Method for removing HCN from crude dinitro toluene

摘要

A process for the preparation of dintrotoluene which comprises (a) nitrating toluene with a nitrating acid, wherein said nitrating acid is a mixture of nitric acid and sulfuric acid, in one or more nitration steps, and separating the nitrating acid from the process stream thus formed, wherein a crude mixture comprising dinitrotoluene and a fraction of said nitrating acid dissolved therein is obtained, said crude mixture further comprising at least 50 ppm of HCN, and (b) washing the crude dinitrotoluene containing mixture in one or more washing steps, wherein, before the first washing step is carried out, the crude mixture is distilled and/or stripped to remove HCN therefrom, wherein a crude dinitrotoluene containing mixture which is essentially free of HCN is obtained.

主权项

1. A process for the preparation of dinitrotoluene which comprises
(a) nitrating toluene with a nitrating acid, wherein said nitrating acid is a mixture of nitric acid and sulfuric acid, in one or more nitration steps, and separating the nitrating acid from the process stream thus formed, wherein a crude mixture comprising dinitrotoluene and a fraction of said nitrating acid dissolved therein is obtained, said crude mixture further comprising at least 50 ppm of HCN, and (b) washing the crude dinitrotoluene containing mixture in one or more washing steps, wherein, before the first washing step is carried out, the crude mixture is distilled and/or stripped in a flash evaporator, stripping or distillation column to remove HCN therefrom, wherein a crude dinitrotoluene containing mixture which is essentially free of HCN is obtained, and the gaseous phase obtained from the top of the flash evaporator, stripping or distillation column is partially condensed in order to recover a condensate containing nitric acid, sulfuric acid and dinitrotoluene while keeping as least 50% of the HCN in the gaseous phase.