Atomistic understanding of gas separation through nanoporous DDR-type zeolite membrane

Molecular dynamics simulations were applied to evaluate the Kr/Xe separation performance by a pure silica DDR type membrane. The external pressure was applied up to 50 MPa in order to transfer the gas atoms through the membrane. The process was also studied at temperatures ranging from 293 to 373 K. The membrane exhibited best Kr atoms permeation (177.25 × 10⁻⁵ mol/(m²∙s∙Pa)) and selectivity at P = 10 MPa and T = 373 K, which indicates that the best separation performance can be achieved by increasing the temperature without applying higher pressures. The potential of the mean force (PMF) of Kr and Xe confirmed the necessity of applying the driving force for penetration of Kr or Xe atoms through the DDR membrane. Furthermore, the PMF curve demonstrated the higher energy barrier for the passage of Xe through the DDR membrane compared with Kr, which was also verified by simulation outputs.