Control of transport properties with a microporous membrane reactor to enhance yields in dehydrogenation reactions

Casanave, D.; Giroir‐Fendler, A.; Sánchez, J.; Loutaty, R.; Dalmon, J.A.

doi:10.1016/0920-5861(95)00129-4

Cited by 77 publications

(40 citation statements)

References 7 publications

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“…The zeolite LTA membranes prepared on DIC-4 modified porous aAl 2 O 3 disks display higher separation selectivities than those ones prepared on APTES modified a-Al 2 O 3 disks due to the stronger binding strength of urethane bonds in comparison with that of the bonds linking to silyl compounds. For binary mixtures separation, through the Na + LTA membrane at 20 C and 1 bar, the mixture separation factors of H 2 /CO 2 , H 2 /N 2 , H 2 / CH 4 and H 2 /C 3 H 8 are found to be 6.7, 5.4, 4.9 and 15.8, respectively, which are higher than those from the corresponding Knudsen coefficients. Further, relative high H 2 permeances of about 2.3 Â 10 À7 mol m À2 s À1 Pa À1 have been obtained.…”

Section: Discussionmentioning

confidence: 69%

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Facile synthesis of LTA molecular sieve membranes on covalently functionalized supports by using diisocyanates as molecular linkers

Huang

Caro

2011

J. Mater. Chem.

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Much effort has been paid towards the preparation of hydrophilic zeolite LTA membranes, and these zeolite LTA membranes have showed excellent performance in hydrophilic separations. However, there are only a few reports on successful shape-selective separations of gas mixtures on zeolite LTA membranes, most separation factors reported so far were lower than the corresponding Knudsen constants. It is often found that zeolite LTA membranes contain inter-crystalline defects to degrade their separation selectivity, which result from the problems that the isolated crystals on the support surface grow together to form a continuous supported LTA layer. In the present work, via urethane bonds formed by the reaction of isocyanate groups with surface hydroxyls, a facile synthesis method is developed for the seeding-free preparation of supported dense zeolite LTA layers by using 1,4-diisocyanate as a molecular binder to anchor the zeolite nutrients onto the support surface. The a-Al 2 O 3 supported zeolite LTA membrane with a thickness of about 3.5 mm displays molecular sieving performance in gas permeation tests.

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Section: Discussionmentioning

confidence: 69%

“…[1][2][3][4][5][6] So far, various types of supported zeolite layers, such as MFI, 7,8 DDR, 9 LTA, 10-14 FAU, 15,16 CHA, 17,18 and AFI, 19 have been successfully prepared on different supports. Among these molecular sieve membranes, the zeolite LTA membrane is of special interest.…”

Section: Introductionmentioning

confidence: 99%

Facile synthesis of LTA molecular sieve membranes on covalently functionalized supports by using diisocyanates as molecular linkers

Huang

Caro

2011

J. Mater. Chem.

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“…A temperature of 723 K was chosen because the experimental studies of isobutane dehydrogenation in a catalytic membrane reactor are normally performed at this temperature [3,[5][6][7]. Previous calculations of viscous flow over diffusion ratio [13] have shown that convective contribution to transport is negligible (less than 3% of the global flux).…”

Section: Membrane Defect Characterization Through Gas Permeations Andmentioning

confidence: 99%

“…Catalyst deactivation has been avoided by feeding hydrogen on the reaction side of the membrane [6,7]. Thus in order to keep high yields, it is even more important to use a membrane that is highly permselective towards hydrogen.…”

Section: Introductionmentioning

confidence: 99%

Experimental study and numerical simulation of hydrogen/isobutane permeation and separation using MFI-zeolite membrane reactor

et al. 2000

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A composite alumina-MFI-zeolite membrane has been prepared by a pore-plugging method. Transport through this membrane is controlled by molecular size and adsorption properties, as expected for a defect-free zeolite composite layer.Single gas transport was studied for hydrogen and isobutane. In the studied temperature range, (323-723 K) for isobutane and (277-723 K) for hydrogen, transports were activated. Isobutane exhibited a flux maximum at 450 K, whereas hydrogen flux declined with temperature.These different permeation behaviors were modeled using Maxwell-Stefan equations taking into account only surface diffusion. Activation energies were obtained from the model by fitting the experimental data. They were calculated to be 31 kJ mol −1 for isobutane and 1.9 kJ mol −1 for hydrogen. The diffusion coefficients calculated at 323 K differed by four orders of magnitude.Separation experiments with a mixture of hydrogen and isobutane in a 293-723 K temperature range were performed. Typical permeation behavior was observed for a mixture of weakly and strongly adsorbed molecules. At room temperature, hydrogen permeation was hindered by stronger adsorbed isobutane molecules in the micropores. H 2 /i-C 4 H 10 separation experiments showed a separation factor of 25 at 723 K, a typical temperature of the isobutane dehydrogenation in membrane reactors. RésuméUne membrane composite alumine-zéolithe MFI est préparée par une méthode de bouchage de pores. Le transport à travers la membrane est contrôlé par la taille des molécules et leurs propriétés d'adsorption, comme on peut s'y attendre dans une couche composite zéolithique sans défaut.Le transport des gas purs est étudié pour l'hydrogène et l'isobutane. Dans les domaines de température étudiés, 323-723 K pour l'isobutane et 277-723 K pour l'hydogène, le transport de ces deux gaz est activé. Le flux d'isobutane présente un maximum à 450 K, alors que celui d'hydrogène diminue avec la température.Ces différents comportements en perméation sont modélisés en utilisant les équations de Maxwell-Stefan appliquées uniquement à la diffusion de surface. L'ajustement de l'équation du modèle aux données expérimentales permet d'obtenir les energies d'activation de diffusion. Celles-ci sont de 31 kJ mol −1 pour l'isobutane et de 1.9 kJ mol −1 pour l'hydrogène. Les coefficients de diffusion calculés à 323 K sont dans un rapport de 10 4 .Des expériences de séparation hydrogène/isobutane sont effectuées dans une gamme de température de 293 à 723 K. Il a été observé un comportement en perméation typique d'un mélange binaire de molécules gazeuses fortement et faiblement * Corresponding author. Fax: +33-4-7244-5399. E-mail address: dalmon@catalyse.univ-lyon.fr (J.-A. Dalmon).0920-5861/00/$ -see front matter ©2000 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 0 -5 8 6 1 ( 9 9 ) 0 0 2 8 3 -7 254 P. Ciavarella et al. / Catalysis Today 56 (2000) [253][254][255][256][257][258][259][260][261][262][263][264] adsorbées. À température ambiante, la perméation d'hydrogène est gênée pa...

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“…Dans une zéolithe, l'hydrogène que l'on adsorbe reste sous forme moléculaire. Cette molécule a un intérêt pour un certain nombre de procédés industriels, par exemple les réactions d'hydrogénation avec des réacteurs à membrane, dans lesquels la zéolithe constitue la membrane poreuse [29]. De part sa petite taille et son interaction relativement faible avec une zéolithe, on s'attendrait à ce que la diffusion de l'hydrogène soit rapide et peu sensible à la structure de la zéolithe.…”

Section: Hydrogène Dans Les Zéolithes Naa Et Naxunclassified

Diffusion à longue distance

Jobic

2000

J. Phys. IV France

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Résumé. La diffusion quasi-élastique des neutrons permet d'étudier le mouvement à longue distance d'atomes ou de molécules en phase condensée ou adsorbée. L'un des avantages de laméthode est de pouvoir mesurer directement le coefficient de diffusion dans un domaine de distance où la loi de Fick est respectée. D'autre part, en utilisant un modèle de diffusion par sauts, on peut déterminer les distances et les temps de sauts élémentaires. Dans le cas d'une diffusion isotrope, les différents modèles de saut existants : Chudley -Elliott, Singwi -Sjolander et Hall -Ross sont passés en revue, et un nouveau modele impliquant une délocalisation de la particule sur son site est présenté. Les cas de diffusion unidimensionnelle normale et à la file indienne sont examinés. Les exemples d'application concernent des molécules adsorbées dans des zéolithes : hydrogène dans les zéolithes NaA et NaX, alcanes dans la structure MFI, et syst+mes unidimensionnels.

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Control of transport properties with a microporous membrane reactor to enhance yields in dehydrogenation reactions

Cited by 77 publications

References 7 publications

Facile synthesis of LTA molecular sieve membranes on covalently functionalized supports by using diisocyanates as molecular linkers

Facile synthesis of LTA molecular sieve membranes on covalently functionalized supports by using diisocyanates as molecular linkers

Experimental study and numerical simulation of hydrogen/isobutane permeation and separation using MFI-zeolite membrane reactor

Diffusion à longue distance

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