Process for the preparation of dinitrotoluene

摘要

Continuous two-stage prodn. of dinitrotoluene (DNT) isomer mixts. by nitration of toluene comprises (1a) isothermal reaction of toluene in a continuous reactor with a nitrating acid contg. (i) 80-100 wt.% inorganic components comprising 60-90 wt.% H2SO4, 1-20 wt.% HNO3 and at least 5 wt.% water, and (ii) 0-20 wt.% organic components comprising 70-100% nitrotoluene isomers plus by-prods., at 0-100 degrees C with a mole ratio of (HNO3):(toluene) = (0.7:1)-(1.2:1); (1b) sepg. the two phases; and (2a) reacting the organic phase under adiabatic conditions at 20-200 degrees C with a nitrating acid as above, with a mole ratio of (HNO3)(mononitrotoluene (MNT)) = (0.7:1)-(1.2:1); (2b) sepg. into two phases; and (2c) concentrating the acid phase by flash evapn. of at least 5% of the water, opt. with heating, making up with 50-100 wt.% HNO3 and returning to the reaction.