Norikazu Nishiyama, Masahiro Yamaguchi, Toru Katayama, Yuichiro Hirota, Manabu Miyamoto, Yasuyuki Egashira, Korekazu Ueyama, Koji Nakanishi, Toshiaki Ohta, Atsushi Mizusawa, Tsuneyuki Satoh
JOURNAL OF MEMBRANE SCIENCE, 306(1-2) 349-354, Dec, 2007
A novel hydrogen permeable membrane was prepared from zeolite Na-A crystals, dissolved in a HCl solution and spin-coated on a Vycor glass plate, The membrane shows high-separation factors for H-2/CH4 (> 1200), H-2/N-2 (> 1600) and H-2/CO (>660) binary gas mixtures at 298 K. Such a highly selective H-2 permeation suggests that the membrane composed of zeolite nano-blocks possesses no 8-membered oxygen rings as permeable pores. The membrane is characterized by X-ray diffraction, Al-27, Si-29 NMR and Al, Si K-edge X-ray absorption near edge structure spectroscopy. A dealuminization from the zeolite framework occurs during the dissolution in acid solutions, but the zeolite nano-blocks still keep the local structure of zeolite although CO-permeable 8-membered oxygen rings disappear. Alumina-like nanoparticles formed by the dealuminization must be embedded in the aggregate of zeolite nano-blocks. (c) 2007 Elsevier B.V. All rights reserved.