Process for the preparation of nitroaromatics

摘要

Continuous prepn. of nitroaromatics (I) comprises nitration of aromatic cpds. in a reactor using a nitrating acid contg. 80-100 wt.% inorganic components (consisting essentially of 60-90 wt.% H2SO4 and 1-20 wt.%. HNO3 and at least 5 wt.% water) and up to 20 wt.% organic components (consisting of 70-100 wt.% nitrated aromatics and the remainder by-prods.). The molar ratio HNO3:aromatic cpd. is 0.8-2.5:1. The reaction mixt. leaving the reactor has a temp. of at least 80 degrees C and consists of an upper prod. phase and a lower acid phase. The prod. phase is worked up and the acid phase which contains some organics is freed from at least 5 wt.% of the water by depressurising evapn. opt. with the addn. of heat. After the depressurising evapn., the liquor is brought into a vacuum directly in the spray stream of a cooling agent, esp. water, thus condensing the liquor. One part of the condensate consisting of cooling agent, condensed liquor and suspended organics is recycled with cooling and the rest of the condensate is subjected to phase sepn.. The sepd. water is transferred to waste water work up and the sepd. organics used again.