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

4 Results and discussion
dried TiO2 sol is calcined at 600ºC. Xu et al. 112 found rutile phase transformation
temperature higher than 600ºC. This might be explained by the difference in sol synthesis
or 30 minutes dwell time instead of 2 hours.
A combination of rutile and anatase TiO2 was observed at 500ºC when the ketone
approach was applied. DEA seems to prevent the anatase rutile transformation compared
to the ketone approach and might be explained by the stronger bonded precursor
modifier.
TiO2 layers prepared similar as the powder discussed above might have the same
microstructural properties and form crystalline mesoporous TiO2 membranes. However,
the microstructural properties of the layers can differ from the powders due to i) the
formation of thin layers instead of agglomerated particles and ii) capillary forces when a
thin layer is applied on a porous substrate.
10 20 30 40 50 60
2Theta [º]
Figure 51 XRD diffraction patterns of dried TiO2 sols calcined at 140, 400, 500, 600ºC. The crystal size
determined with the Scherrer relationship is presented in the inlay.
4.3.2.3 Amine approach - ZrO2
Type I N2-sorption isotherms are obtained when the dried ZrO2 DEA sols were calcined
at 400, 500 and 600ºC (Figure 52). The specific surface area seems to be stable in the
temperature range of 400-500ºC and decreases at higher calcination temperatures (Table
24). The ZrO2 type I N2 sorption isotherm indicates lower specific surface area values
than TiO2 but are similar to the results published in literature. 116
84
600ºC
Crystal size [nm]
500ºC
30
25
20
15
10
5
0
400ºC
140ºC
400 500 600
T [ºC]