Separation of carbon dioxide from nitrogen using ion-exchanged faujasite-type zeolite membranes formed on porous support tubes

Faujasite-type zeolite membranes were reproducibly synthesized by hydrothermal reaction on the outer surface of a porous alpha-alumina support tube of 30 or 200 mm in length. The membrane properties were evaluated by CO2 separation from an equimolar mixture of CO2 and N-2 at a permeation temperature of 40 degrees C. CO2 permeance and CO2/N-2 selectivity of the NaY-type membranes were in the ranges of 0.4 x 10(-6)-2.5 x 10(-6) mol m(-2) s(-1) Pa-1 and 20-50, respectively. The NaY-type membranes were ion-exchanged with alkali and alkaline earth cations. The LiY-type membrane showed the highest N-2 permeance and the lowest CO2/N-2 selectivity. The KY-type membrane gave the highest CO2/N-2 selectivity. The NaY-type membrane was stable against exposure to air at 400 degrees C. Nax-type zeolite membranes, formed by decreasing the ratio of SiO2/Al2O3 in the starting solution, exhibited lower CO2 permeances and higher CO2/N-2 selectivities than those of the NaY-type zeolite membranes. (C) 1998 Elsevier Science B.V. All rights reserved.