Dual-Zone Exhaust Catalyst for Ammonia Slip Without N2O/NOx Penalty
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Solution Overview
Problem
Existing ammonia slip catalysts face a trade-off between ammonia oxidation activity and selectivity towards N2O and NOx, with higher ammonia oxidation leading to increased production of harmful species.
Innovation Solution
A catalyst comprising a copper-containing zeolite with a Cu/Al ratio above a certain value, combined with a material zone containing platinum and no palladium or a specific weight ratio of Pt:Pd, is used to enhance ammonia conversion while reducing N2O and NOx selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If oxidation catalysts comprising precious metals are used to oxidize ammonia, then ammonia conversion is improved, but production of harmful species like N2O and NOx increases
Solution Approach 1:
The invention changes the chemical composition parameters of the catalyst by incorporating alkali metal oxides (K2O, Na2O) and alkaline earth metal oxides (CaO, SrO, BaO) in specific weight ratios (0.1-10% and 0.05-5% respectively based on total catalyst weight). This compositional modification alters the catalytic properties to achieve high ammonia conversion while suppressing harmful N2O and NOx formation, resolving the contradiction between conversion efficiency and harmful byproduct generation.
Solution Approach 2:
The invention uses a composite catalyst material combining precious metals (Pt, Pd) with specific oxides (alkali and alkaline earth metal oxides) on a carrier substrate. This composite structure leverages the synergistic effects of different materials: the precious metals provide ammonia oxidation activity while the added oxides modify the selectivity to reduce harmful species formation, thus achieving both high conversion and low harmful emissions simultaneously.
2Object-generated harmful factors
If SCR catalyst is combined with oxidation catalyst to improve selectivity, then ammonia oxidation selectivity towards nitrogen is improved, but device complexity increases
Solution Approach 1:
The invention merges the SCR catalyst and oxidation catalyst into a single integrated catalyst layer rather than using separate layers or devices. The active components (precious metals, alkali/alkaline earth metal oxides) are combined in one formulation that performs both ammonia oxidation and SCR functions simultaneously, reducing device complexity while maintaining improved selectivity against harmful species.
Solution Approach 2:
The catalyst formulation achieves multi-functionality by incorporating components that simultaneously provide ammonia oxidation activity (precious metals) and SCR activity (copper-containing zeolite), while the alkali and alkaline earth metal oxides enhance selectivity. This single catalyst performs multiple functions (oxidation, SCR, and selective emission control) that would otherwise require separate devices, thereby reducing overall system complexity.
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 catalyst achieves improved ammonia conversion with reduced formation of N2O and NOx, meeting stringent emission standards.
Implementation Method 1
Nitrogen oxides may be converted on an SCR catalyst in the presence of oxygen to nitrogen and water by means of ammonia
Implementation Method 2
oxidation catalysts for the oxidation of ammonia at temperatures as low as possible
Implementation Method 3
carbon monoxide and hydrocarbons are rendered harmless by oxidation on a suitable oxidation catalyst
Data Source
AI summary
The present invention relates to a catalyst comprisinga carrier substrate of the length L, which extends between a first end face ‘a’ and a second end face ‘b’, anddifferently composed material zones A and B arranged on the carrier substrate, whereinmaterial zone A comprises platinum and no palladium or platinum and palladium with a weight ratio of Pt:Pd of ≥1 and,material zone B comprises a copper containing zeolite having a Cu/Al ratio of 0.355 or higher.