Water Resistant Composite Membranes for Carbon Dioxide Separation from Methane

Abstract

Abstract:Membranes that are resistant to water vapor permeation have potential in natural gas sweetening by reducing the need for pretreatment. The perfluorinated polymer Teflon AF1600 has proven resistance to water vapor, which is adapted here in the form of composite membranes consisting of a Teflon AF1600 protective layer on membranes of the polyimide 4,4 -(hexafluoroisopropylidene) diphthalic anhydride 2,3,5,6-tetramethyl-1,4-phenylenediamine (6FDA-TMPDA) as well as Polymer of Intrinsic Micro-porosity (PIM-1). The permeability of CO 2 and CH 4 through the composite membranes was shown to be a function of the respective permeabilities of the individual polymer layers, with the Teflon AF1600 layer providing the majority of the resistance to mass transfer. Upon exposure to water, the composite membranes had reduced water permeation of 7-13% compared to pure membranes of 6FDA-TMPDA and PIM-1, because of the water resistance of the Teflon AF1600 layer. It was observed that water permeated as clusters through the composite structure. Under CO 2 -CH 4 mixed gas conditions, 6FDA-TMPDA layer permselectivity performance was reduced and became comparable to Teflon AF1600, while the PIM-1 layer retained much of its high permselectivity performance. Importantly, at water activities below 0.2 the PIM-1 composite membrane achieved higher permeability for CO 2 compared to water.

Perspective on Gas Separation Membrane Materials from Process Economics Point of View

“…The permeability of gas i in the presence of gas j can be written as where f i is the fugacity of gas i , subscripts 1 and 2 denote feed and permeate sides, respectively, and F i is the fraction of the immobilized concentration in the microvoids for gas i . Competitive sorption among gases is primarily responsible for the decreased gas permeability and selectivity for the mixed gas feed in comparison to the pure gas feed. − …”

The Effect of the Temperature and Moisture to the Permeation Properties of PEO-Based Membranes for Carbon-Dioxide Separation

“…The difference in diffusivity of nitrogen and oxygen is not so prominent as the difference in the sizes of molecules of nitrogen (or oxygen) and carbon dioxide is significantly smaller than in the case of hydrogen and carbon-dioxide. Anyway, their solubility should be kept as low as possible in order to provide good separation [ 31 ].…”