Preparation and gas permeance of c-axis oriented zeolite membrane using ion-exchanged mordenite zeolite crystals oriented in magnetic field

Abstract

C-axis-oriented mordenite (MOR) zeolite membranes were fabricated and evaluated for nitrogen permeance. MOR crystals having Na+ as a counter-ion exhibit b-axis-orientation parallel to a magnetic field, but c-axis-orientation was achieved by exchanging the counter-ion with transition metal or rare earth ions. The oriented seed layers were prepared by dropping each MOR seed slurry on a porous substrate placed in a 10 T magnetic field. The MOR crystals with Mn2+, Co2+, Ni2+, Pr3+, Nd3+, and Gd3+ ions produced c-axis-oriented seed layers parallel to the magnetic field, while the Fe2+, Cu2+, Eu3+, Er3+, and Yb3+ counter-ion MOR crystals exhibited c-axis alignment perpendicular to the field. MOR crystals with Co2+ and Cu2+ counter-ions revealed orientation even in 1 T. The porous substrate with the oriented seed layer was immersed in a zeolite synthesis solution to produce a c-axis-oriented zeolite membrane via a hydrothermal treatment. C-axis-oriented membranes exhibited improved N2 permeation, demonstrating their effectiveness.