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

4 Results and discussion
4.3 Sol-Gel derived membranes
TiO2, ZrO2 and the binary oxides TiO2-ZrO2 and Y2O3-ZrO2 (hereafter referred as YSZ)
can be prepared by means of the sol-gel technique. Generally, the hydrolysis of highly
reactive Ti and Zr-precursors is controlled with precursor modifiers such as ketones and
amines as described in the chapter ‘Theory’.
Y2O3 or TiO2 doped ZrO2 sol-gel derived materials and membranes were studied and
prepared. A thorough study has been performed on polymeric YSZ sols using ketone
acetyl acetone as precursor modifier to prevent a full hydrolysis of the alkoxides in the
presence of pore formers. This approach has been concentrated on the sol and bulk
material properties. The first results obtained for YSZ layers using this approach
(hereafter referred as ketone approach) are discussed.
The second approach is based on the promising diethanolamine precursor modifier
outlined by Van Gestel et al., 82,104,135 Spijksma et al. 80,81 and Aust et al 83 (hereafter
referred as amine approach). This work is concentrated on the study of (TiO2-doped)
ZrO2 powder and membranes using diethanolamine as the precursor modifier.
Diethanolamine in the sol synthesis combines the prevention of fast hydrolysis of the
alkoxides and the higher viscosity (than acetyl acetone), which is beneficial to the coating
procedures. Diisopropanolamine can be an alternative to diethanolamine precursor
modifier.
Acetyl acetone Diethanolamine
The selection of the membrane layer material is mainly based on the microstructure
property results of these bulk materials. Several (TiO2 doped) ZrO2 membranes have
been prepared and characterised. Finally, the permeability, permselectivity and
permeability as function of hydrothermal stability will be discussed.
4.3.1 Polymeric sol characterisation
The 8 mol % Y2O3 doped ZrO2 (8YSZ) sol particle size, viscosity and stability have been
studied for the ketone approach. The sol composition of 25, 50, 66, 75, 90, 100% molar
ratio TiO2 in ZrO2 have been prepared by the amine approach.
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