NOx Storage Catalyst Reactivation via CO2 Decomposition
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Thermally aged nitrogen oxide storage catalytic converters in motor vehicles experience reduced storage capacity due to bond formation between storage components and carrier materials, leading to irreversible sintering and decreased catalytic activity, necessitating a method for reactivation during regular driving that maintains emission neutrality.
Innovation Solution
A method involving the decomposition of strontium and barium compounds on cerium oxide-containing carrier materials using a gas mixture with 5-20% CO2 and optional water and NOx, generated during engine operation with an air-fuel ratio not exceeding λ=1, to reactivate the catalytic converter at temperatures between 375°C and 650°C, utilizing decomposition reactions of barium cerate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the engine operates with high exhaust gas temperatures to maintain catalytic activity, then the catalytic converter remains active, but thermal damage occurs leading to sintering and reduced storage capacity
Solution Approach 1:
The patent changes the chemical parameters of the exhaust gas by controlling the air-fuel ratio to create reducing conditions (lambda < 1.0), which enables the decomposition of barium cerate formed during thermal aging. This chemical parameter change allows reactivation of the storage material without requiring temperature changes, thus resolving the contradiction between maintaining catalytic activity and preventing thermal damage.
Solution Approach 2:
The patent converts the harmful effect of thermal aging (barium cerate formation reducing storage capacity) into a beneficial reactivation process. By introducing reducing conditions with carbon monoxide and hydrogen from the exhaust gas, the barium cerate is decomposed back into active barium oxide, restoring storage capacity. The harmful thermal aging effect is thus transformed into an opportunity for regeneration.
2Object-generated harmful factors
If the engine operates with stoichiometric air-fuel ratio (lambda=1) for emission neutrality, then emissions are controlled, but the exhaust gas lacks sufficient reducing agents for reactivation
Solution Approach 1:
The patent implements dynamic control of the air-fuel ratio, switching between stoichiometric operation (lambda=1) for emission neutrality and reducing operation (lambda<1.0) for reactivation. This dynamic adjustment allows the system to maintain emission control during normal operation while enabling reactivation when thermal aging occurs, resolving the contradiction between emission neutrality and reactivation capability.
Solution Approach 2:
The patent ensures continuous useful action by maintaining the catalytic converter in an active state through periodic reactivation cycles. The reducing conditions are introduced continuously enough to decompose barium cerate and restore storage capacity, ensuring the catalyst remains functional throughout operation without interruption to emission control.
3Quantity of substance
If barium oxide is used as storage component on cerium oxide carrier, then nitrogen oxide storage capacity is achieved, but barium cerate forms at high temperatures reducing storage capacity
Solution Approach 1:
The patent changes the chemical environment parameters by introducing reducing conditions (carbon monoxide and hydrogen from exhaust gas) that selectively decompose barium cerate without affecting the cerium oxide carrier. This parameter change restores the barium oxide storage component while maintaining the stable cerium oxide support, thus resolving the contradiction between achieving storage capacity and maintaining material stability.
Solution Approach 2:
The patent uses carbon monoxide and hydrogen from the exhaust gas as intermediary substances that mediate the decomposition of barium cerate. These reducing agents act as intermediaries that transfer electrons to decompose the barium cerate into barium oxide and carbon dioxide, enabling regeneration without direct thermal treatment and thus maintaining storage material stability.
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 method effectively reactivates thermally aged nitrogen oxide storage catalysts, restoring storage capacity and catalytic activity while ensuring emission neutrality, as demonstrated by increased lean run times and hydrocarbon conversions without damaging noble metal centers.
Implementation Method 1
the compounds of strontium and/or barium with the carrier material are decomposed during regular driving operation of a motor vehicle with a predominantly lean-burn internal combustion engine by treatment with a gas mixture containing 5-20% by volume of carbon dioxide
Implementation Method 2
They should also oxidize the proportion of nitrogen monoxide in the exhaust gas to nitrogen dioxide so that it can react with the alkaline storage material to form nitrates
Implementation Method 3
the nitrates formed are decomposed into nitrogen oxides and reduced to nitrogen using carbon monoxide, hydrogen and hydrocarbons as reducing agents, with the formation of water and carbon dioxide
Data Source
Figure 1~2
Figure 3
AI summary
Nitrogen oxide storage catalysts are used for removal of nitrogen oxides present in the lean exhaust gas of so-called lean-burn engines. Storage catalysts are thermally modified at high temperatures. The modification is a sintering of the catalytically active noble metal components of the catalyst and a formation of compounds of the storage components with the support materials. According to the invention, the formation of compounds of the storage materials can be largely reversed by treatment of the storage material with a gas mixture containing carbon dioxide, optionally steam and optionally nitrogen oxide at temperatures between 200 °C and 950 °C, preferably between 300 °C and 700 °C. The reactivation can be carried out with neutral emissions directly in the vehicle during operation by the adjustment of suitable exhaust conditions and regulating the fuel/air mixture.