AGING AND STABILITY OF MICROPOROUS SOL-GEL-MODIFIED CERAMIC MEMBRANES

Aging experiments on microporous sol-gel-derived nonsupported SiO2 mem branes were performed. Microstructure characterization was performed u sing nitrogen physisorption. It is found that both chemical aging and thermal aging result in densification of the microstructure, without p ore growth. The influence of aging on supported SiO2-modified membrane s was investigated using gas permeation and separation experiments. As for the nonsupported materials, some densification takes place. This leads to lower permeation rates, but a strong positive effect was obse rved on the separation properties. This might be attributed to a decre ase of the pore size. Separation factors ranging from 50 to 125 have b een measured for H-2/CH4 at temperatures in the order of 250 degrees C .