Hydrogen-permeable membranes composed of zeolite nano-blocks

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 H2/CH4 (>1200), H2/N2 (>1600) and H2/CO (>660) binary gas mixtures at 298 K. Such a highly selective H2 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, 27Al, 29Si 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.