| Pyrocatechol and hydroquinone, as important raw material intermediates in fine chemical industries, are used in many fields. The catalytic hydrogenation of phenol by hydrogen peroxide is the advanced technology that produces pyrocatechol and hydroquinone. The produced phenol hydroxylation mixture's moisture content is very high and presently used dehydration method by direct distillation led to higher energy consumption and heat-sensitive loss of products. There will be a big improvement in the separation process of the mixture if applying extraction dehydration. The paper measured the phase equilibrium data of the involved systems and fitted them. The results present that there are biggish hierarchical classification zones if the extractant , 4-methyl-2-pentanone (MIBK) or diisopropyl ether (DIPE), is added and the distribution coefficient and selectivity coefficient are high in the extraction process. The paper discussed the major factors which affect the extract process and drew the conclusion that the appropriate operating conditions for DIPE is the mass ratio of the extractant to the solution (R) 1:3, the speed of agitation 590r/min, the time of agitation within 2h, proper to 1~2h,the time of lamination 1.5~2h, the Re number within 8500~10000; the appropriate operating conditions for MIBK is R=1:3, the speed of agitation 340~390r/min, the time of agitation within 1~1.5h, the time of lamination 0.25~1h, the Re number within 6000~8000.The experiment result of multilevel extractions suggests that the percentage extraction with MIBK or DIPE can reach over 99% under the condition of R=1:3, but as for dihydric phenol MIBK's extract effect is prior to DIPE. So the paper suggests selecting MIBK as the extractant for the dehydration process.On the basis of obtaining the equations of distribution curves, the processes of multilevel extractions were computed by the method of analogue plotting calculation. The results are anastomotic to the foregoing experiments. The original program can predict and guide the separation performance. |
