A method for synthesizing high-purity 4-propylphenol

Abstract

The application discloses a synthesis method of high-purity 4-propylphenol and belongs to the field of chemical synthesis. The synthesis method is as follows: 4-allyl-2,6-di-tert-butylphenol is dissolved in an organic solvent, and an olefin hydrogenation reaction is carried out under the action of a hydrogenation catalyst and hydrogen to obtain 4-propyl-2,6-di-tert-butylphenol; and the 4-propyl-2,6-di-tert-butylphenol is heated and reacted with an acidic compound to remove the tert-butyl group, so as to obtain 4-propylphenol. The synthesis process is simple, the reaction condition is mild, the post-treatment is simple, the yield is high, the product purity is high, and the method is suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis technology, and more specifically to a method for synthesizing high-purity 4-propylphenol. Background Technology

[0002] In recent years, with the rapid development of technology, people's requirements for liquid crystal displays have been continuously increasing, and liquid crystal materials used for displays have received widespread attention from researchers. Liquid crystal materials have expanded from the initial alkylphenol ester structure to various structures such as alkylcyclohexyl (biphenyl) compounds and fluorine-containing compounds. Among them, 4-propylphenol, as one of the compounds of 4-alkylphenol, is a very important liquid crystal material and intermediate.

[0003] Currently, there are various methods for synthesizing 4-propylphenol, but they all have certain drawbacks. For example, using acylphenol as a raw material and employing the direct reduction method with zinc amalgam and hydrochloric acid, although the product purity is high, it causes serious environmental pollution; the synthesis method using alkylbenzene oxidation is costly and not conducive to industrial production; the Friedel-Crafts alkylation method using alcohols, haloalkanes, or alkenes with phenol (CN1681758, CN1504445) results in low product purity due to alkyl rearrangement and ortho-byproducts; the method using anisole as a raw material, reacting with n-alkylacyl chloride to generate p-n-acylanisole, and then reducing it with hydrazine hydrate to obtain alkylphenol uses a ferric oxide-sulfuric acid solid superacid catalyst, resulting in high production costs, and hydrazine hydrate is a strong base, corrosive, and poses safety hazards (CN101381285).

[0004] Therefore, providing a reaction with good selectivity, high yield, high purity, low cost, and applicability to actual industrial production is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a method for synthesizing high-purity 4-propylphenol, which uses 4-allyl-2,6-di-tert-butylphenol as a raw material and prepares 4-propylphenol through a two-step reaction. This synthesis method has good reaction selectivity, high yield, high purity and low cost in the production process, and can be applied to actual industrial production.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for synthesizing high-purity 4-propylphenol specifically includes the following steps: S1, 4-allyl-2,6-di-tert-butylphenol, organic solvent 1, and catalyst are added to a reaction vessel to replace the air in the reaction vessel and to introduce hydrogen gas for hydrogenation reaction; after the reaction is completed, the mixture is filtered, the filter residue is washed, the filtrate and washing liquid are mixed, and the solvent and washing agent are removed by distillation to obtain 4-propyl-2,6-di-tert-butylphenol. S2: The 4-propyl-2,6-di-tert-butylphenol obtained in S1 is mixed with an acidic compound and organic solvent 2 and heated under reflux under nitrogen protection. After the reaction is complete, the organic solvent 2 is removed by vacuum distillation to obtain the crude product. The crude product is then recrystallized from ethanol to obtain 4-propylphenol.

[0008] The chemical reaction equation is as follows:

[0009] The mass ratio of organic solvent 1 to 4-allyl-2,6-di-tert-butylphenol in S1 is 5~10:1, and the mass ratio of catalyst to 4-allyl-2,6-di-tert-butylphenol is 1~10:100. The air in the displacement reactor is replaced three times with nitrogen and three times with hydrogen, with a displacement pressure of 1 MPa for each replacement.

[0010] The hydrogen pressure for filling the gas as described in S1 is 0.1 MPa to 10 MPa.

[0011] Its beneficial effects are: by selecting the above pressure conditions, the required amount of hydrogen gas during the reaction process is guaranteed, thus ensuring the forward reaction.

[0012] The hydrogenation reaction described in S1 has a reaction temperature of 50℃~150℃ and a reaction time of 2-24h.

[0013] The beneficial effects are as follows: selecting the above temperature range satisfies the energy required for the reaction while preventing excessively high temperatures that could exacerbate side reactions. If the temperature is too low, the reaction rate will slow down, affecting the hydrogenation effect; if the temperature is too high, it will lead to over-reaction and the production of unnecessary byproducts. Selecting the above time range allows the reactants to react completely and inhibits the generation of side reactions.

[0014] The washing methanol or ethanol described in S1; The organic solvent 1 is one or a combination of methanol, ethanol, isopropanol, N,N-dimethylformamide, and N,N-dimethylacetamide; The catalyst is a Raney-type catalyst and / or a transition metal supported catalyst; The Raney-type catalyst is one or a combination of Raney nickel, Raney cobalt, Raney palladium, and Raney copper; the transition metal supported catalyst is one or a combination of palladium / carbon, platinum / carbon, palladium / barium sulfate, nickel / alumina, platinum / alumina, palladium / iron tetroxide, nickel-copper / alumina, rhodium / silica, and platinum-rhodium / alumina.

[0015] The acidic compound described in S2 is one or a combination of more of the following: methanesulfonic acid, p-toluenesulfonic acid, and trifluoromethanesulfonic acid.

[0016] The organic solvent 2 is one or a combination of xylene, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, chlorobenzene, butanol, pentanol, and hexanol.

[0017] The amount of the acidic compound is 5% to 20% of the mass of 4-allyl-2,6-di-tert-butylphenol in S1, and the amount of the organic solvent 2 is 5 to 10 times the mass of 4-allyl-2,6-di-tert-butylphenol in S1. The heating reflux temperature is 100℃~160℃, and the time is 5h.

[0018] The effects and advantages of this invention are as follows: (1) Synthesis technology: catalytic hydrogenation reaction is used to ensure high selectivity while reducing the occurrence of side reactions, reducing the generation of waste, and maintaining environmental friendliness; (2) Economic cost: Using a solid acid catalyst for the detert-butylation reaction avoids the high cost problem caused by the use of rare special catalysts, and the reaction is easy to carry out, which has significant economic benefits. (3) Product quality: The product obtained by the present invention through two-step reaction has a purity of up to 99% and can be directly put into subsequent use without worrying about introducing other impurities. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0020] Figure 1 The attached figure shows the hydrogen NMR spectrum of the product prepared in Example 4 of this invention.

[0021] Figure 2 The attached figure is a gas chromatogram of the product prepared in Example 4 of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1 (1) 4-Allyl-2,6-di-tert-butylphenol (25g, 0.1mol), anhydrous ethanol (200g), and Raney nickel (0.25g) were put into a high-pressure reactor. Nitrogen gas was introduced into the reactor for three purgings, followed by hydrogen gas for three purgings at a pressure of 1MPa. Then hydrogen gas (2MPa) was introduced and the temperature was raised to 70°C under stirring. The reaction was kept at this temperature for 6 hours. After the reaction was completed, the reaction solution was filtered. The filter residue was washed twice with a small amount of ethanol. The filtrate and washing liquid were combined and the ethanol solvent was removed by distillation. The residue was kept for later use.

[0024] (2) Add the residue obtained in step (1) to a flask, then add methanesulfonic acid (1.25 g) and n-butanol (200 g), reflux at 100 °C for 5 h under nitrogen protection, distill under reduced pressure to obtain crude product, add 50 g of ethanol for recrystallization to obtain 10.5 g of 4-propylphenol with a selectivity of 90%, a yield of 77.1% and a purity of 96.32%.

[0025] Example 2: (1) 4-Allyl-2,6-di-tert-butylphenol (25g, 0.1mol), anhydrous methanol (200g), and palladium / carbon catalyst (0.75g) were put into a high-pressure reactor. Nitrogen gas was introduced into the reactor for three purgings, followed by hydrogen gas for three purgings at a pressure of 1MPa. Then hydrogen gas (3MPa) was introduced and the temperature was raised to 50°C under stirring. The reaction was kept at this temperature for 10h. After the reaction was completed, the reaction solution was filtered. The filter residue was washed twice with a small amount of methanol. The filtrate and washing liquid were combined and distilled to remove the methanol solvent. The residue was kept for later use.

[0026] (2) Add the residue obtained in step (1) to a flask, then add p-toluenesulfonic acid (2.5 g) and xylene (200 g), reflux at 130 °C for 5 h under nitrogen protection, distill under reduced pressure to obtain crude product, add 50 g of ethanol for recrystallization to obtain 11.4 g of 4-propylphenol with a selectivity of 95%, a yield of 83.7% and a purity of 98.74%.

[0027] Example 3: (1) 4-Allyl-2,6-di-tert-butylphenol (20g, 0.08mol), isopropanol (200g), and platinum / carbon catalyst (1.0g) were put into a high-pressure reactor. Nitrogen gas was introduced into the reactor for three purgings, followed by hydrogen gas for three purgings at a pressure of 1MPa. Then hydrogen gas (3MPa) was introduced and the temperature was raised to 75°C under stirring. The reaction was kept at this temperature for 2h. After the reaction was completed, the reaction solution was filtered. The filter residue was washed twice with a small amount of methanol. The filtrate and washing liquid were combined and distilled to remove methanol and isopropanol solvents. The residue was kept for later use.

[0028] (2) Add the residue obtained in step (1) to a flask, then add trifluoromethanesulfonic acid (4.0 g) and dimethyl sulfoxide (200 g), reflux at 160 °C for 5 h under nitrogen protection, distill under reduced pressure to obtain crude product, add 40 g of ethanol for recrystallization to obtain 9.6 g of 4-propylphenol with a selectivity of 98%, a yield of 88.1% and a purity of 99.16%.

[0029] Example 4: (1) 4-Allyl-2,6-di-tert-butylphenol (20g, 0.08mol), N,N-dimethylformamide (200g), and palladium / barium sulfate catalyst (2.0g) were put into a high-pressure reactor. Nitrogen gas was introduced into the reactor for three purgings, followed by hydrogen gas for three purgings at a pressure of 1MPa. Then hydrogen gas (10MPa) was introduced and the temperature was raised to 100℃ under stirring. The reaction was kept at this temperature for 12h. After the reaction was completed, the reaction solution was filtered. The filter residue was washed twice with a small amount of methanol. The filtrate and washing liquid were combined and distilled to remove methanol and N,N-dimethylformamide solvent. The residue was kept for later use.

[0030] (2) Add the residue obtained in step (1) to a flask, then add p-toluenesulfonic acid (2.5 g) and N,N-dimethylformamide (200 g), reflux at 140 °C for 5 h under nitrogen protection, distill under reduced pressure to obtain crude product, add 40 g of ethanol for recrystallization to obtain 9.7 g of 4-propylphenol with a selectivity of 96%, a yield of 89.0% and a purity of 99.39%.

[0031] Example 5: (1) 4-Allyl-2,6-di-tert-butylphenol (25g, 0.1mol), N,N-dimethylacetamide (200g), and rhodium / silica catalyst (2.5g) were put into a high-pressure reactor. Nitrogen gas was introduced into the reactor for three purgings, followed by hydrogen gas for three purgings at a pressure of 1MPa. Then hydrogen gas (0.1MPa) was introduced. The temperature was raised to 150℃ under stirring and kept at this temperature for 10h. After the reaction was completed, the reaction solution was filtered. The filter residue was washed twice with a small amount of methanol. The filtrate and washing liquid were combined and distilled to remove methanol and N,N-dimethylacetamide solvent. The residue was kept for later use.

[0032] (2) Add the residue obtained in step (1) to a flask, then add trifluoromethanesulfonic acid (2.5 g) and N,N-dimethylacetamide (200 g), reflux at 150 °C for 5 h under nitrogen protection, distill under reduced pressure to obtain crude product, add 40 g of ethanol for recrystallization to obtain 11.6 g of 4-propylphenol with a selectivity of 95%, a yield of 85.2% and a purity of 98.90%.

[0033] Example 6: (1) 4-Allyl-2,6-di-tert-butylphenol (25g, 0.1mol), isopropanol (125g), and palladium / iron oxide catalyst (2.5g) were put into a high-pressure reactor. Nitrogen gas was introduced into the reactor for three purgings, followed by hydrogen gas for three purgings at a pressure of 1MPa. Then hydrogen gas (2MPa) was introduced and the temperature was raised to 60℃ under stirring. The reaction was kept at this temperature for 24h. After the reaction was completed, the reaction solution was filtered. The filter residue was washed twice with a small amount of methanol. The filtrate and washing liquid were combined and distilled to remove methanol and isopropanol solvents. The residue was kept for later use.

[0034] (2) Add the residue obtained in step (1) to a flask, then add trifluoromethanesulfonic acid (2.5 g) and N,N-dimethylacetamide (150 g), reflux at 130 °C for 5 h under nitrogen protection, distill under reduced pressure to obtain crude product, add 40 g of ethanol for recrystallization to obtain 11.4 g of 4-propylphenol with a selectivity of 95%, a yield of 83.7% and a purity of 99.0%.

[0035] Product structural characterization: The product obtained in Example 4 was subjected to 1H NMR spectroscopy analysis. The resulting 1H NMR spectrum is shown below. Figure 1 Analysis shows that the 1H NMR spectrum of the product obtained in Example 4 corresponds completely with that of 4-propylphenol, indicating that the product generated in this application is 4-propylphenol.

[0036] Similarly, the product obtained in Example 4 was subjected to gas chromatography analysis. The gas chromatogram is shown below. Figure 2As can be seen from the figure, the chromatographic peak that appears at 6.391 minutes is 4-propylphenol. Calculation shows that the purity of 4-propylphenol obtained in Example 4 is 99.39%.

[0037] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0038] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for synthesizing high-purity 4-propylphenol, characterized in that, Specifically, the steps include the following: S1, 4-allyl-2,6-di-tert-butylphenol, organic solvent 1, and catalyst are added to a reaction vessel to replace the air in the reaction vessel and to introduce hydrogen gas for hydrogenation reaction; after the reaction is completed, the mixture is filtered, the filter residue is washed, the filtrate and washing liquid are mixed, and organic solvent 1 and washing agent are removed by distillation to obtain 4-propyl-2,6-di-tert-butylphenol. S2: The 4-propyl-2,6-di-tert-butylphenol obtained in S1 is mixed with an acidic compound and organic solvent 2, and heated under reflux under nitrogen protection to remove the tert-butyl group; after the reaction is complete, organic solvent 2 is removed by vacuum distillation to obtain the crude product, which is then recrystallized from ethanol to obtain 4-propylphenol.

2. The method for synthesizing high-purity 4-propylphenol according to claim 1, characterized in that, The mass ratio of organic solvent 1 to 4-allyl-2,6-di-tert-butylphenol in S1 is 5~10:1, and the mass ratio of catalyst to 4-allyl-2,6-di-tert-butylphenol is 1~10:

100.

3. The method for synthesizing high-purity 4-propylphenol according to claim 1, characterized in that, In the displacement reactor described in S1, the air is replaced three times with nitrogen and three times with hydrogen, with a displacement pressure of 1 MPa for each replacement.

4. The method for synthesizing high-purity 4-propylphenol according to claim 1, characterized in that, The hydrogen pressure for filling the gas as described in S1 is 0.1 MPa to 10 MPa; The hydrogenation reaction is carried out at a temperature of 50℃ to 150℃ and for a time of 2-24 hours. The washing process uses methanol or ethanol.

5. The method for synthesizing high-purity 4-propylphenol according to claim 1, characterized in that, The organic solvent 1 mentioned in S1 is one or a combination of methanol, ethanol, isopropanol, N,N-dimethylformamide, and N,N-dimethylacetamide.

6. The method for synthesizing high-purity 4-propylphenol according to claim 1, characterized in that, The catalyst described in S1 is a Raney type catalyst and / or a transition metal supported catalyst; The Raney-type catalyst is one or a combination of Raney nickel, Raney cobalt, Raney palladium, and Raney copper; The transition metal supported catalyst is one or a combination of multiple of the following: palladium / carbon, platinum / carbon, palladium / barium sulfate, nickel / alumina, platinum / alumina, palladium / ferric oxide, nickel-copper / alumina, rhodium / silica, and platinum-rhodium / alumina.

7. The method for synthesizing high-purity 4-propylphenol according to claim 1, characterized in that, The acidic compound mentioned in S2 is one or a combination of more of the following: methanesulfonic acid, p-toluenesulfonic acid, and trifluoromethanesulfonic acid.

8. The method for synthesizing high-purity 4-propylphenol according to claim 1, characterized in that, The organic solvent 2 mentioned in S2 is one or a combination of xylene, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, chlorobenzene, butanol, pentanol, and hexanol.

9. The method for synthesizing high-purity 4-propylphenol according to claim 1, characterized in that, The amount of the acidic compound in S2 is 5% to 20% of the mass of 4-allyl-2,6-di-tert-butylphenol in S1; the amount of the organic solvent 2 is 5 to 10 times the mass of 4-allyl-2,6-di-tert-butylphenol in S1.

10. The method for synthesizing high-purity 4-propylphenol according to claim 1, characterized in that, The heating reflux temperature described in S2 is 100℃~160℃, and the time is 5h.

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