Carbon Molecular Sieve Membranes via Homogeneous Dehydrohalogenation
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Solution Overview
Problem
Conventional methods for producing carbon molecular sieve (CMS) membranes face challenges in achieving improved processability due to the insolubility of precursor polymers in common solvents, leading to uneven dehalogenation and production inefficiencies.
Innovation Solution
A method involving the homogeneously dehydrohalogenation of precursor polymers using an organic amine base to form partially dehydrohalogenated polymers, which are then pyrolyzed to create CMS membranes, ensuring solubility in solvents and avoiding triple bonds and inter-polymer chain crosslinking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional precursor polymers are used for producing CMS membranes, then the production process can proceed, but the polymers are insoluble in common solvents leading to uneven dehalogenation and production inefficiency
Solution Approach 1:
The patent introduces a copolymerization step that changes the chemical composition parameters of the precursor polymer by incorporating comonomers (such as vinyl acetate, methyl acrylate, or ethyl acrylate) into the polymer chain. This compositional modification fundamentally alters the solubility characteristics of the polymer, enabling it to dissolve in common solvents like tetrahydrofuran. The controlled incorporation of these comonomers during polymerization creates a balanced structure that maintains both solubility and the ability to undergo uniform dehalogenation, directly resolving the contradiction between ease of manufacture and manufacturing precision.
2Productivity
If heterogeneous dehalogenation is used on insoluble polymers, then dehalogenation can occur, but it causes uneven dehalogenation with extensive dehalogenation at the surface and limited dehalogenation near the center
Solution Approach 1:
The patent applies preliminary action by ensuring the precursor polymer is in a dissolved state before the dehalogenation step. By dissolving the copolymerized precursor in a suitable solvent to form a homogeneous solution, the polymer chains are separated and accessible to the dehalogenating agent throughout the entire volume. This preliminary dissolution step eliminates the surface-center gradient problem that occurs in heterogeneous systems, allowing uniform dehalogenation to proceed throughout the solution, thereby simultaneously achieving high productivity and manufacturing precision.
3Quantity of substance
If heterogeneous dehalogenation is performed on solid polymers, then dehalogenation can proceed, but it creates triple bonds and inter-polymer chain crosslinking that reduce solubility
Solution Approach 1:
The patent employs parameter changes by conducting the dehalogenation reaction in a homogeneous solution phase rather than in the solid state. This phase change parameter fundamentally alters the reaction pathway and products. In solution, the dehalogenation produces primarily double bonds within isolated polymer chains, avoiding the triple bonds and inter-chain crosslinking that form in heterogeneous solid-state reactions. The dissolved state allows better distribution of the dehalogenating agent and more controlled reaction conditions, achieving substantial dehalogenation while preserving solubility for subsequent membrane formation steps.
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 method enhances the solubility and processability of CMS membranes, allowing for efficient production without melting and enabling the formation of high-quality CMS membranes through a single thermal pyrolysis step.
Implementation Method 1
homogeneously dehydrohalogenating the dissolved halogenated precursor polymer with an organic amine base to form a partially dehydrohalogenated polymer
Implementation Method 2
pyrolyzing the thin film to form the carbon molecular sieve membrane
Implementation Method 3
These homogeneously dehydrohalogenated precursor polymers have double bonds, which crosslink upon heating
Data Source
AI summary
A method of forming a carbon molecular sieve membrane includes dissolving a halogenated precursor polymer in a solvent, thereby forming a dissolved halogenated precursor polymer. Homogeneously dehydrohalogenating the dissolved halogenated precursor polymer with an organic amine base to form a partially dehydrohalogenated polymer. Forming a thin film from the partially dehydrohalogenated polymer. Pyrolyzing the thin film to form the carbon molecular sieve membrane.