Separation And Purification Of M-/P-cresol Using Adsorption Method

Cresols are found in tar and tar like products formed in the thermalcracking of such natural materials as coal and petroleum products, or fromchemical synthesis. Cresols are important fine chemistry raw material, the threeisomeric forms of cresols occur in: o-cresol, m-cresol, and p-cresol. At present,with the continuous development of downstream products of cresol monomer,the demand of high purity monomer increased, but the production scale is small,so there have the obvious contradiction between supply and demand. This paperhave studied the adsorption separation of m-/p-cresol, this method has theadvantages of simple, high separation efficiency, large processing quantity andthe adsorbent can be regenerated, it is an cheap environmentally separationmethod.Based on the previous experiments, the software ASPEN was used tosimulate the dynamic adsorption-distillation process for the separation ofm-/p-cresol. By choosing the correct physical method, adsorption mathematicalmodel and using the sensitivity analysis tool, the effects of operating parametersof each module on the separation were studied, and the optimum processparameters were obtained. The separation of m-/p-cresol process including two times ofadsorption-distillation, each process is divided into adsorption, desorption anddistillation. The adsorption of cresols was simulated by Aspen Adsorption, andthe bed height to diameter ratio, adsorption temperature, bed voidage werediscussed. Besides, the axial concentration distribution of p-cresol and theadsorbent loading at different time were obtained through the simulation. Thedistillation process was simulated using Aspen Plus software, the influences ofthe theoretical plate number, feed location, reflux ratio and temperature on theproducts were investigated. Conclusions are as follows:1, The optimum values of height to diameter ratio, temperature, bedvoidage of Bed1were6,363.15K,0.5. The m-cresol purity was99.99%, therecovery was91.74%, which achieved the separation of m-cresol and p-cresolpreliminarily.2, Due to the addition of desorption agent, mass fraction of p-cresol was27.08%, so there needs further separation by distillation. The plate number, feedlocation and reflux ratio of RAD1were8,3and0.7, respectively. Under thiscondition, the purity of p-cresol was90.56%.3, In order to refine p-cresol, secondary adsorption was carried out, theheight to diameter ratio and void ratio of Bed2were5and0.4，and the purity ofp-cresol was up to46.90%. 4, Plate number, reflux ratio, feed location of RAD2was chosen as9,0.5,3,respectively. At the same time, the p-cresol purity was99.12%, it already meetthe market requirement.5, Using the Aspen Adsorption module, the load curve of adsorption towerwas obtained, according to the load curve the adsorption conditions can beadjusted in time.6, The mass purity and recovery of m-cresol, p-cresol were99.99%and91.74%,99.10%and97.58%.The Aspen simulator provides a useful tool fordesigning and optimizing of m/p-cresol separation processes. These optimalsimulation data can provide reference for further scale-up experiment andindustrial application.