A method for efficiently treating waste liquid of permanent violet nitrification

Abstract

The invention discloses a method for efficiently treating permanent violet nitration wastewater. The method comprises the following steps: layering the wastewater generated by the nitration reaction in the permanent violet production process, adjusting the acid concentration of the water layer by concentrated nitric acid until the concentration is 25%-30%, and returning the water layer to the nitration reaction, and continuously using; and distilling the organic layer, and recovering organic solvents, and stopping distilling while the concentration of 3-nitryl-N-ethylcarbazole is improved to 23%-27%, cooling and crystallizing the organic layer, separating out 3-nitryl-N-ethylcarbazole crystal, filtering, recovering to obtain the 3-nitryl-N-ethylcarbazole, continuously distilling the residual filtrate until the dryness, to obtain the recovered organic solvent and the residue after the distilling, and using the distilled residue as roadbuilding pitch for selling. The method is capable of improving the yield, saving raw materials, and reducing the pressure to the environment caused by the nitration wastewater.

Description

technical field [0001] The invention belongs to the technical field of synthetic chemical industry, and in particular relates to a method for efficiently treating waste liquid of permanent violet nitrification. Background technique [0002] Permanent violet, also known as dioxazine violet, is synthesized from carbazole as a starting material, reacting with ethyl bromide in the presence of a phase transfer catalyst to obtain N-ethyl carbazole, N-ethyl carbazole in chlorobenzene React with dilute nitric acid to obtain N-ethyl-3-nitrocarbazole. N-ethyl-3-nitrocarbazole undergoes catalytic hydrogenation reduction to generate N-ethyl-3-aminocarbazole, and then reacts with tetrachlorobenzoquinone through condensation and ring closure to generate crude permanent violet. [0003] During the nitration process, the target product N-ethyl-3-nitrocarbazole exists in the nitration mother liquor, and about 98% of N-ethyl-3-nitrocarbazole is obtained after pressure filtration and washing....

AI Technical Summary

Problems solved by technology

At present, most manufacturers recover part of the chlorobenzene solvent after simple distillation of the nitration mother liquor, and the remaining residue is treated as production solid waste. On the one hand, it pollutes the environment, and on the other hand, the yield of intermediate products decreases.