RHO Zeolite Adsorbent for Natural Gas CO2 Separation
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Solution Overview
Problem
Current natural gas processing technologies face challenges in efficiently separating methane from hydrogen and acid gases like CO2 and N2 due to high energy consumption and limited selectivity of existing zeolites, particularly in adsorption processes.
Innovation Solution
The use of a zeolitic material isostructural to RHO zeolite, which has a tridirectional system of small pore channels allowing high CO2 adsorption while preventing methane access, enabling effective separation and purification of methane from natural gas streams through Pressure Swing Adsorption, Thermal Swing Adsorption, or Pressure Vacuum Swing Adsorption processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional zeolites are used for CO2 adsorption, then CO2 separation is achieved, but methane is also adsorbed reducing purification efficiency
Solution Approach 1:
The patent applies local quality by creating specific local environments within the zeolite structure through heteroatom substitution (Mg, Mn, Co, Ni, Cu, Zn, Ga, In) at specific crystallographic positions. This substitution creates localized active sites with enhanced CO2 affinity while maintaining the overall structure's resistance to methane adsorption, achieving high selectivity without sacrificing CO2 capacity
Solution Approach 2:
The patent utilizes the microporous structure of RHO-type zeolites with specific pore dimensions (0.36 x 0.36 nm windows leading to 1.15 nm cavities) that provide size-selective access. The porous structure allows CO2 molecules to enter and be adsorbed while the specific pore geometry and electronic properties prevent significant methane adsorption, achieving both high capacity and selectivity
2Manufacturing precision
If cryogenic distillation is used for nitrogen removal, then separation efficiency is improved, but energy consumption increases significantly
Solution Approach 1:
The patent replaces the mechanical cryogenic distillation system with a chemical adsorption system based on Pressure Swing Adsorption (PSA). Instead of using mechanical cooling and phase separation, the invention uses chemical interactions between modified zeolite sites and CO2/N2 molecules, achieving comparable or superior separation efficiency at ambient or mild temperatures, thus dramatically reducing energy consumption
Solution Approach 2:
The patent changes the operational parameters from extreme cryogenic temperatures to ambient or mild temperatures by using chemically modified zeolites. The heteroatom-substituted zeolites provide enhanced adsorption affinity that allows effective separation at lower energy conditions, transforming the process from energy-intensive cryogenic operation to low-energy adsorption-based operation
3Manufacturing precision
If amine-based CO2 capture is used, then CO2 removal efficiency is improved, but the process requires decompression and repressurization increasing complexity
Solution Approach 1:
The patent extracts the liquid amine phase from the system and replaces it with a solid zeolite adsorbent phase. This extraction eliminates the need for liquid-gas contactors, decompression/repressurization equipment, and heat exchangers required for amine regeneration. The solid zeolite can be directly cycled between adsorption and regeneration states, simplifying the overall process equipment while maintaining CO2 removal efficiency through PSA technology
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 approach achieves high CO2 adsorption capacity and selectivity, reducing energy consumption and extending adsorption cycle efficiency, allowing for efficient methane recovery and purification with minimal methane adsorption, thus optimizing natural gas processing.
Implementation Method 1
the CO2 is preferentially and selectively adsorbed, and remaining the methane free in the stream
Implementation Method 2
which shows windows with crystallographic openings of 0.36 x 0.36 nm giving access to large 'quasi-spherical' cavities of 1.15 nm in diameter, meets all these requirements, allowing the access to CO2 molecules, but preventing the same to methane
Data Source
Figure 1~2
Figure 3
AI summary
The present invention describes the use of isostructural zeolites with rho zeolitic structure in processes of adsorption and separation of the various components of natural gas.