CHA Zeolite NOx Storage Catalyst for Cold-Start Exhaust Capture
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Solution Overview
Problem
Existing NOX storage catalysts face limitations in effectively capturing NOX emissions during the cold start-up phase of vehicles due to low exhaust gas temperatures, which are not adequately addressed by traditional three-way catalysts and adsorption or occlusion type catalysts.
Innovation Solution
A NOX storage catalyst comprising a CHA zeolite with ion-exchanged transition metals like Cu, Fe, Co, Ti, Zn, Ag, Mn, and rare earth metals like La, Ce, Nd, Pr, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, supported on the zeolite, with specific weight percentages, and optionally ion-exchanged with alkaline-earth or alkali metals, to enhance NOX storage performance at low temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a three-way catalyst is used, then exhaust gas purification is achieved, but the catalyst takes time to activate and cannot effectively treat exhaust gas during cold start-up
Solution Approach 1:
The patent introduces a NOX storage catalyst that performs preliminary NOX storage during cold start-up conditions before the three-way catalyst activates. The CHA zeolite structure with ion-exchanged metals stores NOX in advance, so when the three-way catalyst becomes active, the stored NOX can be rapidly reduced, effectively addressing emissions during the activation period.
2Quantity of substance
If adsorption or occlusion type catalysts are used to store NOX, then exhaust gas suppression is improved, but storage performance deteriorates at low temperatures during cold start-up
Solution Approach 1:
The patent modifies the chemical and physical parameters of the zeolite catalyst by using CHA structure with specific ion-exchanged metals (Cu, Fe, Co, Ti, Zn, Ag, Mn) and controlled Si/Al ratios (1-50). These parameter changes enable the catalyst to maintain high NOX storage capacity across a broader temperature range, particularly improving low-temperature performance during cold start-up while preserving high-temperature stability.
3Use of energy by moving object
If high efficiency engine technology is applied to improve fuel efficiency, then fuel consumption is reduced, but exhaust gas temperature decreases and NOX storage performance deteriorates
Solution Approach 1:
The patent creates a composite catalyst system combining CHA zeolite framework with multiple ion-exchanged metal components (transition metals and rare earth metals). This composite structure synergistically improves low-temperature NOX storage activity while maintaining thermal stability, allowing effective NOX control even when exhaust gas temperatures are reduced by high efficiency engine technology.
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 catalyst demonstrates improved NOX storage performance at cold start-up conditions, with enhanced NOX storage capacity and stability under hydrothermal treatment, effectively capturing NOX emissions during the initial low-temperature phase.
Implementation Method 1
a NOX storage catalyst includes a CHA zeolite, a transition metal ion-exchanged with the CHA zeolite
Implementation Method 2
a rare earth metal that is different the transition metal and is supported on the CHA zeolite
Data Source
AI summary
A NOX storage catalyst includes CHA zeolite, a transition metal ion-exchanged in the CHA zeolite, and a rare earth metal that is different the transition metal and is supported on the CHA zeolite. A method for preparing a NOX storage catalyst includes preparing a synthetic mother liquid including a zeolite raw material as a source of silica and alumina, a structure-inducing material, a complexing material, and a solvent, reacting the synthetic mother liquid to prepare a CHA zeolite, and supporting a transition metal and a rare earth metal that is different from the transition metal on the prepared CHA zeolite.