Ammonia Decomposition Catalyst Two-Layer Zeolite Structure
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Solution Overview
Problem
Current ammonia decomposition catalysts face challenges in efficiently decomposing ammonia in exhaust gases with high moisture content while minimizing the formation of NOx and N2O by-products, and maintaining durability in the presence of sulfur compounds.
Innovation Solution
A two-layer ammonia decomposition catalyst comprising a lower layer with a noble metal, inorganic oxide, phosphorus, and a first proton type or ion exchange zeolite, and an upper layer with a second proton type or ion exchange zeolite, which effectively decomposes ammonia into nitrogen and water, suppressing NOx formation to 0.6% or less and minimizing N2O production, even in high moisture conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ammonia oxidation catalyst is used to treat ammonia exhaust gas, then ammonia decomposition rate is improved, but NOx formation increases
Solution Approach 1:
The catalyst is divided into two distinct layers: a lower layer containing noble metal and inorganic oxide for ammonia decomposition, and an upper layer containing proton-type or ion-exchanged zeolite for selective nitrogen oxide reduction. This segmentation allows each layer to perform its specific function optimally, achieving high ammonia decomposition while minimizing NOx formation through the selective reduction capability of the zeolite layer.
2Productivity
If conventional ammonia decomposition catalyst is used, then ammonia decomposition is achieved, but catalyst durability decreases in high moisture conditions
Solution Approach 1:
The catalyst employs a composite structure combining noble metal (such as Pt, Pd, or Rh) with inorganic oxide (such as TiO2, SiO2, or Al2O3) in the lower layer, and proton-type or ion-exchanged zeolite (such as H-ZSM-5, H-beta, or Cu-exchanged zeolite) in the upper layer. This composite material structure provides both high catalytic activity for ammonia decomposition and enhanced durability against moisture and sulfur compounds, as the zeolite layer protects the noble metal from deactivation while maintaining catalytic efficiency.
3Object-generated harmful factors
If two-stage catalyst layers are used for ammonia treatment and nitrogen oxide reduction, then ammonia decomposition and NOx reduction are achieved, but apparatus complexity increases
Solution Approach 1:
The invention merges ammonia decomposition and nitrogen oxide reduction functions into a single integrated catalyst unit with two layers. The lower layer performs ammonia decomposition while the upper layer simultaneously reduces nitrogen oxides from the exhaust gas stream. This merging eliminates the need for separate reactors and complex gas flow control systems required by conventional two-stage methods, significantly simplifying the apparatus while achieving both objectives.
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 high ammonia decomposition rates with low NOx and N2O formation, maintaining initial activity and durability over time, especially in exhaust gases with high moisture and sulfur content.
Implementation Method 1
a lower layer having a noble metal, an inorganic oxide, phosphorus, and a first proton type zeolite or a first ion exchange type zeolite ion-exchanged with Cu, Co or Fe ions
Implementation Method 2
an upper layer provided on the lower layer and having a second proton type zeolite or a second ion exchange type zeolite ion-exchanged with Cu, Co or Fe ions
Implementation Method 3
a first ion exchange type zeolite ion-exchanged with Cu, Co or Fe ions; a second ion exchange type zeolite ion-exchanged with Cu, Co or Fe ions
Implementation Method 4
a lower layer having a noble metal, an inorganic oxide, phosphorus, and a first proton type zeolite
Data Source
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AI summary
An ammonia decomposition catalyst to be used for an ammonia exhaust gas having a high moisture content; and a method for purifying the ammonia exhaust gas. An ammonia decomposition catalyst for treating an ammonia exhaust gas containing moisture, the catalyst comprising: a lower layer having a noble metal, an inorganic oxide, phosphorus, and a first proton type zeolite or a first ion exchange type zeolite ion-exchanged with Cu, Co or Fe ions; and an upper layer provided on the lower layer and having a second proton type zeolite or a second ion exchange type zeolite ion-exchanged with Cu, Co or Fe ions.