Study On Reduction Of Mixed Nitrochlorobenzenes And Separation Of Mixed Chloroanilines

The mixture of ortho-nitrobenzene (o-NCB), para-nitrobenzene (p-NCB) and meta-nitrobenzene (m-NCB) can be produced by nitration reaction of chlorobenzene. High purity p-NCB and m-NCB can be got by crystallization and rectification processes. Then ,a mixture containing nitrobenzene, m-NCB, p-NCB and m-NCB still remained. This essay will complete the reduction of mixed nitrobenzenes and separation of mixed amines. We have finished the works below.(1) Reduction of mixed nitrobenzenes: the mixture of nitrobenzene and NCB isomers can be catalytic hydrogenated to produce the mixture of aniline, ortho-chloroaniline (o-CA), para-chloroaniline (p-CA) and meta-chloroaniline (m-CA). We chose alcohol as solvent, 3% Pt/C as catalyst and completed the reduction of the mixture of nitrobenzene and NCB isomers. The influences of some factors such as concentration of raw materials, the amount of catalyst and reaction temperature are discussed and the optimized conditions are determined. We also finished the experiments of reusing recovery solvent and catalyst. This assures the industrial feasibility of our process.(2) The separation of aniline and o-CA: We separated solvent, aniline and o-CA from reduction solution by rectification method and accumulated the mixture of aniline and o-CA to be separated to get pure aniline and o-CA.(3) Most p-CA is purified from the mixture of p-CA and m-CA by crystallization method.(4) The separation of m-CA from the mixture of m-CA and p-CA is carried out by countercurrent dissociation extraction (CDE). This method can solve the problems, such as high consumption of extracting acid and great amount of wastewater, which can be caused by alternative extraction. This method of CDE possesses the advantages of low cost and high profit and can be industrialized. The influences of the factors such as temperature, molecular ration of extracting acid Vs mixed amines, the content of m-CA and concentration of extracting acid are experimented. We also finished continuous countercurrent dissociation extraction experiment. Extracting acid used as the continuous phase, the separation of m-CA and p-CA is carried out by continuous countercurrent dissociation extraction in filling tower equipment. We compared the results of different filling, remain time and height of filling. We calculated stages of extracting tower and molecular ration of extracting acid Vs mixed amines in equilibrium condition...