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

3 Experimental
Another solution was prepared comprising H2O and yttrium nitrate (Treibacher) in 2propanol
to prepare YSZ sols. This hydrolysis solution was added drop wise at 0ºC to the
Zr-solution, and the hydrolysis molar ratio (W) was water/Zr ~4. The final sol contained
variable contents of solids with a nominal molar ratio Zr/Y ~ 85/15. The carboxylic acids
used as catalysts include acetic, propionic, caproic (Ca) and nanonic acid, all of which
were supplied by Aldrich. The different solid contents were obtained by adjusting the
amount of 2-propanol used as solvent. Single oxide titania sols are synthesised using
titanium isopropoxide (Alfa Aesar) instead of zirconium n-propoxide. No binders are
used in order to avoid large pores in the sintering steps.
The structure directing agents (SDA’s) such as, decylamine (C10), cetylamine (C16),
cetyltrimethylammonium (CTA+) and Pluronic F127 are added to zirconia sols with
weight ratios of 0.32, 0.48, 0.73 and 1.2 for C10, C16, CTA+ and F127, respectively.
3.3.1.2 Amine route
Polymeric sols were prepared by mixing a precursor solution and a hydrolysis solution.
The alkoxide (zirconium n-propoxide or titanium n-propoxide Aldrich) was mixed with
with diethanolamine (hereafter referred as DEA) and n-propanol (ACS Reagents Aldrich)
with a molar ratio 1:2:72.6 under argon atmosphere, forming the precursor solution. TiO2
and ZrO2 mixture sols were prepared by mixing the alkoxide precursors, via mixing 10,
25, 50, 66, 75 or 90% of titanium n-propoxide to zirconium n-propoxide. The hydrolysis
solution, consisting of 7-10 mol equivalents (with respect to the alkoxide) of 1.0 M HNO3
(Aldrich) and n-propanol (volume ratio 1.8:50), was added slowly (1.5 mL/min) to the
precursor solution under vigorous stirring in an argon atmosphere. The molar ratio of the
final sol was 1:2:7:120 for respectively the alkoxide, diethanolamine, H2O and
n-propanol.
The effect of acidification on hydrolysis and condensation was investigated by selecting
1.0 M HNO3, 0.1 M HNO3 or H2O. The effect of DEA to stabilise the precursors is
compared to the longer chain diisopropanolamine (hereafter referred as DIPA).
n-Propanol (Reagent plus, 99.7%), DEA and DIPA were purchased from Aldrich and
used as received.
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