L. Gora et al., Highly reproducible high-flux silicalite-1 membranes: optimization of silicalite-1 membrane preparation, SEP PURIF T, 22-3(1-3), 2001, pp. 223-229
Silicalite-1 membranes were prepared on a TiO2 coated porous stainless stee
l support. Different thicknesses of the membranes were achieved by changing
the synthesis temperature. Increasing the crystallization temperature resu
lted in the formation of a monolith-type layer, which is close to a perfect
microporous phase (without pores between crystals forming the layer). The
silicalite-1 membranes were characterized by permeation measurements using
single gases and a mixture of n-butane and i-butane in a Wicke-Kallenbach s
et-up. A direct relationship between the membrane thickness and the selecti
vity of n-butane to iso-butane: was observed; the selectivity improved with
an increase in the membrane thickness. The improvement in the selectivity
was correlated with decreasing the intercrystalline spaces between the crys
tals forming the membrane. The best performing membranes were synthesized i
n the temperature range of 453-463 K. The competitive adsorption of the but
anes at 303 K was governing the separation properties of the membranes. The
selectivity for n-butane in a 50:50 n-butane/iso-butane mixture was as hig
h as 55, and the flux equal to 2.75 mmol/m(2) per s (WK method at 101 kPa,
303 K). The ideal selectivities, calculated from the single component measu
rements towards n-butane, were between 33-48 and n-butane fluxes between 7-
12 mmol/m(2) per s (WK method at 101 kPa, 303 K). Small variations in the s
electivity performance of the membranes synthesized under the same conditio
ns show that the optimized preparation method was highly reproducible. (C)
2001 Elsevier Science B.V, All rights reserved.