High temperature steam investigation of cobalt oxide silica membranes for gas separation

Uhlmann, D, Smart, S and Diniz da Costa, JCD (2010) High temperature steam investigation of cobalt oxide silica membranes for gas separation. Separation and Purification Technology, 76 2: 171-178. doi:10.1016/j.seppur.2010.10.004

Author Uhlmann, D
Smart, S
Diniz da Costa, JCD
Title High temperature steam investigation of cobalt oxide silica membranes for gas separation
Journal name Separation and Purification Technology   Check publisher's open access policy
ISSN 1383-5866
Publication date 2010-12-13
Sub-type Article (original research)
DOI 10.1016/j.seppur.2010.10.004
Volume 76
Issue 2
Start page 171
End page 178
Total pages 8
Place of publication Oxford, United Kingdom
Publisher Pergamon
Collection year 2011
Language eng
Formatted abstract
In this work we investigate the effect of high temperature steam on cobalt and cobalt oxide derived silica with an aim to providing an understanding of the permeation and gas separation performance of cobalt silica membranes exposed to simulated industrial wet gas streams. Cobalt silica (CoSi) and cobalt oxide silica (CoOxSi) xerogels were synthesized and exposed to steam at 500 °C for varying time periods. Subsequent characterization with FTIR and N2 adsorption revealed that CoOxSi xerogels were significantly more hydrostable than CoSi xerogels, with few structural changes observed and only moderate densification (∼43%) of the CoOxSi matrix experienced even after the longest steam exposure. In comparison the CoSi matrix experienced severe densification (∼89%) after only short term steam exposure. CoOxSi was therefore selected as the optimal material for further membrane tests and CoOxSi membranes were subsequently synthesized using sol-gel techniques and exposed to steam in both high temperature long term stability studies and during temperature cycling tests. Exposure to steam had an adverse effect on membrane performance with the largest effect occurring during the initial stages where He permeance dropped from 3.95 × 10-8 to 2.05 × 10-10 mol m-2 s-1 Pa-1 and He/N2 ideal selectivities from 123 to 45, respectively after 135 h of testing. However, following this initial period of steam conditioning, these membranes were able to oppose further deterioration and maintain acceptable steady state performance. Further tests with an increased steam rate showed that nitrogen permeation decreased more significantly than helium, leading to a rise in membrane ideal selectivity, suggesting that steam was competitively blocking the pores available to nitrogen adsorption and/or reducing the diffusion of nitrogen. Steam testing under cycling temperature conditions showed that below 400 °C, the membrane ideal selectivity was low. However, above 400 °C the membrane consistently exhibited a molecular sieving mechanism. In addition water permeation through the membrane varied with temperature suggesting that the membrane matrix continuously underwent reversible structural modification by the combined effect of water and temperature.
© 2010 Elsevier B.V. All rights reserved.
Keyword Cobalt oxide silica
Gas separation
Hydrothermal stability
Molecular-sieve silica
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Chemical Engineering Publications
Official 2011 Collection
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Citation counts: TR Web of Science Citation Count  Cited 26 times in Thomson Reuters Web of Science Article | Citations
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Created: Sun, 13 Mar 2011, 00:02:10 EST