LTA Zeolite DOC for Cold Start NOx Storage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current exhaust gas purification systems, particularly selective catalyst reduction (SCR) systems, face challenges in reducing nitrogen oxides during cold starts and are vulnerable to degradation due to temperature increases during diesel particulate matter filter (DPF) regeneration, with existing catalysts not effectively addressing these issues.
Innovation Solution
The implementation of an LTA zeolite catalyst with improved high-temperature performance in diesel oxidation catalysts (DOC) and selective catalyst reduction (SCR) systems, incorporating metals like Pt, Pd, Rh, Fe, Cu, Ag, Mn, Co, and Mg, and controlled urea injection to manage NOx storage and detachment, along with a diesel particulate matter filter (DPF) for efficient particulate matter reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional catalysts are used in SCR systems, then the system can operate at normal temperatures, but nitrogen oxide purification efficiency is poor during cold starts when SCR is inactive
Solution Approach 1:
The LTA zeolite catalyst performs preliminary NOx storage during the cold start phase when SCR is inactive, capturing nitrogen oxides before they are released after SCR activation. This preliminary action ensures that NOx accumulated during cold operation is subsequently purified, improving overall purification efficiency without requiring the SCR system to be active from the start.
2Object-generated harmful factors
If DPF regeneration is performed to reduce particulate matter, then particulate matter is effectively reduced, but temperature increases cause DOC degradation
Solution Approach 1:
The LTA zeolite catalyst is specifically selected for its ability to maintain structural stability and catalytic activity at high temperatures during DPF regeneration. The catalyst's parameters (crystal structure, composition) are optimized to withstand thermal stress up to 700-800°C, allowing the system to perform DPF regeneration without permanent DOC degradation that would occur with conventional catalysts.
3Productivity
If SCR system is activated to reduce nitrogen oxide, then NOx purification is effective, but the system cannot address NOx emissions during cold starts when SCR remains inactive
Solution Approach 1:
The LTA zeolite catalyst acts as an intermediary between the cold start phase and the active SCR phase. It temporarily stores NOx during cold operation when SCR is inactive, then releases and facilitates the purification of stored NOx after SCR activation, bridging the gap between these two operational states and preventing NOx emissions during the transition period.
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 enhances nitrogen oxide purification efficiency, improves fuel economy, and prevents DOC degradation from temperature increases during DPF regeneration, effectively reducing NOx in the SCR's inactive region during cold starts and maintaining system performance.
Implementation Method 1
The DOC may store NOx in the exhaust gas in an inactive region of the SCR
Implementation Method 2
The DOC may oxidize total hydrocarbon and carbon monoxide in the exhaust gas
Implementation Method 3
as a catalytic reaction of nitrogen oxide and ammonia in exhaust gas by the SCR catalyst, nitrogen oxide is reduced to nitrogen gas (N2) and water (H2O)
Implementation Method 4
a reducing agent (urea) injected in a stream direction of the exhaust gas through an injector is converted into ammonia (NH3) by heat of the exhaust gas
Data Source
AI summary
A device for purifying exhaust gas may be provided to purify exhaust gas in an engine includes an exhaust line through which exhaust gas discharged from the engine passes, a diesel oxidation catalyst (DOC) that is disposed in the exhaust line to purify hydrocarbon (HC) and carbon monoxide (CO) of the exhaust gas, a urea injector that injects a urea aqueous solution into the exhaust line, and a selective catalyst reduction (SCR) that reduces nitrogen oxide of the exhaust gas passing through the DOC by use of the urea aqueous solution, in which the DOC includes an LTA zeolite catalyst.