Separation of N2 from O2 and Other Gases Using FAU-Type Zeolite Membranes.

Abstract

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 α-alumina support tube. Permeation measurements for unary and binary systems for N2 and O2 were performed at 310 K. The membranes showed high permeation rates and high N2/O2 ideal separation factors for unary N2 and O2 gases. However, the separation factor was decreased when an N2-O2 mixture was fed. In order to further examine the permeation mechanism of the membranes, permeation rates were also determined for single-components of H2, CO2, CH4, n-C4H10, i-C4H10 and SF6, as well as for N2-H2, N2-CO2, and N2-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 N2/O2 separation factor of the membrane.