Advances in adsorbents for aromatics/cycloalkanes separation
Due to its energy efficiency and environmental friendliness,adsorption has the potential to replace extractive distillation as a new method for the separation of aromatics/cycloalkanes with the same amount of carbon atoms.The materials used for adsorption separation have evolved from the traditional molecular sieves to new porous materials,including metal-organic frameworks(MOFs),covalent organic frameworks(COFs)and porous molecular crystals(PMCs),which show preferential adsorption of aromatics or cycloalkanes and excellent selectivity.This review investigated the recent progress of MOFs,COFs and PMCs for the separation of benzene/cyclohexane and toluene/methylcyclohexane,focusing on the ideas of structural design,the adsorption and separation performance and mechanisms of the three types of materials.These mechanisms included two different types of mechanisms such as thermodynamic equilibrium and molecular exclusion.Though remarkable progress had been made,some prominent issues still existed in this field.The laws of diffusion and mass transfer of adsorbent as well as the separation performance of materials loaded in fixed bed for mixtures were inadequately researched,the stability and impurity sensitivity of materials were not caught enough attention,the structures of porous materials were overly complex,and the costs of materials needed to be reduced.All of them needed to be taken into account in future research.