SCR Catalyst Capture Material for Vanadia Volatility
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Vanadia-based selective catalytic reduction (SCR) catalysts face volatility issues at high temperatures, limiting their market availability and requiring a solution to prevent vanadia loss, especially when used downstream of a diesel particulate filter (DPF), and there is a need for a deNOx system with zero vanadia loss.
Innovation Solution
A selective catalytic reduction catalyst system incorporating a capture material with high surface area oxides like silica-stabilized titania or alumina to capture volatile vanadium and tungsten compounds, which can be mixed with or positioned downstream of the SCR catalyst, maintaining low fractional monolayer coverage to prevent volatility and ensure stability at extreme temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vanadia-based SCR catalyst is used downstream of DPF, then deNOx performance is improved, but vanadia volatility increases at high temperature
Solution Approach 1:
A capture material is introduced as an intermediary component between the SCR catalyst and exhaust outlet. This capture material specifically captures volatilized vanadia compounds, preventing their release while allowing the SCR catalyst to maintain its deNOx function. The capture material acts as a mediator that separates the deNOx function from the vanadia volatility problem.
Solution Approach 2:
The system employs a composite structure combining SCR catalyst material with capture material. The capture material may be mixed with the catalyst material or positioned downstream, creating a composite system that simultaneously provides deNOx activity and vanadia capture capability. This composite approach allows both functions to work together in the same device.
2Loss of substance
If capture material is added to SCR system, then vanadia loss is reduced, but device complexity increases
Solution Approach 1:
The capture material is merged with the SCR catalyst in a single integrated device. The capture material can be mixed with the catalyst material or positioned immediately downstream within the same housing, eliminating the need for separate capture devices and reducing overall system complexity despite adding functionality.
Solution Approach 2:
The capture material is designed to perform multiple functions: capturing volatilized vanadia compounds, maintaining thermal stability at high temperatures, and potentially providing additional catalytic activity. This multi-functionality reduces the need for additional separate components, offsetting the initial complexity increase.
3Loss of substance
If high surface area oxide is used for capture material, then vanadia capture efficiency is improved, but pressure drop increases
Solution Approach 1:
The capture material with high surface area oxide is positioned specifically in the region where vanadia volatilization occurs (downstream of the SCR catalyst). This localized placement ensures high capture efficiency at the critical location while minimizing the overall volume of high-surface-area material needed, thereby reducing pressure drop across the entire device.
Solution Approach 2:
The capture material utilizes porous high surface area oxide structures that provide extensive capture sites for vanadia compounds. The porous structure increases surface area for capture while maintaining reasonable permeability to exhaust gases, balancing capture efficiency with acceptable pressure drop characteristics.
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 system effectively captures and retains volatile vanadia and tungsten compounds, reducing their release into the exhaust phase, thereby enhancing the thermal stability and durability of the SCR catalyst, allowing for its use in high-temperature conditions without significant surface area loss or pressure drop issues.
Implementation Method 1
The capture material typically comprises a majority phase of high surface area oxides such as silica-stabilized titania, alumina, or stabilized alumina... wherein the capture material maintains a low total fractional monolayer coverage of minority phase oxides
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
An apparatus and method for treating diesel exhaust gases are described. The system consists of two functionalities, the first being a selective catalytic reduction (SCR) catalyst system and the second being a capture material for capturing catalyst components that have appreciable volatility under extreme exposure conditions. The SCR catalyst component is typically based on a majority phase of titania, with added minority-phase catalyst components comprising of one or more of the oxides of vanadium, silicon, tungsten, molybdenum, iron, cerium, phosphorous, copper and/or manganese vanadia. The capture material typically comprises a majority phase of high surface area oxides such as silica-stabilized titania, alumina, or stabilized alumina, for example, wherein the capture material maintains a low total fractional monolayer coverage of minority phase oxides for the duration of the extreme exposure. The method involves treatment of hot exhaust streams by both the catalyst material and capture material, wherein the capture material can be in a mixture with the catalyst material, or can be located downstream thereof, or both, but still be maintained at the extreme temperatures. Volatile catalyst components such as vanadia and tungsta are thus removed from the vapor phase of the exhaust gas.