Ozone-Enhanced SCR Catalyst NOx Conversion
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Solution Overview
Problem
Internal combustion engines, particularly diesel engines, face challenges in reducing emissions of carbon monoxide, unburned hydrocarbons, oxides of nitrogen (NOx), and particulate matter, with existing emissions control devices often ineffective in treating all four classes of pollutants simultaneously, and processes for treating NOx emissions are more efficient with higher NO2 concentrations.
Innovation Solution
An exhaust purification system that includes an upstream catalyst coupled with a passive NOx adsorber, ozone is introduced to convert NO to NO2, and the exhaust stream is then treated with an SCR catalyst, optionally with heating and additional SCR or ASC components, to enhance NOx conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional emissions control devices are used, then some pollutants are treated, but all four classes of pollutants cannot be treated simultaneously effectively
Solution Approach 1:
The patent combines multiple emissions control functions into a single integrated system. The upstream catalyst performs oxidation of CO and HC while the SCR catalyst performs NOx reduction in the same exhaust flow path, allowing simultaneous treatment of multiple pollutant classes (CO, HC, and NOx) with a unified device rather than separate components
Solution Approach 2:
The exhaust purification system is designed to perform multiple functions: the upstream catalyst oxidizes CO to CO2 and HC to H2O, while the SCR catalyst reduces NOx to N2. This multi-functional approach enables the system to treat all four classes of pollutants (CO, HC, NOx, and PM) simultaneously, making the device versatile rather than specialized for a single pollutant type
2Productivity
If NOx treatment processes are used with low NO2 concentration, then the system operates, but treatment speed and efficiency are reduced
Solution Approach 1:
The upstream catalyst performs preliminary oxidation of NO to NO2 before the exhaust reaches the SCR catalyst. This pre-conversion of NO to NO2 ensures that when the exhaust enters the SCR catalyst, there is already a higher concentration of NO2 available, which accelerates the SCR reaction rate and improves overall NOx conversion efficiency
Solution Approach 2:
The system changes the chemical composition parameters of the exhaust gas by oxidizing NO to NO2 in the upstream catalyst. This parameter change (increasing NO2 concentration from typically low levels to higher levels) directly improves the kinetics of the SCR reaction, thereby increasing productivity and conversion rate
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 achieves higher NOx conversion rates, potentially increasing conversion by 4-12% compared to systems lacking ozone conversion and heating, by increasing NO2 levels in the exhaust stream, thereby reducing NOx emissions effectively across a wider temperature range.
Implementation Method 1
means to contact the exhaust stream with ozone, to react NO in the exhaust stream with the ozone to produce NO2
Implementation Method 2
selectively catalytically reducing NO2 to nitrogen by contacting the NO2 produced from the oxidizing step with a reductant in the presence of an SCR catalyst
Implementation Method 3
selectively catalytically reducing NO2 to nitrogen
Implementation Method 4
passive NOx adsorber catalyst
Data Source
Figure 1~1B
Figure 2~2B
Figure 3~3B
AI summary
Exhaust purification system and methods for the reduction of emissions from an exhaust stream, including an upstream catalyst coupled with a passive NOx adsorber catalyst; means to contact the exhaust stream with ozone, to react NO in the exhaust stream with the ozone to produce NO2; and an SCR catalyst.