Separation of N2 from O2 and other gases using FAU-type zeolite membranes

The development of nitrogen-selective membranes is essential to realize a membrane process for the production of oxygen-enriched air. Zeolite membranes have potential for this purpose, while polymeric and carbon membranes are largely oxygen-selective. In this study, FAU-type zeolite membranes containing Na cations were prepared by hydrothermal synthesis on a porous a-alumina support tube. Permeation measurements for unary and binary systems for N-2 and O-2 were performed at 310 K. The membranes showed high permeation rates and high N-2/O-2 ideal separation factors for unary N-2 and O-2 gases. However, the separation factor was decreased when an N-2-O-2 mixture was fed. In order to further examine the permeation mechanism of the membranes, permeation rates were also determined for single-components of H-2, CO2, CH2, n-C4H10, i-C4H10 and SF6, as well as for N-2-H-2, N-2-CO2, and N-2-n-C4H10 mixtures. The permeation properties can be classified based on competitive adsorptivity and diffusivity in the zeolitic pores. Ion-exchange and impregnation with Li cations were not greatly effective in increasing the N-2/O-2 separation factor of the membrane.