Exhaust Catalyst Capture Material for Platinum Volatilization
Solution Overview
Problem
Compression ignition engines produce exhaust gases with low NO2:NO ratios, which can lead to suboptimal performance of SCR catalysts due to platinum volatilization from oxidation catalysts, causing decreased NOx conversion and secondary emissions.
Innovation Solution
An oxidation catalyst with a capture material, such as a Pt-alloying metal or refractory oxide, is positioned on the outlet end surface to trap volatilized platinum, maintaining the NO2:NO ratio and preventing platinum from condensing on downstream SCR catalysts, thereby maintaining optimal SCR performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a platinum-containing oxidation catalyst is used to oxidize NO to NO2, then the NO2:NO ratio in exhaust gas increases, but platinum volatilizes at high temperatures and condenses on downstream SCR catalysts, decreasing NOx conversion efficiency
Solution Approach 1:
A capture material is introduced as an intermediary component between the oxidation catalyst and SCR catalyst. This capture material selectively traps volatilized platinum species through adsorption or chemical interaction, preventing them from reaching and deactivating the SCR catalyst while allowing exhaust gases to pass through unaffected.
Solution Approach 2:
The invention converts the harmful effect of platinum volatilization into a beneficial outcome by positioning a capture material that selectively intercepts platinum species. The capture material acts as a sacrificial element that absorbs the harmful platinum deposits, thereby protecting the SCR catalyst and maintaining its NOx conversion efficiency.
2Temperature
If the oxidation catalyst is exposed to high temperatures for sufficient time, then platinum volatilization occurs, but this leads to platinum deposition on SCR catalysts, causing ammonia oxidation and decreased NOx conversion
Solution Approach 1:
The capture material serves as a protective intermediary layer that intercepts volatilized platinum species before they can reach the SCR catalyst. This mediator component specifically targets and traps platinum deposits, preventing the harmful interaction between volatilized platinum and the SCR catalyst surface.
Solution Approach 2:
The capture material is positioned upstream of the SCR catalyst to perform preliminary trapping of platinum species. By acting in advance, the capture material prevents platinum from reaching the SCR catalyst, thereby avoiding subsequent ammonia oxidation and maintaining catalyst performance.
3Productivity
If platinum is used as catalytic material for NO oxidation, then NO2 generation is enhanced, but platinum loss through volatilization occurs, requiring larger quantities of expensive noble metals
Solution Approach 1:
The capture material is designed to trap and retain volatilized platinum species, effectively recovering the platinum that would otherwise be lost. This recovered platinum remains on the capture material, preventing its complete loss and reducing the need for additional platinum additions to maintain oxidation catalyst performance.
Solution Approach 2:
The capture material acts as an intermediary that intercepts and retains platinum species, creating a barrier between the oxidation catalyst and the environment where platinum would be lost. This mediator system reduces platinum loss while maintaining the oxidation catalyst's productivity.
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 solution effectively captures volatilized platinum, ensuring a higher NO2:NO ratio in the exhaust gas, which enhances the performance of downstream SCR catalysts, reducing undesirable emissions and maintaining NOx conversion efficiency.
Implementation Method 1
a capture material, wherein the capture material is disposed or supported on the outlet end surface... arranged to contact the exhaust gas after the exhaust gas has contacted the catalytic material
Implementation Method 2
The catalytic material for oxidising NO to NO2 typically comprises platinum (Pt)... oxidise nitrogen monoxide (NO) to nitrogen dioxide (NO2), thereby increasing the ratio of NO2:NO
Implementation Method 3
When the first emissions control device is exposed to relatively high temperatures for a sufficient period of time, low levels of platinum (Pt) may volatilise from the catalytic material
Data Source
AI summary
An oxidation catalyst for treating an exhaust gas produced by a compression ignition engine comprising: a substrate having an inlet end surface and an outlet end surface; a catalytic material disposed on the substrate, wherein the catalytic material comprises platinum (Pt); and a capture material, wherein the capture material is disposed on the outlet end surface.