日本ゼオライト学会　刊行物 Publication of Japan Zeolite Association

CHA zeolite membranes with pore diameters close to the kinetic diameter of CH₄ are expected to be used for separation of CO₂ in natural gas. Grain boundaries in zeolite membranes are considered to decrease a membrane performance, however, the selective condensation of CO₂ at grain boundaries may improve the CO₂ selectivity. In this paper, the effect of grain boundaries on the performance of membranes was investigated by non-equilibrium molecular dynamics simulations. It was found that CO₂ permeation against CH₄ is enhanced by the condensation of CO₂ at the grain boundary inside the membrane. This CO₂ condensation increase CO₂ selectivity of CHA membrane that exceed the intrinsic selectivity of perfect crystal CHA membrane. This result suggests that more efficient zeolite membranes could be developed by fine controlling of grain boundaries, which shows higher CO₂ selectivity than fully crystalline membranes.