Development of tubular substrates, silica based membranes and membrane modules for hydrogen separation at high temperature

Microporous membranes and membrane modules have been developed for high temperature separation of hydrogen from other gas molecules. Tubular alpha alumina substrate with 0.7 μm pore size and 40% porosity was prepared as the membrane substrate and an intermediate alpha alumina layer with pore size of 60 nm and porosity of 39% was formed by dip-coating over the substrate. The gas permeation characteristics as well as the stability of the substrate itself and that with the intermediate layer were respectively evaluated. A procedure of preparing defect-less gamma alumina and silica layers over the substrate was applied to make a highly selective membrane for hydrogen gas. Hydrogen gas permeation values in the range 5E−8 to 5E−6 mol/m2 s Pa with H2/N2 ideal separation factors in the range 30-300 have been measured with the silica membranes. Alumina substrate tubes were also used for fabrication of a tubular bundle, using glass-based sealant materials for joining the substrate tubes to a ceramic endplate. The bundle also was used as a support for silica membrane making. The gas permeation and separation performance of the membrane module was evaluated.