Research On The Separation Of Phenol And Cresol From Crude Phenol

Phenol and cresol monomers are important intermediates and raw materials in the chemical industry.They are widely used in the fields of pesticide,medicine,paint,dye,antioxidant and so on.There are a large amount of phenol and cresol in crude phenol producted from the coal gasification.According to the difference of boiling point,phenol and o-cresol can be separated by distillation method.However,the difference of boiling point between m-cresol and p-cresol is 0.2℃,it is difficult to be separated by traditional distillation method.The phenol products and the mixture of m-cresol and p-cresol products were obtained by intermittent decompression distillation of crude phenol.The distillation model was established by Aspen plus V11 software and the parameters were optimized.Through reduced pressure distillation of crude phenol,we had got the phenol product with the yield of 0.369 in which the mass fraction was 0.995 and the relative error between simulated yield experimental yield was 0.155,the phenol product with the yield of 0.169 in which the mass fraction was 0.979 and the relative error between simulated yield experimental yield was 0.205 and the phenol product with the yield of 0.170 in which the mass fraction was 0.861 and the relative error between simulated yield experimental yield was 0.267.Through secondary reduced pressure distillation of crude phenol,we had got the mixture of m-and p-cresol with the yield of 0.590 in which the mass fraction was 0.895.Then,five kinds of three-column continuous distillation schemes were designed to separate crude phenol by using Aspen plus V11 softare according to the different production volume of tower top and tower kettle.The molar contents of phenol,o-cresol,and m-cresol were setted to 0.995,0.990,0.980.The raw material feeding amount of crude phenol was 1000 kg·h^-1,the feeding temperature of crude phenol was 50℃,the feeding pressure was 101.325 k Pa and the plate pressure drop was 0.5k Pa.First,the Aspen plus V11 simple distillation module DSTWU was used to obtain the theoretical tray number,the feed tray number,the reflux ratio and the top recovery rate of each tower.Then based on these results,strict rectification module Rad Frac was used to optimize the theoretical tray number,the feed tray number,the condenser pressure,the reflux ratio and top recovery rate of each tower.Finally,economic analysis was carried out to get the better scheme.Finally,the mixture of m-cresol and p-cresol obtained from secondary distillation of crude phenol（the mass content of m-cresol and p-cresol was about 0.9）was used as raw material.Urea was used as complexing agent and petroleum ether was used as solvent at boiling range of 60-90℃.The influences of reaction temperature,reaction time,crystallization temperature,crystallization time,amount of urea and amount of solvent on the content and yield of m-cresol were investigated by orthogonal experiment and single factor experiment.The better process conditions were chosen:the reaction temperature was 91.0℃and the reaction time was 50min,the mole ratio of urea and m-cresol was 1.31,the mass ratio of solvent and raw material was 2,the crystallization temperature was-5.74℃and the crystallization time was 120 min.In this way,the mass fraction of m-cresol was 0.993,and the yield of m-cresol was 0.686.