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High CO₂ permeability in supported molten-salt membranes with highly dense and aligned pores produced by directional solidification

Lookup NU author(s): Dr Greg MutchORCiD, Dr Evangelos Papaioannou, Professor Ian Metcalfe

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This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND).

Abstract

Composite molten salt-ceramic membranes are promising devices for high-temperature CO₂ separation. Intensive material properties impact on separation performance as do membrane geometry (thickness) and microstructure (pore volume fraction, size, connectivity, and tortuosity factor). Although controlling pore size is considered somewhat routine, achieving pore alignment and connectivity is still challenging. Here we report the production of the first gas separation membrane using a porous ceramic matrix obtained from a directionally-solidified magnesium-stabilised zirconia (MgSZ) – MgO fibrilar eutectic as the membrane support. MgO was removed from the parent material by acid-etching to create a porous matrix with highly aligned pores with diameters of ∼1 μm. X-ray nano-computed tomography of a central portion (∼32,000 μm³) of the support identified ∼21% porosity, with all pores aligned within 10° and ∼76% percolating along the longest sampled length. Employing the matrix as a support for a carbonate molten salt, a high CO₂ permeability of 1.41x10^-10 mol m^-1.s^-1.Pa^-1 at 815 °C was achieved, among the highest reported for supported molten-carbonate membranes (typically 10^-12 to 10^-10 mol m^-1.s^-1.Pa^-1 at similar temperatures). We suggest that the high permeability is attributable to the excellent pore characteristics resulting from directional solidification, namely a dense array of parallel, micron-scale pores connecting the feed and permeate sides of the membrane.

Publication metadata

Author(s): Grima L, Mutch GA, Oliete PB, Bucheli W, Merino RI, Papaioannou EI, Bailey JJ, Kok MD, Brett DJL, Shearing PR, Metcalfe IS, Sanjuan ML

Publication type: Article

Publication status: Published

Journal: Journal of Membrane Science

Year: 2021

Volume: 630

Print publication date: 15/07/2021

Online publication date: 12/01/2021

Acceptance date: 05/01/2021

Date deposited: 15/01/2021

ISSN (print): 0376-7388

ISSN (electronic): 1873-3123

Publisher: Elsevier BV

URL: https://doi.org/10.1016/j.memsci.2021.119057

DOI: 10.1016/j.memsci.2021.119057

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