Hydrogen purification for PEM fuel cells using membranes prepared by ion-exchange of Na-LTA/carbon membranes

Abstract

Modified LTA membranes supported on macroporous carbon discs have been synthesized for the separation of H 2 and CO. These membranes have been prepared by hydrothermal synthesis following the secondary growth method and subsequently ion-exchanged with different alkaline cations in order to modify the zeolite pore size. Their permeation properties have been studied for the purification of a hydrogen stream (50 vol.%) containing carbon monoxide (1.25 vol.%). For this purpose, a Wicke–Kallenbach cell has been used to perform the separation experiments. Single gas permeation properties and bicomponent mixtures were carried out at three different temperatures (298 K, 398 K and 423 K). Our results indicate that even the K-LTA form would be suitable for the purification of H 2 at room temperature. The Rb- and Cs-forms exhibit the best performance, in which CO permeation is blocked at all temperatures studied. As a result, a high purity H 2 stream may be obtained by employing the Rb- and Cs-membranes derived from Na-LTA/carbon membranes.