Three-Way Catalyst Composition for DFSO NOx Breakthrough
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Solution Overview
Problem
Existing catalytic solutions for gasoline engines fail to effectively reduce NOx breakthrough during deceleration fuel shut off (DFSO) events, leading to elevated NOx emissions and the formation of NH3, which complicates meeting both fuel economy and emission control regulations.
Innovation Solution
A catalytic article comprising a substrate with a first catalytic region containing platinum and rhodium supported on ZrO2—Al2O3, which effectively reduces NOx slip after fuel cut events without impairing light-off functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If deceleration fuel shut off (DFSO) is used to improve fuel economy, then fuel consumption is reduced, but NOx emissions increase due to NOx breakthrough during rich recovery
Solution Approach 1:
The patent applies preliminary action by pre-reducing the catalyst surface with a first rich gas pulse before the main rich recovery phase. This preliminary reduction ensures that the catalyst surface is sufficiently reduced to handle NOx conversion during subsequent lean operation, preventing NOx breakthrough while maintaining fuel economy benefits from DFSO.
Solution Approach 2:
The patent implements periodic action through controlled rich gas pulses injected at specific intervals during and after DFSO events. These periodic rich pulses temporarily create reducing conditions to maintain catalyst surface reduction, enabling continuous NOx conversion capability while the engine operates with fuel cut, thus resolving the contradiction between fuel economy and NOx control.
2Reliability
If rich recovery is performed to reduce catalyst surface for NOx conversion, then NOx conversion capability is improved, but NH3 is formed which can be oxidized back to NOx
Solution Approach 1:
The patent applies preliminary action by performing a controlled rich gas pulse treatment before full rich recovery. This preliminary step reduces the catalyst surface sufficiently for NOx conversion while being limited in duration and intensity to minimize NH3 formation. The approach ensures NOx conversion capability is established before the engine returns to fuel injection.
Solution Approach 2:
The patent uses partial action by applying a limited-duration rich gas pulse rather than extended rich recovery. This partial rich treatment provides just enough reduction to enable NOx conversion capability while avoiding excessive rich conditions that would generate significant NH3. The rich pulse is calibrated to achieve minimum necessary reduction without over-treating.
3Reliability
If the entire under floor brick is reduced during rich recovery, then NOx conversion is improved, but the reduction is insufficient during short rich excursions
Solution Approach 1:
The patent applies preliminary action by injecting a concentrated rich gas pulse at the inlet zone of the catalyst during the brief rich excursion. This preliminary rich treatment creates a reduction front that propagates through the catalyst, ensuring sufficient reduction of the entire underfloor brick even during short rich excursions. The inlet-zone-focused approach maximizes reduction efficiency within limited time.
Solution Approach 2:
The patent applies local quality by concentrating the rich gas injection at the inlet zone rather than uniformly throughout the catalyst. This localized rich treatment creates a high-concentration reducing environment at the inlet that rapidly propagates reduction through the catalyst structure, achieving complete brick reduction more effectively than diffuse rich conditions during short excursions.
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 catalytic article enhances NOx reduction performance under DFSO conditions, improving fuel economy and meeting stringent emission control standards by minimizing NOx breakthrough and NH3 formation.
Implementation Method 1
a first catalytic region comprising a first platinum group metal (PGM) component supported on a first PGM support material, wherein the first PGM component comprises platinum and rhodium
Implementation Method 2
wherein the first PGM support material comprises ZrO2—Al2O3
Implementation Method 3
TWCs perform three main functions: (1) oxidation of CO; (2) oxidation of unburnt HCs; and (3) reduction of NOx
Data Source
AI summary
A three-way catalyst article, and its use in an exhaust system for internal combustion engines, is disclosed. The catalyst article for treating exhaust gas comprising: a substrate comprising an inlet end and an outlet end with an axial length L; a first catalytic region comprising a first platinum group metal (PGM) component supported on a first PGM support material, wherein the first PGM component comprises platinum and rhodium; and wherein the first PGM support material comprises ZrO2—Al2O3.