Gas Separation Membrane with Low Monovalent Ion Support
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Solution Overview
Problem
Existing gas separation elements and modules face challenges in maintaining robustness and selectivity, especially in humid environments, due to high concentrations of monovalent metal ions in the porous support, which affect the cross-linking of siloxane layers and reduce their gas separation efficiency.
Innovation Solution
The development of gas separation elements with a porous support containing less than 10 mg/m2 of monovalent metal ions, combined with a polysiloxane discriminating layer of average thickness at least 0.7 μm, provides enhanced robustness and selectivity for separating CO2 and higher alkanes from methane.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the porous support contains high concentrations of monovalent metal ions, then the cross-linking of siloxane layers is enhanced, but the gas separation selectivity and robustness deteriorate
Solution Approach 1:
The invention extracts and removes monovalent metal ions from the porous support through chemical treatment processes. The support undergoes treatment with acids or chelating agents to extract metal ions, reducing their concentration to below 10 mg/m2, thereby eliminating their harmful effect on siloxane cross-linking while maintaining the structural integrity of the support
Solution Approach 2:
The invention changes the chemical composition parameter of the porous support by controlling the concentration of monovalent metal ions to be below 10 mg/m2. This parameter change fundamentally alters the interaction between the support and siloxane layers, enabling proper cross-linking and achieving high gas separation selectivity for CO2/CH4 and CnH2n+2/CH4 pairs
2Productivity
If the discriminating layer is made thinner to increase gas flux, then the permeance improves, but the selectivity and stability in humid environments deteriorate
Solution Approach 1:
The invention optimizes the thickness parameter of the discriminating layer to at least 0.7 μm, which balances gas permeance and selectivity. This thickness parameter ensures sufficient mechanical strength and chemical stability in humid environments while maintaining high flux rates for CO2 and higher alkanes separation
Solution Approach 2:
The invention uses a composite structure consisting of a porous support and a polysiloxane discriminating layer. The support provides mechanical strength and the discriminating layer provides selective permeability. This composite approach allows the layer to maintain both high flux and high selectivity by combining materials with complementary properties
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution results in gas separation elements and modules that are stable in humid conditions, exhibit good permeance and selectivity, and are particularly effective in separating higher alkanes from methane, offering improved performance compared to traditional modules with higher monovalent metal ion content.
Implementation Method 1
high concentrations of monovalent metal ions in the porous support, which affect the cross-linking of siloxane layers
Implementation Method 2
a permeate which has passed through a membrane and into the permeate spacer and a retentate which does not pass through the membrane
Data Source
AI summary
A gas separation element comprising a membrane sheet and a permeate spacer, wherein the membrane sheet comprises a porous support and a discriminating layer, CHARACTERISED IN THAT:(a) the porous support comprises less than 10 mg/m2 of monovalent metal ions; and(b) the discriminating layer has an average thickness of at least 0.7 μm.