Optimal Process Design Of 3550 T/a Parachlorotrifluoromethylbenzene

p-Chlorotrifluoromethylbenzene is an important raw material of chemical pesticides and biological pharmaceuticals,which is mainly used in the production of high efficient and value-added pesticides and pharmaceuticals,such as 3,4-dichlorotrifluoromethylbenzene,4-chloro-3,5-dinitrotrifluoromethylbenzene,tri-fluralin,flusulfaxide,carboxyfluoxane,fipronil,and fluoxetine hydrochloride.In the existing production process of p-chlorotrifluoromethylbenzene with the use of p-chlorotoluene as a raw material,the yield of p-chlorotrifluoromethylbenzene is less than 90%.And the amounts of chlorine gas and hydrogen fluoride is 2.05 and 1.20 times of the theoretical ones.The discharge of "three wastes" is high.These problems seriously restrict the production of p-chlorotrifluoromethylbenzene as well as its application.This work has carried out the process optimization design of the project with an annual output of 3550 tons of p-chlorotrifluoromethylbenzene.(1)In view of the main problems of low chlorination reaction yield and low effective utilization rate of chlorine gas in the current synthesis process,this design adds a dehydration process of raw material,p-chlorotoluene.After dehydration,the moisture content of p-chlorotoluene feedstock is reduced from 0.5%(5000 ppm)to 0.05%(500 ppm).Decreasing water content can reduce the formation amount of byproduct,p-chlorobenzoic acid.(2)At the same time,using azodiisobutyronitrile as a catalyst,the yield of p-chlorotrichloromethylbenzene is further increased above 98%,and the spent amount of chlorine gas is reduced to 1.77 times of the theoretical value.(3)High pressure fluorination technology is used to fluorinate 4-chlorotrichloromethylbenzene with hydrogen fluoride.The yield of p-chlorotrifluoromethylbenzene is above 98% and the spent amount of hydrogen fluoride is reduced to 1.11 times of the theoretical one.(4)The by-product hydrogen chloride can be absorbed to produce 30% industrial hydrochloric acid,hydrogen fluoride/hydrogen chloride can be absorbed to produce industrial mixed acid for quartz sand purification in the photovoltaic industry.(5)Hydrogen chloride tail gas emission is decreased to 244.6g/t product,hydrogen fluoride tail gas emission decreased to 12.4g/t product,and hazardous waste production decreased to 25.25kg/t product.The industrial process of an annual output of 3550 tons of p-chlorotrifluoromethylbenzene has been designed.The designing work includes production scheme and process optimization,material and heat balances,typical equipment calculation,instrument selection,process flow chart drawing with control points,equipment layout drawing,environmental protection and energy consumption evaluation,social and economic benefit analysis,etc.The design and calculation of dehydration of p-chlorotoluene,chlorination of p-chlorotoluene,fluorination of p-chlorotrichloromethylbenzene,rectification and neutralization of p-chlorotrifluoromethylbenzene are performed.For an annual output of3550 tons of p-chlorotrifluoromethylbenzene,2554.38 tons of p-chlorotoluene,4407.79 tons of liquid chlorine,1.91 tons of diisobutyronitrile,and 1338.86 tons of hydrogen fluoride are needed.The total yield of p-chlorotrifluoromethylbenzene reaches 97.69%.The p-chlorotrifluoromethylbenzene production process includes the p-chlorotoluene dehydration,azodiisobutyronitrile catalysis,high pressure fluorination,semi-continuous distillation technologies.Compared with the traditional process,this design improves the conversion rate of chlorination and fluorination,significantly increasing the yield of p-chlorotrifluoromethylbenzene.Hydrogen chloride and hydrogen fluoride byproducts are used to produce industrial grade acids,reducing the discharge of wastes.The project design strictly follows the engineering ethics,on this basis,fully considers the potential impact of this design practice on society,health,safety,law,culture and the environment,etc.After adopting the safety and environmental protection measures in this design,the construction of project can meet the requirements of the bottom line of environmental quality,ecological protection red line,and resource utilization online,which has a good demonstration role in the relative industry.