Ultra-small pore amorphous adsorbent for CO2/CH4 separation
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Solution Overview
Problem
Current methods for natural gas purification, such as amine scrubbing and cryogenic distillation, are energy-intensive and inefficient for removing nitrogen and carbon dioxide from methane, particularly in sub-quality natural gas, due to the small difference in kinetic diameters of these gases, which poses challenges in zeolite pore diameter control and thermal stability.
Innovation Solution
A method involving the ion-exchange and calcination of sodium aluminosilicate zeolites to form a highly selective ultra-small pore amorphous adsorbent, which allows carbon dioxide adsorption while denying methane, using a decationized and back-ion-exchanged Linde Type A zeolite with controlled pore aperture sizes, enhancing selectivity and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional amine scrubbing or cryogenic distillation is used for natural gas purification, then carbon dioxide and nitrogen can be removed from methane, but the process becomes energy-intensive and operationally complex
Solution Approach 1:
The patent replaces mechanical separation systems (cryogenic distillation requiring turboexpanders and recompressors) with a chemical adsorption system using zeolite-based molecular sieves. The zeolite's microporous structure provides selective adsorption of CO2 and N2 over CH4 at ambient or near-ambient conditions, eliminating the need for extreme temperature cooling and mechanical compression equipment.
Solution Approach 2:
The patent employs zeolite-based porous materials with specifically engineered micropore sizes (0.3-1.5 nm) that act as molecular sieves. The pore aperture is tuned to selectively accommodate CO2 (0.33 nm) and N2 (0.36 nm) molecules while excluding larger CH4 molecules (0.38 nm), enabling separation based on molecular size differences without energy-intensive mechanical processes.
2Productivity
If zeolite pore diameter is increased to facilitate gas diffusion, then mass transfer improves, but selectivity between CO2, N2, and CH4 decreases
Solution Approach 1:
The patent optimizes the zeolite pore aperture parameter to a specific range (0.3-1.5 nm mean diameter) that balances two competing requirements: small enough to provide steric exclusion of CH4 molecules (0.38 nm) while large enough to allow diffusion of CO2 (0.33 nm) and N2 (0.36 nm). This precise parameter control enables both selectivity and adequate mass transfer without requiring extreme pore size reductions that would slow diffusion.
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 method effectively upgrades natural gas by selectively removing nitrogen and carbon dioxide, improving gas quality, and is thermally stable and environmentally friendly, suitable for use in remote locations with lower-economic formations.
Implementation Method 1
calcinating the ion-exchanged zeolite at a calcination temperature such that the ion-exchanged zeolite collapses and forms a decationized amorphous adsorbent
Implementation Method 2
The highly selective ultra-small pore amorphous adsorbent has a pore aperture size operable to permit carbon dioxide to adsorb into the amorphous adsorbent and operable to deny methane from adsorbing into the amorphous adsorbent
Implementation Method 3
introducing an ion-exchange material to a sodium aluminosilicate zeolite such that an ion-exchanged zeolite forms
Data Source
AI summary
A method of forming the highly selective ultra-small pore amorphous adsorbent includes introducing an ion-exchange material to a sodium aluminosilicate zeolite such that an ion-exchanged zeolite forms, calcinating the ion-exchanged zeolite at a calcination temperature such that the ion-exchanged zeolite collapses and forms the decationized amorphous adsorbent, and introducing a back ion-exchange material to the decationized amorphous adsorbent such that the highly selective ultra-small pore amorphous adsorbent forms. The highly selective ultra-small pore amorphous adsorbent has a pore aperture size operable to permit carbon dioxide to adsorb into the amorphous adsorbent and operable to deny methane from adsorbing into the amorphous adsorbent.