Two-stage nitration of toluene to produce dinitrotoluene has an adiabatic and then an isothermal stage so as to give heat savings and improve safety

摘要

Two-stage nitration of toluene to produce dinitrotoluene involves a first adiabatic stage and a second isothermal stage. Two-stage nitration of toluene to produce dinitrotoluene comprises (1) adiabatically reacting toluene with nitrating acid such that the toluene is >= 90 % reacted and a maximum of 50 % is reacted to dinitrotoluene, separating the mononitrotoluene-containing organic phase and the aqueous sulfuric acid-containing phase, concentrating the acid aqueous phase by flash evaporation and recycling the concentrated sulfuric acid to the first or second stage or to a concentration process in the second stage; and (2) isothermally completing the nitration of the mononitrotoluene-containing organic phase, separating the organic and aqueous sulfuric acid-containing phases, concentrating the acid, aqueous phase by vacuum evaporation and recycling the acid to the first or second stage.