Low Temperature SCR Catalyst for NOx Reduction
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Solution Overview
Problem
Conventional SCR systems fail to effectively reduce NOx emissions at low exhaust temperatures, requiring costly platinum-infused oxidation catalysts or engine adjustments that lead to excess pollutants and fuel consumption, and existing materials in SCR catalysts either fail to reduce NOx or cause catalyst clogging.
Innovation Solution
A low temperature SCR catalyst system using a unique combination of single and mixed transition metals loaded on specific oxides, which reduces NOx efficiently at temperatures between 60° C. and 250° C., is mechanically stable up to 450° C., and has a low affinity for inhibiting substances like SO2 and water, eliminating the need for additional platinum and minimizing NO2 requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional SCR catalysts are used, then NOx reduction is effective at normal-to-high temperatures, but NOx reduction fails at low exhaust temperatures
Solution Approach 1:
The patent divides the SCR catalyst into multiple zones with different catalytic materials optimized for different temperature ranges. The first zone contains materials effective at low temperatures (60-250°C) while subsequent zones handle normal-to-high temperatures, allowing the catalyst to maintain NOx reduction effectiveness across the entire exhaust temperature spectrum
Solution Approach 2:
The patent employs composite catalytic materials combining multiple metal compounds (such as iron, copper, zinc, or manganese oxides) with support materials like alumina or silica. These composite materials provide broad temperature activity windows, enabling effective NOx reduction from 60°C to 450°C without requiring engine reconfiguration
2Reliability
If oxidation catalyst is infused with large quantities of platinum to convert NO to NO2 at low temperatures, then NOx reduction improves, but cost increases and additional drawbacks are introduced
Solution Approach 1:
The patent replaces expensive platinum with cheaper alternative materials such as iron oxide, copper oxide, zinc oxide, or manganese oxide that can achieve the same NO to NO2 conversion function at low temperatures. These alternative materials significantly reduce catalyst manufacturing cost while maintaining effectiveness in the 60-250°C range
Solution Approach 2:
The patent changes the chemical composition parameters of the catalyst by using different metal oxides with appropriate redox properties. These material parameter changes enable effective low-temperature NOx reduction without requiring platinum, thereby reducing cost while maintaining reliability
3Reliability
If engine operating conditions are adjusted to increase exhaust temperature and NO2 generation, then NOx reduction improves, but excess pollutants and fuel consumption increase
Solution Approach 1:
The patent changes the catalyst's operational parameters by using materials active at lower temperatures, allowing the engine to operate at its optimal efficiency point without reconfiguration. The catalyst effectively reduces NOx at the engine's natural exhaust temperature range, preventing excess pollutant generation and unnecessary fuel consumption
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 achieves 100% NOx reduction at temperatures below 175° C. and maintains efficiency across a wide temperature range, reducing NOx emissions without clogging or requiring excessive platinum, while being cost-effective and mechanically stable.
Implementation Method 1
The catalytic layer is made from at least one of V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ag, Ge, and Nb. The combined carrier layer and catalytic layer are configured to reduce NOx in an exhaust gas stream at an exhaust temperature between about 60°C. and about 250°C.
Implementation Method 2
it is difficult to provide enough ammonia for effective NOx reduction. To convert more NO to NO2 in low exhaust temperature operating ranges, an oxidation catalyst may be infused with large quantities of platinum.
Data Source
AI summary
According to one embodiment, described herein is an exhaust gas after-treatment system that is coupleable in exhaust gas stream receiving communication with an internal combustion engine. The exhaust gas after-treatment system includes a low temperature SCR catalyst configured to reduce NOx in exhaust gas having a temperature below a temperature threshold. The system also includes a normal-to-high temperature SCR catalyst configured to reduce NOx in exhaust gas having a temperature above the temperature threshold.