A preparation method of benzotriazole ultraviolet absorber

Abstract

The invention discloses a method for preparing a benzotriazole ultraviolet absorber. The method for preparing a benzotriazole ultraviolet absorber of the invention comprises the following steps: in the presence of a base and a solvent, a compound as shown in formula II is reacted with hydrogen in a microreactor in a continuous flow to obtain a compound as shown in formula I. The preparation method of the invention can obtain a product with high yield and high purity; and is efficient, simple to operate, highly safe and environmentally friendly.

Description

Technical Field

[0001] The invention belongs to the field of preparation methods of benzotriazole compounds, and in particular relates to a preparation method of a benzotriazole ultraviolet absorber. Background Art

[0002] Benzotriazole compounds are the largest and most diverse class of UV absorbers, and research is also very active both at home and abroad. This type of UV absorber has the characteristics of low toxicity, low volatility, and good UV stability. It is widely used in the photochemical modification of polymer materials, sunscreen cosmetics, and lighting materials. It can improve the stability, weather resistance, and anti-aging properties of polymer materials.

[0003] UV absorber 2-(2′-hydroxy-5′-methylphenyl)benzotriazole (BTA), trade name UV-P, is a classic benzotriazole UV absorber that can efficiently absorb external ultraviolet rays and avoid many problems such as aging of polymer materials and cancer of skin cells caused by excessive ultraviolet radiation. It is now widely used in organic glass, polyvinyl chloride, polystyrene, etc. to extend the service life of polymer materials.

[0004] At present, the mature UV-P synthesis method used in industry is generally a two-step synthesis process. The first step is to diazotize aromatic amines to form diazonium salts, and the diazonium salts react with phenolic compounds to form 2′-hydroxy-5′-methylphenylazobenzene (HAB); the second step is to reduce and close the azo intermediate to form the ultraviolet absorber UV-P. The process route of the first step is mature, but there are problems in the second step, such as the easy breakage of the azo bond and the easy generation of amine by-products, which have always been the focus of research.

[0005] In her master's thesis "Study on the Synthesis Process of Benzotriazole Ultraviolet Absorbers", Zhu Yinghua disclosed a method for preparing benzotriazole light stabilizers from azobenzene compounds through two-step reduction of glucose and zinc powder, achieving a high yield. However, the zinc powder in this process has a large environmental pollution, a complex reaction flow, and a high production cost. At the same time, the yield and purity are low, and there is still much room for improvement.

[0006] Patent CN103351349A discloses a method for preparing UV-P by using sodium sulfide and Raney nickel as reducing agents for hydrogenation reduction at normal pressure. This process produces sulfur-containing waste liquid, which can pollute the water environment and has the disadvantages of a complex reaction process.

[0007] Patent CN102432613A breaks away from the traditional azo intermediate model and uses new raw materials to prepare UV-P in a completely new synthetic route. Although this process route is highly innovative, the process takes a long time, the cost of hydrogen peroxide treatment involved in the reaction is high, and the product yield needs to be improved. Summary of the invention

[0008] The technical problem to be solved by the present invention is that the yield and purity of UV-P are low, the preparation process is complicated and polluting, and a preparation method of a benzotriazole ultraviolet absorber is provided. The preparation method of the present invention has the advantages of high yield, high purity, convenient operation, and green safety.

[0009] The present invention provides a method for preparing a compound as shown in formula I, which comprises the following steps:

[0010] In the presence of a base and a solvent, the compound represented by formula II is reacted with hydrogen in a microreactor in a continuous flow to obtain a compound represented by formula I;

[0011]

[0012] In the preparation method, the base can be a conventional base for such reactions in the art, preferably an alkali metal base, and more preferably sodium hydroxide.

[0013] In the preparation method, the molar ratio of the base to the compound represented by formula II can be a conventional molar ratio for such reactions in the art, preferably (2-8):1.

[0014] In the preparation method, the solvent may be a conventional solvent for such reactions in the art, preferably a mixed solvent of water and an alcohol solvent.

[0015] In the preparation method, the alcohol solvent is preferably C 1-3 Alcoholic solvents, such as ethanol.

[0016] In the preparation method, the volume ratio of the alcohol solvent to the water is preferably (0.1-2):1, for example 1:1.

[0017] In the preparation method, the mixed solvent is preferably a mixed solvent of the water and the ethanol, and more preferably a mixed solvent of the water and the ethanol in a volume ratio of 1:1 (v / v).

[0018] In the preparation method, the solvent may not be specifically limited as long as it does not affect the reaction. The mass ratio of the solvent to the compound represented by formula II may be (5-10):1.

[0019] In the preparation method, the continuous flow reaction is preferably carried out in the presence of a catalyst.

[0020] In the preparation method, the catalyst is preferably fixed on the inner wall of the microreactor.

[0021] In the preparation method, the catalyst can be supported on a conventional carrier, preferably supported on carbon.

[0022] In the preparation method, the catalyst may be a conventional catalyst in the art, preferably Ni or Pd.

[0023] In the preparation method, the molar ratio of the catalyst to the compound represented by formula II can be a conventional molar ratio for such reactions in the art, preferably (0.01%-0.2%):1.

[0024] In the preparation method, the materials can be used in a variety of ways to carry out continuous flow reaction, such as feeding each material together, feeding each material separately, or mixing the materials and feeding them separately with the remaining materials. In the present invention, the mixture of the compound shown in formula II, the base and the solvent is used as material I, and the hydrogen is used as material II, and preferably they are respectively subjected to continuous flow reaction through a microreactor; more preferably, the material II is fed after the material I is fed.

[0025] The material I is preferably mixed by a high-pressure constant flow pump and then enters the microreactor for continuous flow reaction. The material I can be preheated to 50-100°C, preferably 80-90°C.

[0026] In the preparation method, the hydrogen can enter the microreactor via a gas mass flow meter.

[0027] In the preparation method, the continuous flow reaction is preferably carried out under a protective gas, such as nitrogen or an inert gas.

[0028] In the preparation method, before the material I and the hydrogen enter the microreactor, protective gas can be introduced into the microreactor for replacement multiple times, preferably 2-5 times, and more preferably three times.

[0029] In the preparation method, the continuous flow reaction can be carried out at a temperature of 80-90°C.

[0030] In the preparation method, the residence time of the hydrogen and the compound represented by formula II for the continuous flow reaction can be 1-20 minutes, preferably 2 minutes.

[0031] In the preparation method, the continuous flow reaction can also be carried out under pressure, preferably at 0.2-4 MPa, and more preferably at 1.5-2.5 MPa.

[0032] In the preparation method, after the reaction is completed, post-processing may be further included, and the post-processing step includes the following steps:

[0033] After the continuous flow reaction is completed, the reaction mixture can be separated into hydrogen and reaction liquid by a gas-liquid separator;

[0034] The reaction solution is adjusted to a pH of 2-4 with an acid, and then filtered, washed and dried; preferably the pH is 3.

[0035] In the post-treatment, the acid may be an inorganic acid, preferably sulfuric acid, such as concentrated sulfuric acid;

[0036] The washing solvent may be C 1-3 Alcohols (e.g. methanol);

[0037] The drying temperature may be 50-70°C, preferably 60°C.

[0038] In one embodiment of the present invention, the continuous flow reaction can be carried out in the presence of a catalyst, the catalyst can be Ni or Pd, and the molar ratio of the catalyst to the compound represented by formula II can be (0.01%-0.2%): 1;

[0039] The continuous flow reaction can be carried out at a temperature of 80-90°C;

[0040] The continuous flow reaction can also be carried out at 1.5-2.5 MPa.

[0041] In one embodiment of the present invention, the continuous flow reaction can be carried out in the presence of a catalyst, the catalyst can be Ni or Pd, and the molar ratio of the catalyst to the compound represented by formula II can be (0.01%-0.2%): 1;

[0042] The continuous flow reaction can be carried out at a temperature of 80-90°C;

[0043] The continuous flow reaction can also be carried out at 1.5-2.5Mpa;

[0044] The molar ratio of the base to the compound represented by formula II may be (2-8): 1;

[0045] The mass ratio of the solvent to the compound represented by formula II may be (5-10): 1;

[0046] The solvent may be a mixed solvent of the water and the ethanol in a ratio of 1:1 (v / v).

[0047] In one embodiment of the present invention, the continuous flow reaction can be carried out in the presence of a catalyst, the catalyst can be Ni or Pd, and the molar ratio of the catalyst to the compound represented by formula II can be (0.01%-0.2%): 1;

[0048] The continuous flow reaction can be carried out at a temperature of 80-90°C;

[0049] The continuous flow reaction can also be carried out at 1.5-2.5Mpa;

[0050] The molar ratio of the base to the compound represented by formula II may be (2-8): 1;

[0051] The mass ratio of the solvent to the compound represented by formula II may be (5-10): 1;

[0052] The solvent may be a mixed solvent of the water and the ethanol in a ratio of 1:1 (v / v);

[0053] The base is an alkali metal base;

[0054] The residence time of the hydrogen and the compound represented by formula II for the continuous flow reaction may be 1-20 min;

[0055] The continuous flow reaction may be carried out under a protective gas, such as nitrogen or an inert gas.

[0056] On the basis of being in accordance with the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0057] The reagents and raw materials used in the present invention are commercially available.

[0058] The positive improvement effect of the present invention is that the reaction is more rapid and complete through the microreactor, the reaction yield can reach more than 92%, and the product purity can reach more than 99%; the operation is safe and convenient, and the entire reaction process is safe and environmentally friendly. DETAILED DESCRIPTION

[0059] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0060] Example 1

[0061] (1) Reduction hydrogenation

[0062] The chip with catalyst Ni fixed is placed on the microchannel in the microreactor, and the gas in the microchannel is replaced 3 times with nitrogen, and the temperature in the microchannel reactor is set to 90°C. Take 2g of azo intermediate (2-nitro-(2′-hydroxy-5′-methyl)azobenzene, as shown in Formula II), 2g of sodium hydroxide, and dissolve in a mixed solution of 30mL of water and 30mL of ethanol, and place it in the raw material tank A. After the reactor reaches 90°C, start the metering pump to pump the mixed solution into the microreactor. After the feed is stable, open the hydrogen cylinder, start the gas mass flowmeter to continuously pass hydrogen, set the hydrogen pressure to 1.5MPa (hydrogen, solution residence time 2min), and the whole set of equipment is operated at back pressure. After the reaction, the mixture passes through the gas-liquid separator at the outlet, collects the liquid phase product, and the gas is directly emptied.

[0063]

[0064] (2) Post-reaction treatment

[0065] The liquid product was adjusted to pH 3 with concentrated sulfuric acid, filtered, washed with methanol, and precipitated. After drying at 60°C, it was weighed to obtain 1.61 g of UV-P (as shown in Formula I), with a yield of 92.3%, a purity of 99.4%, and a retention time of 6.2 min.

[0066] HPLC test conditions: C18 reverse phase column, mobile phase 100% methanol, flow rate 0.8 mL / min, UV absorption wavelength 290 nm.

[0067] Example 2

[0068] (1) Reduction hydrogenation

[0069] The catalyst Pd / C fixed chip is placed on the microchannel in the microreactor, and the gas in the microchannel is replaced with nitrogen three times, and the temperature in the microchannel reactor is set to 90°C. Take 2g of azo intermediate (as shown in Formula II), 2g of sodium hydroxide, and dissolve in a mixed solution of 30mL of water and 30mL of ethanol, and place it in the raw material tank A. After the reactor reaches 90°C, start the metering pump to pump the mixed solution into the reactor, start the gas mass flowmeter to continuously introduce hydrogen, and set the hydrogen pressure to 2.5MPa. After the reaction, the mixture passes through the gas-liquid separator at the outlet to collect the liquid phase product, and the gas is directly emptied.

[0070]

[0071] (2) Post-reaction treatment

[0072] The liquid product was adjusted to pH 3 with concentrated sulfuric acid, filtered, washed with methanol, and weighed after drying at 60°C to obtain 1.62 g of UV-P (as shown in Formula I) with a yield of 92.5%. The purity was 99.1% as determined by liquid chromatography under the same conditions as in Example 1.

[0073] Example 3

[0074] (1) Reduction hydrogenation

[0075] Place the chip with catalyst Ni fixed in the microchannel of the microreactor, replace the gas in the microchannel with nitrogen three times, and set the temperature in the microchannel reactor to 80°C. Take 2g of azo intermediate (as shown in Formula II), 2g of sodium hydroxide, dissolve in a mixed solution of 30mL of water and 30mL of ethanol, and place it in the raw material tank A. After the reactor reaches 80°C, start the metering pump to pump the mixed solution into the reactor, start the gas mass flowmeter to continuously introduce hydrogen, and set the hydrogen pressure to 2.5MPa. After the reaction, the mixture passes through the gas-liquid separator at the outlet to collect the liquid phase product, and the gas is directly discharged.

[0076]

[0077] (2) Post-reaction treatment

[0078] The liquid product was adjusted to pH 3 with concentrated sulfuric acid, filtered, washed with methanol, and precipitated, dried at 60°C, and weighed to obtain 1.61 g of UV-P with a yield of 92.3%. The purity was 99.3% as determined by liquid chromatography under the same conditions as in Example 1.

[0079] It can be concluded from the above examples that after the azo intermediate is subjected to reduction hydrogenation reaction through a microchannel reactor, the yield is above 92% and the purity is above 99%. Both the yield and purity are improved, and even if the preset temperature, hydrogen pressure, and catalyst type are slightly changed, very good yield and purity can still be achieved. In addition, the operation is simple, safe, and environmentally friendly throughout the reaction process.

Claims

1. A method for preparing a compound as shown in formula I, It is characterized in that In the presence of a base and a solvent, the compound represented by formula II is reacted with hydrogen in a microreactor in a continuous flow to obtain a compound represented by formula I; The alkali is sodium hydroxide; The solvent is a mixed solvent of water and an alcohol solvent; the alcohol solvent is C 1-3 Alcohol solvents; The continuous flow reaction is carried out at a temperature of 80-90°C; The continuous flow reaction is carried out at 1.5-2.5Mpa; The continuous flow reaction is carried out in the presence of a catalyst; The catalyst is supported on carbon, and the catalyst is Ni or Pd; The continuous flow reaction is carried out under nitrogen or inert gas.

2. The method for preparing the compound of formula I as claimed in claim 1, It is characterized in that The preparation method meets one or more of the following conditions: ① The molar ratio of the base to the compound represented by formula II is (2-8):1; ② The mass ratio of the solvent to the compound represented by formula II is (5-10):1; and ③ the residence time of the hydrogen and the compound as shown in formula II for the continuous flow reaction is 1-20 min.

3. A method for preparing the compound of formula I as claimed in claim 2, It is characterized in that The preparation method meets one or more of the following conditions: ① The volume ratio of the alcohol solvent to the water is (0.1-2):1; ② The catalyst is fixed on the inner wall of the microreactor; ③ The molar ratio of the catalyst to the compound represented by formula II is (0.01%-0.2%): 1; and ④ the residence time of the continuous flow reaction between the hydrogen and the compound as shown in formula II is 2 minutes.

4. The method for preparing the compound of formula I as claimed in claim 3, It is characterized in that The solvent is a mixed solvent of ethanol and water.

5. The method for preparing the compound of formula I as claimed in claim 4, It is characterized in that The solvent is a mixed solvent of water and ethanol in a volume ratio of 1:

1.

6. A method for preparing the compound of formula I as claimed in claim 1, It is characterized in that The mixture of the compound shown in formula II, the base and the solvent is used as material I, and the hydrogen is used as material II, and they are respectively passed through microreactors for continuous flow reaction.

7. A method for preparing the compound of formula I as claimed in claim 6, It is characterized in that The preparation method meets one or more of the following conditions: ① The material I is mixed by a high-pressure constant flow pump and then enters the microreactor for continuous flow reaction; ② The material I is preheated to 50-100°C; ③ The hydrogen enters the microreactor through a gas mass flow meter; ④ Material II is fed after material I is fed; ⑤ Before the material I and the hydrogen enter the microreactor, a protective gas is introduced into the microreactor for replacement 2-5 times.

8. The method for preparing the compound of formula I as claimed in claim 7, It is characterized in that The material I is first preheated to 80-90°C; And / or, before the material I and the hydrogen enter the microreactor, protective gas is introduced into the microreactor for replacement three times.

9. A method for preparing a compound of formula I as claimed in any one of claims 1 to 8, It is characterized in that After the continuous flow reaction is completed, the continuous flow reaction further includes post-processing, and the post-processing step includes: after the continuous flow reaction is completed, the reaction mixture is separated into hydrogen and reaction liquid by a gas-liquid separator; The reaction solution is adjusted to a pH of 2-4 with an acid, filtered, washed and dried; The acid is an inorganic acid; The solvent used for the washing is C 1-3 Alcohols.

10. A method for preparing the compound of formula I as claimed in claim 9, It is characterized in that The acid is dilute hydrochloric acid or dilute sulfuric acid; and / or the drying temperature is 50-70°C.

11. A method for preparing the compound of formula I as claimed in claim 1, It is characterized in that The continuous flow reaction is carried out in the presence of a catalyst, the catalyst is Ni or Pd, and the molar ratio of the catalyst to the compound represented by formula II is (0.01%-0.2%): 1; The continuous flow reaction is carried out at a temperature of 80-90°C; The continuous flow reaction is carried out at 1.5-2.5 MPa.

12. A method for preparing the compound of formula I as claimed in claim 11, It is characterized in that The molar ratio of the base to the compound represented by formula II is (2-8):1; The mass ratio of the solvent to the compound represented by formula II is (5-10): 1; The solvent is a mixed solvent of water and ethanol in a volume ratio of 1:

1.

13. A method for preparing a compound of formula I as claimed in claim 11 or 12, It is characterized in that The alkali is sodium hydroxide; The residence time of the hydrogen and the compound represented by formula II for the continuous flow reaction is 1-20 min; The continuous flow reaction is carried out under a protective gas, and the protective gas is nitrogen or an inert gas.

Images