A method for synthesizing p-hydroxybenzonitrile from p-methoxybenzonitrile

Abstract

The application discloses a method for synthesizing p-hydroxybenzonitrile from p-methoxybenzonitrile, which comprises the following steps: carrying out a demethylation reaction of p-methoxybenzonitrile and phenol under alkaline conditions to directly generate the target product p-hydroxybenzonitrile. Different from a high-temperature melting reaction in the prior art, the scheme realizes efficient conversion of raw materials to products through a one-step method, and solves the problems of low purity and low yield of p-methylbenzonitrile caused by low reaction conversion rate in the prior art.

Description

Technical Field

[0001] This invention relates to the field of p-hydroxybenzonitrile synthesis technology, and in particular to a method for synthesizing p-hydroxybenzonitrile using p-methoxybenzonitrile as a raw material. Background Technology

[0002] 4-Cyanophenol is an extremely important fine chemical raw material and intermediate with applications in multiple fields. For example, in pesticides, it is widely used as the organophosphorus insecticides fenitrothion and benzoylphos; it also has broad applications in liquid crystal materials, corrosion inhibitors, and fragrances. There are many methods for its preparation, such as the highly selective catalytic synthesis method for 4-cyanophenol disclosed in the applicant's previous Chinese patent application (publication number CN118851941A). This method uses 4-hydroxybenzoic acid and urea as starting materials, and uses a dehydrating agent and a metal composite catalyst to promote the amidation reaction rate, synthesizing 4-cyanophenol in one step. This is currently the main process for the industrial production of 4-cyanophenol. However, this method requires high temperatures (above 300℃) and sophisticated equipment, and the low material conversion rate results in low purity and yield of the obtained 4-cyanophenol. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a method for synthesizing p-hydroxybenzonitrile from p-methoxybenzonitrile, which solves the problem that the low reaction conversion rate in existing technologies leads to low purity and yield of the obtained p-methylbenzonitrile.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for synthesizing p-hydroxybenzonitrile from p-methoxybenzonitrile, comprising the steps of:

[0006] Pretreatment: Add p-methoxybenzonitrile, phenol, base, solvent and phase transfer catalyst to the reaction flask, and purge the reaction flask with nitrogen;

[0007] Demethylation reaction: under inert gas protection, the reaction is carried out at a temperature range of 220~240℃ for 4~6 hours;

[0008] Acidification and extraction: After the demethylation reaction was completed, the temperature was lowered to room temperature, and the system was acidified with hydrochloric acid to neutralize the sodium salt in the system. The pH was adjusted to weakly acidic, and then the organic phase of the product was extracted with ethyl acetate.

[0009] Vacuum distillation: The filtrate after extraction is subjected to vacuum distillation to obtain phenol and solvent, while anisole is separated.

[0010] Decolorization: Dissolve the distilled substrate in a solvent, add activated carbon for decolorization, filter and transfer the clarified liquid to a crystallization vessel;

[0011] Crystallization and drying: The clarified liquid in the crystallization vessel is cooled to -1~5℃ for freeze crystallization, and then centrifuged, rinsed and vacuum dried to finally obtain high-purity p-hydroxybenzonitrile product.

[0012] Furthermore, during the demethylation reaction, the reaction process is monitored by gas chromatography, and the reaction is considered complete when the residual amount of the raw material p-methoxybenzonitrile is ≤0.2%.

[0013] Furthermore, the base includes sodium carbonate or sodium bicarbonate.

[0014] Furthermore, the molar ratio of p-methoxybenzonitrile to phenol is 1:1.1 to 1:1.4.

[0015] Furthermore, the solvent includes N-methylpyrrolidone.

[0016] Furthermore, the phase transfer catalyst includes potassium chloride or polyethylene glycol 400.

[0017] Furthermore, during the decolorization process, activated carbon at a concentration of 2‰ of the solution mass is added for decolorization treatment.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] This invention uses p-methoxybenzonitrile as a raw material and employs the reaction of phenol and alkali to provide alkaline conditions to achieve the synthesis of p-hydroxybenzonitrile in a one-step process. Compared with existing technologies, this invention has a lower reaction temperature, lower equipment requirements, shorter reaction time, and higher conversion rate. The purity of p-methylbenzonitrile reaches over 99.5%, and the reaction yield can reach over 95%. This solves the problem of low purity and yield of p-methylbenzonitrile due to low reaction conversion rate in existing technologies. The solvent used can be recycled after distillation, and no highly polluting byproducts are generated during the reaction process, making it more environmentally friendly. Attached Figure Description

[0020] Figure 1 This is the gas chromatographic analysis spectrum of crude p-hydroxybenzonitrile in Example 1 of the present invention (peak sequence of crude p-hydroxybenzonitrile is 2).

[0021] Figure 2 This is the gas chromatographic analysis spectrum of the p-hydroxybenzonitrile product from Example 1 of the present invention (the peak sequence of the p-hydroxybenzonitrile product is 3). Detailed Implementation

[0022] The present invention will be further described in detail below through specific embodiments:

[0023] See appendix Figure 1 and 2 As shown, a method for synthesizing p-hydroxybenzonitrile from p-methoxybenzonitrile is provided. Methoxybenzonitrile, phenol, base, solvent, and phase transfer catalyst are added to a reaction flask, and the flask is purged with nitrogen. The reaction flask is then placed in a parallel reactor, equipped with a reflux device and a nitrogen balloon to purge the condenser. A demethylation reaction is then carried out under inert gas (nitrogen) protection at a temperature range of 220–240°C. The reaction progress is monitored by gas chromatography (i.e., samples are taken for gas chromatography analysis during the reaction). The reaction is considered complete when the residual p-methoxybenzonitrile content is ≤0.2%. After the reaction, the temperature is lowered to room temperature, and the product is analyzed by mass... The system was acidified with 32% hydrochloric acid to neutralize the sodium salt and adjust the pH to a weakly acidic level (pH 6-7). The organic phase was then extracted with ethyl acetate. Vacuum distillation was performed at 60-120°C and -0.05-0.09 MPa to recover and recycle phenol and solvent, while separating the byproduct anisole. The distilled substrate (crude product) was dissolved in a solvent, and activated carbon (2‰ of the solution mass) was added for decolorization. After filtration, the clarified liquid was transferred to a crystallization vessel and cooled to -1-5°C for freeze crystallization. Following centrifugation, rinsing, and vacuum drying, high-purity p-hydroxybenzonitrile was finally obtained. The base included sodium carbonate or sodium bicarbonate; the solvent included N-methylpyrrolidone; and the phase transfer catalyst included potassium chloride or polyethylene glycol 400.

[0024] The detection conditions for gas chromatography analysis of samples taken during the reaction process, and for gas chromatography detection of crude p-hydroxybenzonitrile and the finished product, were as follows: GC9790 gas chromatograph (column: SE-54, 30m × 0.32mm; vaporization chamber temperature: 250℃; detection chamber temperature: 280℃; column oven temperature: 260℃; carrier gas (nitrogen) flow rate: 35mL / min; hydrogen flow rate: 25mL / min; air flow rate: 300mL / min; split flow rate: 250mL / min).

[0025] Please refer to the table below to conduct the experiment and statistically analyze the results:

[0026]

[0027] In the above experiments, the yield of the finished product was greater than 94%, and the highest reached 95.7%. The purity was all above 99.5%. At the same time, the highest reaction temperature was much lower than the 300℃ in the existing technology. The reaction temperature was lower, the equipment requirements were lower, and the reaction time was shorter.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for synthesizing p-hydroxybenzonitrile from p-methoxybenzonitrile, characterized in that, Including the following steps: Pretreatment: Add p-methoxybenzonitrile, phenol, base, solvent and phase transfer catalyst to the reaction flask, and purge the reaction flask with nitrogen; Demethylation reaction: under inert gas protection, the reaction is carried out at a temperature range of 220~240℃ for 4~6 hours; Acidification and extraction: After the demethylation reaction was completed, the temperature was lowered to room temperature, and the system was acidified with hydrochloric acid to neutralize the sodium salt in the system. The pH was adjusted to weakly acidic, and then the organic phase of the product was extracted with ethyl acetate. Vacuum distillation: The filtrate after extraction is subjected to vacuum distillation to obtain phenol and solvent, while anisole is separated. Decolorization: Dissolve the distilled substrate in a solvent, add activated carbon for decolorization, filter and transfer the clarified liquid to a crystallization vessel; Crystallization and drying: The clarified liquid in the crystallization vessel is cooled to -1~5℃ for freeze crystallization, and then centrifuged, rinsed and vacuum dried to finally obtain high-purity p-hydroxybenzonitrile product.

2. The method for synthesizing p-hydroxybenzonitrile from p-methoxybenzonitrile as described in claim 1, characterized in that, During the demethylation reaction, the reaction process is monitored by gas chromatography. The reaction is considered complete when the residual amount of p-methoxybenzonitrile in the raw material is ≤0.2%.

3. The method for synthesizing p-hydroxybenzonitrile from p-methoxybenzonitrile as described in claim 1, characterized in that, Bases include sodium carbonate or sodium bicarbonate.

4. The method for synthesizing p-hydroxybenzonitrile from p-methoxybenzonitrile as described in claim 1, characterized in that, The molar ratio of p-methoxybenzonitrile to phenol is 1:1.1 to 1:1.

4.

5. The method for synthesizing p-hydroxybenzonitrile from p-methoxybenzonitrile as described in claim 1, characterized in that, Solvents include N-methylpyrrolidone.

6. The method for synthesizing p-hydroxybenzonitrile from p-methoxybenzonitrile as described in claim 1, characterized in that, Phase transfer catalysts include potassium chloride or polyethylene glycol 400.

7. The method for synthesizing p-hydroxybenzonitrile from p-methoxybenzonitrile as described in claim 1, characterized in that, During decolorization, activated carbon at a concentration of 2‰ of the solution mass is added for decolorization treatment.

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