Preparation and analytical methods of benzotriazole_Kain Industrial Additives

Background and overview^[1]

Benzotriazole (English name Benzotriazole, abbreviated as BTA; also known as benzotriazole, benzotriazole, benzotriazole, indene) is an important fine chemical product. Benzotriazole has a wide range of uses. It is mainly used as a corrosion inhibitor for copper and copper alloys, metal rust inhibitors, photographic antifogging agents and organic synthesis intermediates. It is also widely used as a coating additive and a preservative for synthetic detergents. , anticoagulants, lubricating oil additives, synthetic dye intermediates, etc. Benzotriazole can be used in conjunction with a variety of corrosion inhibitors to improve the corrosion inhibition effect; it can also be used in conjunction with a variety of scale inhibitors and bactericidal algaecides to produce better effects on closed circulating cooling water systems. Corrosion inhibition effect. For example, adding benzotriazole to automobile antifreeze and paint can protect materials; during mechanical processing, adding benzotriazole to cutting oil can prevent the processed copper from discoloring. In recent years, with the vigorous efforts to save industrial water, water quality stabilizers are widely used in chemical industry, fertilizer, steel and other industrial fields, and the amount used is increasing day by day. With the continuous development of the chemical industry, automobile industry and metal processing industry in various countries, as well as the continuous improvement of people’s living standards, the demand for benzotriazole is increasing.

Preparation^[1]

CN201510774530.6 provides a synthesis method of benzotriazole that does not require acetic acid, has few side reactions, little pollution, high yield and short reaction time, and can be continuously produced. In order to solve the above technical problems, the technical solution of the present invention is: a synthesis method of benzotriazole. The innovative point is that benzotriazole is synthesized in one step through the pressurization method of o-phenylenediamine. The specific steps are as follows:

(1) Feeding: Put o-phenylenediamine, sodium nitrite and water into the stainless steel reactor in a ratio of 1:1.1~1.2:10~15;

(2) Temperature and pressure increase: start stirring, raise the temperature, raise the temperature to 240~260℃, control the pressure between 3.0~4.0MPa, and keep the reaction for 3~3.5 hours;

(3) Transfer to the acidification kettle: lower the temperature to 120~130°C, and transfer the reaction product to the acidification kettle; (4) Adjust pH and layer: use concentrated sulfuric acid to adjust the pH value from 11.7 to 5.0, and layer;

(5) Purification and collection: The stratified oil layer enters the distillation kettle for vacuum purification, and the 202-204°C/15mmHg fraction is collected.

The advantage of the present invention is that the synthesis method of benzotriazole of the present invention is to synthesize benzotriazole in one step through the pressurization method of o-phenylenediamine. There is no need to add acetic acid in this synthesis method, and the method has side effects. The reaction is small, the pollution is small, the yield is high and the reaction time is short, benzotriazole can be produced continuously, thereby improving production efficiency.

Crystallization^[2]

Since benzotriazole is slightly soluble in water, cooling crystallization technology can be used to purify benzotriazole. However, the speed of cooling directly affects the crystallization effect of benzotriazole. For example, if If the cooling rate is too fast, the product will not be formed or even agglomerate, the crystal form will not meet the requirements, and the product will be needle-shaped; if the cooling rate is too slow, it will also affect the production efficiency of benzotriazole. CN201210248902.8 provides a cooling crystallization method of benzotriazole, which includes filtering the decolorized crude benzotriazole, then cooling and cooling to crystallize, and finally centrifuging and drying to obtain a finished product, which is characterized by: The cooling process described above is: add 7°C chilled water to the reaction kettle, stir and cool the materials. When the temperature drops to 40±1°C, stop stirring, and pass the outer jacket through the 7°C cooling water. water, let the material cool down slowly and naturally, and crystallize at rest for 2 hours. During the crystallization process, stir slowly to promote the washing out of the crystals. When the crystallization time reaches 4-6 hours, the temperature will naturally drop to 35±1 ℃, and then stir slowly. When the temperature drops to 30±1℃, start stirring. When the temperature drops to 25℃, the cooling and crystallization process is completed, and the material is sent to the centrifuge for dehydration. deal with. The advantage of the present invention is that the benzotriazole produced by slow cooling crystallization has a needle-like product shape and high product purity, which can reach 99.8%.

Analysis methods^[3]

Benzotriazole is a precipitation film type corrosion inhibitor and is a good inhibitor for non-ferrous metals such as copper and silver.Rust and anti-corrosion protective agent, especially for copper and copper alloys, has a unique and excellent corrosion inhibition protection effect, and is most effective in inhibiting surface discoloration and corrosion of copper or copper alloys. Therefore, it is widely used in the surface corrosion treatment of copper or copper alloy parts, the passivation protection treatment of brass imitation gold plating, the coating protection and gas phase storage of copper and copper alloys, etc. Therefore, the correct determination of benzotriazole is very important. seems very important.

The determination of benzotriazole is subject to many interference factors. It is of great significance to eliminate interference and improve the accuracy of the determination of benzotriazole. Therefore, in response to the above problems, CN201711391890.3 provides a fast and accurate analysis method of water-based cleaning agent for PCB boards. Includes the following steps:

S1: Provide water-based cleaning agent for PCB boards containing benzotriazole;

S2: Adjust the pH value of the PCB board containing benzotriazole to 8-9 with a water-based cleaning agent and an inorganic base, then dilute it with a diluent, filter it, and obtain the first liquid to be tested, and use ultraviolet spectroscopy Analyze the first liquid to be tested using photometry to obtain the estimated benzotriazole content in the sample to be tested;

S3: According to the estimated benzotriazole content in the sample to be tested, dilute the PCB board water-based cleaning agent with diluent to 1-20ppm to obtain the second liquid to be tested;

S4: Use HPLC to analyze the second test solution and obtain the accurate benzotriazole content through the standard curve.