Method for electrochemical synthesis of ultraviolet light absorber UV-P

Abstract

The invention provides a preparation method of an ultraviolet light absorber UV-P. The preparation method comprises the following steps: carrying out electrolytic catalytic reduction on 2-(2 '-hydroxy-5'-methylphenyl) nitrogen oxide as shown in a formula II in the presence of a solvent and alkali to obtain an ultraviolet light absorber as shown in a formula I; according to the method, 2-(2 '-hydroxy-5'-methylphenyl) nitric oxide is directly reduced into the ultraviolet light absorber UV-P in an electrolytic catalytic reduction mode; the reaction is lower than the conventional chemical reaction temperature and common reaction, and is safe and reliable; no additional catalyst is needed in the reaction, electrolyte salt used for electrolysis can be repeatedly used, almost no loss exists, resources are saved, and the reaction is rapid and the current efficiency is high in the electrolysis process; electrocatalysis is used in the reaction, so that the method is more environment-friendly, and further cost reduction is facilitated.

Description

Technical Field

[0001] The invention belongs to the technical field of ultraviolet absorber UV-P preparation, and in particular relates to a method for electrochemically synthesizing ultraviolet absorber UV-P. Background Art

[0002] UV absorber 2-(2 ， -Hydroxy-5'-methylphenyl)benzotriazole (also known as UV-P) is a commonly used benzotriazole ultraviolet absorber. Colorless or three yellow crystals, melting point 130 ~ 131 ℃. UV-P is a highly efficient ultraviolet absorber that can effectively absorb ultraviolet rays of 290-400μm. It is mainly used in organic glass, polyvinyl chloride, polystyrene, polyacrylonitrile, polypropylene, unsaturated resin, polycarbonate, polymethyl methacrylate, polyethylene, ABS resin, epoxy resin, fiber resin, polyester, chlorinated polyester, acetate fiber, etc.

[0003] At present, the main methods for synthesizing 2-(2,-hydroxy-5'-methylphenyl)benzotriazole include: Patent CN102285926 B reported that under alkaline conditions, the UV-P azo intermediate was reduced once with glucose, and then zinc chloride and aluminum powder were reduced twice, and the product was obtained by filtering, acidification, filtering, and washing. Patent CN105153058A reported that platinum chloride aqueous solution and magnesium nitrate hexahydrate aqueous solution were used as raw materials, and hydrogenation-solid base bifunctional catalysts were obtained after impregnation, drying, and roasting. A fixed bed reactor was used, 1,4-dioxane was used as a solvent, and the UV-P azo intermediate was reduced. After cooling, gas-liquid separation, filtration, concentration, and recrystallization, the product UV-P was obtained. CN102659698A reported that nitrogen oxides were used as raw materials, silicon dioxide-loaded silver ions were used as catalysts, dimethylbenzene triethylamine was added to the reaction system, and hydrogen was introduced for hydrogenation to obtain benzotriazole compounds.

[0004] The above-mentioned method for preparing 2-(2,-hydroxy-5'-methylphenyl)benzotriazole has the problem of using metal powder as a reducing agent, resulting in large amounts of solid waste and serious environmental pollution, or the problem of a small number of catalyst applications, resulting in high production costs. Summary of the invention

[0005] In order to solve the above problems, the present invention discloses a method for preparing a benzotriazole ultraviolet absorber UV-P, which has mild reaction conditions and is environmentally friendly.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] The present invention provides a method for preparing a benzotriazole ultraviolet absorber UV-P, comprising the following steps: ，-hydroxy-5'-methylphenyl) nitrogen oxide is electrocatalytically reduced in the presence of a solvent and a base to obtain 2-(2,-hydroxy-5'-methylphenyl)benzotriazole of formula I;

[0008] The reaction formula is:

[0009]

[0010] Wherein, the solvent is any one or two of water, methanol, ethanol, isopropanol, tetrahydrofuran, toluene and dichloromethane.

[0011] Preferably, the solvent is a mixture of methanol and water.

[0012] Furthermore, the base is any one of NaOH, KOH, LiOH and triethylamine; preferably, the base is KOH.

[0013] Furthermore, the molar ratio of the nitrogen oxide compound, the solvent and the base is 1-20:100-320:1-20.

[0014] Furthermore, when the solvent is methanol and water, the molar ratio of the nitrogen oxide: water: alcohol: base is 1-20: 1-20: 100-300: 1-20; preferably, the molar ratio of the nitrogen oxide: water: alcohol: base is 1-10: 1-5: 100-200: 1-10.

[0015] Furthermore, the electrolysis temperature of the electrolytic catalytic reduction is 10-65°C, and the time is 15-30h; preferably, the electrolysis temperature of the electrolytic catalytic reduction is 50-60°C.

[0016] Furthermore, the anode material of the electrolytic catalytic oxidation is any one of platinum, DSA (dimensionally stable anode), stainless steel, graphite electrode, and titanium plate. Preferably, the anode material of the electrolytic catalytic oxidation is a graphite electrode.

[0017] Furthermore, the cathode material of the electrolytic catalytic oxidation is any one of monel alloy, graphite electrode, lead plate, stainless steel, lead alloy, and nickel foam. Preferably, the cathode material of the electrolytic catalytic oxidation is lead alloy.

[0018] Furthermore, the current density of the electrolytic catalytic oxidation is maintained at 500 to 3000 A / m 2 Preferably, the current density of the electrolytic catalytic oxidation is 800-1500 A / m 2 .

[0019] As a preferred embodiment of the present invention, the method of the present invention is carried out according to the following steps: 2-(2 ，-hydroxy-5'-methylphenyl) nitrogen oxide was put into the electrolysis reaction bottle, and then the solvent (water, methanol) and potassium hydroxide were added respectively. After stirring and dissolving, the mixture was heated at 1200A / m 2 Electrolytic catalytic reduction under current density, the anode material is a graphite electrode, the cathode material is a lead alloy, after electrolysis for a period of time, the reaction solution is concentrated and then washed with water to obtain 2-(2,-hydroxy-5'-methylphenyl)benzotriazole.

[0020] The beneficial effects of the present invention are:

[0021] (1) The present invention directly converts 2-(2 ， The reaction temperature of the present invention is lower than that of conventional chemical reactions, and the reaction is safe and reliable.

[0022] (2) The reaction of the present invention does not require the use of additional catalysts, and the electrolyte salt used for electrolysis can be reused repeatedly with almost no loss, thus saving resources. The electrolysis process reacts rapidly and has high current efficiency.

[0023] (3) The reaction of the present invention uses electrocatalysis, which is more environmentally friendly and also helps to further reduce costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Prepare UV-P infrared spectrum for Example 1 of the present invention; DETAILED DESCRIPTION

[0025] The present invention will be further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0026] Example 1

[0027] Preparation of compound UV-P

[0028] 50g of 2-(2 ， -hydroxy-5'-methylphenyl) nitrogen oxide was put into the electrolysis reaction bottle, and then 25g water, 1000g methanol and 50g potassium hydroxide were added respectively, stirred and heated. After the temperature rose to 60°C, the reaction was carried out at 1200A / m 2 Electrolytic catalytic reduction was carried out under current density, the anode material was graphite electrolysis, and the cathode material was lead alloy. After 20 hours of electrolysis, the reaction solution was concentrated, washed and filtered to obtain a solid product. After drying, it weighed 38.27g, the content was 99.12%, and the yield was 81.26%.

[0029] Example 1 Preparation of UV-P infrared spectrum Figure 1 As shown, 3409cm -1The broad absorption peak at 3065cm is the characteristic peak of -OH on the benzene ring. -1 The peak of CH stretching vibration on the benzene ring is 2951cm -1 The peak of CH stretching vibration of methyl group is 1597cm -1 、1560cm -1 、1513cm -1 The peak at 1210 cm is the skeleton stretching vibration peak of the benzene ring. -1 The peak is the stretching vibration peak of CO.

[0030] Example 2

[0031] Preparation of compound UV-P

[0032] 50g of 2-(2 ， -hydroxy-5'-methylphenyl) nitrogen oxide was put into the electrolysis reaction bottle, and then 25g water, 1000g methanol and 50g potassium hydroxide were added respectively, stirred and heated. After the temperature rose to 60°C, the reaction was carried out at 1200A / m 2 Electrolytic catalytic reduction was carried out under current density, the anode material was a graphite electrode, and the cathode material was a lead alloy. After 20 hours of electrolysis, the reaction solution was concentrated, washed and filtered to obtain a solid product. After drying, it weighed 38.25 g, with a content of 98.32% and a yield of 80.36%.

[0033] Example 3

[0034] Preparation of compound UV-P

[0035] 50g of 2-(2 ， -hydroxy-5'-methylphenyl) nitrogen oxide was put into the electrolysis reaction bottle, and then 30g water, 1000g methanol and 25g potassium hydroxide were added respectively, stirred and heated. After the temperature rose to 60°C, the 2 Electrolytic catalytic reduction was carried out under current density, the anode material was a graphite electrode, and the cathode material was a lead alloy. After 20 hours of electrolysis, the reaction solution was concentrated, washed and filtered to obtain a solid product. After drying, it weighed 41.35 g, with a content of 88.69% and a yield of 81.56%.

[0036] Comparative Example 1

[0037] The benzotriazole ultraviolet absorber UV-P was prepared by the same method as in Example 1, except for the selection of the anode material; the content (HPLC) and yield of the obtained product were as follows:

[0038]

[0039]

[0040] When a graphite electrode is used as the electrolysis anode, the electrolysis current has no attenuation trend within 20 hours of electrolysis, the electrolysis product content is high, the current efficiency is high, and the electrolysis conversion rate is high.

[0041] When using Pt plate as electrolysis anode, the single flow is relatively stable within 20 hours of electrolysis, but the price of Pt plate is relatively high and the cost of use is not suitable for large-scale production.

[0042] When DSA (dimensionally stable anode) is used as the electrolysis anode, although products are generated during the electrolysis process, the electrode surface is corroded and peeled off.

[0043] When stainless steel is used as the electrolytic anode, the initial current density is high during the electrolysis process. However, after a few hours of electrolysis, the electrode plate corrodes and falls off, resulting in a significant drop in current.

[0044] Using titanium as the anode, there is almost no current and almost no product generation.

[0045] Comparative Example 2

[0046] The benzotriazole ultraviolet absorber UV-P was prepared by the same method as in Example 1, except for the selection of the cathode material; the content (HPLC) and yield of the obtained product were as follows:

[0047] Cathode material UV absorber UV-P product content (HPLC) Yield Lead Alloy 99.12％ 81.26％ Stainless steel 73.56％ 68.53％ Nickel Foam 65.56％ 49.35％ Graphite Electrode 2.63％ 0％ iron plate 2.12％ 0％

[0048] When stainless steel and nickel foam are used as cathodes, the surface of the electrode plates will be corroded to varying degrees within 20 hours of electrolysis, and the electrolysis yield is low, so it is not recommended.

[0049] When using iron plates and graphite electrodes as cathodes, the current density is very low and almost no product is generated during the same electrolysis time.

[0050] Comparative Example 3

[0051] The benzotriazole ultraviolet absorber UV-P was prepared by the same method as in Example 1, except for the selection of the electrolyte ratio; the obtained product content (HPLC) and yield results are as follows:

[0052]

[0053]

[0054] The molar ratio of nitrogen oxides: water: alcohol: alkali is 50:100:1000:50. In this ratio, due to the increase in the amount of water, the probability of electrolyzing water during electrolysis increases, resulting in rapid corrosion of the electrode plates.

[0055] The molar ratio of nitrogen oxide: water: alcohol: base is 50:25:1000:5. In this ratio, the reaction yield is lower due to the reduction in the amount of base.

[0056] Comparative Example 4

[0057] The benzotriazole ultraviolet absorber UV-P was prepared by the same method as in Example 1, except for the choice of current density; the content (HPLC) and yield of the obtained product were as follows:

[0058]

[0059] When the current density is 200A / m 2 When the current density is too low, the electrolysis conversion rate is reduced.

[0060] When the current density is 3500A / m 2 When the current is too high, the anode plate is broken down, causing the coating on the surface of the anode plate to fall off, resulting in low current efficiency.

[0061] Comparative Example 5

[0062] The benzotriazole ultraviolet absorber UV-P was prepared by the same method as in Example 1, except for the choice of temperature; the content (HPLC) and yield of the obtained product were as follows:

[0063]

[0064] When the temperature is 70℃, the solvent is continuously lost due to the high temperature exceeding the boiling point of the solvent.

[0065] When the temperature is 30°C, the reaction is slow due to the low temperature, resulting in low current efficiency.

[0066] It should be noted that the above content only illustrates the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications all fall within the protection scope of the claims of the present invention.

Claims

1. A method for electrochemically synthesizing an ultraviolet absorber UV-P, It is characterized in that The following steps are involved: The 2-(2 ， -hydroxy-5'-methylphenyl) nitrogen oxide is electrolytically catalytically reduced in the presence of a solvent and a base, and the reaction solution is concentrated and then washed with water to obtain a UV absorber UV-P compound of formula I; 2. A method for electrochemically synthesizing ultraviolet absorber UV-P according to claim 1, It is characterized in that The molar ratio of the nitrogen oxide compound, the solvent and the base is 1-20:100-320:1-20.

3. A method for electrochemically synthesizing ultraviolet absorber UV-P according to claim 1, It is characterized in that The solvent is one or more of water, methanol, ethanol, isopropanol, tetrahydrofuran, toluene and dichloromethane.

4. The method for electrochemically synthesizing ultraviolet absorber UV-P according to claim 1, It is characterized in that The solvent is a mixture of water and methanol.

5. The method for electrochemically synthesizing ultraviolet absorber UV-P according to claim 1, It is characterized in that The base is one or more of NaOH, KOH, LiOH and triethylamine.

6. A method for electrochemically synthesizing ultraviolet absorber UV-P according to claim 1, It is characterized in that The temperature of the electrolytic catalytic reduction is 10-65° C. and the time is 15-30 hours.

7. The method for electrochemically synthesizing ultraviolet absorber UV-P according to claim 1, It is characterized in that The anode material of the electrolytic catalytic oxidation is one of platinum, DSA, stainless steel, graphite electrode and titanium plate.

8. The method for electrochemically synthesizing ultraviolet absorber UV-P according to claim 1, It is characterized in that The cathode material for electrolytic catalytic oxidation is one of monel alloy, graphite electrode, lead plate, stainless steel, lead alloy and nickel foam.

9. The method for electrochemically synthesizing ultraviolet absorber UV-P according to claim 1, It is characterized in that The current density of the electrolytic catalytic oxidation is 500-3000A / m 2 .

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