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Preparation of highly selective zeolite ZSM-5 membranes by a post-synthetic coking treatment

Yan, Yushan and Davis, Mark E. and Gavalas, George R. (1997) Preparation of highly selective zeolite ZSM-5 membranes by a post-synthetic coking treatment. Journal of Membrane Science, 123 (1). pp. 95-103. ISSN 0376-7388. doi:10.1016/S0376-7388(96)00206-2.

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Zeolite ZSM-5 membranes with high n-butane:isobutane selectivities, e.g., 322 at 185°C, are obtained by a selective deposition of coke into non-zeolitic pores. The zeolite membranes are prepared by in situ crystallization on either bare porous α-Al_2O_3 support disks or disks that are pretreated to include a diffusion barrier. The post-synthetic coking treatment is accomplished by impregnating these membranes with liquid 1,3,5-triisopropylbenzene (TIPB) for 24 h at room temperature and then calcining them in air at 500°C for 2 h. Calcination at 500°C for up to 30 h does not destroy the high n-butane:isobutane selectivity. Thermogravimetric analysis (TGA) experiments on two model pore systems ZSM-5 (5.5 Å) and Vycor glass (40–50 Å) suggest that micro-defects are selectively eliminated by the TIPB coking treatment while the intracrystalline pore space of the ZSM-5 is not affected. The elimination of non-zeolitic pores results in a large increase of n-butane:isobutane pure gas flux ratio (45 vs. 320 at 185°C) accompanied by a fourfold reduction of the n-butane flux. The permeation experiments reveal that the n-butane flux increases nonlinearly with the partial pressure in the feed while the n-butane:isobutane pure gas flux ratio remains relatively unchanged.

Item Type:Article
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Davis, Mark E.0000-0001-8294-1477
Gavalas, George R.0000-0003-1468-6835
Additional Information:© 1997 Elsevier. Received 8 April 1996; revised 5 July 1996; accepted 5 July 1996. The authors would like to thank Christopher B. Dartt for his help with the UV diffuse reflectance measurements and Neil E Fernandes, John E. Lewis and Dr. Masahito Yoshikawa for their assistance with the TGA experiments. This research was funded by National Science Foundation Grant No. CTS-9504901.
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Subject Keywords:ZSM5 Zeolite; Separation; Coking; Selectivity
Issue or Number:1
Record Number:CaltechAUTHORS:20151007-090425546
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Official Citation:Yushan Yan, Mark E. Davis, George R. Gavalas, Preparation of highly selective zeolite ZSM-5 membranes by a post-synthetic coking treatment, Journal of Membrane Science, Volume 123, Issue 1, 8 January 1997, Pages 95-103, ISSN 0376-7388, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:60844
Deposited By: George Porter
Deposited On:13 Oct 2015 21:33
Last Modified:10 Nov 2021 22:40

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