(740e) Propylene/Propane Separation through FAU-Type Zeolite Membrane

Due to close boiling points of propane and
propylene as well as their low boiling points, distillation separation of
propane/propylene mixtures produced at the ethylene center has a large energy
demands.   Membrane gas separation would be a promising candidate to save
separation energy dramatically.  In this presentation, we would like to
show our recent results on FAU-type zeolite membrane for such C3 mixture
separation.  FAU-type membrane was synthesized on the outer surface of
porous alpha-alumina tube with 10 mm i.d. and 3 cm length (Noritake Co.
Limited) by a secondary growth method consisting of seeding of FAU-seeds on the
outer surface of support and its hydrothermal growth.  The resultant
membrane was treated in aqueous solutions containing with a variety of kinds of
cation such as alkali and alkaline earth cation, and transition metal
cation.  Among them, we found that Ag-FAU membrane exceptionally showed
high separation factor.  For the equimolar C3 gas mixtures,  the
permeance of propane was 4.13x10^-8 mol m^-2 s^-1
Pa^-1 with the separation factor of 55.3 at 353 K.Figure 1 compares
the permeances of propane and propylene in the unary and binary systems. 
Whereas the propylene permeances in the both systems were almost the same, the
permeance of propane was markedly decreased in the presence of propylene,
indicating that propylene strongly adsorbed in the membrane inhibited the
permeation of propane.  In addition, such a separation factor exceeding 50
will be able to enable us to produce polymer-grade propylene in one step of
membrane separation. 

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