Study on Micro-channel Chlorobenzene Nitrification Process
In order to obtain better production efficiency of nitrochlorobenzene and change the phenomenon of low yield and poor selectivity,chlorobenzene was used as the starting react-ant to synthesize nitrochlorobenzene in a silicon carbide microchannel reactor.The effects of molar ratio of chlorobenzene to nitric acid,molar ratio of sulfuric acid to nitric acid,prehea-ting temperature,reaction temperature and residence time on the reaction were investigated and optimized.When the mass fraction of nitric acid is 95％,the mass fraction of sulfuric acid is 85％,n(chlorobenzene)∶n(nitric acid)=1∶1.2,n(nitric acid)∶n(sulfuric acid)=1∶2.1,the preheating temperature of mixed acid is 60℃,the reaction temperature is 85℃,and the residence time is 20 s,the conversion rate of chlorobenzene is 99.5％,and the yield of mononitrochlorobenzene is 99.2％.At the same time,the waste acid after the reaction is reprocessed and reused for many times,which improves the utilization rate of waste acid and saves the cost.At the same time,the kinetics was investigated in the micro-channel reactor,and the apparent activation energy Ea=33.43 kJ·mol-1 and the pre-expo-nential factor A=27 905.25 L·(K·mol·min)-1 were obtained.The process reaction time is greatly reduced,less by-products,high yield and selectivity,more green safety and envi-ronmental protection,to achieve a green and safe production of nitrochlorobenzene,improve production efficiency.
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