The Separation Of Chloroxylenol From The Heat-sensitive System With High Boiling Point

4-chloro-3,5-dimethylphenol, widely used as one kind of broad-spectrumantibiotics, is mainly synthesized by the chlorination of3,5-dimethylphenol inindustry. In this reaction,2-chloro-3,5-dimethylphenol,2,4-dichloro-3,5-dimethylphenol and other by-products are generated. It is difficult to separate4-chloro-3,5-dimethylphenol from the mixture due to the complicated compositions andthe polymerization under high temperature. The product needs to be recrystallizedafter rectification to meet the requirements for quality. It brings about two problems:the product cost is higher due to the recrystallization and the thermal hazard is also aserious problem for the separation. On the basis of the thermal stability theory, ascheme of batch distillation under vacuum is presented to combat these problems inthis article. The operation parameters such as the pressure and the reflux ratio areoptimized and the influential factors of the thermal hazard are investigated.The process for the separation of4-chloro-3,5-dimethyl phenol, with a capacity of8.5t/d, is simulated through PRO/II. The rigorous calculation is on the basis of theNRTL model and Inside-Out algorithm. The major parameters such as reflux ratio,number of the theoretical plates and the operating pressure are determined. Thecolumn diameters and the height of the packing are calculated and the type of thecolumn internals including the liquid distributor, the bed-limiter and the liquidcollector are selected.