Electrode for preparing phenylacetic acid by electrochemical oxidation of beta-phenethyl alcohol and preparation method and application thereof

Abstract

The invention belongs to the technical field of electrochemistry, and particularly relates to an electrode applied to preparation of phenylacetic acid by electrochemical oxidation of beta-phenethyl alcohol and a preparation method and application thereof. The electrode comprises a substrate and a plating layer arranged on the surface of the substrate, and the plating layer comprises iron, cobalt and nickel. According to the electrode, beta-phenethyl alcohol can be converted into phenylacetic acid through high-selectivity electrochemical catalysis, the selectivity and the current efficiency of the product phenylacetic acid are both larger than 90%, side reactions such as oxygen evolution can be greatly inhibited in the electrolysis process, the oxygen content is smaller than 5%, and it is guaranteed that the electrolysis reaction is carried out safely.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrochemistry, and particularly relates to an electrode for preparing phenylacetic acid by electrochemical oxidation of beta-phenylethanol, a preparation method and application. BACKGROUND

[0002] Phenylacetic acid is an intermediate for organic synthesis of medicines, pesticides, food, spices and materials. In the pharmaceutical industry, it is used for the production of penicillin, dibazole and other medicines. In agriculture, it is mainly used for the production of insecticides and herbicides. In food, it is widely used for seasoning and preservation due to its good antibacterial and preservative effects. In addition, phenylacetic acid can be used for the production of polyester resins, plastics and other organic chemicals. Phenylacetic acid has strong market demand, and its application in the chemical industry will gradually expand in the coming years.

[0003] There are mainly two production processes for phenylacetic acid at present. The first one is to use benzyl chloride as raw material to prepare phenylacetic acid through cyanation, hydrolysis and other steps. The whole process involves highly toxic cyanide, and the process is more dangerous and generates more waste. The second one is to use benzyl chloride as raw material to prepare phenylacetic acid by carbonylation method. The design of catalyst is the key factor in this method, which can easily lead to catalyst deactivation in the preparation process. SUMMARY

[0004] In order to solve the above problems, the application provides an electrode for preparing phenylacetic acid by electrochemical oxidation of beta-phenylethanol, a preparation method and application.

[0005] To this end, the application provides the following technical solutions.

[0006] The first aspect of the application provides an electrode for preparing phenylacetic acid by electrochemical oxidation of beta-phenylethanol, which comprises a substrate and a plating layer arranged on the surface of the substrate; the plating layer comprises iron, cobalt and nickel.

[0007] As an optional embodiment, the thickness of the plating layer is 2-10 μm. The thickness of the plating layer can be one of 2 μm, 4 μm, 6 μm, 8 μm or 10 μm, but is not limited to the listed values.

[0008] As an optional embodiment, the substrate comprises a nickel plate, a nickel foil, a foamed nickel, a nickel wire mesh or a nickel tensile net.

[0009] The second aspect of the application provides a preparation method of an electrode for preparing phenylacetic acid by electrochemical oxidation of beta-phenylethanol, which comprises: placing a substrate in an electroplating solution, electroplating and calcining.

[0010] The electroplating solution comprises iron salt, nickel salt and cobalt salt.

[0011] As an optional implementation, the iron salt includes divalent iron salts and / or trivalent iron salts;

[0012] Preferably, the iron salt includes at least one of ferric sulfate, ferrous sulfate, ferric chloride, ferrous chloride, ferric nitrate, and ferrous nitrate.

[0013] Preferably, the cobalt salt comprises a divalent cobalt salt;

[0014] Preferably, the cobalt salt includes at least one of cobalt nitrate, cobalt sulfate, and cobalt chloride;

[0015] Preferably, the nickel salt comprises a divalent nickel salt;

[0016] Preferably, the nickel salt includes at least one of nickel chloride, nickel nitrate, and nickel sulfate.

[0017] As an optional implementation, the total mass content of iron salts, cobalt salts and nickel salts in the electroplating solution is 8-20%; the mass content can be one of 8%, 12%, 15%, 18%, and 20%, but is not limited to the values ​​listed.

[0018] As an optional implementation, the mass ratio of the iron salt, cobalt salt, and nickel salt is (10-25):(15-35):(40-75); the mass ratio of the iron salt, cobalt salt, and nickel salt can be one of 10:15:75, 15:20:65, 20:20:60, or 25:35:40, but is not limited to the listed ratios.

[0019] As an optional embodiment, the electroplating solution further includes a buffer, which includes at least one of boric acid, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium sulfate, and potassium acetate; preferably, the mass content of the buffer in the electroplating solution is 3-15%; the mass content can be one of 3%, 5%, 8%, 10%, and 13%, but is not limited to the listed values.

[0020] As an optional implementation, the electroplating solution further includes an acidity regulator, which includes at least one of potassium hydroxide, sodium hydroxide, and calcium hydroxide.

[0021] As an optional implementation, the electroplating temperature is 10-50°C; the electroplating temperature can be one of 10°C, 20°C, 30°C, 40°C or 50°C, but is not limited to the listed values.

[0022] As an optional implementation, the electroplating current density is 1-10 mA / cm². 2 The current density can be 1 mA / cm². 2 2mA / cm 2 4mA / cm2 , 6 mA / cm 2 , 8 mA / cm 2 or 10 mA / cm 2 , but not limited to the listed values.

[0023] As an optional embodiment, the plating time is 5-20 min; the plating time can be one of 5 min, 10 min, 15 min or 20 min, but not limited to the listed values.

[0024] As an optional embodiment, the pH value of the plating solution is 3-6; the pH value of the plating solution can be 3, 4, 5, 6 or meet the range.

[0025] As an optional embodiment, the calcination temperature is 200-400℃; the calcination temperature can be one of 200℃, 300℃ or 400℃, but not limited to the listed values.

[0026] As an optional embodiment, the calcination time is 2-4 h; the calcination time can be one of 2 h, 3 h or 4 h, but not limited to the listed values.

[0027] As an optional embodiment, the calcination heating rate is 2-5℃ / min. The calcination heating rate can be one of 2℃ / min, 3℃ / min, 4℃ / min or 5℃ / min, but not limited to the listed values.

[0028] The third aspect of the present application provides a method for preparing phenylacetic acid by electrochemical oxidation of β-phenylethanol, comprising the following steps: using the above electrode or the electrode prepared by the above preparation method as an anode, using a nickel-based material as a cathode, electrolyzing, acidifying, and preparing β-phenylethanol into phenylacetic acid.

[0029] As an optional embodiment, the current density of the electrolysis is 1000-3000 A / m 2 ; the current density can be one of 1000 A / m 2 , 1500 A / m 2 , 2000 A / m 2 , 2500 A / m 2 or 3000 A / m 2 , but not limited to the listed values.

[0030] As an optional embodiment, the voltage of the electrolysis is 2-4 V; the voltage can be one of 2 V, 2.5 V, 3 V, 3.5 V or 4 V, but not limited to the listed values.

[0031] As an optional implementation, the temperature of the electrolysis is 20-60℃; the temperature of the electrolysis can be one of 20℃, 30℃, 40℃ or 50℃, but is not limited to the listed values.

[0032] As an optional implementation, the electrolysis is performed by using a diaphragm-free electrolysis cell; the electrolysis cell is a nickel electrolysis cell.

[0033] As an optional implementation, the nickel-based material includes a nickel plate, a nickel foil, a nickel foam, a nickel wire mesh or a nickel tensile net.

[0034] As an optional implementation, when the electrolysis is performed, the mass concentration of β-phenylethanol in the electrolyte is 5-20wt%; the mass concentration of β-phenylethanol in the electrolyte can be one of 5wt%, 10wt%, 15wt% or 20wt%, but is not limited to the listed values. The present application regulates the mass concentration of β-phenylethanol in the electrolyte, the current density and other parameters, which is conducive to inhibiting the oxygen evolution side reaction and improving the current efficiency of the electrolysis reaction.

[0035] As an optional implementation, the mass concentration of the alkaline substance in the electrolyte is 10-20wt%. The alkaline substance includes potassium hydroxide, sodium hydroxide and the like; the mass concentration of the alkaline substance in the electrolyte can be one of 10%, 12%, 14%, 16%, 18% or 20%, but is not limited to the listed values.

[0036] The technical scheme of the present application has the following advantages:

[0037] 1. The electrode for preparing phenylacetic acid by electrochemical oxidation of β-phenylethanol provided by the present application comprises a substrate and a plating layer arranged on the surface of the substrate; the plating layer comprises iron, cobalt and nickel. The electrode can electrochemically catalyze the conversion of β-phenylethanol into phenylacetic acid with high selectivity, and the selectivity and current efficiency of the product phenylacetic acid are both >90%, and the oxygen evolution and other side reactions can be greatly inhibited during the electrolysis, so that the oxygen content is <5%, especially <2%, ensuring the safe performance of the electrolysis reaction.

[0038] 2. The method for preparing phenylacetic acid by electrochemical oxidation of β-phenylethanol provided by the present application, β-phenylethanol is easy to undergo elimination reaction under alkaline conditions, affecting the product selectivity, and the electrode of the present application can efficiently convert β-phenylethanol into phenylacetic acid, with high efficiency, and the preparation of phenylacetic acid does not involve toxic cyanide, the catalytic effect of the electrode prepared by the present application is high, and the problems such as deactivation are not easy to occur, solving the defects of the prior art of preparing phenylacetic acid by using benzyl chloride as a raw material. DETAILED DESCRIPTION

[0039] The following examples are provided to better further understand the present application and are not limited to the best mode contemplated, do not constitute limitations on the scope of the application, and are not intended to convey any idea of the scope of the present application, any product identical or similar to the present application obtained by the disclosure of the present application or by combining the present application with other prior art features falls within the scope of the present application.

[0040] The specific experimental steps or conditions not indicated in the examples can be performed according to the conventional experimental steps described in the literature in the art or the operation or conditions. The reagents or instruments not indicated by the manufacturer are conventional reagent products that can be obtained by purchase.

[0041] The embodiment of the present application provides a preparation method of an electrode applied to electrochemical oxidation of beta-phenylethanol to prepare phenylacetic acid, comprising the following steps:

[0042] (1) Pretreatment of the substrate; for example, cutting the substrate into a fixed shape, polishing the substrate with sandpaper to make its surface smooth, washing with water to remove the surface oxide layer. Ultrasonic treatment in 3M HCl, ethanol, water, acetone for 30min to make the surface hydrophilic.

[0043] (2) Preparation of electroplating solution; preparation of iron salt, cobalt salt and nickel salt into electroplating solution;

[0044] (3) Electroplating;

[0045] (4) The electroplated substrate is washed with water to remove the surface salt solution, dried and calcined. The calcination can be carried out in but not limited to air atmosphere.

[0046] The embodiment of the present application provides a method for preparing phenylacetic acid by electrochemical oxidation of beta-phenylethanol, comprising the following steps: using the electrode provided by the present application as an anode, a nickel-based material as a cathode, applying a current density to the electrode in an alkaline membrane-free electrolyte, electrolysis, preparing beta-phenylethanol into phenylacetate, and obtaining phenylacetic acid after acidification. Optionally, the electrolyte is acidified to pH 3-5; acidification is carried out by using an acid reagent, and the acid reagent is a conventional reagent in the art, such as hydrochloric acid, nitric acid, sulfuric acid, etc.

[0047] When electrolysis is carried out, the electrolytic cell can be but is not limited to a plate-frame electrolytic cell.

[0048] The electrolytic cell is a membrane-free system.

[0049] The beta-phenylethanol used in the following examples is purchased from Aladdin Reagent Company.

[0050] Example 1

[0051] The embodiment provides an electrode applied to electrochemical oxidation of beta-phenylethanol to prepare phenylacetic acid, comprising the following steps:

[0052] 1.5 g of ferrous sulfate, 3 g of cobalt nitrate, 10.5 g of nickel nitrate, 5 g of potassium acetate, 5 g of potassium hydroxide were dissolved in 75 g of water, and stirred to obtain an electroplating solution. The above pretreated nickel plate was used as a substrate, the temperature was controlled at 25℃, the current density was controlled at 5 mA / cm 2 , the pH of the electroplating solution was controlled between 3-6, and electroplated for 10 min. The electroplated material was calcined at 300℃ for 2h under an air atmosphere at a heating rate of 3℃ / min to obtain an electrode, which was recorded as FeCoNi@Ni.

[0053] The embodiment also provides a method for electrochemically oxidizing β-phenylethanol to prepare phenylacetic acid, comprising the following steps:

[0054] The above FeCoNi@Ni was used as an anode, a nickel plate was used as a cathode, a diaphragmless plate frame electrolytic cell was used, a potassium hydroxide solution and β-phenylethanol were mixed to prepare an electrolyte, the concentration of potassium hydroxide in the electrolyte was 15wt%, and the concentration of β-phenylethanol was 10wt%. The electrolysis reaction was carried out under the conditions that the temperature was 30℃, the current density was 1000 A / m 2 , and the voltage was 3V. The concentrations of raw materials and phenylacetic acid were detected every 2h, and the selectivity and current efficiency of phenylacetic acid were calculated. When the raw material was not detected, it was considered that the reaction was completed. The electrolyte was acidified to pH 3-5 by using a hydrochloric acid solution to prepare phenylacetic acid.

[0055] Example 2

[0056] The embodiment provides an electrode applied to electrochemically oxidizing β-phenylethanol to prepare phenylacetic acid, comprising the following steps:

[0057] 1.875 g of ferric nitrate, 3.75 g of cobalt chloride, 6.875 g of nickel sulfate, 8.75 g of potassium acetate, and 2.5 g of potassium hydroxide were dissolved in 75 g of water and stirred to obtain an electroplating solution. The pretreated nickel plate was used as a substrate, the temperature was controlled at 30℃, the current density was controlled at 6 mA / cm 2 , the pH of the electroplating solution was controlled between 3-6, and electroplated for 10 min. The electroplated material was calcined at 350℃ for 2h under an air atmosphere at a heating rate of 4℃ / min to obtain an electrode, which was recorded as FeCoNi@Ni.

[0058] The embodiment also provides a method for electrochemically oxidizing β-phenylethanol to prepare phenylacetic acid, comprising the following steps:

[0059] FeCoNi@Ni as anode, nickel plate as cathode, using diaphragmless plate frame electrolytic cell, mixing potassium hydroxide solution and β-phenylethanol to prepare electrolyte, the concentration of potassium hydroxide in electrolyte is 18wt%, and the concentration of β-phenylethanol is 15wt%. The electrolysis reaction is carried out at a temperature of 40℃, a current density of 1500A / m 2 , and a voltage of 3.1V. The raw material and phenylacetic acid concentration are detected every 2h, and the selectivity of phenylacetic acid and current efficiency are calculated. When the raw material is not detected, it is considered that the reaction is completed. Hydrochloric acid solution is used to acidify the electrolyte to pH between 3-5 to prepare phenylacetic acid.

[0060] Example 3

[0061] The embodiment provides an electrode applied to electrochemical oxidation of β-phenylethanol to prepare phenylacetic acid, comprising the following steps:

[0062] 2g of ferric nitrate, 3.2g of cobalt chloride, 4.8g of nickel sulfate, 11.25g of potassium dihydrogen phosphate and 3.75g of sodium hydroxide are dissolved in 75g of water, and fully stirred to obtain an electroplating solution. A pretreated nickel plate is used as a substrate, the temperature is controlled at 40℃, the current density is controlled at 8mA / cm 2 , the pH of the electroplating solution is controlled between 3-6, and the electroplating is performed for 8min. The electroplated material is calcined at 400℃ for 2h at an air atmosphere and a temperature increasing rate of 3℃ / min to obtain an electrode, which is recorded as FeCoNi@Ni.

[0063] The embodiment also provides a method for electrochemical oxidation of β-phenylethanol to prepare phenylacetic acid, comprising the following steps:

[0064] FeCoNi@Ni as anode, nickel plate as cathode, using diaphragmless plate frame electrolytic cell, mixing potassium hydroxide solution and β-phenylethanol to prepare electrolyte, the concentration of potassium hydroxide in electrolyte is 20wt%, and the concentration of β-phenylethanol is 20wt%. The electrolysis reaction is carried out at a temperature of 40℃, a current density of 2000A / m 2 , and a voltage of 2.6V. The raw material and phenylacetic acid concentration are detected every 2h, and the selectivity of phenylacetic acid and current efficiency are calculated. When the raw material is not detected, it is considered that the reaction is completed. Hydrochloric acid solution is used to acidify the electrolyte to pH between 3-5 to prepare phenylacetic acid.

[0065] Comparative Example 1

[0066] The comparative example provides a method for electrochemical oxidation of β-phenylethanol to prepare phenylacetic acid, which is different from example 1 in that ferrous sulfate is removed when preparing the electrode, and the electrode is recorded as CoNi@Ni.

[0067] Comparative Example 2

[0068] The comparative example provides a method for electrochemically oxidizing β-phenylethanol to prepare phenylacetic acid, which is different from example 1 in that cobalt nitrate is removed when preparing the electrode, and the electrode is denoted as FeNi@Ni.

[0069] Test example

[0070] The test example provides the performance of each example and comparative example in preparing phenylacetic acid, which is specifically as follows:

[0071] The test method of the selectivity S of phenylacetic acid is as follows: after diluting the electrolyte, the concentration of phenylacetic acid is tested by using an external standard method through liquid chromatography. A C18 chromatographic column is used, the mobile phase comprises methanol and water in a volume ratio of 6:4, and the detection wavelength is 254 nm. The selectivity calculation formula is as follows:

[0072]

[0073] The calculation formula of the current efficiency FE of phenylacetic acid is as follows:

[0074]

[0075] Wherein, FE is the current efficiency of phenylacetic acid; n 苯乙酸 is the amount of substance of the generated phenylacetic acid, in mol; I is the applied current, in A; t is the reaction time, in s.

[0076] The test method of the oxygen content is as follows: the oxygen content in the electrolysis process is obtained by using gas chromatography.

[0077] Table 1: Performance test results of each example and comparative example

[0078] Example Phenylacetic acid selectivity / % Phenylacetic acid current efficiency / % Oxygen content (%) Example 1 98 95 0.4 Example 2 95 93 0.7 Example 3 90 88 1.3 Comparative Example 1 76 72 4 Comparative Example 2 74 68 4.4

[0079] From the above test results, it can be seen that the electrode of the present application comprises a substrate and a plating layer arranged on the surface of the substrate, the plating layer comprises iron, cobalt and nickel, the electrode can electrochemically catalyze the conversion of β-phenylethanol into phenylacetic acid with high selectivity, the selectivity and current efficiency of the product phenylacetic acid are both > 90%, and the oxygen content is < 2%, which is conducive to the safe performance of the electrolysis reaction.

[0080] Obviously, the above examples are merely examples for clearly illustrating but not limitation on the embodiments. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments need not and cannot be exhausted. The changes or variations thus derived are still within the protection scope of the present application.

Claims

1. An electrode used in the electrochemical oxidation of β-phenylethanol to prepare phenylacetic acid, characterized in that, It includes a substrate and a plating layer disposed on the surface of the substrate; the plating layer includes iron, cobalt, and nickel.

2. The electrode according to claim 1, characterized in that, The thickness of the coating is 2-10 μm.

3. The electrode according to claim 1 or 2, characterized in that, The substrate includes nickel plate, nickel foil, nickel foam, nickel wire mesh, or nickel stretched mesh.

4. A method for preparing an electrode used in the electrochemical oxidation of β-phenylethanol to prepare phenylacetic acid, characterized in that, include: The substrate is placed in an electroplating solution, electroplated, and then calcined. The electroplating solution includes iron salts, nickel salts, and cobalt salts.

5. The preparation method according to claim 4, characterized in that, The iron salts include divalent iron salts and / or trivalent iron salts; Preferably, the iron salt includes at least one of ferric sulfate, ferrous sulfate, ferric chloride, ferrous chloride, ferric nitrate, and ferrous nitrate. Preferably, the cobalt salt comprises a divalent cobalt salt; Preferably, the cobalt salt includes at least one of cobalt nitrate, cobalt sulfate, and cobalt chloride; Preferably, the nickel salt comprises a divalent nickel salt; Preferably, the nickel salt includes at least one of nickel chloride, nickel nitrate, and nickel sulfate.

6. The preparation method according to claim 5, characterized in that, The total mass content of iron salts, cobalt salts and nickel salts in the electroplating solution is 8-20%; And / or, the mass ratio of the iron salt, cobalt salt, and nickel salt is (10-25):(15-35):(40-75); And / or, the electroplating solution further includes a buffer, the buffer including at least one of boric acid, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, potassium sulfate, and potassium acetate; preferably, the mass content of the buffer in the electroplating solution is 3-15%; And / or, the electroplating solution further includes an acidity regulator, which includes at least one of potassium hydroxide, sodium hydroxide, and calcium hydroxide.

7. The preparation method according to any one of claims 4-6, characterized in that, The electroplating temperature is 10-50℃; And / or, the current density of the electroplating is 1-10 mA / cm². 2 ; And / or, the electroplating time is 5-20 min; And / or, the pH value of the electroplating solution is 3-6; And / or, the calcination temperature is 200-400℃; And / or, the calcination time is 2-4 hours; And / or, the calcination heating rate is 2-5℃ / min.

8. A method for preparing phenylacetic acid by electrochemical oxidation of β-phenylethanol, characterized in that, The process includes the following steps: using the electrode described in any one of claims 1-3 or the electrode prepared by the method described in any one of claims 4-7 as the anode, using a nickel-based material as the cathode, electrolyzing, acidifying, and converting β-phenylethanol into phenylacetic acid.

9. The method according to claim 8, characterized in that, The current density of the electrolysis is 1000-3000 A / m. 2 ; And / or, the voltage of the electrolysis is 2-4V; And / or, the electrolysis temperature is 20-60°C; And / or, the electrolysis is carried out using a diaphragmless electrolytic cell; And / or, the nickel-based material includes nickel plate, nickel foil, nickel foam, nickel wire mesh, or nickel stretched mesh.

10. The method according to claim 8 or 9, characterized in that, During the electrolysis, the mass concentration of β-phenylethanol in the electrolyte is 5-20 wt%. And / or, the mass concentration of alkaline substances in the electrolyte is 10-20 wt%.

Images