Segmented Ion Exchange Membrane for Alkali Chloride Electrolysis
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Solution Overview
Problem
Existing ion exchange membranes for alkali chloride electrolysis face challenges in maintaining high water permeability while suppressing water supply to the cathode chamber, leading to decreased current efficiency and poor caustic alkali quality due to chloride ion passage.
Innovation Solution
The membrane consists of layers with specific thicknesses and ion exchange capacities, including a fluorinated polymer layer with carboxylic acid functional groups and sulfonic acid functional groups, reinforced with threads, and an inorganic particle layer to control water permeability and electrolysis voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the thickness of the fluorinated polymer layer having carboxylic acid functional groups is reduced to increase water permeability, then water permeability is improved, but chloride ions pass through the membrane deteriorating caustic alkali quality
Solution Approach 1:
The membrane is divided into multiple functional layers: a first layer with carboxylic acid groups (9-28 μm thick) that blocks chloride ions, a second layer with sulfonic acid groups containing reinforcing material that provides structural support and additional ion exchange capacity, and a third layer with sulfonic acid groups that enhances water permeability. This segmentation allows each layer to perform its specific function optimally without compromising overall performance
Solution Approach 2:
The invention uses composite material structure combining fluorinated polymers with different functional groups (carboxylic acid and sulfonic acid) in specific layers, along with reinforcing material (PTFE threads and organic peroxide). This composite approach enables the membrane to simultaneously achieve high water permeability, low electrolysis voltage, and high caustic alkali quality by leveraging the complementary properties of different materials
2Productivity
If water is supplied to the cathode chamber to adjust catholyte concentration, then current efficiency is maintained, but the method requires continuous water supply and complex concentration control
Solution Approach 1:
The membrane structure itself performs the function of water supply and concentration control. The optimized membrane with specific layer thicknesses and high water permeability automatically transports water from the anode to cathode side, maintaining uniform catholyte concentration without requiring external water supply systems or complex control mechanisms. The membrane's inherent properties replace the need for active concentration management
3Object-generated harmful factors
If the film thickness of the fluorinated polymer layer is reduced to achieve high water permeability, then water permeability increases, but mechanical strength decreases requiring additional reinforcing material
Solution Approach 1:
Reinforcing material consisting of PTFE threads and organic peroxide is introduced as an intermediary component within the second layer (sulfonic acid group layer). This reinforcing material provides mechanical strength and dimensional stability to the thin membrane structure, enabling the use of reduced film thickness (9-28 μm for the first layer) to achieve high water permeability while maintaining sufficient mechanical integrity for practical application
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
This configuration achieves high water permeability, low electrolysis voltage, and high caustic alkali quality in the produced alkali hydroxide solution by optimizing the membrane's structural layers and reinforcement.
Implementation Method 1
the water permeability is large... the water permeability... is represented by a molar amount ratio of the water moved per mole of alkali ions
Implementation Method 2
ion exchange membrane for alkali chloride electrolysis... electrolyte membrane made of a fluorinated polymer having ion exchange groups
Implementation Method 3
electrolyzing an aqueous alkali chloride solution such as saline to produce an alkali hydroxide and chlorine
Data Source
AI summary
To provide an ion exchange membrane for alkali chloride electrolysis which is a membrane having a high water permeability and being capable of maintaining a low electrolysis voltage while suppressing the amount of water supplied to a cathode chamber to be minimum, and which is capable of forming an aqueous alkali hydroxide solution having a high caustic alkali quality. The ion exchange membrane for alkali chloride electrolysis comprises a layer 12 made of a fluorinated polymer having carboxylic acid functional groups, and a layer 14A and a layer 14B made of a fluorinated polymer having sulfonic acid functional groups, wherein a reinforcing material 20 containing reinforcing threads 22 is disposed between the layer 14A and the layer 14B, the thickness when dried, of the layer 12 is from 9 to 28 μm, the layer 14B includes a layer having an ion exchange capacity of from 1.3 to 2.5 meq/g, the thickness when dried, of the layer 14B is from 6 to 100 μm, the layer 14A includes a layer having an ion exchange capacity of from 0.9 to 1.25 meq/g, and the thickness when dried, of the layer 14A is from 40 to 110 μm.