Supported Carbon Molecular Sieve Membranes Defect Reduction

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing carbon molecular sieve (CMS) membranes face defects due to stresses during pyrolysis and phase instability issues when forming the polymer layer, which affects their separation efficiency and commercial viability.

Innovation Solution

A supported CMS membrane is formed by using a carbon forming polymer with similar chemistry to the polymer textile, which fuses and carbonizes together, avoiding defects by matching thermal expansion and contraction properties, and is graphitically bonded to a carbon textile, creating a continuous film for gas separation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a ceramic support is used for the polymer film during pyrolysis, then the support can survive the pyrolysis conditions, but the ceramic expands during pyrolysis while the polymer contracts causing tensile stresses that create defects

Engineering Contradiction:

Improvesurvival of support during pyrolysisVSAvoiddefect formation in separating layer

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The invention uses a polymer support with similar thermal expansion and contraction properties to the polymer separating layer, creating homogeneous thermal behavior during pyrolysis. This prevents the differential stress that occurs with ceramic supports, eliminating the root cause of defect formation while maintaining support survival during the process.

Inventive Principle:

Principle #33Homogeneity

Solution Approach 2:

The invention creates a composite structure where the support and separating layer are both polymeric materials with matched thermal properties. This composite approach allows the support to survive pyrolysis conditions while maintaining dimensional compatibility with the separating layer, preventing defect formation through proper material selection and combination.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If phase inversion is used to form an asymmetric polymeric film, then the film can be formed with solvent and dissolved resin, but phase instability from counter diffusion of solvents and nonsolvents causes defects in the polymeric layer

Engineering Contradiction:

Improvefilm formation processVSAvoiddefect formation in separating layer

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The invention extracts the problematic phase inversion step from the manufacturing process. By using direct polymer coating followed by crosslinking and pyrolysis, the method eliminates the counter diffusion of solvents and nonsolvents that causes phase instability and defects, while still achieving successful film formation through a simplified process sequence.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention replaces the complex phase inversion mechanism with a simpler crosslinking and carbonization mechanism. Instead of relying on solvent-nonsolvent counter diffusion to create the asymmetric structure, the method uses controlled crosslinking followed by pyrolysis to form the desired membrane structure without the defect-prone phase instability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If the separating layer is made thin (less than 25 micrometers) to achieve sufficient gas flow, then commercial practicality is improved, but the layer becomes more susceptible to defects from stress and phase instability

Engineering Contradiction:

Improvegas flow (permeance)VSAvoiddefect-free separating layer

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The invention performs preliminary crosslinking of the polymer layer before pyrolysis, creating a pre-stabilized structure that is more resistant to stress during the subsequent carbonization process. This preliminary action strengthens the thin layer, making it less susceptible to defect formation while maintaining the thin geometry needed for high gas flow and commercial practicality.

Inventive Principle:

Principle #10Preliminary action

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 enables the production of defect-free, thin CMS membranes with enhanced gas separation performance, suitable for separating gases with similar molecular sizes, such as hydrogen/ethylene and ethane/ethylene, and can be used in gas separation modules for applications like natural gas processing.

Implementation Method 1

heating the polymer film and textile together to fuse them to one another to form a laminate

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 2

pyrolyzing the laminate in an atmosphere that is essentially devoid of oxygen to carbonize the polymer film and textile together

Methodology Applied

Scientific EffectPyrolysis: Pyrolysis

Data Source

PatentEP3638407B1Supported carbon molecular sieve membranes and method to form them

Publication Date: 2023.05.03 DOW GLOBAL TECHNOLOGIES LLC

Figure 1
Figure 2

AI summary

A supported carbon molecular sieve (CMS) membrane is made by contacting a film of a carbon forming polymer on a polymer textile to form a laminate. The laminate is then heated to a temperature for a time under an atmosphere sufficient to carbonize the film and polymer textile to form the supported CMS membrane. The supported CMS membrane formed is a laminate having a carbon separating layer graphitically bonded to a carbon textile, wherein the carbon separating layer is a continuous film. The supported CMS membranes are particularly useful for separating gases such as olefins from their corresponding paraffins.