MFI Zeolite Composite Membrane for Olefin Separation
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Solution Overview
Problem
Existing composite membranes used for separating olefin-containing mixtures suffer from high catalytic activity, leading to isomerization and formation of undesired products, and have limited mechanical stability, making them unsuitable for efficient separation of isomeric olefins with narrow boiling ranges.
Innovation Solution
Composite membranes with a microporous separation layer of MFI zeolite and a porous substrate, where the molar ratio of silicon to aluminum is greater than 120, and the substrate has low aluminum content, reducing catalytic activity and ensuring mechanical stability, are produced through hydrothermal synthesis and subsequent calcination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a composite membrane with MFI zeolite separation layer is used for separating olefin-containing mixtures, then separation selectivity is improved, but catalytic activity increases leading to isomerization and formation of undesired products
Solution Approach 1:
The patent applies local quality by creating a substrate layer with specific aluminum content characteristics. The substrate contains at least one zone with low aluminum content (less than 10 wt%, particularly less than 1 wt%) adjacent to the separation layer, while other regions may have different aluminum content. This localized control of aluminum distribution allows the membrane to achieve high separation selectivity through the MFI zeolite separation layer while the low-aluminum zone suppresses catalytic activity and prevents unwanted side reactions.
2Strength
If the separation layer thickness is increased to ensure mechanical stability, then mechanical stability is improved, but transmembrane flow density decreases
Solution Approach 1:
The patent applies segmentation by dividing the membrane structure into functionally distinct layers: a porous substrate layer and a microporous separation layer. The substrate layer provides mechanical stability and structural support, while the thin separation layer (typically a few micrometers thick) provides separation functionality. This segmentation allows each layer to be optimized for its specific function - the substrate can be thicker for strength while the separation layer remains thin for high permeability.
Solution Approach 2:
The patent uses composite materials by combining the porous substrate with the MFI zeolite separation layer to create a composite membrane structure. The substrate material (which may be ceramic, metallic, or polymeric) provides mechanical integrity, while the MFI zeolite layer provides selective separation. This composite approach allows the membrane to simultaneously achieve both mechanical stability and high transmembrane flow density that would be difficult to achieve with a single material.
3Measurement precision
If organic membranes are used for separating linear and branched hydrocarbon isomers, then separation based on steric requirements is achieved, but thermal and chemical stability is greatly limited
Solution Approach 1:
The patent applies parameter changes by transitioning from organic membrane materials to inorganic MFI zeolite materials. This fundamental material parameter change enables the membrane to withstand high temperatures and harsh chemical environments while maintaining its separation functionality. The MFI zeolite structure provides both the steric selectivity needed for isomer separation and the thermal/chemical stability required for reliable operation in demanding conditions.
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 reduced isomerization and byproduct formation, maintaining high mechanical stability and achieving efficient separation of olefin mixtures with improved selectivity and permeability, as demonstrated by permeation measurements showing high 1-butene concentration in the permeate.
Implementation Method 1
a material stream (feed) to be separated is separated in a selectively acting membrane and is separated into a permeate, i.e. a material stream passing through the membrane
Implementation Method 2
the separation layer containing a zeolite of the MFI type
Implementation Method 3
the membranes which result therefrom and are used for separating n-butane/isobutane mixtures are purely ceramic membranes
Implementation Method 4
the actual layer having separation activity is applied from a zeolite of the MFI type on a macroporous substrate, by an in situ hydrothermal synthesis
Implementation Method 5
Composite membranes with a microporous separation layer of MFI zeolite and a porous substrate... are produced through hydrothermal synthesis and subsequent calcination
Data Source
AI summary
Composite membranes comprising at least one porous substrate layer and at least one microporous separation layer, comprising at least one zeolite of the MFI type, are described, the separation layer being produced by a hydrothermal synthesis in which the molar ratio of silicon to aluminum is greater than 120 and the separation layer contains less than 10% by weight of aluminum in elemental or chemically bound form in a zone of at least 100 nm adjacent to the separation layer.