Desalination 193 (2006) 211–214 0011-9164/06/$– See front matter © 2006 Elsevier B.V. All rights reserved Presented at the International Congress on Membranes and Membrane Processes (ICOM), Seoul, Korea, 21–26 August 2005. *Corresponding author. Gas permeation properties of carbon molecular sieve membranes dispersed with palladium nano particles via supercritical CO 2 impregnation H. Suda a* , S. Yoda b , A. Hasegawa c , T. Tsuji c , K. Otake b , K. Haraya a a Research Institute for Innovation in Sustainable Chemistry(ISC), National Institute of Advanced Industrial Science and Technology (AIST), Higashi 1-1, Tsukuba, Ibaraki, 305-8565, Japan Tel. +81 (29) 861-4675; Fax +81 (29) 861-4675; email: h.suda@aist.go.jp b Nanotechnology Research Institute(NRI), National Institute of Advanced Industrial Science and Technology (AIST), Higashi 1-1, Tsukuba, Ibaraki 305-8568, Japan c College of Industrial Technology, Nihon University, 1-2-1 Izumicho, Narashino, Chiba 275-8575, Japan. Received 11 March 2005; accepted 21 April 2005 Abstract In the present study, the gas permeation properties of carbon molecular sieve (CMS) membranes dispersed with palladium nano particles via supercritical CO 2 impregnation method were investigated. The palladium nano particles located near the permeation path consisting of slit-like micropore mouth were shown to function mainly as a selective permeation barrier, resulting in the excellent permselectivity for H 2 /N 2 gas pairs. Keywords: Gas permeation; Carbon molecular sieve membrane; Palladium; Nano particles; Supercritical CO 2 impregnation 1. Introduction Separation of gases such as hydrogen-con- taining gas mixture with inorganic membrane technology has been attracting much attention [1]. Among those inorganic membranes, a carbon molecular sieve (CMS) membrane is known to exhibit outstanding gas separation performance [2–4]. This is due to the presence of permeation path consisting of slit-like micropores with 0.3– 0.5 nm in size, through which gases selectively permeate depending on their kinetic gas diameter [5,6]. This implies that some influence may arise in the sorption, diffusion and permeation of gases by the incorporation of a selective permeation