Separation of nitrogen dioxide from the gas mixture with nitrogen by use of ZIF materials; computer simulation studies

The separation of nitrogen dioxide (NO2) from the gas mixture with nitrogen (N-2) by selective adsorption and diffusion in three Zeolitic Imidazolate Frameworks (ZIFs) is examined by Gibbs Ensemble Monte Carlo (GEMC) and Molecular Dynamics (MD) computer simulations at 373 K, which is a temperature that can be found in the exhaust gases of combustion engines and furnaces. This temperature ensures that the chemical equilibrium reaction between NO2 and N2O4 can be neglected since at this temperature almost only NO2 exists. At 373 K, the membrane selectivity of NO2 over N-2 is predicted to be about 4.2 (ZIF-90), 5.2 (ZIF-8), and 10.6 (ZIF-78). In addition, it is shown that N2O4 can be neither adsorbed nor diffuses inside these ZIF materials, which makes these ZIFs a promising materials for separation by membranes. Due to molecular sieving, only N-2 and NO2 can pass the ZIF membranes.