CHARACTERIZATION OF CERAMIC MEMBRANES .1. THERMAL AND HYDROTHERMAL STABILITIES OF COMMERCIAL 40 ANGSTROM MEMBRANES

The thermal stability (up to 640-degrees-C) and hydrothermal (up to 90% of steam) stability of commercial microporous ceramic membranes with an approximately 40 angstrom pore diameter were characterized by dynamic capillary condensation porometry and gas permeation. The pore size of the membrane remained relatively constant under the thermal treatment for up to 110 h. The N2 gas permeance increased from approximately 60 to approximately 120 m3/m2 h atm, likely attributed to the removal of adsorbed moisture during storage. The pore size increased to approximately 50 and approximately 65 angstrom under hydrothermal treatment at 640-degrees-C with a stream containing 5 and 90% steam, respectively. The largest changes in membrane structures occurred within the first few hours of treatment. The corresponding increases in the gas permeance correlated well with the enlargement in the pore diameter, indicating the porous structure based upon the ratio of tortuosity to porosity likely remained constant during the hydrothermal treatment.