SCR-HCT Catalyst for Emission Control
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Solution Overview
Problem
Current three-way conversion (TWC) catalyst systems face challenges in meeting stringent emission standards, particularly in reducing hydrocarbon (HC) breakthrough during cold start and nitrogen oxide (NOx) breakthrough at hot stages, as they generate ammonia and have limited efficiency in converting these emissions.
Innovation Solution
The implementation of an emissions treatment system that includes a first three-way conversion catalyst (TWC-1) followed by a selective catalytic reduction-hydrocarbon trap (SCR-HCT) catalyst, which combines a selective catalytic reduction (SCR) catalyst with a hydrocarbon trap (HCT) downstream of TWC-1, and a third catalyst with platinum group metals (PGM) downstream of the SCR-HCT, utilizing specific molecular sieves and zeolites to enhance emission conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional TWC catalyst system is used, then the system structure is simple, but HC breakthrough during cold start and NOx breakthrough at hot stages cannot be sufficiently reduced
Solution Approach 1:
The patent combines SCR catalyst and HCT material into a single integrated catalyst component (SCR-HCT catalyst) that performs both selective catalytic reduction of NOx and hydrocarbon trapping functions simultaneously, resolving the contradiction by merging multiple emission control functions into one device rather than using separate catalysts
Solution Approach 2:
The patent uses composite catalyst materials comprising SCR catalytic material (e.g., copper-exchanged chabazite zeolite) and HCT material (e.g., zeolite with specific pore structure) deposited on a monolithic substrate, creating a composite material system that achieves both NOx conversion and HC trapping in a single catalyst component
2Productivity
If TWC catalyst generates ammonia, then the catalytic conversion process is active, but ammonia leads to NOx breakthrough and reduces emission control effectiveness
Solution Approach 1:
The patent converts the harmful ammonia generated by TWC catalyst into a beneficial reductant for NOx reduction by positioning the SCR-HCT catalyst downstream of TWC, where the ammonia produced by TWC is utilized by the SCR catalyst to reduce NOx emissions through the reaction: 4NO + 4NH3 + O2 → 4N2 + 6H2O
Solution Approach 2:
The SCR-HCT catalyst acts as an intermediary component between TWC and the exhaust system, capturing and converting the ammonia produced by TWC before it can cause NOx breakthrough, thereby mediating the interaction between ammonia generation and NOx control
3Reliability
If HC adsorbent components are added to delay HC release, then cold start HC emissions are reduced, but system complexity increases and NOx breakthrough at hot stage persists
Solution Approach 1:
The patent merges the HC adsorbent function with SCR catalytic function into a single SCR-HCT catalyst component, where the HCT material (zeolite with specific pore structure) provides hydrocarbon trapping capability while the SCR catalytic material provides NOx reduction capability, eliminating the need for separate HC adsorbent components
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 system effectively reduces HC and NOx emissions by trapping hydrocarbons during cold start and converting NOx during hot stages, improving overall emission control and meeting stringent regulations such as US LEV III and EURO 7 standards.
Implementation Method 1
an SCR-HCT catalyst comprising a selective catalytic reduction (SCR) catalyst and a hydrocarbon trap (HCT) downstream of the TWC-1 in the exhaust conduit
Implementation Method 2
an HCT material that comprises a second molecular sieve that is different from the first molecular sieve
Implementation Method 3
The SCR-HCT catalyst comprises an SCR catalytic material that comprises a first molecular sieve and an HCT material that comprises a second molecular sieve
Implementation Method 4
a third catalyst downstream of the SCR-HCT catalyst in the exhaust conduit, the third catalyst comprising a platinum group metal (PGM)
Data Source
Figure 1A~2
Figure 3~5B
Figure 6
AI summary
An emissions treatment system for an exhaust stream of an internal combustion engine including hydrocarbons, carbon monoxide, and nitrogen oxides is provided. The disclosed system can include an exhaust conduit in fluid communication with the internal combustion engine via an exhaust manifold; a first three-way conversion catalyst (TWC-1) located downstream of the internal combustion engine in the exhaust conduit; an SCR-HCT catalyst comprising a selective catalytic reduction catalyst and a hydrocarbon trap downstream of the TWC-1 in the exhaust conduit; and a third catalyst downstream of the SCR-HCT combination in the exhaust conduit, the third catalyst comprising a platinum group metal (PGM) e.g., in an amount effective to oxidize hydrocarbons. Methods of making and using such systems and components thereof are also provided.