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.