Membrane Gas Separation

6.4
Conclusions 
Defect - free membranes comprising zeolites and amorphous glassy perfl uoropolymers can 
be prepared by modifying the surface of the fi ller. The pure gas permeation experiments 
of a series of Tefl on AF 1600 membranes with various amounts of 80 and 350 nm silicalite - 1 
crystals cannot be interpreted on the basis of the Maxwell model, but are compatible with 
a model in which a barrier to transport exists on the zeolite surface and a lower density 
polymer layer surrounds the crystals. With a small zeolite size (80 nm) the low density 
layers around the crystals may coalesce and form percolation paths of lesser resistance and 
less selectivity. Silicalite - 1 crystals improve the CO 
2
/CH 
4
selectivity of Hyfl on AD60X, 
and drive the N 
2
/CH 
4
selectivity beyond the Robeson ’ s upper bound. It also turns out 
that the presence of silicalite - 1 crystals, like fumed silica, promote the inversion of the 
methane/butane selectivity of Tefl on AF2400 in mixed gas experiments.
0,1
1
10
0,1
1
10
100
P(
n -C
4
H
10
) / 10
-15
 Nm
3
 m m
-2
 Pa
-1
 s
-1
P(
n
-C
4
H
10
)/P(CH
4
), (-)
AF24_1500_40
AF 2400 + 0, 25, 40% FS, pure gases
AF 2400 + 0, 18, 30, 40% FS, mixture
(a)
0,5
0,7
0,9
1,1
1,3
1,5
0,4
0,6
0,8
1
1,2
p(n-C
4
H
10
) / 10
5
 Pa