Synergy of pore size and silanols in an -SVR-type zeolite for efficient dynamic benzene/cyclohexane separation.

The efficient purification of cyclohexane is critical, serving as an essential feedstock to produce resins, nylon fibers and pharmaceutical intermediates. However, efficient purification remains a challenging task due to the similarity of cyclohexane and benzene molecules in terms of size and boiling point. In this work, we reported on the synergy of pore size and silanols inside an -SVR-type zeolite for the efficient production of ultrapure cyclohexane (benzene <1 ppm) from benzene/cyclohexane mixture. Under ambient conditions, the SSZ-74 zeolite demonstrated the highest mass-based productivity of 14.5 L/kg for ultrapure cyclohexane among several common zeolites with a considerable dynamic selectivity of ~9.5. The separation ability was evaluated through density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations. The unique ordered silanols inside the zeolite frameworks demonstrated strong but reversible interactions with benzene through SiOH…π interactions, as revealed by in situ Fourier Transform infrared (FTIR) spectra.