A method for synthesizing p-hydroxybenzoic acid
By reacting phenol, carbon monoxide and carbonate under the action of alkaline catalysts, the problems of low yield and high cost in the existing technology are solved, and an efficient and environmentally friendly production process is achieved, and large-scale industrialization potential is provided.
Patent Information
- Application Number
- CN202411630173.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-15
- Publication Date
- 2025-06-24
- Estimated Expiration
- 2044-11-15
AI Technical Summary
The industrial production methods of parabenzoic acid in the prior art, such as the Kolbe-Schmitt reaction, have low yields and high costs, making it difficult to meet market demand.
Under the catalytic action of the basic catalyst, phenol, carbon monoxide and carbonate undergo a benzene ring carboxylation reaction to form para-hydroxybenzoic acid. The mass ratio of the catalyst to phenol is between 0.05:1 and 0.5:1, preferably 0.1:1-0.3:1.
The high yield of parabenzoic acid (greater than 85%) has been achieved, the product is easy to separate, has good color, and has few waste emissions, and has the potential for large-scale industrialization.
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Abstract
Description
Technical Field
[0001] The present invention relates to the fields of liquid crystal intermediates and food preservatives, and specifically relates to a synthesis method of p-hydroxybenzoic acid. Background Art
[0002] p-Hydroxybenzoic acid is a widely used organic synthesis raw material. Its main application fields are as preservatives and mold inhibitors in food, cosmetics, and medicine, which can play a role in extending the shelf life of products. In 2023, the total output of the main varieties of food additives in China was about 16 million tons. As an important part of food additives, the market demand for p-hydroxybenzoic acid has increased accordingly. p-Hydroxybenzoic acid is used as a pesticide intermediate for synthesizing insecticides, fungicides, etc. Another important use of p-hydroxybenzoic acid is the synthesis of liquid crystal polymers. The liquid crystal product Xydar is a polymer of p-hydroxybenzoic acid, hydroquinone, and phthalic acid. X-7G is a polymer of p-hydroxybenzoic acid and polyethylene terephthalate in the molten state. Vectra is a molten polymer of p-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid. Tian is a polymer of p-hydroxybenzoic acid, 2-hydroxy-6-naphthoic acid, and hydroquinone. Driven by the downstream market demand, the p-hydroxybenzoic acid market in China has developed rapidly, and the market demand has been increasing.
[0003] The Kolbe–Schmitt reaction (carboxylation of potassium phenoxide and carbon dioxide) is the current industrial production method of p-hydroxybenzoic acid. Only potassium phenoxide can react with carbon dioxide to form p-hydroxybenzoic acid. The product p-hydroxybenzoic acid will react with another molecule of potassium phenoxide to form potassium p-hydroxybenzoate and phenol. Phenol cannot undergo the Kolbe–Schmitt reaction with carbon dioxide. Therefore, the yield of p-hydroxybenzoic acid is less than 50%. Industrially, p-hydroxybenzoic acid can also be obtained from salicylic acid through salification, rearrangement, and neutralization, but the cost is relatively high. Summary of the Invention
[0004] Aiming at the deficiencies of the prior art, the present invention provides a synthesis method of p-hydroxybenzoic acid. This method has a simple process, a high yield of the target product, is easy to separate, and has less waste discharge.
[0005] The object of the present invention is achieved through the following technical solutions: Under the catalytic action of an alkaline catalyst, phenol, carbon monoxide, and carbonate undergo a benzene ring carboxylation reaction to generate p-hydroxybenzoic acid.
[0006] The reaction chemical formula of the present invention is: In the above technical solution, the alkaline catalyst is a biochar-supported copper-magnesium oxide catalyst, and the mass ratio of the catalyst to phenol is 0.05:1 - 0.5:1, preferably 0.1:1 - 0.3:1.
[0007] In the above technical solution, the carbonate is one or more of lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, and magnesium carbonate.
[0008] In the above technical solution, for the biochar-supported copper-magnesium oxide catalyst, the biochar is yeast pyrolysis char; the mass percentage content of copper is 1-7%, preferably 2-5%; the mass percentage content of magnesium is 1-20%, preferably 4-10%.
[0009] In the above technical solution, the molar ratio of phenol to carbonate is 1:1 - 1:2, preferably 1:1 - 1:1.5; the pressure of carbon monoxide is 0.1 - 10 MPa, preferably 0.1 - 5 MPa.
[0010] In the above technical solution, the reaction temperature is 150 - 290 °C, preferably 200 - 280 °C; the reaction time is 2 - 24 h, preferably 6 - 18 h.
[0011] Preparation process of yeast pyrolysis char: In an inert atmosphere, dry yeast powder is pyrolyzed at a temperature of 600 - 1000 °C for 1 - 4 h, preferably 700 - 800 °C, preferably 1 - 2 h; it is ground into powder to obtain yeast biochar. Using the above-prepared yeast biochar as a carrier, active metals are loaded by the impregnation method. Then it is calcined in an air atmosphere at a temperature of 350 - 550 °C for 1 - 4 h, preferably 400 - 500 °C, preferably 1 - 2 h. The soluble copper salt is one or more of copper chloride, copper nitrate, copper sulfate, copper phosphate, or copper acetate; the soluble magnesium salt is one or more of magnesium chloride, magnesium nitrate, magnesium sulfate, magnesium phosphate, or magnesium acetate; the inert atmosphere is one or more of nitrogen or argon;
[0012] Compared with the prior art, the present invention has the following beneficial effects:
[0013] (1) The method of the present invention is different from the Kolbe–Schmitt reaction. The yield of p-hydroxybenzoic acid is 85%, the product is easy to separate, and the color is good; the discharge of three wastes is small, and it has the potential for large-scale industrialization. It can produce p-hydroxybenzoic acid meeting the requirements of liquid crystal grade, and has high social and economic benefits;
[0014] (2) The raw materials of the present invention are cheap and easily available, the process is simple, the target product is convenient to separate, and the yield is high. Specific embodiments
[0015] The technical solution of the present invention is described in detail below with reference to the embodiments, but the scope of the present invention is not limited to the following embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.
[0016] Example 1
[0017] Take 10 g of dry yeast powder in a quartz boat, place the quartz boat in a tube furnace, and pass nitrogen at room temperature for 30 min (gas flow rate is 10 mL / min). Then, while keeping the nitrogen gas flow rate unchanged, heat up to 700 °C (heating rate is 5 °C / min). Still keeping the nitrogen gas flow rate unchanged, after pyrolyzing at 700 °C for 1 h, slowly cool down to 30 °C (cooling rate is 5 °C / min). Grind the black solid in the quartz boat into powder in an agate mortar to obtain biochar support 1 with a mass of 3.7 g.
[0018] Take 10 g of dry yeast powder in a quartz boat, place the quartz boat in a tube furnace, and pass nitrogen at room temperature for 30 min (gas flow rate is 10 mL / min). Then, while keeping the nitrogen gas flow rate unchanged, heat up to 800 °C (heating rate is 5 °C / min). Still keeping the nitrogen gas flow rate unchanged, after pyrolyzing at 800 °C for 1 h, slowly cool down to 30 °C (cooling rate is 5 °C / min). Grind the black solid in the quartz boat into powder in an agate mortar to obtain biochar support 2 with a mass of 3.8 g.
[0019] Dissolve 0.1260 g of copper nitrate and 0.2630 g of magnesium nitrate in 10 mL of deionized water, add 2 g of the above biochar support 1, stir for 12 hours, and filter. The impregnated biochar is dried in a hot oven at 120 °C for 12 hours, then placed in a quartz tube and calcined in air atmosphere at 400 °C for 2 hours, cooled to room temperature, and then ground and sieved to obtain catalyst 1.
[0020] Dissolve 0.1947 g of copper nitrate and 0.8131 g of magnesium nitrate in 10 mL of deionized water, add 2 g of the above biochar support 2, stir for 12 hours, and filter. The impregnated biochar is dried in a hot oven at 120 °C for 12 hours, then placed in a quartz tube and calcined in air atmosphere at 450 °C for 2 hours, cooled to room temperature, and then ground and sieved to obtain catalyst 2.
[0021] Dissolve 0.3472 g of copper nitrate and 1.4504 g of magnesium nitrate in 10 mL of deionized water, add 2 g of the above biochar support 2, stir for 12 hours, and filter. The impregnated biochar is dried in a hot oven at 120 °C for 12 hours, then placed in a quartz tube and calcined in air atmosphere at 500 °C for 2 hours, cooled to room temperature, and then ground and sieved to obtain catalyst 3.
[0022] Example 2
[0023] In a 100 mL high-pressure reactor, 9.4 g of phenol, 0.94 g of catalyst 1 prepared in Example 1, and 13.8 g of potassium carbonate were successively added. The reactor was filled with 0.1 MPa of carbon monoxide. The reaction was carried out at 280 °C for 6 h. After the reaction was completed, it was cooled to room temperature, and the excess carbon monoxide was slowly released. 30 mL of deionized water was added to the reaction system, and the catalyst was recovered by centrifugation. The catalyst was washed 3 times with deionized water (10 mL each time). The aqueous layers were combined, and the pH was adjusted to 3 using 10% sulfuric acid by mass concentration. A white solid was precipitated, and p-hydroxybenzoic acid was obtained by suction filtration, with a yield of 85% (11.73 g, purity: 99.6%).
[0024] Example 3
[0025] In a 100 mL high-pressure reactor, 9.4 g of phenol, 2.82 g of catalyst 2 prepared in Example 1, and 15.9 g of sodium carbonate were successively added. The reactor was filled with 5 MPa of carbon monoxide. The reaction was carried out at 200 °C for 18 h. After the reaction was completed, it was cooled to room temperature, and the excess carbon monoxide was slowly released. 30 mL of deionized water was added to the reaction system, and the catalyst was recovered by centrifugation. The catalyst was washed 3 times with deionized water (10 mL each time). The aqueous layers were combined, and the pH was adjusted to 3 using 10% sulfuric acid by mass concentration. A white solid was precipitated, and p-hydroxybenzoic acid was obtained by suction filtration, with a yield of 86% (11.9 g, purity: 99.5%).
[0026] Example 4
[0027] In a 100 mL high-pressure reactor, 9.4 g of phenol, 1.2 g of catalyst 3 prepared in Example 1, and 8.1 g of lithium carbonate were successively added. The reactor was filled with 0.5 MPa of carbon monoxide. The reaction was carried out at 230 °C for 10 h. After the reaction was completed, it was cooled to room temperature, and the excess carbon monoxide was slowly released. 30 mL of deionized water was added to the reaction system, and the catalyst was recovered by centrifugation. The catalyst was washed 3 times with deionized water (10 mL each time). The aqueous layers were combined, and the pH was adjusted to 3 using 10% sulfuric acid by mass concentration. A white solid was precipitated, and p-hydroxybenzoic acid was obtained by suction filtration, with a yield of 86% (11.9 g, purity: 99.8%).
[0028] Example 5
[0029] In a 100 mL high-pressure reactor, 9.4 g of phenol, 1 g of the catalyst 2 prepared in Example 1, and 8.5 g of magnesium carbonate were added successively. The reactor was filled with 2 MPa of carbon monoxide. The reaction was carried out at 260 °C for 12 h. After the reaction was completed, it was cooled to room temperature, and the excess carbon monoxide was slowly released. 30 mL of deionized water was added to the reaction system, and the catalyst was recovered by centrifugation. The catalyst was washed 3 times with deionized water (10 mL each time). The aqueous layers were combined, and the pH was adjusted to 3 using 10% sulfuric acid by mass concentration, and a white solid was precipitated. p-Hydroxybenzoic acid was obtained by suction filtration, with a yield of 88% (12.2 g, purity: 99.4%).
[0030] Example 6
[0031] In a 100 mL high-pressure reactor, 9.4 g of phenol, 2 g of the catalyst 1 prepared in Example 1, and 33 g of cesium carbonate were added successively. The reactor was filled with 0.2 MPa of carbon monoxide. The reaction was carried out at 210 °C for 8 h. After the reaction was completed, it was cooled to room temperature, and the excess carbon monoxide was slowly released. 30 mL of deionized water was added to the reaction system, and the catalyst was recovered by centrifugation. The catalyst was washed 3 times with deionized water (10 mL each time). The aqueous layers were combined, and the pH was adjusted to 3 using 10% sulfuric acid by mass concentration, and a white solid was precipitated. p-Hydroxybenzoic acid was obtained by suction filtration, with a yield of 92% (12.7 g, purity: 99.7%).
[0032] Example 7
[0033] In a 100 mL high-pressure reactor, 9.4 g of phenol, 2 g of the catalyst 3 prepared in Example 1, and 24 g of rubidium carbonate were added successively. The reactor was filled with 0.1 MPa of carbon monoxide. The reaction was carried out at 150 °C for 24 h. After the reaction was completed, it was cooled to room temperature, and the excess carbon monoxide was slowly released. 30 mL of deionized water was added to the reaction system, and the catalyst was recovered by centrifugation. The catalyst was washed 3 times with deionized water (10 mL each time). The aqueous layers were combined, and the pH was adjusted to 3 using 10% sulfuric acid by mass concentration, and a white solid was precipitated. p-Hydroxybenzoic acid was obtained by suction filtration, with a yield of 93% (12.8 g, purity: 99.7%).
[0034] Example 8
[0035] In a 100 mL high-pressure reactor, 9.4 g of phenol, 2 g of catalyst 1 prepared in Example 1, and 13.8 g of potassium carbonate were successively added. The reactor was filled with 10 MPa of carbon monoxide. The reaction was carried out at 290 °C for 2 h. After the reaction was completed, it was cooled to room temperature, and the excess carbon monoxide was slowly released. 30 mL of deionized water was added to the reaction system, and the catalyst was recovered by centrifugation. The catalyst was washed 3 times with deionized water (10 mL each time). The aqueous layers were combined, and the pH was adjusted to 3 with 10% sulfuric acid by mass concentration to precipitate white solids. The p-hydroxybenzoic acid was obtained by suction filtration with a yield of 91% (12.6 g, purity: 99.6%).
[0036] Comparative Example
[0037] 1. Compared with the Kolbe–Schmitt reaction (Chem. Rev. 1957, 583-620), only potassium phenoxide can react with carbon dioxide in the Kolbe–Schmitt reaction to prepare p-hydroxybenzoic acid, while phenol does not react. The product p-hydroxybenzoic acid will react with potassium phenoxide to form potassium p-hydroxybenzoate and phenol. Therefore, the yield of p-hydroxybenzoic acid is less than 50%. The method disclosed in the present invention is different from the Kolbe–Schmitt reaction. Under the action of a catalyst, phenol directly reacts with potassium carbonate and carbon monoxide to prepare p-hydroxybenzoic acid, and the yield is greater than 85%.
[0038] 2. Compared with the literature reports (Chem. Commun., 2005, 486-488), the present invention has obvious advantages and differences: (1) The present invention does not use noble metal catalysts, with low cost; (2) The product selectivity is greater than 80%, while the selectivity of the literature (Chem.Commun., 2005, 486-488) is only 59%; (3) The present invention does not use oxygen; (4) The noble metal catalyst used in the literature (Chem.Commun., 2005, 486-488) is difficult to recycle and reuse.
[0039] 3. Comparing with the reaction without using a catalyst (the process and conditions are the same as in Example 7, the difference is that no catalyst is added during the reaction), when no catalyst is used, the reaction does not occur.
[0040] 4. Comparing with the results at other reaction temperatures, the reaction temperature of the present invention (150-290 °C) has obvious advantages. When the reaction temperature is lower than 150 °C (the process and conditions are the same as in Example 7, the difference is that the reaction temperature is lower than 140 °C), the product yield is 22%; when the reaction temperature is higher than 290 °C (the process and conditions are the same as in Example 7, the difference is that the reaction temperature is higher than 290 °C), the product yield is 65%, and a large amount of tar is produced.
[0041] 5. Compared with the catalysts prepared using other carriers and other active metals, the catalyst of the present invention has obvious advantages. The catalyst preparation scheme is the same as the preparation method of Catalyst 3 of the present invention, and the difference lies in the types and contents of the carriers or active metals used. The catalytic reaction process and conditions are the same as those in Example 7, and the difference lies in using different catalysts (product yields of different catalysts in Table 1).
[0042] Table 1 Product Yields of Different Catalysts
[0043]
Claims
1. A method for synthesizing p-hydroxybenzoic acid, characterized in that: Under the catalytic action of biochar-supported copper-magnesium oxide catalyst, phenol, carbon monoxide, and carbonate undergo benzene ring carboxylation reaction to produce p-hydroxybenzoic acid. The mass ratio of catalyst to phenol is 0.05:1-0.5:1; The molar ratio of phenol to carbonate is 1:1-1:2, and the pressure of carbon monoxide is 0.1-10MPa; The reaction temperature is 150-290°C, and the reaction time is 2-24h; The biochar is loaded with copper and magnesium oxide catalyst, and the biochar is yeast pyrolysis carbon; the mass percentage of copper is 1-7%; the mass percentage of magnesium is 1-20%.
2. The synthesis method according to claim 1, characterized in that: The biochar-loaded copper-magnesium oxide catalyst has a mass ratio of the catalyst to phenol of 0.1:1-0.3:
1.
3. The synthesis method according to claim 1, characterized in that: The carbonate is one or more of lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate and magnesium carbonate.
4. The synthesis method according to claim 1, characterized in that: The biochar is loaded with copper and magnesium oxide catalyst, and the biochar is yeast pyrolysis carbon; the mass percentage of copper is 2-5%; and the mass percentage of magnesium is 4-10%.
5. The synthesis method according to claim 1 or 3, characterized in that: The molar ratio of phenol to carbonate is 1:1-1:1.
5.
6. The synthesis method according to claim 1, characterized in that: The pressure of carbon monoxide is 0.1-5MPa.
7. The synthesis method according to claim 1, characterized in that: The reaction temperature is 200-280°C; the reaction time is 6-18h.
Citation Information
Patent Citations
Biochar-loaded monatomic catalyst and application thereof in synthesis of quinazoline compounds
CN116037101A