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Indexed by:期刊论文

Date of Publication:2018-11-23

Journal:CHEMICAL ENGINEERING SCIENCE

Included Journals:SCIE、Scopus

Volume:190

Page Number:286-296

ISSN No.:0009-2509

Key Words:Silica membrane; Mercury adsorption; Micropore transport; Effective medium theory; Oscillator model

Abstract:This work investigates the effect of condensable Hg vapour on the transport of N-2 gas across cobalt oxide silica (CoOxSi) membranes. Experimental results suggest that Hg significantly affects N-2 permeation at 100 and 200 degrees C, though this effect is negligible at 300 degrees C. This effect was found to have a correlation with Hg adsorption on CoOxSi xerogels. In order to understand the Hg effect in the transport phenomena of N-2 permeation, the oscillator model was used to model gas transport through pores with different sizes. By including effective medium theory (EMT), the oscillator model fitted well the experimental results and gave good prediction of mass transfer in ultra-microporous materials with a tri-modal pore size distribution, such as silica membranes. It is postulated that Hg seeks lower level potentials in micro-pores, and therefore Hg molecules tend to block small pores (2.5-4 angstrom from 2.9 angstrom), or reduce the average pore size of larger pores (6.7-7.8 angstrom and 12-14 angstrom). Although N-2 permeation decreased with the presence of Hg, it did not decrease when the Hg load was increased by a factor of ten; this strongly suggests the adsorption of Hg molecules in the smaller pores (2.5-4.0 angstrom), or along the pore wall for the larger pore ranges (6.7-7.8 angstrom and 12-14 angstrom). (C) 2018 Elsevier Ltd. All rights reserved.