The Adsorption of Durene and Prehnitene on Metal–Organic Frameworks

Tetratoluene has the following three isomers: durene (DR), prehnitene (PR), and isodurene (IR). DR and PR often coexist during the separation of C10 heavy aromatics at different levels. They are both important organic chemical raw materials and their separation is the key to the high-efficiency industrial utilization of C10 heavy aromatics. In this paper, six metal–organic frameworks (MOFs), including ZU-61, MIL-101, UIO-66, UIO-66-NH2, Mg-MOF-74, and MIL-53(Al), were used as the adsorbents of DR and PR. Their skeletons were structurally optimized using VASP software (latest v. 6.4.3). The adsorption capacity and isosteric heats of both pure components and mixtures (the molar ratio was 1:1) in gas were calculated using Grand Canonical Monte Carlo simulation from 10 kPa to 300 kPa at 298 K. The results indicated that all adsorption processes were physical. ZU-61, UIO-66, UIO-66-NH2, and Mg-MOF-74 presented suitable capacity differences for DR and PR at 300 kPa. The selectivity values of these frameworks were all above 1.5. Thus, the four MOFs were prepared using the solvothermal method and characterized by SEM and XRD. Then, the competitive adsorption of DR and PR in liquid on the four MOFs was carried out as well. The results showed good agreement with the simulation in general, with a lower adsorption attained capacity due to the different phase states of both DR and PR. This study can guide the separation of tetratoluene isomers in C10 heavy aromatics.