Separation of Hydrocarbon Isomer Vapors with Silicalite Zeolite Membranes

Abstract

The permeation behavior of n-octane, isooctane, and n-hexane vapors through continuous, silicalite zeolite membranes on porous alumina supports was investigated between 383 and 523 K. For binary and ternary mixtures, n-octane permeated through the membrane faster than either n-hexane or isooctane, and a selectivity for n-octane over isooctane of 40 was obtained in a ternary mixture at 413 K. Selectivity was a function of temperature, however, and lower selectivities were obtained above and below 413 K. The n-octane/n-hexane selectivity was 9 at 413 K and decreased with increasing temperature. Permeances were a strong function of other organics present in the feed. The permeance of n-octane increased a factor of 16 in the presence of isooctane and n-hexane. The pure component permeances thus could not be used to predict separations for mixtures. Whereas n-octane was always the faster permeating compound in mixtures, pure isooctane permeated up to 5 times faster than pure n-octane, and pure n-hexane permeated faster than pure isooctane. That is, the largest molecule did not have the lowest permeance for pure components, and the smallest molecule did not have the highest permeance in mixtures. Thus relative permeances could not be predicted on the basis of size or shape alone. The permeances of the pure compounds were activated with activation energies between 18 and 45 kJ/mol. The mixed feed permeances also increased with temperature but did not follow an exponential relationship. Transport limitations caused by membrane saturation, diffusion through boundary layers on the feed side, and diffusion through the alumina support were not important.

Permeation Flux of Organic Molecules through Silica-surfactant Nanochannels in a Porous Alumina Membrane

“…Membranes made of zeolites are used for catalysts, 5 pervaporation 6,7 and high temperature separation of hydrocarbon isomer vapors. 8 Ceramics such as alumina are hard and heat-resistant materials made with nonmetallic minerals, and ceramic membranes for gas separation 13 and catalysts 14 have been synthesized.…”

“…A variety of preparation and application methods of inorganic membranes have been reported. [4][5][6][7][8][9][10][11][12][13][14][15] Zeolites 4-8 and ceramics 9-14 are frequently used as sources of inorganic membranes. Zeolites are porous crystalline materials, which have a high surface area to volume ratio.…”

“…Membranes made of zeolites are used for catalysts, 5 pervaporation 6,7 and high temperature separation of hydrocarbon isomer vapors. 8 Ceramics such as alumina are hard and heat-resistant materials made with nonmetallic minerals, and ceramic membranes for gas separation 13 and catalysts 14 have been synthesized.Mesoporous silica has also been adopted as a source material in the synthesis of inorganic membranes. 9,15 Mesoporous silica is an ordered material that has three different mesophases: lamellar, cubic and hexagonal.…”

Application of Microwave Heating on the Facile Synthesis of Porous Molecular Sieve Membranes

“…MFI type (including Al-free silicalite-1 and its Al-containing analogue ZSM-5) zeolite membranes have been widely studied in hydrocarbon separations due to its ease crystallization as well as high thermal and chemical stabilities (Arruebo et al, 2006;Coronas et al, 1998;Funke et al, 1996). However, the studies of microwave heating synthesis of MFI zeolite membranes are rather few.…”

A Review of Carbon Dioxide Selective Membranes: A Topical Report

“…These supported zeolite membranes have a thin and continuing zeolite separation layer with the porous support providing mechanical strength to the membrane. Membranes of various zeolites, such as ZSM-5 [30][31][32][33][34][35][36][37], Y type [38][39][40][41][42][43], silicalite [44][45][46][47][48][49][50], A type [42,51,52], P type [53], modernite [33], and silicoaluminophosphate [54][55][56] have been synthesized on porous supports.…”