SO2/NO2 Separation Driven by NO2 Dimerization on SSZ-13 Zeolite Membrane

The molecular state is crucial for precise gas separation using a zeolite membrane, yet the state control remains a big challenge. Herein, we report a NO2 dimerization facilitated high performance SO2/NO2 separation on a SSZ-13 zeolite membrane. The NO2 dimerization is triggered by temperature and pressure to form N2O4 with big molecular size, and N2O4 diffusion into the zeolite pore is inhibited on the basis of size exclusion, leading to high separation selectivity. Consequently, SO2 rather than NO2 preferentially permeates through the SSZ-13 membrane with a high SO2 permeance of 2 × 10-7 mol m-2 s-1 Pa-1 and high SO2/NO2 separation factor of 22, ∼50-fold of that measured without dimerization. The dimerization effect for SO2/NO2 separation prevails in other small-pore zeolites such as NaA. This advanced function is revealed through membrane separation using single and mixture gases.