Efficient separation of SO2/NO2 on in-situ synthesized NaA zeolite membrane

Abstract

SO2 and NO2 mixture widely exists in the desorbed gas from industrial flue gas adsorption purification process, separating the mixture into pure gas provides the key step for success in recycling them into profitable chemicals. However, effective SO2/NO2 separation is challenged due to the similar properties of both gases. In this work, we report the synthesis of an industrially-favored NaA zeolite membrane and the utilization of this membrane for SO2/NO2 separation in order to address the above-mentioned challenge. Various characterizations illustrate that the in-situ synthesis endows the NaA zeolite membrane with well-intergrown crystals, high continuity, and crystal-comparable thickness. The separation measurements at different feed pressure, temperature, and gas composition demonstrate that the NaA zeolite membrane shows superior separation performance (SO2/NO2 separation factor of 40.0, SO2 permeance of 2.93 × 10−7 mol m−2 Pa−1 s−1 at 293 K and 0.2 MPa) with strong stability (more than 7 d) compared to the previous best-performing zeolite membrane. The strong competitiveness of SO2 over NO2 on the low-silica membrane is revealed through molecular simulation, showing that the great affinity of SO2 with highly-polar zeolite structure benefits the SO2 gas preferential adsorption and energetically barrier-free permeation through the eight-membered ring of NaA zeolite. This work not only showcases an efficient strategy for the SO2/NO2 separation, but also expands the gas separation application of zeolite membranes.