Hydroxyl-Functionalized CARDO Polyimide Membranes for Sour Gas
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Solution Overview
Problem
Current membranes for sour natural gas purification face challenges in achieving both favorable diffusivity and solubility of gas molecules, particularly due to the incorporation of hydroxyl groups which can lead to reduced gas permeability and plasticization issues, especially when dealing with gas mixtures containing hydrogen sulfide.
Innovation Solution
Development of polymeric membranes containing hydroxyl-functionalized 9,9-bis(4-aminophenyl)fluorene (CARDO) moieties, which enhance gas-polymer affinity and increase dynamic free volume, allowing for improved solubility and diffusivity of gas molecules while resisting plasticization at elevated pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If hydroxyl groups are incorporated into the polymer backbone, then gas-polymer affinity and solubility are improved, but gas permeability decreases due to interchain hydrogen-bond interactions bringing polymeric chains closer
Solution Approach 1:
The patent introduces hydroxyl groups at specific local positions within the polymer structure (at the CARDO moiety) rather than uniformly throughout. This localized functionalization creates specific interaction sites for gas molecules while maintaining overall chain spacing through the rigid cardo structure, thus improving solubility without proportionally reducing permeability.
Solution Approach 2:
The patent creates a composite polymer structure combining hydroxyl-functionalized CARDO moieties with other polymer components. This composite approach allows the hydroxyl groups to provide enhanced gas-polymer affinity and solubility while the overall composite structure maintains adequate free volume and chain spacing to preserve gas permeability.
2Quantity of substance
If membranes are designed to improve solubility properties, then gas permeability decreases, creating a permeability-selectivity trade-off
Solution Approach 1:
The patent modifies the chemical parameters of the polymer by incorporating hydroxyl-functionalized CARDO moieties, which change the interaction parameters between gas and polymer. Simultaneously, the rigid cardo structure and specific molecular weight range maintain physical parameters like free volume and chain mobility, achieving improved solubility without severe permeability loss.
3Productivity
If membranes are used for sour natural gas purification with H2S, then plasticization occurs due to high affinity of H2S molecules to polymeric materials
Solution Approach 1:
The patent employs a polymer structure where the hydroxyl-functionalized CARDO moieties provide temporary, reversible interaction sites for H2S molecules. These interactions are strong enough to enable selective purification but weak enough to prevent permanent plasticization, effectively creating a 'disposable' interaction mechanism that resets with each gas cycle.
4Productivity
If gas feed pressure is elevated to improve productivity, then membrane performance deteriorates due to plasticization
Solution Approach 1:
The patent incorporates hydroxyl groups that create favorable gas-polymer affinity interactions before gas molecules can cause plasticization. This pre-established interaction network acts as a cushioning mechanism that dissipates the stress of elevated pressures and prevents the onset of plasticization, allowing stable operation at high feed pressures.
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 enhanced permeability and selectivity for CO2 and H2S, along with resistance to plasticization, improving the efficiency and productivity of natural gas separation processes.
Implementation Method 1
hydroxyl groups can form interchain hydrogen-bond interactions which brings the polymeric chains closer
Implementation Method 2
separation of a gas mixture... based on their size and affinity differences
Implementation Method 3
separation of a gas mixture... based on their size and affinity differences
Data Source
AI summary
This disclosure relates to polymeric membranes that incorporate a hydroxyl-functionalized CARDO moiety that can be used in sour natural gas separation and purification applications.