Inorganic Microporous Membranes for Gas Separation in Fossil Fuel ...

4 Results and discussion
4 Results and discussion
The first section deals with the support and supporting ceramic membrane layers. The
second section includes the properties and potentials of deca-dodecasil 3R and dodecasil
1H zeolite materials and of the first dodecasil 1H layers. The final section describes the
properties of sol-gel derived TiO2-(Y2O3)ZrO2 membranes including the sol, the
microstructure and the membrane layer characterisation and discussions.
4.1 Supports and intermediate layers
Supports were made of α-Al2O3 material (AKP30) and were prepared by colloidal
filtration as reported by Nijmeijer et al. 87 The supports have a diameter of 36 mm and a
thickness of 2-2.4 mm (Figure 22-A). AKP30 alumina bulk material has a surface area
7.1 m 2 /g measured by gas physisorption, which is comparable with the 6.9 m 2 /g reported
by the supplier. The particle size is 340 nm (D50) and the purity >99.99%. The purity
was analysed by means of X-ray fluorescence resulting in only 8 ppm Ni, 5 ppm Zn and 2
ppm Fe. The porosity of the colloidal filtrated and (1100ºC) fired substrate is 31% with
an average pore size of ~80 nm and is comparable with similar prepared substrate. 87,99
α-Al2O3 SEM surface image is presented in Figure 22-B.
36 mm
A B
Figure 22 A) 36 mm in diameter produced α-Al2O3 support and B) the surface SEM image.
The intermediate layers are prepared with γ-Al2O3 to form layers of good quality to
support the final membrane layers. However, the final membrane layers might be
supported in the future by mesoporous titania or zirconia materials to produce chemically
more stable membranes with matching thermal expansion coefficients with titania or
zirconia functional membrane layers.
The intermediate layers are prepared from Boehmite sols having particle sizes (d50)
typically ~30 nm (Figure 23) and are comparable with results reported in literature. 87,99
50
α-Al2O3