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

4 Results and discussion
4.3.4 Gas permeation
The results of all He and SF6 gas permeation measurements are summarized in Figure 73.
The membrane numbers are listed in Table 30. The permselectivity of the membranes
that have been calcined at 400ºC and of the γ-Al2O3 membrane are all similar to what can
be expected from the Knudsen diffusion (6.0). An increase in the calcination temperature,
to 500ºC, results in a strong reduction of He permeation from 4⋅10 -8 mol/s⋅m 2 ⋅Pa to
approximately 2⋅10 -9 mol/s⋅m 2 ⋅Pa. A calcination temperature of 600ºC causes a
significant increase in the He permeance to at least 2⋅10 -8 mol/s⋅m 2 ⋅Pa and a He/SF6
permselectivity of up to 30. It should be noted that both the He and the SF6 permeability
of membrane #204 significantly exceed those of all other membranes, which suggests
that this particular membrane contains substantially more large pores or defects. All other
results indicate that mass transport through the Ti0.5Zr0.5O2 layers calcined above 400ºC is
no longer dominated by the Knudsen diffusion, but that at least for the He transport there
is a substantial contribution from micropore diffusion.
He Permeance (10 -8 mol/s m 2 Pa)
109 15
10
5
0
Permeance
Permselectivity
Double Coating
Support 400ºC 400ºC 500ºC 500ºC 600ºC 600ºC
#109 #206 #208 #132 #202 #205 #204
Figure 73: He permeance and He/SF6 permselectivity of Ti0.5Zr0.5O2 membranes calcined at 400, 500 and
600ºC measured at 200ºC.
Table 30 Overview of characterised membranes with gas permeation
Final layer Calcination temperature Membrane #
γ-Al2O3 600ºC 109
Ti0.5Zr0.5O2 400ºC 206, 209
500ºC 132, 143, 202
600ºC 204, 205
106
35
30
25
20
15
10
5
0
He/SF 6 Permselectivity