Page 126 - Adsorbents fundamentals and applications

CARBON MOLECULAR SIEVES 111

10 −1
ACF (Kuraray)
Amount adsorbed, q [kg/kg] 10 −2 FT20
FT10
FT15

FT25

GAC(FS400)
(a) Trichloroethylene
10 −3
10 −1
(b) Tetrachloroethylene
Amount adsorbed, q [kg/kg] 10 −2 GAC(FS400) ACF (Kuraray)

FT10
FT15
FT20
FT25
10 −3
10 −6 10 −5 10 −4 10 −3
3
Concentration in aqueous phase, C [kg/m ]
Figure 5.21. Adsorption isotherms of trichloroethylene and tetrachloroethylene from aqueous
◦
solution on a number of ACF’s at 20 C (Sakoda et al., 1987, with permission).

in separation processes involving wet-gas streams. Their molecular sieving prop-
erties derive from their unique pore structure (see Figure 5.1 for pore size dis-
tribution). As a result of the foregoing and a number of other promising features
(Walker et al., 1966; Juntgen, 1977; Walker, 1990; Cabrera et al., 1993; Jones
and Koros, 1994; Koros, 1995; Acharya and Foley, 2000), CMS’s have attracted
considerable interest. Since the 1970’s, CMS’s have been produced commer-
cially on the basis of proprietary processes. Although the details of the processes
vary, they are similar and are based on the pioneering work of Walker. CMS’s
have been used worldwide for the production of nitrogen from air (Notaro
et al., 1999).
The early research focused on the preparation of CMS’s and their sieving
properties. The following three approaches were taken for their preparation:

1. Carbonization of polymers, such as poly(vinylidene chloride) (PVDC)
(Walker et al., 1966; Dacey and Thomas, 1954; Dubinin et al., 1964;
Lamond et al., 1965); Saran (90/10 mixture of vinylidene chloride and
vinyl chloride); and cellulose, sugar, and coconut shell.