Patent ID: 6984762

Claim:
A process for the production of dinitrotoluene by the two-stage nitration of toluene, comprising a) in a first stage, (i) reacting toluene adiabatically with nitrating acid, wherein at least 90% of the toluene is reacted off and no more than 70% of the toluene used reacts to form dinitrotoluene, (ii) separating the organic phase containing mononitrotoluene and the aqueous acid phase containing sulfuric acid, (iii) concentrating the aqueous acid phase containing sulfuric acid by flash evaporation and (iv) recycling the resultant concentrated sulfuric acid into the reaction in the first stage, the reaction in the second stage, the vacuum evaporator in the second stage, or a combination thereof; and b) in a second stage, (i) completely reacting isothermally the organic phase containing mononitrotoluene from the first stage with nitrating acid, (ii) separating the organic phase and the aqueous acid phase containing sulfuric acid, (iii) concentrating the aqueous acid phase containing sulfuric acid by vacuum evaporation, and (iv) recycling the resultant concentrated sulfuric acid into the reaction in the first stage, the reaction in the second stage, or a combination thereof.