Zeolite Separation Membrane Void Control for High Gas Selectivity
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Solution Overview
Problem
Existing zeolite membranes face challenges in maintaining high separation ratios under both low and high differential pressure conditions due to defects that allow low-permeability substances to leak, and increasing membrane thickness to reduce defects decreases permeance.
Innovation Solution
A separation membrane complex with a porous support and a zeolite membrane having specific void indices, characterized by a small void index Ik ≥ 10×10−15 and a large void index Ip ≤ 200×10−22, is produced through a method involving pretreatment, seed crystal deposition, and hydrothermal synthesis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the zeolite membrane is increased to reduce defects and improve separation ratio, then the separation ratio improves under low differential pressure conditions, but the permeance to the high-permeability substance decreases
Solution Approach 1:
The invention changes the physical parameters of the membrane system by introducing a porous support layer with specific pore size distribution. The support layer has pores larger than the zeolite membrane pores, creating a hierarchical structure that maintains high permeance while the zeolite layer provides selective separation. This parameter change in the support structure resolves the contradiction between thickness and permeance.
Solution Approach 2:
The invention creates a composite membrane system consisting of a porous support layer and a zeolite membrane layer. The support layer provides mechanical strength and high permeance pathways, while the zeolite layer provides molecular sieving capability. This composite structure allows the system to achieve both high separation ratio and high permeance simultaneously, resolving the technical contradiction.
2Reliability
If the number of defects in the zeolite membrane is reduced to improve separation ratio, then separation performance improves under low differential pressure conditions, but separation ratio decreases under high differential pressure conditions
Solution Approach 1:
The invention segments the membrane function into two distinct layers: the porous support layer handles the mechanical and permeance requirements, while the thin zeolite membrane layer handles the selective separation. This segmentation allows the zeolite layer to remain thin (reducing defects) while the support layer provides the necessary structural integrity and permeance, enabling high separation ratio across varying pressure conditions.
Solution Approach 2:
The invention utilizes porous materials with different pore size characteristics - the support layer has larger pores for high permeance, while the zeolite layer has smaller, more uniform pores for selective separation. This hierarchical porous structure allows the system to maintain high separation ratio under both low and high differential pressure conditions by directing flow through appropriate pathways.
3Productivity
If the zeolite membrane is made thinner to maintain permeance, then permeance to the high-permeability substance is maintained, but the number of defects increases reducing separation ratio
Solution Approach 1:
The composite structure combines a thin zeolite membrane (maintaining permeance) with a porous support layer (providing structural support and additional separation pathways). The support layer compensates for the reduced thickness of the zeolite membrane, maintaining separation ratio even when the zeolite layer is thin. This resolves the contradiction between thinness and defect reduction.
Solution Approach 2:
The invention changes the overall membrane system parameters by adding the porous support layer, which has different pore size and structural parameters than the zeolite membrane. This parameter change in the composite system allows the zeolite layer to be thin (high permeance) while the support layer provides the necessary separation capability through its porous structure.
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 complex achieves high separation ratios by minimizing defects, maintaining permeance under varying pressure conditions, and effectively separating gases like CO2 and CH4.
Implementation Method 1
use the molecular-sieving function of the zeolite in applications such as separation of specific molecules
Implementation Method 2
use the molecular-sieving function of the zeolite in applications such as separation of specific molecules or adsorption of molecules
Implementation Method 3
growing a zeolite from the seed crystal by hydrothermal synthesis
Data Source
AI summary
A separation membrane complex includes a porous support and a separation membrane formed on the support. The separation membrane has a small void. A small void index Ik expressed by (Σ(Sk1.5))/(Sm1.5) and indicating the abundance ratio of small voids is higher than or equal to 10×10−15, and a large void index Ip expressed by (Σ(Sp2))/(Sm2) and indicating the abundance ratio of large voids is lower than 200×10−22, where Sm is the surface area of the separation membrane, Sk is the area per small void, and Sp is the area per large void. Accordingly, the separation membrane complex can achieve a high separation ratio.