Rapid thermal processing of tubular cobalt oxide silica membranes

This work is the first demonstration of rapid thermal processing techniques as applied to metal oxide/silica membranes on tubular geometries. A procedure was developed which combined fast sol–gel synthesis, rapid calcination steps and a thermal annealing stage to reduce the membrane fabrication time by more than two-thirds, from a conventional process taking seven or more days to less than two. A significant aspect of this major development was the use of a pre-hydrolysed silica precursor ethyl silicate 40 (ES40), instead of the generally preferred tetraethyl orthosilicate (TEOS) which eliminated the need for the researcher specific and time consuming sol–gel reaction stages prior to membrane fabrication. As a result, modified-silica membranes containing cobalt oxides could be directly calcined at 600 °C, instead of conventional thermal process which require slow ramping rates of ≤1 °C min−1 to avoid cracking. As-prepared membranes delivered H2 permeances of 5 × 10−7 mol m−2 s−1 Pa−1 at 450 °C and H2/N2 permselectivities of 54. The RTP techniques demonstrated in this work greatly reduced the production time and should both allow researchers to significantly increase their productivity and ultimately reduce the barriers for deployment of inorganic membranes into industrial applications.