Multi-layer Co-polyimide Membranes for Sour Gas Separation
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Solution Overview
Problem
Current membrane technologies for natural gas separations, particularly for sour gas, face challenges in achieving high permeability and selectivity while maintaining long-term stability and resistance to contaminants, leading to inefficiencies and high costs in industrial applications.
Innovation Solution
Development of multi-layer composite co-polyimide membranes with specific monomers like 6FDA and CARDO, using a consecutive coating process involving pre-wetting, deposition of permselective layers, and optional cross-linking, to create defect-free membranes with enhanced CO2 and H2S separation capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional membrane materials like cellulose acetate are used, then CO2/CH4 separation capability is achieved, but H2S/CH4 separation capability and mechanical stability are insufficient
Solution Approach 1:
The patent employs glassy polyimide composite membranes combining multiple polymer components with distinct functions: one component provides high CO2/CH4 selectivity while another component ensures mechanical strength and H2S resistance. This composite structure resolves the contradiction by integrating materials that individually excel at different separation tasks into a unified membrane system.
2Quantity of substance
If rubbery polymeric membranes are used for H2S/CH4 separation, then H2S permeability is improved, but CO2/CH4 separation capability and mechanical stability deteriorate
Solution Approach 1:
The patent divides the separation function into distinct segments within the membrane structure. The glassy polyimide matrix provides size-based size selectivity for CO2/CH4 separation, while specific functional groups or phases within the composite structure facilitate H2S permeation through solubility mechanisms. This segmentation allows each component to optimize its specific separation task without compromising overall performance.
3Productivity
If existing polymeric membranes are used, then gas separation is achieved, but performance deteriorates under high pressure and contaminant exposure due to plasticization
Solution Approach 1:
The patent modifies the physical and chemical parameters of the polyimide membrane through compositional adjustments and cross-linking. By controlling the glass transition temperature, free volume, and polymer chain rigidity, the membrane maintains its glassy state and rejection mechanisms under high pressure conditions, preventing plasticization while preserving separation performance.
Solution Approach 2:
The patent incorporates pretreatment layers or surface modifications on the membrane before exposure to contaminants. These preliminary structures prevent heavy hydrocarbon and water vapor from reaching and plasticizing the selective polyimide layer, thereby protecting long-term stability while maintaining gas separation productivity.
4Reliability
If conventional separation technologies like absorption and adsorption are used, then acid gas removal is achieved, but energy requirements and capital costs increase
Solution Approach 1:
The patent replaces thermal-based absorption and adsorption processes with a membrane-based separation system that operates isothermally. The glassy polyimide membrane utilizes size exclusion and solubility differences to separate acid gases from natural gas without requiring thermal regeneration cycles, thereby eliminating the high energy inputs associated with conventional amine absorption and pressure swing adsorption technologies.
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 membranes exhibit superior CO2/CH4 and H2S/CH4 selectivities and permeances, maintaining performance under aggressive conditions, including high pressures and high H2S concentrations, outperforming traditional materials like cellulose acetate and reducing energy and capital costs.
Implementation Method 1
The membranes exhibit superior CO2/CH4 and H2S/CH4 selectivities and permeances
Implementation Method 2
since rubbery polymeric materials separate based on solubility selectivity
Implementation Method 3
optional cross-linking
Implementation Method 4
pre-wetting
Data Source
AI summary
Methods and systems for producing and using multi-layer composite co-polyimide membranes, one method for producing including preparing a microporous or mesoporous membrane support material for coating; applying a sealing layer to the membrane support material to prevent intrusion into the membrane support material of co-polyimide polymer; applying a first permselective co-polyimide layer atop and in contact with the sealing layer; and applying a second permselective co-polyimide layer atop and in contact with the first permselective co-polyimide layer.