Catalytic Oxygen Removal in Hydrogen PSA Beds
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Solution Overview
Problem
Conventional adsorbents in pressure swing adsorption (PSA) units have a low oxygen capacity, leading to significant hydrogen recovery drops and increased bed volume when attempting to remove oxygen from hydrogen streams, particularly in applications like hydrogen production from water electrolysis, where oxygen levels are low.
Innovation Solution
Incorporating a copper, palladium, or platinum catalyst material within the PSA bed, combined with dehydration and nitrogen removal adsorbents like silica gel and zeolites, to facilitate oxygen removal through an oxidation/reduction mechanism, thereby maintaining high hydrogen recovery and reducing PSA bed volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional adsorbents are used in PSA units to remove oxygen, then oxygen removal is achieved, but PSA bed volume increases substantially and hydrogen recovery drops
Solution Approach 1:
The patent changes the fundamental mechanism from physical adsorption to catalytic oxidation. By using a copper-based catalyst instead of conventional adsorbents, oxygen is removed through chemical reaction (oxidation) rather than adsorption, fundamentally changing the parameter of removal mechanism to achieve high oxygen removal without the volume and recovery penalties of adsorbent-based systems
Solution Approach 2:
The patent replaces the mechanical/physical adsorption system with a chemical catalysis system. The copper catalyst facilitates the oxidation of oxygen through chemical reaction, substituting the mechanical adsorption process with a chemical transformation process that achieves superior oxygen removal performance
2Reliability
If conventional adsorbents are used in PSA units to remove oxygen, then oxygen removal is achieved, but PSA bed volume increases substantially
Solution Approach 1:
The patent changes the removal mechanism from adsorption to catalytic oxidation, which has much higher oxygen capacity per unit volume. The copper-based catalyst enables efficient oxygen removal in a compact volume by facilitating chemical reaction rather than relying on adsorption capacity
Solution Approach 2:
The patent employs a composite catalyst system comprising copper-based material supported on alumina or other carriers. This composite structure provides high catalytic activity for oxygen removal while maintaining compact volume, combining the benefits of high surface area support with active copper sites for oxidation
3Reliability
If copper catalyst is used for oxygen removal, then oxygen is effectively removed, but water is produced which can inhibit the oxidation reaction and condense
Solution Approach 1:
The patent extracts and removes the harmful byproduct (water) from the system using a separate dehydration adsorbent bed. This allows the oxidation reaction to proceed efficiently by continuously removing the water that would otherwise inhibit the reaction and cause condensation problems
Solution Approach 2:
The patent introduces a dehydration adsorbent as an intermediary component that mediates between the oxidation catalyst and the downstream system. This intermediary removes water from the gas stream, preventing water from interfering with the oxidation reaction and protecting downstream equipment from condensation
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 configuration achieves high hydrogen purity with minimal hydrogen recovery loss, reducing PSA bed volume and enabling complete hydrogen gas purification while effectively removing oxygen and nitrogen impurities, even in saturated hydrogen streams from water electrolyzers.
Implementation Method 1
the catalyst material functions by an oxidation/reduction mechanism: i.e., oxygen is chemisorbed during the high-pressure feed step in the PSA cycle, and then copper is reduced (thereby forming water) during the regeneration/counter-current purge step
Implementation Method 2
Incorporating a copper, palladium, or platinum catalyst material within the PSA bed, combined with dehydration and nitrogen removal adsorbents like silica gel and zeolites, to facilitate oxygen removal through an oxidation/reduction mechanism
Implementation Method 3
a layer of dehydration adsorbent such as silica gel, activated alumina, or 13X zeolite can be used in the PSA or temperature swing adsorption (TSA) unit for water removal
Implementation Method 4
A layer of CaX zeolite or 5A zeolite may be added at the product end of the bed when needed to remove nitrogen
Data Source
AI summary
An adsorption process is provided to remove oxygen from a hydrogen stream through the use of a copper material in combination with layers of adsorbent to remove water and nitrogen from a hydrogen stream. This process is particularly useful for purification of hydrogen product gas from water electrolyzers with the hydrogen product gas having greater than 99.9 mol % purity.