Aging and Stability of Microporous Sol-Gel-Modified Ceramic Membranes

Abstract

Aging experiments on microporous sol-gel-derived nonsupported Si02 membranes were performed. Microstructure characterization was performed using nitrogen physisorption. It is found that both chemical aging and thermal aging result in densification of the microstructure, without pore growth. The influence of aging on supported SiO2-modified membranes 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 observed on the separation properties. This might be attributed to a decrease of the pore size. Separation factors ranging from 50 to 125 have been measured for H2/CH4 at temperatures in the order of 250 "C.

Nickel-Doped Silica Membranes for Separation of Helium from Organic Gas Mixtures

“…In general, however, organic membranes were found to have quite low He fluxes and poor thermal and chemical stability. As reported by de Lange et al (11), micropores of solgel derived from silica membrane were densified by the exposure to lean water vapor in the temperature range 250-3008C. Silica is one of the most attractive inorganic membrane materials because of its possible amorphous structures in a wide temperature range and its pore sizes of less than 1 nm, features that are quite useful for high permselectivity in gas separation.…”

Exposing the Molecular Sieving Architecture of Amorphous Silica Using Positron Annihilation Spectroscopy

“…The major peaks occur at 5.3 and 9.1 Å for the respective methods, with the HK value similar to that found in literature for MSS measured using the same method. [5,20] …”

“…[5,20] This is far too high for effective sieving of gases reported for these materials. Density functional theory (DFT) has recently emerged to replace these methods and is being promoted as a more fundamentally derived statistical method to accurately predict pore features from isotherms.…”

Planar bilayer lipid membranes supported on mesoporous aerogels, xerogels, and Vycor® glass: an epifluorescence microscopy study

“…A fairly large range of pore structure and pore sizes can be formed [23,28,32,33]. Although the underlying chemistry is simple, variation of one or more experimental parameters can dramatically affect the microstructure of the resulting aerogels and xerogels.…”