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Isomorphously substituted B-MFI hollow fibre membranes for p-xylene separation from C8 aromatic mixtures

Deng, Z., Nicolas, C.-H., Guo, Y., Giroir-Fendler, A. and Pera-Titus, M. 2011. Isomorphously substituted B-MFI hollow fibre membranes for p-xylene separation from C8 aromatic mixtures. Separation and Purification Technology 80 (2) , pp. 232-239. 10.1016/j.seppur.2011.05.014

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Abstract

In this study, Al-MFI and B-MFI (Si/B = 100 and Si/B = 50) hollow fibres with nanocomposite architecture have been prepared on α-alumina by pore-plugging hydrothermal synthesis at 443 K for 89 h using a precursor clear solution with molar composition 1 SiO2: 0.45 TPAOH: 27.8 H2O: xH3BO3 (x = 0–0.02). The synthesized materials were characterized by XRD, SEM, ICP-AES and 29Si, 27Al- and 11B-MAS-NMR, revealing the genesis of well-intergrown materials with isomorphously substituted boron in the MFI unit cell. The pure ethylbenzene permeance within these membranes decreased in the order Al-MFI > B-MFI (Si/B = 50) > B-MFI (Si/B = 100). All the MFI materials were selective to p-xylene in the vapour permeation of ternary p-/m-/o-xylene mixtures and quaternary p-/m-/o-xylene/ethylbenzene model mixtures in the temperature range 400–650 K and for total feed vapour pressures lower than 4.5 kPa. The p-/m-xylene separation factor increased in the sense Al-MFI < B-MFI (Si/B = 100) ≈ B-MFI (Si/B = 50). The p-/m-xylene and p-/o-xylene separation factors, as well as p-xylene mixture fluxes, decreased with the ethylbenzene feed concentration, probably due to configurational entropy effects in the mixture adsorption patterns. The membranes showed however slightly preferential p-xylene permeation than ethylbenzene at low total aromatic vapour pressures despite the similar kinetic diameter of both molecules (5.8 vs. 6.0 Å), the B-MFI (Si/B = 50) material achieving a p-xylene/ethylbenzene separation factor as high as 5.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Cardiff Catalysis Institute (CCI)
Publisher: Elsevier
ISSN: 1383-5866
Date of Acceptance: 10 May 2011
Last Modified: 13 Oct 2020 15:00
URI: http://orca.cardiff.ac.uk/id/eprint/135431

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