Establishment of adsorption isotherms of m- and p-cresols in chromatographic process with aluminum terephthalate metal-organic framework as stationary phase

Abstract

Close boiling points pose great challenges to the separation of the isomers m-cresol and p-cresol. Metal−organic frameworks (MOFs) material with uniform pore structure, high specific surface area and good chemical stability is a potential adsorbent. In this study, m-cresol and p-cresol were separated by a chromatographic process with aluminum terephthalate metal-organic framework (MIL-53(Al)) as stationary phase and acetonitrile as mobile phase. In view of the unique “breathing” effect of MOFs materials, according to the kinetic process and thermodynamic equilibrium of adsorption and desorption, the hybrid adsorption isotherm equations were established, which can reflect the “breathing” effect by combining the Langmuir adsorption process of narrow pore and the multi-stage adsorption process of large pore. The parameters of adsorption isotherm were determined by inverse method and genetic algorithm, and the adaptability of the equilibrium dispersive chromatography model based on this adsorption isotherm to the single-component adsorption process and two-component competitive adsorption process was proved under different injection concentration, injection time and flow velocity conditions. The separation process of m-cresol and p-cresol was optimized by the chromatographic model and genetic algorithm. Under the optimized conditions, the separated m-cresol and p-cresol were obtained with the purity values of 96.26% and 93.23%, and the recovery values of 96.93% and 96.59%, respectively.