Main applications of p-chlorophenol_Kain Industrial Additives

Background and overview^[1-2]

P-Chlorophenol is white crystal, yellow or pink when impure, and has an unpleasant pungent odor. The relative density is 1.306, the melting point is 37°C, the boiling point is 217°C, and the refractive index is 1.5579 (40°C). Slightly soluble in water, soluble in benzene, ethanol, and ether, and can evaporate with steam. It is prepared by chlorination of phenol or co-thermal hydrolysis of p-chloroaniline with diazonium salt and sulfuric acid. Used as drug and dye intermediates, alcohol denaturant and selective solvent for refining mineral oil, etc. As an important intermediate, research on preparation methods of p-chlorophenol has always attracted people's attention. Recent domestic literature has also reported gratifying research achievements. The development of production processes and engineering and the development of derivative products are relatively lagging behind. Therefore, , it is necessary to organize efforts to conduct a systematic discussion on improving the recovery of p-chlorophenol in industrial devices and subsequent product process development, thereby improving my country's overall technical level in this field.

Apply^[2-4]

P-chlorophenol was once widely used in the production of fungicides triadimefon, triadimefonol and other agricultural chemicals. In the past year or two, due to the decline in domestic triadimefon production, some p-chlorophenol production units were under-operated, and thus It has also caused a tight supply of by-product o-chlorophenol. Therefore, the development of p-chlorophenol derivatives is a subject of considerable practical significance. According to literature reports, p-chlorophenol reacts with phthalic anhydride under the catalysis of boric acid and fuming sulfuric acid to obtain 1,4-dihydroxyanthraquinone, which is an important dye intermediate. At present, almost all existing 1,4-dihydroxyanthraquinones in China adopt the hydroquinone route. Compared with the p-chlorophenol route, the hydroquinone route has a lower yield and the price of hydroquinone is high. Therefore, if the p-chlorophenol route is used instead, the preparation cost of 1,4-dihydroxyanthraquinone can be greatly reduced, and environmental pollution can be reduced at the same time. 1,4-dihydroxyanthraquinone in Western industrialized countries mainly uses the p-chlorophenol route, and its process technology is relatively mature and worthy of reference by domestic manufacturers.

In addition, it can also be used to prepare 5-chlorosalicylic acid. The steps are: 1. In the mixed solvent of non-water-soluble solution and water, add p-chlorophenol and strong base, and the molar ratio of chlorophenol and strong base 1:1, remove the water through oil-water separation method to obtain a suspension of p-chlorophenol sodium salt; 2. Add to the suspension of p-chlorophenol sodium salt, which can both dissolve p-chlorophenol sodium salt and absorb carbon dioxide The catalyst is then placed in a carbon dioxide atmosphere, and then the temperature is raised to 100-150°C, and the reaction is continued until carbon dioxide is no longer absorbed. The temperature is lowered and the carbon dioxide is eliminated to obtain a mixed liquid; 3. The mixed liquid is refined to obtain 5-chlorosalicylic acid. . The method is simple, easy to operate and has low synthesis cost.

Preparation of 5-chloro-2-hydroxy-3-nitroacetophenone. The preparation method is that in the presence of a catalyst, p-chlorophenol and an acetylation reagent are reacted under solvent-free conditions, and distilled under reduced pressure to obtain p-chlorophenol acetate and glacial acetic acid as a by-product. Add Lewis acid to p-chlorophenol acetate to perform Friis rearrangement reaction. After the reaction is complete, add water to the system and stir to obtain solid precipitation. Recrystallize methanol to obtain 5-chloro-2-hydroxyacetophenone. Add ice. Dissolve acetic acid, then add nitrating reagent dropwise, stir and filter to obtain 5-chloro-2-hydroxy-3-nitroacetophenone. The invention reduces production costs, has short reaction cycle, high purity, high yield, simple operation and easy industrialization.

Preparation^[2]

The preparation of p-chlorophenol by chlorination of phenol is currently the main method used in industry. According to different chlorinating agents, it can be divided into three types: chlorine method, sulfuryl chloride method and copper chloride method.

1. Chlorine method

Phenol can undergo a chlorination reaction with chlorine at a very high speed without a catalyst to produce p-chlorophenol, o-chlorophenol and a small amount of m-chlorophenol. The reaction conditions have a great influence on the selectivity of the target product p-chlorophenol. Influence.

According to Japanese patent reports, phenol reacts with chlorine in the presence of an inert solvent. The reaction temperature is controlled at about 40°C, and the yield of p-chlorophenol is 52%. In the method described in the literature, acetic acid is used as the solvent, and a mixture of chlorine and carbon dichloride is passed into the phenol solution at 30 to 85°C. The conversion rate is controlled at 65% to 70%, and the selectivity of p-chlorophenol is above 60%. Catalysts are commonly used in the preparation methods reported in the recent literature. The literature uses triphenylphosphine (Ph3P) as the catalyst, and phenol is reacted with chlorine at 80°C to prepare p-chlorophenol with a selectivity of 70%. The French patent discloses a method for preparing p-chlorophenol by reacting phenol and chlorine using thiodiphenyl ether as a catalyst. The reaction temperature is 55°C, the conversion rate is 72.7%, and the selectivity reaches 66.5%. If no catalyst is used, the selectivity is 54.5 %. The research results of domestic scholars show that by controlling the reaction conditions such as the amount of chlorine, the yield of p-chlorophenol can reach 90%.

2. Sulfuryl chloride method

Phenol reacts with sulfuryl chloride in the presence of a catalyst to produce p-chlorophenol. The catalysts used mainly include ferric chloride, aluminum trichloride, etc. The selectivity of the target product is very high. Therefore, this process route is a Western A mature process commonly used in industrially developed countries. Some patent documents from the 1960s to 1970s reported a method for preparing p-chlorophenol from sulfuryl chloride in the presence of iron and organic sulfides. When iron powder was used as a catalyst, the yield of p-chlorophenol could reach 80%, and the organic sulfide The existence of is helpful to improve the selectivity of para products.

3. Copper chloride method

Dissolve phenol in acetic acid,�Reaction with copper chloride under pressure can produce p-chlorophenol, with a yield of 86%. If DMF is used as the solvent, the selectivity of p-chlorophenol will be above 85%. The copper chloride method can also be carried out under normal pressure. The reaction process is to pass chlorine gas into the hydrochloric acid solution of phenol and copper chloride at 95°C under nitrogen protection. The yield of p-chlorophenol is 81.1%. Injecting nitrogen can convert the cuprous chloride produced by the reaction into copper chloride, thereby increasing the concentration of the reactants.