Proceedings of the 18th Annual Conference on Fossil Energy Materials. Page: 18 of 308
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There was some variation in the properties of the membranes with time at temperature. This is illustrated in Figure
5. Here the results of repeated permeation measurements of H2 on membrane S2 are shown. It is evident that the
permeation of hydrogen increased by about 30 %between the first and the last measurement at 400 C.0
a
0
a
00.25
0.2
0.15
0.1
0.050'
200 300400
500
600
H2(1)
H2(2)
A H2(3)
A H2(4)700
T(K)
Figure 5. Results of repeated measurements of H2 permeance for Membrane S2 at each temperature. H2
permeance was first measured at a given temperature and then again after the permeance measurement for
each of the other gases, for a total of four H2 measurements at each temperature.a
a)
C',35
30
25
20
1510
5
0-
200300
400 500
T(K)600
H2/C3H8
o He/C3H8
A H2/CO2
A He/CO2700
Figure 6. Measured selectivity for Membrane S2 with respect to temperature of the four gas combinations
indicated.
Generally, for pore diameters > 2nm, the dominant permeation mechanisms in operation are Knudsen diffusion and
surface transport, together with molecular diffusion and viscous flow (Poiseuille or laminar flow) at larger pore
diameters. For pore diameters of about lnm and smaller, other mechanisms, which are covered by the term
"nanopore diffusion," become operative. Several mechanisms of gas transport through a membrane are summarized6
Membrane S2
"
Membrane S2 "
S o
e., Q
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Judkins, RR. Proceedings of the 18th Annual Conference on Fossil Energy Materials., report, November 2, 2004; [Tennessee]. (https://digital.library.unt.edu/ark:/67531/metadc892433/m1/18/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.