Method of synthesis of 2, 4-dinitrotoluene
The synthetic methods
1. From the nitrification of p-nitrotoluene: the nitrification waste acid (sulfuric acid concentration of 77%) into the nitrification kettle, and then into the melted p-nitrotoluene, stirring, the kettle temperature down to about 55℃. Then add mixed acid (consisting of 31.75% nitric acid and 64.85% sulfuric acid) in two batches, the first batch of feeding temperature is 52-56℃, the second batch of feeding process temperature from 54℃ gradually rises to 70℃, about 6-7h after feeding, reaction continues at 75℃ for nearly 3h.
After the reaction is completed, dilute it with cold water under stirring and let it cool. After all the reactants in the upper layer have solidified, the waste acid (part of the formula) is released. Reheat the reactant and melt it, stir it a little and let it cool. After the reactant solidifies, put the waste acid again. Melt the reactants and neutralize them with a liquid base at 68-70 ° C to a pH of 5-6.
2, 4-dinitrotoluene was obtained by spraying cold water for cooling, cooling to 35℃, filtration and water washing. Raw material consumption quota: p-nitrotoluene 774kg/t, sulfuric acid (95.5%) 785kg/t, nitric acid (98%) 362kg/t.
2. From nitrification of toluene: first, crude nitrotoluene with 97% yield, containing 62-63% of o-nitrotoluene, 33-34% of p-nitrotoluene and 3-4% of m-nitrotoluene.
This crude nitrotoluene is dripped with mixed acid. The crude dinitrotoluene (CAS number [25321-14-6], which is a mixture of three isomers) was obtained by stirring and nitrification with 98.6% yield.
The general situation of the material balance during nitrification is as follows. 2, 4-dinitrotoluene mixture is dissolved in methanol or ethanol, and then cooled, so that 2, 4-dinitrotoluene crystallization, separation, distillation, 2, 4-dinitrotoluene.
The production of pure 2, 4-dinitrotoluene mainly uses the former method, that is, the method of nitrification of p-nitrotoluene, industrial purity ≥95%.