Eggshell Noble Metal Promoters for CO Combustion and NOx Reduction
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Solution Overview
Problem
Existing CO to CO2 combustion promoters in fluid catalytic cracking (FCC) units require large amounts of noble metals to achieve complete combustion of carbon monoxide, leading to issues like carbon monoxide afterburning and increased NOx formation, and the sintered noble metal continues to catalyze NOx forming reactions, causing equipment damage.
Innovation Solution
A CO to CO2 combustion promoter with a noble metal distribution in an eggshell configuration on microsphere-sized porous silica and/or alumina particles, where the noble metal concentration increases towards the outer surface, reducing the overall metal usage and minimizing NOx formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If uniform distribution of noble metal throughout the particle is used, then complete CO combustion is achieved, but large amounts of noble metal are required
Solution Approach 1:
The patent applies local quality by concentrating the noble metal specifically in the outer shell region of the particle rather than distributing it uniformly throughout. The outer shell contains the majority of the noble metal content, while the core contains little to none. This localized distribution achieves complete CO combustion because the outer shell provides sufficient catalytic activity for CO oxidation, while significantly reducing the total noble metal amount required compared to uniform distribution approaches.
2Reliability
If high concentration of noble metal is used, then CO combustion is complete, but NOx formation increases
Solution Approach 1:
The patent reduces NOx formation by locally concentrating the noble metal only in the outer shell where it is needed for CO combustion, rather than distributing it uniformly throughout the particle. This localized approach ensures that CO combustion is complete at the active sites in the outer shell, while minimizing the total noble metal content that could otherwise catalyze NOx forming reactions throughout the entire particle structure.
Solution Approach 2:
The patent extracts the noble metal from the particle core, leaving it concentrated only in the outer shell. This extraction removes the unnecessary noble metal from the core region where it would otherwise contribute to NOx formation, while maintaining the essential CO combustion function in the outer shell.
3Reliability
If uniform noble metal distribution is used, then CO combustion is effective, but sintered metal continues to catalyze NOx forming reactions
Solution Approach 1:
The patent addresses the continued catalysis of NOx forming reactions by concentrating the noble metal locally in the outer shell rather than distributing it uniformly throughout the particle. This localized concentration ensures that the noble metal remains active for CO combustion in the outer shell region, while the absence of noble metal in the core reduces the overall catalytic activity for NOx forming reactions that would otherwise persist after sintering.
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 eggshell distribution allows for effective CO combustion with less noble metal, reducing the risk of afterburning and NOx emissions, while the sintered metal is quickly removed as fines, maintaining catalyst efficiency and minimizing NOx formation.
Implementation Method 1
CO to CO2 combustion promoters are added to the FCC catalyst inventory of the regenerator with the objective to achieve a complete combustion of carbon monoxide in the regenerator dense phase
Implementation Method 2
The oxidation of carbon monoxide is highly exothermic and can result in so-called 'carbon monoxide afterburning'
Implementation Method 3
The oxidation of carbon monoxide is highly exothermic and can result in so-called 'carbon monoxide afterburning'
Implementation Method 4
a metal active for catalysing NOx decomposition in a shell around the platinum or palladium
Data Source
AI summary
Described herein are compositions, inventories, and mixtures particles having an attrition index between 5 and 25, as measured according to ASTM D-5757 for a sieve fraction of between 40 and 105 microns.