Zeolite A-type membranes are usually synthesized from hydrogels and rarely
synthesized from clear solutions mostly in batch systems. Few studies were carried
out using semi-continuous systems for zeolite A membrane synthesis. Zeolite A
membranes are mainly used in pervaporation processes for separation of water from
water/organic mixtures because of their hydrophilic property.
In this study, zeolite A membranes were synthesized on -alumina supports from a
clear solution with a molar composition of 49Na2O: 1Al2O: 5SiO2: 980H2O.
Synthesis was done both in a batch system and in a flow system in which solution
was circulated through the support under atmospheric pressure. Effects of synthesis
temperature, time, flow rate and seeding on membrane formation were investigated.
The membranes were characterized by X-ray diffraction (XRD), scanning electron
microscopy (SEM), single gas permeation measurements and pervaporation tests.
In batch system, pure zeolite A membranes having cubic form of zeolite A was
obtained for the syntheses carried out at 60° / C for 24 h and 80° / C for 8 h.
Thicknesses of the membranes synthesized at 80° / C and 60° / C were about 2 µ / m and
4 µ / m, respectively. N2 permeances were 2*10-8 mol/m2sPa and 8*10-8 mol/m2sPa
for of the membranes synthesized in the batch system at 60° / C and 80° / C,
respectively. When synthesis was carried out in flow system pure and continuous
zeolite A membranes were obtained for all conditions. Membranes synthesized at
60° / C and 80° / C had thicknesses of about 1.5 and 2 µ / m, respectively. Lower N2
permeations were obtained for the membranes synthesized in flow system. It was
observed that flow rate and seeding did not significantly affect the thickness of the
membrane layer. The membranes synthesized in this study are significantly thinner
than the membranes reported in the literature. Single gas permeation tests at 25° / C
for the membranes showed that comparable membranes with the ones in literature
were obtained in this study. For a double layer membrane synthesized in flow
system at 80° / C for 8h separation factor about 3700 was obtained for the separation
of 92:8 (wt.%) ethanol/water mixture at 45° / C.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/2/12608697/index.pdf |
| Date | 01 September 2007 |
| Creators | Akbay, Sezin |
| Contributors | Kalipcilar, Halil |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for METU campus |
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