Segmented Exhaust Catalyst for NOx Reduction and Sulfation Prevention
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Solution Overview
Problem
Existing exhaust gas treatment systems for internal combustion engines face challenges in preventing sulfation, improving robustness to chemical fouling and poisoning, and achieving fast NOx reduction under transient conditions while being cost-effective.
Innovation Solution
An exhaust gas treatment system comprising a first catalyst with a vanadium oxide coating supported on a titanium oxidic support and a second catalyst with a palladium coating on a zirconium, silicon, and aluminum oxidic support, along with a hydrocarbon injector, to enhance NOx reduction and robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a close-coupled SCR (ccSCR) based on Cu-Zeolite is used, then the system can provide NOx reduction, but the catalyst becomes sulfated over time and loses DeNOx capability
Solution Approach 1:
The patent divides the exhaust treatment function into two separate catalysts: a first catalyst (Pd-based oxidation catalyst) and a second catalyst (Vanadium-based SCR catalyst). This segmentation prevents the SCR catalyst from direct exposure to sulfur-containing exhaust gases, as the oxidation catalyst treats the exhaust first, thereby preventing sulfation of the SCR catalyst and maintaining its DeNOx capability over time.
Solution Approach 2:
The Pd-based oxidation catalyst acts as an intermediary between the exhaust gas and the Vanadium-based SCR catalyst. It performs oxidation reactions first, converting harmful substances before the exhaust reaches the SCR catalyst, thereby protecting the SCR catalyst from sulfation and other chemical fouling while still enabling effective NOx reduction.
2Reliability
If traditional catalyst arrangements are used, then the system structure is simple, but the system lacks robustness to chemical fouling and poisoning
Solution Approach 1:
The patent employs a segmented catalyst system with two distinct catalysts having different functions and compositions. The first catalyst (Pd-based) provides oxidation functionality and resistance to chemical fouling, while the second catalyst (Vanadium-based) provides SCR functionality. This segmentation enhances overall chemical fouling resistance compared to a single-catalyst system.
Solution Approach 2:
The patent uses composite material strategies by combining different catalytic materials (Pd-based oxidation catalyst and Vanadium-based SCR catalyst) in a sequential arrangement. Each catalyst is formulated with specific support materials and promoters to optimize its resistance to chemical fouling and poisoning, creating a composite system that is more robust than individual catalysts alone.
3Productivity
If a single catalyst is used for NOx reduction, then the system is cost-effective, but the DeNOx response is slow under transient conditions
Solution Approach 1:
The patent segments the catalytic treatment into two stages: oxidation (first catalyst) and SCR (second catalyst). This segmentation enables faster DeNOx response under transient conditions because the oxidation catalyst quickly prepares the exhaust composition, and the SCR catalyst immediately reduces NOx, creating a more responsive system compared to a single-catalyst approach.
Solution Approach 2:
The first catalyst performs preliminary oxidation actions on the exhaust gases before they reach the SCR catalyst. This preliminary treatment prepares the exhaust composition for more efficient and faster NOx reduction in the second catalyst, improving the overall DeNOx response speed during transient operating conditions.
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 system effectively prevents sulfation, improves chemical fouling resistance, and achieves fast NOx reduction under transient conditions while maintaining cost-effectiveness.
Implementation Method 1
a first catalyst having an inlet end and an outlet end and comprising a coating and a first substrate, wherein the coating comprises a vanadium oxide supported on a first oxidic support comprising titanium
Implementation Method 2
a hydrocarbon injector for injecting a fluid comprising hydrocarbons into the exhaust gas stream
Implementation Method 3
a second catalyst having an inlet end and an outlet end and comprising a coating and a second substrate, wherein the coating comprises palladium on a second oxidic support comprising one or more of zirconium, silicon, aluminum and titanium
Data Source
AI summary
The present disclosure relates to an exhaust gas treatment system for treating an exhaust gas stream leaving an internal combustion engine, wherein said exhaust gas treatment system comprises (i) a first catalyst comprising a coating and a first substrate, wherein the coating comprises a vanadium oxide supported on a first oxidic support comprising titanium; (ii) a hydrocarbon injector for injecting a fluid comprising hydrocarbons into the exhaust gas stream exiting the outlet end of the first catalyst according to (i); (iii) a second catalyst comprising a coating and a second substrate, wherein the coating comprises palladium on a second oxidic support comprising one or more of zirconium, silicon, aluminum and titanium.