Study On A Clean Process Of Para-Aminobenzotrifluoride

Para-aminobenzotrifluoride is an important fluorine-containing intermediate.It is useful in the synthesis of pharmaceutics,pesticides and dyes,such as fipronil, fluazinam,tau-fluvalinate,leflunomide,fluvoxamine,and so on.Here,a synthetic process of the title compound is researched and developed, using para-methylaniline as the main starting material,and comprising three reaction steps such as isocyanation,chlorination and fluorination.The key problems,including greener feedstocks,greener procedures and recycle of by-products,are resolved.A middle-scale trial is preformed to confirm the industrial value of the process.The main research contents and features include:1.synthetic mute.The title compound is synthesized starting from para-methylaniline through 3 steps.The lab-experimental and middle-scale trial are finished.2.non-phosgene synthesis of p-tolyisocyanate.P-tolyisocyanate is prepared by reacting bis(trichloromethyl)carbonate with p-toluidine in 94%yield and 99%purity. By using BTC to replace the high toxic gaseous phosgene,the preparations are operationally safe and environmentally friendly.3.light chlorination.Para-(trichloromethyl)phenyl isocyanate is synthesized in 98%yield and purity by chlorination of p-tolylisocyanate under UV light and 130℃, which is advanced in high yield and simple work-up.4.one-pot synthesis,p-(Trifluoromethyl)aniline is prepared by reacting p-(trichloromethyl)phenyl isocyanate with anhydrous hydrogen fluoride in 85%.The synthesis comprises two reactions:Cl-F exchange and solvotysis of-NCO,which being conducted in one pot. 5.melt crystallization.The title compound is purified above 99%by melt crystallization under low temperature,which keep away from the thermo-decompose of the product.6.by-product recycle and waste treatment.The main by-product HCl gas is absorbed with water to produce industrial hydrochloridic acid.The excessive HF is re-used circularly.In conclusion,it is the first industrial research and development of the 3-step process of para-aminobenzotrifluoride from p-toluidine domestically,with simple operations,good yields,high purities and little waste.The process is suit to large-scalely manufacture of the title compound.