Membrane Gas Separation

 ® 
  /PEG membrane with 
50 wt.% of PEG presented high CO 
2
fl ux in the whole operating pressure range ( 
>
0.3 m 
3
/
m 
2
h bar for CO 
2
/N 
2
mixture).
4
8
12
16
20
0,1
0,2
0,3
0,4
Flux of CO
2
[m
3
/( m
2
h bar)]
Fugacity[bar]
Figure 12.14 Flux of CO 
2
as a function of fugacity in single gas. ( -
䊏
- 0% PEG, -
䊊
- 10% 
PEG, -
䉱
- 20% PEG, -
䉮
- 30% PEG, -
䉬
- 40% PEG and -
夽
- 50% PEG [Reprinted with 
permission 93 ]

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Tailoring Polymeric Membrane Based on Segmented Block Copolymers
247
The selectivity of membranes for mixed gas has been different compared to the selec-
tivity based on single gas. Although the data are not collected in the same operating 
pressure as in single gas experiments, all results are in the same operating range (see 
Figures 12.14 and 12.15 ). The observed CO 
2
/gas selectivities based on single gas meas-
urement are higher than mixed gas selectivities due to the plasticization effect. Membranes 
with high PEG content presented better performance under all operating conditions, and 
the best improvement was observed for CO 
2
/H 
2
mixed gas (selectivity
>
9.4 and CO 
2
fl ux 
>
0.31 m 
3
/m 
2
h bar). Selectivity is constant for the whole pressure range. This result is in 
reasonable agreement with that reported earlier for homogeneous fi lms [65] . The CO 
2
/N 
2
selectivity is between 63 and 70 depending on the feed pressure, and CO 
2
fl ux is higher 
than 0.23 m 
3
/m 
2
h bar. The CO 
2
/CH 
4
selectivity for Pebax