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Titolo:
Separation of xylene isomer vapors with oriented MFI membranes made by seeded growth
Autore:
Xomeritakis, G; Lai, ZP; Tsapatsis, M;
Indirizzi:
Univ Massachusetts, Dept Chem Engn, Goessmann Lab, Amherst, MA 01003 USA Univ Massachusetts Amherst MA USA 01003 ssmann Lab, Amherst, MA 01003 USA
Titolo Testata:
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
fascicolo: 2, volume: 40, anno: 2001,
pagine: 544 - 552
SICI:
0888-5885(20010124)40:2<544:SOXIVW>2.0.ZU;2-U
Fonte:
ISI
Lingua:
ENG
Soggetto:
SILICALITE-ZEOLITE MEMBRANES; SHAPE-SELECTIVE ADSORPTION; ZSM-5 TUBULAR MEMBRANES; SECONDARY GROWTH; PERMEATION PROPERTIES; SORPTION; FILMS; MICROSTRUCTURE; PERVAPORATION; AROMATICS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Engineering, Computing & Technology
Citazioni:
39
Recensione:
Indirizzi per estratti:
Indirizzo: Tsapatsis, M Univ Massachusetts, Dept Chem Engn, Goessmann Lab, Amherst, MA 01003 USA Univ Massachusetts Amherst MA USA 01003 mherst, MA 01003 USA
Citazione:
G. Xomeritakis et al., "Separation of xylene isomer vapors with oriented MFI membranes made by seeded growth", IND ENG RES, 40(2), 2001, pp. 544-552

Abstract

Oriented MFI membranes made by secondary growth on the surface of alpha -Al2O3 support disks have been evaluated for the separation of xylene isomersvapors in the temperature range 22-275 degreesC and feed partial pressuresup to similar to0.7-0.9 kPa. It is found that the separation performance of these membranes is directly related to the synthesis conditions and the resulting membrane microstructure. Thick (12-18 mum) and c-oriented membranes (type A membranes) made by 24-h growth at 175 degreesC exhibit single-component p-xylene/o-xylene permselectivity as high as 150 at 100 degreesC butvery modest separation factors (usually <5) are obtained with binary feed mixtures, a result of a drastic increase in the flux of o-xylene in the presence of p-xylene. Thin (2-3 <mu>m) and (h0h)-oriented membranes (type B membranes) made by 120-h growth at 90 degreesC exhibit comparable single-component and binary permeation behavior but suffer from lower selectivities/separation factors (up to 12) as a result of cracks formed after calcination for template removal. It is found that the addition of n-hexane in a binaryp-xylenelo-xylene feed in the case of type A membranes or the dip-coating of type B membranes with a surfactant-templated silica sol results in a considerable improvement of mixture separation factors up to 60 or 30-300, respectively. This improvement is attributed to preferrential adsorption of n-hexane in nonzeolitic micropores/grain boundaries in the case of type A membranes or to selective sealing of cracks by mesostructured silica in the case of type B membranes. Both type A and type B membranes exhibit, at 100-125 degreesC, p-xylene permeance [(2-5) x 10(-8) mol m(-2) s(-1) Pa-1] and p-xylene/oxylene separation factors (60-300) that are comparable to or higherthan the values reported for other MFI membranes in the literature.

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Documento generato il 29/09/20 alle ore 16:19:34