Atomic Aluminum Carbon Molecular Sieve Membrane for Hydrogen Separation
Solution Overview
Problem
Current carbon molecular sieve membranes (CMSMs) face challenges in achieving high selectivity and permeation properties for efficient hydrogen purification from gaseous mixtures, and they require improvements for better performance as membrane reactors or for solvent dehydration.
Innovation Solution
A supported carbon molecular sieve membrane is developed by incorporating aluminum in an atomic state into the membrane structure. This is achieved by dipping a porous support into a solution containing phenol formaldehyde resin and aluminum ions, followed by carbonization. The resulting membrane has a smaller pore diameter and a uniform narrow pore size distribution, enhancing its hydrophilicity and permeation properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional carbon molecular sieve membranes are used for hydrogen purification, then the membrane structure is simple and manufacturing is easy, but the permeability and selectivity are insufficient for efficient hydrogen purification
Solution Approach 1:
The patent creates a composite membrane structure by incorporating aluminum atoms into the carbon molecular sieve matrix during pyrolysis. This composite approach combines the size-exclusion properties of carbon molecular sieves with the hydrophilic characteristics and catalytic activity of aluminum, achieving enhanced hydrogen purification performance with permeability and selectivity exceeding conventional CMSMs
Solution Approach 2:
The invention introduces aluminum atoms at specific locations within the membrane structure to create localized regions with enhanced properties. The aluminum atoms are distributed throughout the carbon matrix, creating local hydrophilic zones and catalytic sites that improve overall membrane performance for hydrogen separation without requiring complete structural redesign
2Reliability
If Palladium based membranes are used for hydrogen separation, then hydrogen permeance and selectivity are maximized, but the cost is high and stability decreases at low temperatures due to hydrogen embrittlement
Solution Approach 1:
The patent replaces expensive precious metal membranes with carbon-based molecular sieve membranes that are cost-effective and can be manufactured from inexpensive precursors. While carbon membranes have different stability characteristics, they offer sufficient long-term stability for industrial applications and eliminate the high cost and low-temperature embrittlement issues of palladium membranes
Solution Approach 2:
The invention modifies the operational parameters of the membrane by optimizing the pyrolysis temperature and aluminum content to achieve stable performance at lower temperatures (above -50°C) compared to palladium membranes. The aluminum incorporation enhances the membrane's resistance to hydrogen embrittlement and improves stability in the presence of impurities like H2S
3Reliability
If microporous membranes (zeolite, silica) are used for hydrogen separation, then size exclusion separation is achieved, but defect free membranes are difficult to prepare and silica membranes are not stable at high temperatures in presence of water
Solution Approach 1:
The patent uses carbon molecular sieve membranes as a cost-effective alternative to expensive and difficult-to-manufacture zeolite membranes. The carbon-based approach allows for simpler fabrication processes while achieving comparable or superior performance, and the membranes can be produced at lower costs without requiring complex hydrothermal synthesis procedures
4Productivity
If the pore size of carbon molecular sieve membranes is increased to improve permeability, then gas flux increases, but selectivity decreases due to larger pore sizes reducing molecular sieving effect
Solution Approach 1:
The patent optimizes the pore size parameters by controlling the pyrolysis temperature and aluminum content to achieve an optimal pore diameter range (0.3-0.8 nm). This parameter optimization balances permeability and selectivity, creating a narrow pore size distribution that maintains molecular sieving effectiveness while allowing sufficient gas flux for industrial applications
Solution Approach 2:
The aluminum incorporation creates a composite structure that modifies the pore characteristics of the carbon molecular sieve. The aluminum atoms affect the pore wall properties and create a more uniform pore size distribution, enhancing both the permeability and selectivity simultaneously through the synergistic effect of the composite material system
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 incorporation of atomic aluminum in the CMSM results in a membrane with significantly improved permeability, selectivity, and chemical stability at high pressures and temperatures, making it suitable for industrial gas separations such as hydrogen separation. The membrane can operate at ambient temperature or lower temperatures up to -50°C, and it is cost-effective due to the use of inexpensive precursors.
Implementation Method 1
CMSMs are product of the pyrolysis of a thermosetting polymer in a non-oxidant atmosphere
Implementation Method 2
The resulted amorphous carbon structure contains micro and ultra-micro pores which are responsible for the separation of the gases by molecular sieving (size separation)
Implementation Method 3
They are produced from low-cost materials and can separate gases at room temperature... through the interaction of the gas molecule with the pore wall
Data Source
AI summary
A supported carbon molecular sieve membrane having aluminum atomically distributed in it, wherein: the aluminum is present in an amount of equal to or lower than 15 wt. % of the carbon molecular sieve membrane; the membrane comprises a pore size distribution in which at least 70% of the pores have a pore size from 0.25 to 0.7 nm; and which is obtainable by dip-coating a support with a solution comprising a phenolic-resin and aluminum ions, followed by carbonization. The carbon content of the carbon molecular sieve membrane is from 75 wt. % to 95 wt. %, the oxygen content is from 2.5 wt. % to 8 wt. %, and the hydrogen content is from 1.5 wt. % to 6% wt. %. These CMSMs are useful for gas separation, H2 recovery from natural gas grids, H2 production from biomass, solvent dehydration, obtaining oxygen-enriched air, or dehydrogenation of methylcyclohexane, and as a catalytic membrane reactor or part of a catalytic membrane reactor.