Dual Layer-Coated Membranes for Gas Separation
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Solution Overview
Problem
Conventional polymeric membranes used in gas separations, such as cellulose acetate membranes, face challenges with selectivity, durability, resistance to hydrocarbon contaminants, solvent swelling, and CO2 plasticization, leading to reduced performance over time, especially in natural gas upgrading processes with high CO2 concentrations.
Innovation Solution
A dual layer-coated asymmetric membrane is developed, featuring a hydrogel coating layer and a hydrophobic fluoropolymer layer on a porous polymeric support, which enhances selectivity and resistance to solvent swelling and plasticization, maintaining high permeance and flux stability over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cellulose acetate membranes are used for gas separation, then low capital cost and high-energy efficiency are achieved, but selectivity, durability, and resistance to hydrocarbon contaminants and CO2 plasticization deteriorate
Solution Approach 1:
The patent applies composite materials by combining cellulose acetate membrane with multiple coating layers including hydrophobic fluoropolymer coating and crosslinking agents. This composite structure provides both the cost-effectiveness of CA membrane and the enhanced resistance to hydrocarbon contaminants and CO2 plasticization through the coating layers that form a protective barrier.
Solution Approach 2:
The patent utilizes parameter changes by applying crosslinking treatments that modify the chemical structure of the membrane polymer. The crosslinking increases the glass transition temperature and reduces polymer chain mobility, thereby enhancing resistance to solvent swelling and CO2 plasticization while maintaining gas separation performance.
2Reliability
If cellulose acetate membranes are used for gas separation, then low capital cost and high-energy efficiency are achieved, but selectivity and performance durability deteriorate
Solution Approach 1:
The patent applies composite materials by combining cellulose acetate membrane with multiple coating layers including hydrophobic fluoropolymer coating and crosslinking agents. This composite structure provides both the cost-effectiveness of CA membrane and the enhanced resistance to hydrocarbon contaminants and CO2 plasticization through the coating layers that form a protective barrier.
3Manufacturing precision
If membranes are used to separate CO2 from natural gas, then CO2 removal is achieved, but feed side temperature drops significantly due to J-T effect and liquid condensation occurs
Solution Approach 1:
The patent applies the intermediary principle by introducing a heat exchange system that acts as a mediator between the feed gas stream and the permeate stream. This heat exchange recovers the cooling effect and prevents excessive temperature drop that would cause condensation, while maintaining efficient CO2 separation.
4Productivity
If high CO2 concentration gas is processed through membranes, then CO2 permeation increases, but membrane plasticization occurs leading to swelling and decreased selectivity
Solution Approach 1:
The patent utilizes parameter changes by applying crosslinking treatments that modify the chemical structure of the membrane polymer. The crosslinking increases the glass transition temperature and reduces polymer chain mobility, thereby enhancing resistance to solvent swelling and CO2 plasticization while maintaining gas separation performance.
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 dual layer-coated membrane exhibits sustained selectivity and permeance with minimal flux decline, even in the presence of high CO2 concentrations and liquid hydrocarbon contaminants, making it suitable for natural gas upgrading and other gas separation applications.
Implementation Method 1
a second coating layer comprising a hydrophobic fluoropolymer
Implementation Method 2
A pressure differential is maintained between the upstream and downstream sides, providing the driving force for permeation
Implementation Method 3
the permeation behavior of CO2 in CA membranes is different when compared to some other glassy polymers in that above a certain pressure level, the permeability coefficient begins to increase with pressure due to the onset of plasticization by the CO2
Implementation Method 4
the feed side temperature drops significantly due to CO2 permeation (J-T effect)
Data Source
AI summary
The invention discloses dual layer-coated membranes and methods for making and using these membranes. The dual layer-coated membranes have a relatively porous and substantial void-containing selective asymmetric membrane support, a first coating layer comprising a hydrogel, and a second coating layer comprising a hydrophobic fluoropolymer. The membrane support has low selectivity and high permeance. The dual layer coating improves the selectivity of the membrane support and maintains the membrane performance with time. The dual layer-coated membranes are suitable for a variety of liquid, gas, and vapor separations such as water purification, non-aqueous liquid separation such as deep desulfurization of gasoline and diesel fuels, ethanol/water separations, pervaporation dehydration of aqueous/organic mixtures, fuel gas conditioning, CO2/CH4, He/CH4, CO2/N2, H2/CH4, O2/N2, olefin/paraffin, iso/normal paraffins separations, and other light gas mixture separations. The dual layer-coated membranes are especially useful for natural gas liquid (NGL) recovery and CO2 removal from natural gas.