阅读说明：本技术 一种苯并三唑类紫外线吸收剂的制备方法 (Preparation method of benzotriazole ultraviolet absorbent ) 是由 张宇 校大伟 李小安 韩彬 姚琪 黄琼淋 高武 于 2020-12-11 设计创作，主要内容包括：一种苯并三唑类紫外线吸收剂的制备方法,包括以下步骤：(1)将邻硝基偶氮苯化合物、有机试剂混合,搅拌溶解后,加入贵金属负载催化剂；(2)再加入碱性助剂,用氮气置换3次；(3)通入氢气,在氢气压力0.2-3MPa、温度30-110℃下反应4-24h；(4)冷却至室温后过滤,滤渣回收备用,滤液减压蒸馏即可。本发明提供的方法反应条件温和、步骤简单、产物分离提纯方便,最终产率≥95%,产物纯度≥99%。(A preparation method of a benzotriazole ultraviolet absorbent comprises the following steps: (1) mixing an o-nitroazobenzene compound and an organic reagent, stirring and dissolving, and adding a noble metal supported catalyst; (2) adding an alkaline assistant, and replacing for 3 times by nitrogen; (3) introducing hydrogen, and reacting for 4-24h at the hydrogen pressure of 0.2-3MPa and the temperature of 30-110 ℃; (4) cooling to room temperature, filtering, recovering the filter residue, and distilling the filtrate under reduced pressure. The method provided by the invention has the advantages of mild reaction conditions, simple steps, convenience in product separation and purification, and the final yield is more than or equal to 95%, and the product purity is more than or equal to 99%.)

1. A preparation method of benzotriazole ultraviolet absorbent is characterized in that: the method comprises the following steps:

(1) mixing an o-nitroazobenzene compound and an organic reagent, stirring and dissolving, and adding a noble metal supported catalyst;

(2) adding an alkaline assistant, and replacing for 3 times by nitrogen;

(3) introducing hydrogen, and reacting for 4-24h at the hydrogen pressure of 0.2-3MPa and the temperature of 30-110 ℃;

(4) cooling to room temperature, filtering, recovering the filter residue, and distilling the filtrate under reduced pressure;

the structural general formula of the benzotriazole ultraviolet absorbent is as follows:

，

wherein the content of the first and second substances,

。

2. the method for producing the benzotriazole-based ultraviolet absorber according to claim 1, wherein: the structural general formula of the o-nitroazobenzene compound is as follows:

。

3. the method for producing the benzotriazole-based ultraviolet absorber according to claim 2, wherein: the mass ratio of the o-nitroazobenzene compound, the organic reagent, the noble metal supported catalyst and the alkaline auxiliary agent is 1: (5-10): (0.01-0.05): (0.05-0.8).

4. The method for producing the benzotriazole-based ultraviolet absorber according to claim 3, wherein: the noble metal in the noble metal supported catalyst is any one of rhodium, ruthenium, palladium or platinum.

5. The method for producing the benzotriazole-based ultraviolet absorber according to claim 3, wherein: the alkaline auxiliary agent is Na₂CO₃、K₂CO₃、NaHCO₃、KHCO₃Triethylamine, NaOH, KOH, Ca (OH)₂、Mg(OH)₂Or ammonia gas.

6. The method for producing the benzotriazole-based ultraviolet absorber according to claim 3, wherein: the organic reagent is any one of DMF, methanol, absolute ethyl alcohol, methyl acetate, ethyl acetate, toluene or xylene.

7. The method for producing the benzotriazole-based ultraviolet absorber according to claim 4, wherein: the loading amount of the noble metal in the noble metal loaded catalyst is 1-10%.

8. The method for producing the benzotriazole-based ultraviolet absorber according to claim 4 or 7, characterized in that: the carrier in the noble metal supported catalyst is active carbon or SiO₂Or TiO₂。

9. The method for producing the benzotriazole-based ultraviolet absorber according to claim 1, wherein: the reduced pressure distillation condition is reduced pressure distillation under-0.1 MPa and at 35-40 ℃.

Technical Field

The invention belongs to the technical field of ultraviolet absorbers, and particularly relates to a preparation method of a benzotriazole ultraviolet absorber.

Background

The ultraviolet absorbent is an additive for slowing down the aging of high molecular materials under sunlight, and is also used for fine chemicals such as sunscreen cosmetics and the like.

2- [ 2' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl) ] benzotriazole, which is a benzotriazole ultraviolet absorbent, namely an ultraviolet absorbent UV234 (CAS No.: 70321-86-7), and is white to light yellow granular crystalline powder, and has the following structure:

UV234 is a relatively high molecular weight ultraviolet absorber of the benzotriazole class, molecular weight 447.6. It features low volatility, excellent ultraviolet absorption and good compatibility with various materials, which makes it especially suitable for high surface area products such as films and fibers; and is excellent in heat resistance and suitable for polymers which are generally required to be processed at high temperatures, such as polycarbonates, polyesters, polyamides, aromatic copolymers, etc.; UV234 is low toxic and is approved by many countries for use in food-contact polymeric articles, suitable for packaging food, pharmaceutical products, and the like. Due to the excellent properties of the UV234, the research on the synthesis of the UV absorber UV234 is of practical significance.

The synthesis process of UV234 disclosed in the prior art is mainly a zinc powder reduction process, and has the problems of high catalysis cost, low catalysis efficiency, high three-waste pollution, frequent impurity generation of the obtained product and the like.

The literature Ding Ming et al, the synthesis of UV-326, reports a synthesis process for preparing benzotriazole UV-326 by zinc powder reduction, wherein zinc slag needs to be filtered after the reaction is finished, the reaction solution needs to be extracted for many times to remove impurities, and the final yield is only 60.9%.

The literature "synthetic research of ultraviolet absorber UV 234" reports that the UV234 is prepared by adopting a hydrogenation reduction method, the method takes Pt/C or Raney nickel as a catalyst in solvents such as toluene and the like, and the literature only explains that the method is a foreign research hotspot, but the yield and the quality of the product are not ideal.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a preparation method of a benzotriazole ultraviolet absorbent, namely UV234, wherein the conversion rate of raw materials is more than or equal to 99.8%, the yield of products is high, and the purity is high.

A preparation method of a benzotriazole ultraviolet absorbent comprises the following steps:

(1) mixing an o-nitroazobenzene compound and an organic reagent, stirring and dissolving, and adding a noble metal supported catalyst;

(2) adding an alkaline assistant, and replacing for 3 times by nitrogen;

(3) introducing hydrogen, and reacting for 4-24h at the hydrogen pressure of 0.2-3MPa and the temperature of 30-110 ℃;

(4) cooling to room temperature, filtering, recovering the filter residue, and distilling the filtrate under reduced pressure;

the structural general formula of the benzotriazole ultraviolet absorbent is as follows:

，

wherein the content of the first and second substances,。

preferably, the structural general formula of the o-nitroazobenzene compound is as follows:

。

preferably, the mass ratio of the o-nitroazobenzene compound, the organic reagent, the noble metal supported catalyst and the alkaline assistant is 1: (5-10): (0.01-0.05): (0.05-0.8).

Preferably, the noble metal in the noble metal supported catalyst is any one of rhodium, ruthenium, palladium or platinum.

Preferably, the alkaline assistant is Na₂CO₃、K₂CO₃、NaHCO₃、KHCO₃Triethylamine, NaOH, KOH, Ca (OH)₂、Mg(OH)₂Or ammonia gas

Preferably, the organic reagent is any one of DMF, methanol, absolute ethanol, methyl acetate, ethyl acetate, toluene or xylene.

Preferably, the noble metal loading in the noble metal supported catalyst is 1 to 10%.

Preferably, the carrier in the noble metal supported catalyst is activated carbon or SiO₂Or TiO₂。

Preferably, the reduced pressure distillation condition is reduced pressure distillation at-0.1 MPa and 35-40 ℃.

Preferably, the o-nitroazobenzene compound is 2-nitro-2 '-hydroxy-3', 5 '-di (alpha, alpha-dimethylbenzyl) azobenzene, and the benzotriazole ultraviolet absorber is 2- [ 2' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl)]Benzotriazole (UV 234) wherein-R is-H, -R₁Is composed of，-R₂Is composed of。

Preferably, the o-nitroazobenzene compound is 2-nitro-4-chloro-2 '-hydroxy-3', 5 '-di-tert-butylazobenzene, and the benzotriazole ultraviolet absorbent is 2- (2' -hydroxy-3 ',5' -di-tert-butylphenyl) -5-chlorobenzotriazole (UV 327), wherein-R is-Cl, -R₁is-C (CH)₃)₃，-R₂is-C (CH)₃)₃。

Preferably, the o-nitroazobenzene compound is 2-nitro-4-chloro-2 '-hydroxy-3' -tert-butyl-5 '-methylazobenzene, and the benzotriazole ultraviolet absorbent is 2- (2' -hydroxy-3 '-tert-butyl-5' -methyl) -5-chlorobenzotriazole (UV 326), wherein, -R is-Cl, -R₁is-C (CH)₃)₃，-R₂is-CH₃。

Preferably, the o-nitroazobenzene compound is 2-nitro-2 ' -hydroxy-3 ',5' -dipentylazoxybenzene, and the benzotriazole ultraviolet absorbent is 2- (2' -hydroxy-3 ', 5-Ditert-amyl-phenyl) benzotriazole (UV 328), wherein-R is-H, -R₁is-C₅H₁₁，-R₂is-C₅H₁₁。

The reaction formula involved in the invention is as follows:

。

the invention has the advantages that:

the method provided by the invention has the advantages of mild reaction conditions, simple steps, convenience in product separation and purification, and the final yield is more than or equal to 95%, and the product purity is more than or equal to 99%. And the filter residue catalyst recovered by filtering after the reaction and the distilled reaction solvent can be recycled, so that the production cost is reduced, the three wastes are reduced, the problems of low reaction yield, high catalysis cost, low catalysis efficiency, high pollution of the generated three wastes and the like in the prior art are solved, and the method is suitable for large-scale industrial production.

Detailed Description

Example 1

A preparation method of a benzotriazole ultraviolet absorbent, wherein the benzotriazole ultraviolet absorbent is 2- [ 2' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl) ] benzotriazole (UV 234),

the preparation method comprises the following steps:

(1) adding 100kg of 2-nitro-2 ' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl) azobenzene and 500kg of methanol into a pressure reaction kettle, mixing, stirring and dissolving, and adding 1kg of Rh/C catalyst with 1% rhodium loading;

(2) then 5kg of KOH is added, and nitrogen is used for replacing 3 times;

(3) introducing hydrogen, and reacting for 24 hours at the hydrogen pressure of 0.2MPa and the temperature of 30 ℃;

(4) cooling to room temperature, filtering, recovering filter residue as catalyst, distilling the filtrate under reduced pressure at-0.1 MPa and 35-40 deg.C to obtain 2- [ 2' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl) ] benzotriazole (UV 234) as white to light yellow crystal powder; the distilled reaction solvent methanol is recovered for standby.

This example gives 88.94 kg of the product 2- [ 2' -hydroxy-3 ',5' -bis (. alpha.,. alpha. -dimethylbenzyl) ] benzotriazole (UV 234) in 95.3% yield and 99.4% purity by HPLC. Elemental analysis results: c, 80.59; h, 6.48; n, 9.41; and O, 3.52. Theoretical value of elemental analysis: c, 80.51; h, 6.53; n, 9.39; and O, 3.57.

Example 2

A preparation method of a benzotriazole ultraviolet absorbent, wherein the benzotriazole ultraviolet absorbent is 2- [ 2' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl) ] benzotriazole (UV 234),

the preparation method comprises the following steps:

(1) adding 100kg of 2-nitro-2 ' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl) azobenzene and 1000kg of absolute ethyl alcohol into a pressure reaction kettle, mixing, stirring and dissolving, adding 5kg of Ru/TiO with 10% ruthenium loading capacity₂A catalyst;

(2) then 80kg of triethylamine is added, and nitrogen is used for replacement for 3 times;

(3) introducing hydrogen, and reacting for 8 hours at the hydrogen pressure of 3MPa and the temperature of 70 ℃;

(4) cooling to room temperature, filtering, recovering filter residue as catalyst, distilling the filtrate under reduced pressure at-0.1 MPa and 35-40 deg.C to obtain 2- [ 2' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl) ] benzotriazole (UV 234) as white to light yellow crystal powder; distilled is reaction solvent absolute ethyl alcohol, and is recovered for standby.

This example provides 89.59kg of the product 2- [ 2' -hydroxy-3 ',5' -bis (. alpha.,. alpha. -dimethylbenzyl) ] benzotriazole (UV 234) in 96.0% yield and 99.2% purity by HPLC (high performance liquid chromatography). Elemental analysis results: c, 80.47; h, 6.50; n, 9.44; and O, 3.59. Theoretical value of elemental analysis: c, 80.51; h, 6.53; n, 9.39; and O, 3.57.

Example 3

A preparation method of a benzotriazole ultraviolet absorbent, wherein the benzotriazole ultraviolet absorbent is 2- [ 2' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl) ] benzotriazole (UV 234),

the preparation method comprises the following steps:

(1) adding 100kg of 2-nitro-2 ' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl) azobenzene and 600kg of DMF into a pressure reaction kettle, mixing, stirring for dissolving, adding 3kg of Pd/SiO with 5% palladium loading capacity₂A catalyst;

(2) then 30kg of anhydrous sodium carbonate is added, and nitrogen is used for replacing for 3 times;

(3) introducing hydrogen, and reacting for 6h at the hydrogen pressure of 1MPa and the temperature of 110 ℃;

(4) cooling to room temperature, filtering, recovering filter residue as catalyst, distilling the filtrate under reduced pressure at-0.1 MPa and 35-40 deg.C to obtain 2- [ 2' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl) ] benzotriazole (UV 234) as white to light yellow crystal powder; the reaction solvent DMF is distilled out and recovered for later use.

This example provides 90.06kg of the product 2- [ 2' -hydroxy-3 ',5' -bis (. alpha.,. alpha. -dimethylbenzyl) ] benzotriazole (UV 234) in 96.5% yield with a purity of 99.0% by HPLC. Elemental analysis results: c, 80.56; h, 6.58; n, 9.36; and O, 3.50. Theoretical value of elemental analysis: c, 80.51; h, 6.53; n, 9.39; and O, 3.57.

Example 4

A preparation method of a benzotriazole ultraviolet absorbent, wherein the benzotriazole ultraviolet absorbent is 2- [ 2' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl) ] benzotriazole (UV 234),

the preparation method comprises the following steps:

(1) adding 100kg of 2-nitro-2 ' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl) azobenzene and 500kg of methyl acetate into a pressure reaction kettle, mixing, stirring and dissolving, and adding 5kg of Pd/C catalyst with 10% palladium loading capacity;

(2) then 20kg of anhydrous potassium carbonate is added, and nitrogen is used for replacement for 3 times;

(3) introducing hydrogen, and reacting for 5 hours at the hydrogen pressure of 1.5MPa and the temperature of 60 ℃;

(4) cooling to room temperature, filtering, recovering filter residue as catalyst, distilling the filtrate under reduced pressure at-0.1 MPa and 35-40 deg.C to obtain 2- [ 2' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl) ] benzotriazole (UV 234) as white to light yellow crystal powder; the distilled reaction solvent methyl acetate is recovered for standby.

This example gives 88.75 kg of the product 2- [ 2' -hydroxy-3 ',5' -bis (. alpha.,. alpha. -dimethylbenzyl) ] benzotriazole (UV 234) in 95.1% yield and 99.5% purity by HPLC (high performance liquid chromatography). Elemental analysis results: c, 80.60; h, 6.42; n, 9.43; and O, 3.55. Theoretical value of elemental analysis: c, 80.51; h, 6.53; n, 9.39; and O, 3.57.

Example 5

A preparation method of a benzotriazole ultraviolet absorbent, wherein the benzotriazole ultraviolet absorbent is 2- [ 2' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl) ] benzotriazole (UV 234),

the preparation method comprises the following steps:

(1) adding 100kg of 2-nitro-2 ' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl) azobenzene and 1000kg of ethyl acetate into a pressure reaction kettle, mixing, stirring and dissolving, and adding 1kg of Pt/C catalyst with 10% platinum load;

(2) after 3 times of replacement with nitrogen, 30kg of ammonia gas was added;

(3) introducing hydrogen, and reacting for 20 hours at the hydrogen pressure of 3MPa and the temperature of 40 ℃;

(4) cooling to room temperature, filtering, recovering filter residue as catalyst, distilling the filtrate under reduced pressure at-0.1 MPa and 35-40 deg.C to obtain 2- [ 2' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl) ] benzotriazole (UV 234) as white to light yellow crystal powder; the reaction solvent ethyl acetate is distilled out and recovered for later use.

This example gives 90.81kg of the product 2- [ 2' -hydroxy-3 ',5' -bis (. alpha.,. alpha. -dimethylbenzyl) ] benzotriazole (UV 234) in 97.3% yield and 99.3% purity by HPLC (high performance liquid chromatography). Elemental analysis results: c, 80.39; h, 6.61; n, 9.50; and O, 3.51. Theoretical value of elemental analysis: c, 80.51; h, 6.53; n, 9.39; and O, 3.57.

Example 6

A preparation method of a benzotriazole ultraviolet absorbent, wherein the benzotriazole ultraviolet absorbent is 2- [ 2' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl) ] benzotriazole (UV 234),

the preparation method comprises the following steps:

(1) 100kg of 2-nitro-2 ' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl) azobenzene and 800kg of toluene are added into a pressure reaction kettle, mixed and stirred to be dissolved, and then 5kg of Rh/SiO with 5 percent of rhodium loading is added₂A catalyst;

(2) then 50kg of sodium bicarbonate is added, and nitrogen is used for replacing 3 times;

(3) introducing hydrogen, and reacting for 8 hours at the hydrogen pressure of 0.5MPa and the temperature of 100 ℃;

(4) cooling to room temperature, filtering, recovering filter residue as catalyst, distilling the filtrate under reduced pressure at-0.1 MPa and 35-40 deg.C to obtain 2- [ 2' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl) ] benzotriazole (UV 234) as white to light yellow crystal powder; the distilled reaction solvent toluene is recovered for standby.

This example provides 90.43kg of the product 2- [ 2' -hydroxy-3 ',5' -bis (. alpha.,. alpha. -dimethylbenzyl) ] benzotriazole (UV 234) in 96.9% yield and 99.5% purity by HPLC (high performance liquid chromatography). Elemental analysis results: c, 80.66; h, 6.71; n, 9.24; and O, 3.39. Theoretical value of elemental analysis: c, 80.51; h, 6.53; n, 9.39; and O, 3.57.

Example 7

A preparation method of a benzotriazole ultraviolet absorbent, wherein the benzotriazole ultraviolet absorbent is 2- [ 2' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl) ] benzotriazole (UV 234),

the preparation method comprises the following steps:

(1) 100kg of 2-nitro-2 ' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl) azobenzene and 600kg of xylene are added into a pressure reaction kettle, mixed and stirred to be dissolved, and then 2kg of Pt/TiO with 10 percent of platinum loading is added₂A catalyst;

(2) then 30kg of calcium hydroxide is added, and nitrogen is used for replacement for 3 times;

(3) introducing hydrogen, and reacting for 12h at the hydrogen pressure of 3MPa and the temperature of 90 ℃;

(4) cooling to room temperature, filtering, recovering filter residue as catalyst, distilling the filtrate under reduced pressure at-0.1 MPa and 35-40 deg.C to obtain 2- [ 2' -hydroxy-3 ',5' -di (alpha, alpha-dimethylbenzyl) ] benzotriazole (UV 234) as white to light yellow crystal powder; the distilled reaction solvent xylene is recovered for standby.

This example provides 89.03 kg of the product 2- [ 2' -hydroxy-3 ',5' -bis (. alpha.,. alpha. -dimethylbenzyl) ] benzotriazole (UV 234) in 95.4% yield and 99.1% purity by HPLC. Elemental analysis results: c, 80.51; h, 6.52; n, 9.38; and O, 3.59. Theoretical value of elemental analysis: c, 80.51; h, 6.53; n, 9.39; and O, 3.57.

Example 8

A preparation method of a benzotriazole ultraviolet absorbent is provided, wherein the benzotriazole ultraviolet absorbent is 2- (2' -hydroxy 3',5' -di-tert-butylphenyl) -5-chlorobenzotriazole (UV 327),

the preparation method comprises the following steps:

(1) adding 100kg of 2-nitro-4-chloro-2 ' -hydroxy-3 ',5' -di-tert-butylazobenzene and 1000kg of methanol into a pressure reaction kettle, mixing, stirring and dissolving, and adding 5kg of Rh/C catalyst with 1% rhodium loading;

(2) then 5kg of KOH is added, and nitrogen is used for replacing 3 times;

(3) introducing hydrogen, and reacting for 22h at the hydrogen pressure of 0.2MPa and the temperature of 40 ℃;

(4) cooling to room temperature, filtering, recovering filter residue as catalyst, distilling the filtrate under reduced pressure at-0.1 MPa and 35-40 deg.C to obtain 2- (2' -hydroxy 3',5' -di-tert-butylphenyl) -5-chlorobenzotriazole (UV 327) as white to light yellow crystal powder; the distilled reaction solvent methanol is recovered for standby.

This example gives 87.69kg of the product 2- (2' -hydroxy-3 ',5' -di-tert-butylphenyl) -5-chlorobenzotriazole (UV 327) in 95.5% yield with a purity of 99.6% by HPLC. Elemental analysis results: c, 67.0; h, 6.84; cl, 10.18; n, 11.65; o, 4.33. Theoretical value of elemental analysis: c, 67.12; h, 6.76; cl, 9.91; n, 11.74; and O, 4.47.

Example 9

A preparation method of a benzotriazole ultraviolet absorbent is provided, wherein the benzotriazole ultraviolet absorbent is 2- (2' -hydroxy 3' -tert-butyl-5 ' -methyl) -5-chlorobenzotriazole (UV 326),

the preparation method comprises the following steps:

(1) 100kg of 2-nitro-4-chloro-2 ' -hydroxy-3 ' -tert-butyl-5 ' -methylazobenzene and 700kg of methyl acetate are added into a pressure reaction kettle, mixed, stirred and dissolved, and then 2kg of Pd/SiO with 5% palladium loading is added₂A catalyst;

(2) then 50kg of triethylamine is added, and nitrogen is used for replacement for 3 times;

(3) introducing hydrogen, and reacting for 14h at the hydrogen pressure of 2.0MPa and the temperature of 60 ℃;

(4) cooling to room temperature, filtering, recovering the filter residue as a catalyst for later use, and distilling the filtrate under reduced pressure at-0.1 MPa and at 35-40 ℃ to obtain a product 2- (2' -hydroxy-3 ' -tert-butyl-5 ' -methyl) -5-chlorobenzotriazole (UV 326) which is white to light yellow crystal powder; the distilled reaction solvent methyl acetate is recovered for standby.

This example provided 88.13kg of the product 2- (2' -hydroxy-3 ' -tert-butyl-5 ' -methyl) -5-chlorobenzotriazole (UV 326) in 97.1% yield and 99.5% purity by HPLC. Elemental analysis results: c, 64.81; h, 5.68; cl, 11.34; n, 13.17; and O, 5.0. Theoretical value of elemental analysis: c, 64.66; h, 5.75; cl, 11.23; n, 13.31; and O, 5.07.

Example 10

A preparation method of a benzotriazole ultraviolet absorbent is provided, wherein the benzotriazole ultraviolet absorbent is 2- (2' -hydroxy-3 ',5' -ditert-amyl-phenyl) benzotriazole (UV 328),

the preparation method comprises the following steps:

(1) 100kg of 2-nitro-2 '-hydroxy-3'Adding 5' -ditert-amyl azobenzene and 900kg DMF into a pressure reaction kettle, mixing, stirring to dissolve, adding 4kg Pt/TiO with 3% platinum loading₂A catalyst;

(2) then 20kg of sodium bicarbonate is added, and nitrogen is used for replacing 3 times;

(3) introducing hydrogen, and reacting for 6 hours at the hydrogen pressure of 3MPa and the temperature of 80 ℃;

(4) cooling to room temperature, filtering, recovering the filter residue as catalyst, and distilling the filtrate under reduced pressure at-0.1 MPa and 35-40 deg.C to obtain 2- (2' -hydroxy-3 ',5' -ditert-pentylphenyl) benzotriazole (UV 328) as white to pale yellow crystal powder; the reaction solvent DMF is distilled out and recovered for later use.

This example gave 87.41kg of the product, 2- (2' -hydroxy-3 ',5' -ditert-pentylphenyl) benzotriazole (UV 328) in 95.4% yield and 99.2% purity by HPLC (high performance liquid chromatography). Elemental analysis results: c, 75.01; h, 8.53; n, 12.06; and O, 4.4. Theoretical value of elemental analysis: c, 75.18; h, 8.32; n, 11.95; and O, 4.55.