Separation of ethyltoluene isomers by nonporous adaptive crystals of perethylated and perbromoethylated pillararenes

Abstract

The separation of p-ethyltoluene (PET) and m-ethyltoluene (MET) is one of the most challenging steps to isolate PET from C9 aromatic compounds due to their very close boiling points. Many kinds of separation methods have been developed, but they involve low efficiency and great energy consumption. Herein, we investigate the adsorptive properties of perethylated pillar[5]arene (EtP5), perethylated pillar[6]arene (EtP6), perbromoethylated pillar[5]arene (BrP5) and perbromoethylated pillar[6]arene (BrP6) for ethyltoluene isomers. Results show that EtP6 and BrP5 crystals separate PET from a PET/MET equimolar mixture with purities of 95.4% and 92.0%, respectively. Both of them show no decrease in selectivity upon cycling for 5 times. Relatively, EtP5 and BrP6 crystals fail in this separation due to poor PET capture ability and low selectivity, respectively.