A Al2O3 hollow fibre substrate with an outstanding asymmetric micro-structure, which consists of a thin sponge-like layer and a plurality of micro-channels, has been successfully developed.
The thinner outer sponge-like layer allows the formation of a thin Pd membrane of approximately 1 mm,
and it is substantially more permeable than the previous counterparts.
As a result, a hydrogen permeation flux of 0.87 mol s1 m2 can be achieved at 450 C and a pressure
difference of 165 KPa.
The hydrogen permeation was further investigated by using Pd membranes of different thicknesses
(1.0 and 3.3 mm) and the substrates sintered at different temperatures (1300 and 1400 C).
The negative impact of Pd penetration on hydrogen permeation was clearly observed,
especially for thinner Pd membrane.
Further pre-treatments, aiming at the suppression of such intermediate layer, are suggested as a route to enhance hydrogen permeation through the composite membrane.