Sulfur-Free CMS Membranes for Olefin Separation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current carbon molecular sieve (CMS) membranes face challenges in effectively separating gases with similar molecular sizes, such as ethane from ethylene and propylene, and are prone to sulfur poisoning when incorporating certain metals.
Innovation Solution
Incorporating a transition metal, such as iron, into a sulfur-free polyimide precursor polymer, specifically 3,5-diaminobenzoic acid (DABA) based polyimides, and pyrolyzing them under controlled conditions to form defect-free CMS membranes with enhanced selectivity and stability, avoiding sulfur contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If certain metals are incorporated into CMS membranes to improve gas separation selectivity, then separation performance is improved, but sulfur poisoning occurs reducing stability
Solution Approach 1:
The invention removes sulfur from the polyimide precursor polymer structure to eliminate the source of sulfur poisoning. By using a sulfur-free polyimide as the precursor, the resulting CMS membrane does not contain sulfur that could poison incorporated metals, thus maintaining both high separation selectivity and long-term stability.
Solution Approach 2:
The invention creates a composite material system by incorporating transition metals into a sulfur-free polyimide-derived CMS matrix. This composite structure combines the high selectivity benefits of metal incorporation with the stability advantages of eliminating sulfur, achieving both improved separation performance and enhanced reliability.
2Manufacturing precision
If polyimide precursors are pyrolyzed to form CMS membranes, then separation performance exceeds polymeric membranes, but sulfur contamination from the polyimide reduces membrane stability
Solution Approach 1:
The invention extracts and removes sulfur from the polyimide precursor polymer structure before pyrolysis. By using a sulfur-free polyimide as the starting material, the pyrolysis process produces a CMS membrane without sulfur contamination, eliminating the source of instability while preserving the high separation performance characteristics.
3Adaptability or versatility
If transition metals are incorporated into CMS membranes, then affinity for particular gas molecules is improved, but sulfur poisoning from residual sulfur reduces effectiveness
Solution Approach 1:
The invention removes sulfur from the polymer precursor structure to eliminate the harmful interaction between sulfur and transition metals. By using a sulfur-free polyimide precursor, the incorporated transition metals remain active and effective for their intended function of providing affinity for particular gas molecules without suffering from sulfur poisoning.
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 resulting CMS membranes exhibit improved selectivity and stability, enabling efficient separation of gases like ethylene from ethane and propylene with reduced sulfur poisoning risks, maintaining performance over extended periods.
Implementation Method 1
pyrolyzing them under controlled conditions to form defect-free CMS membranes
Implementation Method 2
Gas transport through such membranes is commonly modeled by the sorption-diffusion mechanism
Implementation Method 3
Gas transport through such membranes is commonly modeled by the sorption-diffusion mechanism
Data Source
Figure 1
AI summary
A carbon molecular sieve (CMS) membrane having improved separation characteristics for separating olefins from their corresponding paraffins is comprised of carbon with at most trace amounts of sulfur and a transition metal, wherein the transition metal is one or more of a group 4-10 and 12 transition metal. The CMS membrane may be made by pyrolyzing a precursor polymer devoid of sulfur in which the precursor polymer has had a transition metal incorporated into it. The pyrolyzing for the precursor having the transition metal incorporated into it is performed in a nonoxidizing atmosphere and at a heating rate and temperature such that the metal has a valence greater than zero (i.e., not metal bonded) to a valence desirably closer to its maximum valence.