Zeolite membrane synthesis is conventionally carried out in batch systems. Recently, several
attempts have been performed to synthesize zeolite membranes in flow systems which can
allow preparation of membranes with large specific surface areas.
Membranes synthesized in the recirculating flow system had comparable N2/SF6 and n-
C4H10/i-C4H10 ideal selectivities with the membranes prepared in the batch system, indicating
that good quality membranes can be produced by this method. The objective of this study is to
separate organic/water mixtures by pervaporation by using MFI type membranes synthesized
in the flow system. Effect of number of synthesis steps and synthesis method on the
separation factor and flux was investigated.
Membranes were synthesized from clear solutions with a molar composition of
80SiO2:16TPAOH:1536H2O at 95oC and atmospheric pressure. The synthesis solution was recirculated through the tubular alumina support with a flow rate of 6 ml/min for 72 h. The
membranes were characterized by X-ray diffraction for phase identification and scanning
electron microscopy for morphology determination. Single gas permeances of N2, H2, CH4,
CO2, n-C4H10 and i-C4H10 were measured between 25 and 200oC. Mixtures of 5 wt%
ethanol/water, 2-propanol/water and acetone/water were separated by pervaporation at
different temperatures.
The single gas permeances decreased with increasing temperature for weakly adsorbed gases.
For n-C4H10 the permeance passed through a maximum and i-C4H10 permeance was nearly
constant. For a membrane synthesized by two consecutive synthesis steps, the ideal
selectivity for n-C4H10/i-C4H10 was 132 at 200oC. The selectivity in the pervaporation
separation of ethanol-water mixture was 43 with a permeate flux of 0.2 kg/m2h at 25oC. With
increasing temperature, selectivity decreased but the flux increased, the selectivity was 23 and
the flux was 1.9 kg/m2h at 85oC. 2-propanol/water and acetone/water separation factors were
36 and 1024 with 0.2 and 0.1 kg/m2h fluxes, respectively. The separation factors and fluxes
for membranes synthesized in the flow system were comparable with membranes synthesized
in the batch system.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12608646/index.pdf |
| Date | 01 August 2007 |
| Creators | Dede, Ozlem |
| 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 public access |
Page generated in 0.0357 seconds