Membrane based separation techniques have been widely used and developed over
decades. Generally polymeric membranes are used in membrane based gas
separation / however their gas separation performances are not sufficient enough for
industrial feasibility. On the other hand inorganic membranes have good separation
performance but they have processing difficulties. As a consequence mixed matrix
membranes (MMMs) which comprise of inorganic particles dispersed in organic
matrices are developed. Moreover, to enhance the interaction between polymer and
zeolite particles ternary mixed matrix membranes are introduced by using low
molecular weight additives as third component and promising results were obtained
at 35 ° / C. Better understanding on gas transport mechanism of these membranes
could be achieved by studying the effect of preparation and operating parameters.
This study investigates the effect of operation temperature and annealing time and
temperature on gas separation performance of MMMs. The membranes used in this
study consist of glassy polyethersulfone (PES) polymer, SAPO-34 particles and 2-
v
hidroxy 5-methyl aniline (HMA) as compatibilizer. The membranes fabricated in
previous study were used and some membranes were used as synthesized while
post annealing (at 120° / C, 0.2atm, N2 atm, 7-30 days) applied to some membranes
before they are tested. The temperature dependent gas transport properties of the
membranes were characterized by single gas permeation measurements of H2, CO2,
and CH4 gases between 35 ° / C-120 ° / C. The membranes also characterized by
scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and
differential scanning calorimetry (DSC).
Annealing time and temperature affected the reproducibility and stability of the
mixed matrix membranes and by applying post annealing step to mixed matrix
membranes at higher temperatures and longer times, more stable membranes were
obtained. For pure PES membranes thermally stable performances were obtained
without any need of extra treatment.
The permeabilities of all studied gases increased with increasing operation
temperature. Also the selectivities of H2/CO2 were increased while CO2/CH4, H2/CH4
selectivities were decreased with temperature. The best separation performance
belongs to PES/SAPO-34/HMA mixed matrix membrane at each temperature. When
the temperature increased from 35 ° / C to 120 ° / C H2/CO2 selectivity for PES/SAPO-
34/HMA membrane was increased from 3.2 to 4.6 and H2 permeability increased
from 8 Barrer to 26.50 Barrer. This results show that for H2/CO2 separation working
at higher temperatures will be more advantageous. The activation energies were
found in the order of / CH4 > / H2> / CO2 for all types of membranes. Activation energies
were in the same order of magnitude for all membranes but the PES/SAPO-34
membrane activation energies were slightly lower than PES membrane.
Furthermore, PES/SAPO-34/HMA membrane has activation energies higher than
PES/SAPO-34 membrane and is very close to pure membrane which shows that
HMA acts as a compatibilizer between two phases.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12612957/index.pdf |
| Date | 01 February 2011 |
| Creators | Oral, Edibe Eda |
| Contributors | Yilmaz, Levent |
| 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 |
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