Investigating the helium purification performance of Si-RHO zeolite membrane at the atomistic scale

چکیده مقاله

Natural gas, consisting primarily of methane, is currently the most viable source of helium. Besides, as attractive and versatile materials, zeolites are crucial to a variety of industrial activities due to their unique chemistry and structure, which their applications underlie in catalysis, ion exchange, and gas separation fields. Here, we accomplished a systematic molecular dynamics simulation to explore the performance of a pure silica form of 3D RHO (Si-RHO) zeolite membrane for separating helium and methane gas mixture. The effects of applied pressure difference (up to 8 MPa) and initial feed composition on the separation efficiency at the room temperature were also evaluated. The results indicated that He molecules can simply penetrate through the Si-RHO, whereas no CH₄ molecules were seen on the permeate side. Therefore, an ultrahigh selective separation of helium over to methane was achieved. The permeance of gas molecules across the Si-RHO was determined theoretically. The maximum helium permeance of 8.25 × 10⁵ GPU was obtained under applied pressure of 1 MPa. Consequently, simultaneously providing high selectivity and permeance and of helium across the Si-RHO caused the Robeson’s upper bound to be overcome, which proves the high efficiency of the membrane for this separation. Furthermore, the van der Waals interactions and the potential of the mean force analysis were employed to explore the permeation of gas molecules through the Si-RHO. In summary, the results suggest that the Si-RHO zeolite membrane can be promising candidate for helium recovery and purification. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.