Transport of liquid and supercritical CO₂ and selected organic solvents through surface modified mesoporous γ-alumina and titania membranes

ABSTRACT

The permeation of liquid and supercritical CO₂ and the organic solvents toluene, heptane, and 1-propanol were investigated in unmodified hydrophilic and modified hydrophobic mesoporous γ-alumina and titania tubular ceramic membranes. These ceramic membranes are solvent resistant, thermally stable, and hydrophilic in nature. Viscosity-corrected solvent flux was used to evaluate the applicability of Darcy’s law, which is governed by convective transport. The permeability coefficients were dependent on solvent type due to unique solvent–membrane interactions, which is a deviation from Darcy’s law. Surface chemistry of modified membranes was evaluated using contact angle measurements, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, and Energy Dispersive X-ray Spectroscopy.

KEYWORDS:

• Liquid and supercritical CO₂
• ceramic membrane
• surface modification
• Darcy’s law
• organosilane
• solvent transport

Nomenclature

$J$	=	volumetric solvent flux (m3⋅m−2⋅s−1)
$k_m$	=	membrane permeability coefficient (m)
$k_{m,eff}$	=	membrane effective permeability coefficient (m)
$\mathrm{\Delta }P$	=	transmembrane pressure (bar)
$r_p$	=	membrane pore radius (nm)
$r_{p,eff}$	=	membrane pore radius (nm)

symbols Greek

$\epsilon$	=	membrane porosity (%)
$\eta$	=	viscosity$(\mathrm{P}\mathrm{a}\cdot \mathrm{s})$
$\varphi$	=	fractional loss in membrane cross-sectional pore area
$\tau$	=	membrane tortuosity

Acknowledgments

This paper was prepared with the support of the National Science Foundation (NSF) Science and Technology Center for Environmentally Responsible Solvents and Processes (CHE-9876674). Contact angle measurement was conducted using the instrument of Dr. Debasish Kuila (North Carolina A&T State University).

Additional information

Funding

This work was supported by the NSF [CHE-9876674].