Perfluoropolymer Membrane for Ionic Liquid Dehydration
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Solution Overview
Problem
Current membrane separation methods for removing water from ionic liquids are inefficient, leading to significant loss of expensive ionic liquids and instability at high temperatures, making them uneconomical and ineffective over a wide range of concentrations.
Innovation Solution
The use of selectively permeable perfluoropolymer membranes, particularly those comprising perfluoro-2,2-dimethyl-1,3-dioxole (PDD) and tetrafluoroethylene (TFE), which provide high water flux and selectivity, maintaining stability and effectiveness over a range of temperatures and concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If commercial polyamide membranes are used for reverse osmosis to remove water from ionic liquids, then water removal is achieved, but significant quantities of expensive ionic liquid are lost in the permeate waste stream
Solution Approach 1:
The patent changes the membrane material parameter from commercial polyamide to perfluorinated polymer, which fundamentally alters the separation characteristics. This parameter change enables high water flux while maintaining ionic liquid retention, resolving the contradiction between water removal efficiency and ionic liquid loss by modifying the membrane's chemical properties to be selective for water permeation.
Solution Approach 2:
The patent employs composite membrane structures combining perfluorinated polymers with specific pore architectures. This composite approach creates a material that simultaneously provides high water permeability through hydrophilic channels while maintaining selectivity against ionic liquid molecules, thus achieving both high productivity and low substance loss.
2Productivity
If high pressure is applied in reverse osmosis to achieve significant water flux, then water removal rate increases, but the process becomes uneconomical due to high energy consumption
Solution Approach 1:
The patent replaces the mechanical pressure-driven reverse osmosis system with a pervaporation system driven by vapor pressure gradients and membrane selectivity. This substitution eliminates the need for high-pressure pumps and compressors, achieving high water flux through selective permeation at near-ambient pressures, thereby dramatically reducing energy consumption while maintaining high productivity.
3Productivity
If conventional membranes are used for water removal from ionic liquids, then the process works at lower water concentrations, but water flux decreases to zero at high ionic liquid content
Solution Approach 1:
The patent changes the membrane material parameter to perfluorinated polymers with specific hydrophobic-hydrophilic balance and pore characteristics. This parameter change enables the membrane to maintain high water flux across the entire composition range from 5-95 wt% water, as the perfluorinated structure provides consistent selective permeation properties regardless of feed composition, achieving both high productivity and broad adaptability.
4Reliability
If polyvinyl alcohol membranes are exposed to ionic liquids at elevated temperatures to improve separation, then separation factor decreases, but the membrane becomes unstable
Solution Approach 1:
The patent uses composite perfluorinated polymer membranes with enhanced thermal and chemical stability. This composite material structure maintains membrane integrity and separation performance at elevated temperatures (50-100°C), as the perfluorinated backbone provides resistance to ionic liquid degradation and thermal stress, achieving both high reliability and sustained productivity under harsh operating 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
These membranes achieve significantly higher water/ionic liquid separation factors and water flux compared to existing commercial membranes, ensuring efficient dehydration of ionic liquids with minimal loss of the costly ionic liquids, enabling their effective recovery and reuse.
Implementation Method 1
membrane separation of water and small organic molecules (such as methanol, ethanol and acetone) from mixtures, including solutions, with ionic liquids using polymeric membranes comprising perfluorinated monomer repeat units
Implementation Method 2
Reverse osmosis (RO) and pervaporation are membrane separation methods that have been employed for drying of aqueous IL solutions
Implementation Method 3
Pervaporation mode membrane separations were also evaluated with commercial polysulfone membranes
Data Source
AI summary
A membrane separation process using a highly fluorinated polymer membrane that selectively permeates water of an aqueous ionic liquid solution to provide dry ionic liquid. Preferably the polymer is a polymer that includes polymerized perfluoro-2,2-dimethyl-1,3-dioxole (PDD). The process is also capable of removing small molecular compounds such as organic solvents that can be present in the solution. This membrane separation process is suitable for drying the aqueous ionic liquid byproduct from precipitating solutions of biomass dissolved in ionic liquid, and is thus instrumental to providing usable lignocellulosic products for energy consumption and other industrial uses in an environmentally benign manner.