Optimization of Aluminium Oxide/Acid‐Treated Palygorskite by Response Surface Methodology and its Application in Adsorptive Separation of the Methanol‐Dimethyl Carbonate Azeotrope

Abstract

AbstractA low‐cost composite adsorbent aluminium oxide/acid‐treated palygorskite (Al2O3/HPal) was prepared by the total incipient wetness method and succesfully applied for the separation of methanol‐dimethyl carbonate (MeOH‐DMC) azeotrope for the first time. Major synthetic factors influencing the final separation performance were explored by the response surface methodology (RSM) based on Box‐Behnken design (BBD). Adsorbents under optimized synthesis conditions were characterized by XRD, FT‐IR, SEM, TEM and BET analysis. Adsorptive separation performance of Al2O3/HPal were investigated by both static and dynamic experiments. The adsorption capacities for MeOH and DMC were 335.52 mg g−1 and 23.92 mg g−1, respectively, while the selectivity S and the separation factor α towards MeOH equaled to 14.03 and 6.1. Kinetic curves fitted the pseudo‐second‐order model. Isotherm study results indicated two different adsorption behaviors for this azeotrope where heterogeneous multi‐layer adsorption was observed for DMC but monolayer adsorption occurred for MeOH with surface inhomogeneity. Moreover, thermodynamic study suggested that the driving force of the MeOH‐DMC system on Al2O3/HPal included both enthalpy and entropy effects.