Verfahren zur adiabatischen Herstellung von 3,4-Dichlornitrobenzol

1,2-Dichlorbenzol kann unter adiabatischen Reaktionsbedingungen sehr selektiv zu 3,4-Dichlornitrobenzol umgesetzt werden, indem man 1,2-Dichlorbenzol mit Salpetersäure, Schwefelsäure und Wasser gleichzeitig oder sukzessiv in ihrer Gesamtmenge intensiv miteinander vermischt, wozu eine Mischenergie von 1-50 Watt pro Liter des gesamten Reaktionsgemisches, bevorzugt 3-30 W/l, angewandt wird, und bei der Vermischung eine Temperatur von 0 bis 60 DEG C einhält. 3,4-Dichloronitrobenzene (I) production from 1,2-dichlorobenzene (II) involves feeding the reactants into a reactor with mixers to give nitration mixture with 1-5 wt.% nitric acid and 70-92 wt.% sulfuric acid and a (II):nitric acid molar ratio of 0.9-1.5; vigorous mixing at 1-50 W/l reaction mixture; reaction under adiabatic conditions at 0-60 degrees C in mixing and at least 100 degrees C at the end of reaction; phase separation; and distilling water. Production of 3,4-dichloronitrobenzene (I) by reacting 1,2-dichlorobenzene (II) with a mixture of nitric acid (HNO3), sulfuric acid (H2SO4) and water (H2O) to form a mixture of mainly (I) and water of reaction, comprises: (a) feeding (II), HNO3, H2SO4 and H2O into a reactor with mixers in any sequence, so that the nitration mixture contains 1-5 wt.% HNO3 and 70-92 wt.% H2SO4; (b) water is added as diluent for HNO3 and/or H2SO4 and the (II):HNO3 molar ratio is 0.9-1.5; (c) rapid and intensive mixing at a mixing power of 1-50, preferably 3-30 W/l total reaction mixture; (d) carrying out reaction under adiabatic conditions, by feeding the reactants at such temperatures that mixing takes place at 0-60 degrees C and the temperature does not exceed 100 degrees C at the end of reaction; (e) separating the reaction mixture into an organic and an inorganic phase; and (f) working up the largely HNO3-free inorganic phase by distilling off water.