Ljp. Van Den Broeke et al., Transport and separation properties of a silicalite-1 membrane - II. Variable separation factor, CHEM ENG SC, 54(2), 1999, pp. 259-269
Results for the permeation of binary mixtures through a silicalite-l membra
ne are presented. The binary separation factor for mixtures of CH4-N-2, CO2
-N-2, and CO2-CH4 is studied as a function of the feed composition and as a
function of the feed pressure. A comparison is made between the separation
factor calculated from the binary fluxes and the so-called ideal separatio
n factor? which is given by the ratio of the one-component flux. In general
, the binary separation cannot be predicted from the one-component data alo
ne. At ambient temperature the separation obtained with the silicalite-l me
mbrane is based on a difference in equilibrium adsorption. It is found that
the separation factor is a function of both the composition and the pressu
re. The fact that the separation factor varies with the feed composition an
d the feed pressure cannot be explained with the extended Langmuir model us
ed to describe the binary equilibrium adsorption. A reasonable description
of the separation factor as a function of the pressure and composition is p
ossible with the ideal adsorbed solution theory. Using the permeation and s
eparation properties for the CO2/N-2/silicalite-1 system a membrane cascade
is designed. The surface area of the membrane cascade has been calculated
with both the binary and the ideal separation factor. (C) 1998 Elsevier Sci
ence Ltd. All rights reserved.