are completely solidified and adhere to the reactor wall. If the reaction is complete, turn off the carbon dioxide gas supply and start the cooling device to reduce the temperature to below 100°C. Add water to the reactor, adjust the acid solution according to the dissolution of the materials, and adjust the pH value to precipitate solids. Filter the precipitated solids to obtain a crude product, and record the quality and morphology of the crude product. Refine the crude product by adding water and a weak base to adjust the pH value to 8-9. Decolorize with activated carbon. After filtering, adjust the pH value to 1-2 to obtain the final product and record its quality and morphology information.

[0019] In step S102, after the potassium formate is completely melted, the hydroquinone and potassium carbonate are added, and the molar ratio of the hydroquinone to the potassium carbonate is controlled to be within a preset range.

[0020] According to the settings, a melting state monitoring signal of potassium formate is obtained. The melting state monitoring signal is used to determine whether the potassium formate is completely melted. If it is determined that the potassium formate is completely melted, a preset molar ratio range of hydroquinone to potassium carbonate is obtained. Based on the molar ratio range, the feed mass of hydroquinone and potassium carbonate is calculated. The feed mass is used to determine the feed amount of hydroquinone and potassium carbonate. The feed amount is used to control the order and rate of addition of hydroquinone and potassium carbonate. Based on the addition order and rate, the mixing uniformity of the reaction system is monitored. The mixing uniformity is used to determine whether the reaction system has reached the pre-reaction state. If the reaction system has reached the pre-reaction state, a reaction start signal is obtained.

[0021] Step S103, by continuing to heat and stir, the reaction temperature reaches a predetermined temperature, CO2 gas is introduced, and the flow rate of the CO2 is controlled to be within a preset range.

[0022] Measure the initial temperature inside the reactor and generate current temperature data. Compare the current temperature with the preset reaction temperature of 200°C to generate a temperature difference. If the temperature difference is greater than zero, adjust the heating power and generate a heating control signal. Based on the heating control signal, heat and stir the reactor to generate heating data. Monitor the temperature inside the reactor and generate real-time temperature data. When the real-time temperature data reaches the preset reaction temperature of 200°C, a temperature compliance signal is generated. Based on the temperature compliance signal, initiate the CO2 gas supply and generate a gas supply signal. Monitor the CO2 gas flow rate and generate flow monitoring data. Adjust the CO2 gas flow rate to the preset range of 10L / min to generate a flow control signal.

[0023] Step S104: judging whether the reaction is finished according to the solidification degree of the liquid on the wall of the reactor, and controlling the reaction time within a preset range.

[0024] A temperature sensor is used to monitor the temperature inside the reactor in real time to obtain temperature data during the reaction process. Based on the preset reaction temperature of 200°C, determine whether the temperature has reached the set value. If the temperature reaches 200°C, start the gas flow meter to monitor the CO2 flow and obtain CO2 flow data. Use a timer to record the reaction time and obtain reaction time data. Use a visual sensor to collect the image of the slurry on the reactor wall to obtain the slurry status information. Use an image analysis algorithm to process the slurry image to determine whether the slurry is completely solidified. If the slurry is completely solidified, combined with the reaction time data, determine whether the reaction time is within the range of 6-7 hours. If the reaction time is within the preset range, stop the timer and CO2 injection. According to the reaction end signal, control the cooling system to reduce the reactor temperature to below 100°C.

[0025] Step S105 , adding water and stirring to dissolve the solidified material, then adjusting the pH to a preset range with an acid solution, filtering to obtain a crude product after solid precipitation.

[0026] Obtain a liquid in which the solidified material is cooled to below 100°C and record the liquid temperature. Use water to mix and stir the liquid to dissolve the solidified material to generate a mixed liquid. Obtain the pH value of the mixed liquid and set the target pH range to 1-2. Use an acid solution to adjust the pH value of the mixed liquid. When the pH value reaches the set range, stop adjusting the acid solution. Precipitate the solid in the mixed liquid, observe the solid formation, and generate a suspension. Use a filtration device to filter the suspension, collect the filter cake, and obtain the crude product. Measure the mass of the crude product and record the crude product weight data. Obtain a solution after the crude product is dissolved in water, add ammonia water to adjust the pH value to 8-9, and generate an alkaline solution. Use activated carbon to decolorize the alkaline solution, filter the decolorized solution, and obtain a refined filtrate.

[0027] Step S106, dissolving the crude product by adjusting the pH to a preset range with an alkaline solution, adding activated carbon for decolorization, and filtering. The alkaline solution is at least one of aqueous ammonia, aqueous sodium carbonate solution, or aqueous sodium sulfite solution.

[0028] Obtain the solution after the crude product is dissolved and measure the initial pH value of the solution. Based on the initial pH value, calculate the required amount of alkaline solution to be added so that the pH value of the solution reaches the preset range of 8-9. Use at least one of ammonia water, sodium carbonate aqueous solution or sodium sulfite aqueous solution and gradually add it to the solution. Monitor the changes in the pH value of the solution to determine whether it reaches the preset pH range. If the pH value does not reach the preset range, continue to add an appropriate amount of alkaline solution until the pH value reaches 8-9. After reaching the preset pH value, heat the solution to the set temperature to accelerate the dissolution process. Add an appropriate amount of activated carbon to the heated solution for decolorization. Filter the decolorized solution to remove the activated carbon and other insoluble matter. Collect the filtrate, measure the transparency and color of the filtrate, and determine the decolorization effect.

[0029] Step S107: adjusting the pH of the filtrate to a preset range with an acid solution to precipitate solids and filtering to obtain a filter cake, and repeating the alkaline dissolution and acid precipitation steps for a preset number of times.

[0030] Perform a pH test on the filtrate to obtain the current pH value. Compare the current pH value with the preset pH range to determine whether acid solution adjustment is needed. Based on the comparison results, add a quantitative acid solution to the filtrate to adjust the pH to the preset range. Observe the precipitation of solids in the filtrate to determine whether the solids have been completely precipitated. Use a filter to filter the filtrate to separate the solid filter cake. Mix the filter cake with an appropriate amount of water and adjust the pH to 8-9 with ammonia water to completely dissolve the filter cake. Add activated carbon to the dissolved solution to remove impurities in the solution. Filter the solution to remove the activated carbon and impurities. Add an acid solution to the filtered solution and adjust the pH to 1-2 to precipitate the solid again.

[0031] Step S108: vacuum drying or low-temperature drying is performed on the filter cake to obtain a 2,5-dihydroxyterephthalic acid product with a purity not lower than a preset value and a yield not lower than a preset value.

[0032] Obtain the initial humidity value of the filter cake and use a humidity sensor to detect the moisture content of the filter cake. Set a preset humidity and preset purity, and select an appropriate drying method based on the preset humidity values. If the humidity value of the filter cake is higher than the preset humidity, use vacuum drying, controlling the temperature to 50°C and the pressure to -0.095 MPa. If the humidity value of the filter cake is lower than or equal to the preset humidity, use low-temperature drying, controlling the temperature to 30°C. Monitor humidity changes during the drying process in real time, and use a humidity sensor to continuously detect the moisture content of the filter cake. Terminate the drying process when the humidity reaches the preset humidity value during the drying process. Detect the purity of the dried filter cake and use a liquid chromatograph to analyze the 2,5-dihydroxyterephthalic acid content in the filter cake. If the purity of the filter cake is lower than the preset purity, repeat the drying process and adjust the drying parameters. If the purity of the filter cake reaches or exceeds the preset purity, terminate the process and obtain the final product.

[0033] A 2,5-dihydroxyterephthalic acid is prepared by the above method.

[0034] The synthetic route is:

[0035]

[0036] In a specific embodiment, 30 g of potassium formate is added to a 250 ml four-necked flask, and the oil bath is heated to (165-168 ° C) and stirred to melt. After the potassium formate is completely dissolved, 10 g of hydroquinone and 15.2 g of potassium carbonate are added, and the temperature is continued to be raised and stirred. When T = 200 ° C, CO2 is started at a flow rate of 10 L / min. The temperature is controlled and the reaction is carried out until the feed liquid in the system sticks to the wall of the reactor and is completely solidified. The reaction is then terminated (a total of 7-8 hours). The CO2 is stopped, and the temperature is cooled to below 100 ° C. After adding water and stirring to dissolve, acid is added to precipitate the solid, and 21.74 g of the crude product is obtained by filtration.

[0037] Refining: Add 500 ml of water to the crude product and adjust the pH to 8-9 with aqueous ammonia to dissolve completely (heating may be appropriate). Add an appropriate amount of activated carbon for decolorization and filter. Adjust the filtrate to pH 1-2 with hydrochloric acid to remove the precipitated solid and filter to obtain a filter cake. Wash and slurry the filter cake to yield 19.27 g. Dry and dry to yield 15.0 g of a yellow-green solid, for a yield of 83.3%.

[0038] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the principles of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A method for synthesizing 2,5-dihydroxyterephthalic acid, characterized in that: The method comprises: Obtaining raw materials including potassium formate, hydroquinone and potassium carbonate, adding the potassium formate into a reaction kettle and heating the kettle to a predetermined temperature range and stirring to melt; After the potassium formate is completely melted, adding the hydroquinone and potassium carbonate, and controlling the molar ratio of the hydroquinone to potassium carbonate to be within a preset range; By continuing to heat and stir, the reaction temperature reaches a predetermined temperature, and CO2 gas is introduced, and the flow rate of the CO2 is controlled within a preset range; According to the solidification degree of the liquid on the wall of the reactor, the reaction is judged to be complete and the reaction time is controlled within the preset range; The solid was dissolved by adding water and stirring, and then the pH was adjusted to a preset range with an acid solution. After the solid was precipitated, it was filtered to obtain a crude product; dissolving the crude product by adjusting the pH to a preset range with an alkaline solution, adding activated carbon for decolorization, and filtering afterward, wherein the alkaline solution is at least one of aqueous ammonia, aqueous sodium carbonate, or aqueous sodium sulfite solution; The filtrate is adjusted to a preset pH range with an acid solution to precipitate solids and filter to obtain a filter cake, and the alkaline dissolution and acid precipitation steps are repeated for a preset number of times; The filter cake is treated by vacuum drying or low-temperature drying to obtain a 2,5-dihydroxyterephthalic acid product.

2. The method according to claim 1, characterized in that The step of obtaining raw materials including potassium formate, hydroquinone, and potassium carbonate, adding the potassium formate into a reaction kettle, heating the reaction kettle to a predetermined temperature range, and stirring to dissolve the mixture comprises: Obtain raw materials including potassium formate, hydroquinone and potassium carbonate, and record their quality and status information; Add potassium formate to the reactor, set the temperature of the heating device to 165-168°C, and start the stirring device; Determine whether potassium formate is completely melted. If so, add hydroquinone and potassium carbonate. Adjust the temperature of the heating device to 200°C, start the carbon dioxide gas supply, and set the flow rate to 10L / min; Monitor the state of the material in the reactor to determine whether the material is completely solidified and adheres to the reactor wall; If the reaction is complete, shut off the carbon dioxide gas supply and start the cooling device to reduce the temperature to below 100°C; Add water to the reactor, adjust the acid solution according to the dissolution of the material, and adjust the pH value to precipitate the solid; Filter the precipitated solid to obtain a crude product, and record the quality and morphology of the crude product; The crude product was refined, water and weak base were added to adjust the pH value to 8-9, activated carbon was used for decolorization, and the pH value was adjusted to 1-2 after filtration to obtain the final product and record its quality and morphology information.

3. The method according to claim 1, characterized in that After the potassium formate is completely melted, the hydroquinone and potassium carbonate are added, and the molar ratio of the hydroquinone to the potassium carbonate is controlled to be within a preset range, comprising: According to the setting, a monitoring signal of the melting state of potassium formate is obtained; Use the melting state monitoring signal to determine whether potassium formate is completely melted; If it is determined that the potassium formate is completely melted, obtaining a preset molar ratio range of hydroquinone to potassium carbonate; Calculate the feed mass of hydroquinone and potassium carbonate according to the molar ratio range; The feed amounts of hydroquinone and potassium carbonate are determined by feed mass; The addition order and rate of hydroquinone and potassium carbonate are controlled by the feed amount; Monitor the mixing uniformity of the reaction system based on the order and rate of addition; Use mixing uniformity to determine whether the reaction system has reached the pre-reaction state; If the reaction system reaches the pre-reaction state, a reaction start signal is obtained.

4. The method according to claim 1, wherein The step of continuing to heat and stir until the reaction temperature reaches a predetermined temperature, starting to introduce CO2 gas, and controlling the introduction flow rate of the CO2 to be within a preset range comprises: Measure the initial temperature in the reactor and generate current temperature data; Compare the current temperature with the preset reaction temperature of 200°C to generate a temperature difference; If the temperature difference is greater than zero, the heating power is adjusted to generate a heating control signal; According to the heating control signal, the temperature of the stirred reactor is increased to generate temperature increase data; Monitor the temperature inside the reactor and generate real-time temperature data; When the real-time temperature data reaches the preset reaction temperature of 200°C, a temperature reaching standard signal is generated; According to the temperature reaching standard signal, start CO2 gas supply and generate gas supply signal; Monitor CO2 gas flow and generate flow monitoring data; Adjust the CO2 gas flow rate to the preset range of 10L / min and generate a flow control signal.

5. The method according to claim 1, wherein The method of judging whether the reaction is completed based on the solidification degree of the liquid on the wall of the reactor and controlling the reaction time within a preset range includes: Use temperature sensors to monitor the internal temperature of the reactor in real time and obtain temperature data during the reaction process; According to the preset reaction temperature of 200℃, determine whether the temperature reaches the set value; If the temperature reaches 200°C, start the gas flow meter to monitor the CO2 flow and obtain CO2 flow data; A timer was used to record the reaction time and obtain reaction time data; The image of the liquid on the wall of the reactor is collected by a visual sensor to obtain the liquid state information; Use image analysis algorithms to process the liquid image to determine whether the liquid is completely solidified; If the liquid is completely solidified, combine the reaction time data to determine whether the reaction time is within the range of 6-7 hours; If the reaction time is within the preset range, stop the timer and CO2 injection; According to the reaction end signal, the cooling system is controlled to reduce the temperature of the reactor to below 100°C.

6. The method according to claim 1, characterized in that The method comprises adding water and stirring to dissolve the solidified material, adjusting the pH to a preset range with an acid solution, filtering the precipitated solid to obtain a crude product, and comprising: Get the liquid after the solidified material is cooled to below 100°C and record the liquid temperature; Mixing and stirring water and liquid to dissolve the solidified material and generate a mixed liquid; Obtain the pH value of the mixed solution and set the target pH range to 1-2; The pH value of the mixed solution is adjusted using an acid solution, and when the pH value reaches the set range, the adjustment of the acid solution is stopped; Separate the solids from the mixed solution, observe the solid formation, and generate a suspension; Filter the suspension using a filtering device, collect the filter cake, and obtain the crude product; Measure the mass of the crude product and record the crude product weight data; Obtain a solution after dissolving the crude product in water, and add ammonia water to adjust the pH value to 8-9 to generate an alkaline solution; The alkaline solution is decolorized by using activated carbon, and the decolorized solution is filtered to obtain a refined filtrate.

7. The method according to claim 1, characterized in that The crude product is dissolved by adjusting the pH to a preset range with an alkaline solution, and then filtered after adding activated carbon for decolorization, wherein the alkaline solution is at least one of aqueous ammonia, aqueous sodium carbonate solution or aqueous sodium sulfite solution, comprising: Obtain the solution after the crude product is dissolved and measure the initial pH value of the solution; Based on the initial pH value, calculate the amount of alkaline solution required to make the solution pH reach the preset range of 8-9; At least one of aqueous ammonia and aqueous sodium carbonate or aqueous sodium sulfite solution is gradually added to the solution; Monitor the pH value of the solution to determine whether it reaches the preset pH range; If the pH value does not reach the preset range, continue to add appropriate amount of alkaline solution until the pH value reaches 8-9; After reaching the preset pH value, the solution is heated to the set temperature to accelerate the dissolution process; Add an appropriate amount of activated carbon to the heated solution for decolorization; Filter the decolorized solution to remove activated carbon and other insoluble matter; Collect the filtrate, measure the transparency and color of the filtrate, and determine the decolorization effect.

8. The method according to claim 1, characterized in that The filtrate is adjusted to a pH within a preset range with an acid solution to precipitate solids and filter to obtain a filter cake, and the alkali dissolution and acid precipitation steps are repeated for a preset number of times, comprising: Conduct pH test on the filtrate to obtain the current pH value; Compare the current pH value with the preset pH range to determine whether acid solution adjustment is needed; According to the comparison results, a quantitative acid solution is added to the filtrate to adjust the pH to a preset range; Observe the precipitation of solids in the filtrate to determine whether the solids have been completely precipitated; The filtrate is filtered using a filter to separate the solid filter cake; Mix the filter cake with an appropriate amount of water and adjust the pH to 8-9 with ammonia water to completely dissolve the filter cake; Add activated carbon to the dissolved solution to remove impurities in the solution; Filter the solution to remove activated carbon and impurities; Acid solution was added to the filtered solution to adjust the pH to 1-2, so that the solid was precipitated again.

9. The method according to claim 1, characterized in that The method of treating the filter cake by vacuum drying or low-temperature drying to obtain a 2,5-dihydroxyterephthalic acid product comprises: Obtaining a 2,5-dihydroxyterephthalic acid product with a purity not lower than a preset value and a yield not lower than a preset value, Obtain the initial humidity value of the filter cake and use a humidity sensor to detect the moisture content of the filter cake; Set the preset humidity and preset purity, and select the appropriate drying method according to the preset humidity value; The humidity value of the filter cake is higher than the preset humidity, so it is vacuum dried with the temperature controlled at 50°C and the pressure at -0.095MPa; The humidity value of the filter cake is lower than or equal to the preset humidity, and low-temperature drying is adopted, with the temperature controlled at 30°C; Real-time monitoring of humidity changes during the drying process, using humidity sensors to continuously detect the moisture content of the filter cake; When the humidity reaches the preset humidity value during the drying process, the drying process is terminated; The purity of the dried filter cake was tested and the 2,5-dihydroxyterephthalic acid content in the filter cake was analyzed using a liquid chromatograph; If the purity of the filter cake is lower than the preset purity, re-dry it and adjust the drying parameters; When the purity of the filter cake reaches or exceeds the preset purity, the treatment process is terminated and the final product is obtained.

10. A 2,5-dihydroxyterephthalic acid, characterized in that The method according to any one of claims 1 to 9 is used for preparation.

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