Study On The Separation Of M-Cresol And P-Cresol By Adsorption

As an important raw material,the domestic market for m/p-cresol is huge.Due to the small boiling point difference,m/p-cresol is difficult to rectify and separate.The alkylation method,as the current mainstream method,has the problems of long process flow,serious pollution,and large equipment investment.The import volume of m/p-cresol is increasing year by year.In view of the above problems,this article uses the adsorption separation method to study the separation and purification of m/p-cresol,and obtain a high-purity m/p-cresol product.In order to determine the adsorption performance of the adsorbent A181 for m/p-cresol,the effect of adsorption temperature(25～70°C)and initial concentration of cresol(5～25mg/ml)on adsorption was studied through a single-component static adsorption experiment.The experimental data show that low temperature is beneficial to the adsorption.The saturated adsorption capacity of m/p-cresol is 9.81mg/g and 63.24mg/g,respectively,and the increase of the concentration increases the adsorption equilibrium rate.In two-component conditions,the two cresols have a competitive adsorption effect,and low temperature is beneficial to improve the selectivity of p-cresol.The adsorption mechanism of m/p-cresol was studied,and the static adsorption experimental data were fitted.The data shows that the adsorption process conforms to the Langmuir isotherm adsorption model and the quasi-second-order kinetic model,and the fitted linear correlation coefficients are all greater than 0.99.Through fitting data,it shows that the increase of cresol concentration and adsorption temperature increases the absorption rate,and p-cresol is always greater than m-cresol.In addition,the adsorption of p-cresol is an exothermic process,and m-cresol is an endothermic process.The enthalpy change of the two cresol monomers is |?H|<40k J/mol 、 ?G<0,indicating that the adsorption of m/p-cresol is a spontaneous physical adsorption process.The dynamic adsorption performance of m/p-cresol was studied by fixed-bed adsorption experiment,and the adsorption breakthrough curve was measured.The results show that the m/p-cresol curve has a large degree of separation and excellent separation effect.The purity of m-cresol obtained through the adsorption process can reach more than 99.50%.On this basis,the desorption performance of 16 kinds of desorbents was studied.The results show that the increase in polarity of the desorbent and the decrease in molecular size are beneficial to increase the desorption rate of m/p-cresol,among which D15 is the pair of m/p-cresol.The desorption rate of phenol can reach 95.27% and 99.68%,respectively,which has the characteristics of high desorption rate,D18 is 87.67% and 18.68%,respectively,which has high selectivity.