Silicalite-1 Membrane: Synthesis, Modification, Characterization And Its Performance For The Reactive Separation Of Para-Xylene From Xylene Isomers
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Date
2010-05
Authors
Yeong, Yin Fong
Journal Title
Journal ISSN
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Publisher
Universiti Sains Malaysia
Abstract
Reactive separation of para-xylene from xylene isomers in a catalytic
membrane reactor depends on the right choice of catalytic membrane. This
membrane should not only catalyze xylene isomerization reaction but also separate
para-xylene (p-xylene) from its isomers (ortho-xylene (o-xylene) and meta-xylene
(m-xylene)). In the present study, silicalite-1 and two types of acid-functionalized
silicalite-1 membranes: (1) propylsulfonic acid-functionalized silicalite-1 membrane
and (2) arenesulfonic acid-functionalized silicalite-1 membrane were synthesized on
disc type -alumina support, pre-coated with mesoporous silica layer. The physical
and chemical properties of the membranes were characterized using different
techniques such as XRD, SEM, TEM, 29Si MAS NMR, 13C CP-MAS NMR, FTIR,
TGA, EA, NH3-TPD, acid-base titration and nitrogen adsorption–desorption. The
nitrogen permeation and permporosimetry tests were conducted to evaluate the
quality and the presence of non-zeolite pores in the membranes.
Design of experiments (DoE) was applied in the optimization process of
p-xylene separation from p-/o-xylene binary mixture and p-/o-/m-xylene ternary
xylene mixture using silicalite-1 membrane. The optimum p-xylene flux of
3.83 x 10-6 mol/m2.s and p-/o-xylene separation factor of 46 were obtained at a
temperature of 198 oC, p-xylene feed partial pressure of 0.15 kPa and p-xylene feed
composition of 0.80. The optimum p-xylene flux of 5.94 x 10-6 mol/m2.s, p-/o-xylene
separation factor of 19 and p-/m-xylene separation factor of 20 were achieve at
temperature of 198 oC and p-xylene feed partial pressure of 0.22 kPa in ternary
xylene mixture separation. The Maxwell-Stefan diffusion model, in combination
with the Ideal Adsorbed Solution (IAS) theory and single-component adsorption
parameter were used to predict the permeation flux of p-xylene and o-xylene for
binary xylene mixture through a silicalite-1 membrane in the temperature range of
150 oC – 250 oC.
Description
Keywords
Para-xylene from xylene isomers in a catalytic membrane reactor , depends on the right choice of catalytic membrane