Rhodium-Phosphorus Catalyst Layer for Low-Temperature NOx Purification
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Solution Overview
Problem
Conventional exhaust gas purification catalysts exhibit insufficient NOx purifying performance, particularly at low to medium temperatures.
Innovation Solution
An exhaust gas purification catalyst comprising a substrate with a catalyst layer containing rhodium, phosphorus, and a rare earth element other than cerium, with specific mass ratios, to enhance NOx purifying performance at low to medium temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional exhaust gas purification catalysts are used, then the catalyst structure is simple and easy to manufacture, but the NOx purifying performance at low to medium temperatures is insufficient
Solution Approach 1:
The patent applies composite materials by combining rhodium, phosphorus, and rare earth elements (other than cerium) in a catalyst layer. This composite composition enhances NOx purifying performance at low to medium temperatures while maintaining structural simplicity. The synergistic effect of these materials resolves the contradiction between performance improvement and complexity increase.
Solution Approach 2:
The patent changes the chemical composition parameters of the catalyst layer by incorporating specific ratios of rhodium, phosphorus, and rare earth elements. This parameter optimization improves NOx purification efficiency at low to medium temperatures without significantly complicating the overall catalyst structure, thus resolving the technical contradiction.
2Reliability
If the catalyst layer contains only traditional noble metals, then the manufacturing process is simple, but the purifying performance at low to medium temperatures is insufficient
Solution Approach 1:
The patent introduces a composite catalyst layer containing rhodium, phosphorus, and rare earth elements (other than cerium). This composite formulation improves exhaust gas purifying performance at low to medium temperatures while maintaining ease of manufacture through conventional impregnation and calcination processes.
Solution Approach 2:
Phosphorus acts as an intermediary element in the catalyst layer, facilitating the interaction between rhodium and rare earth elements. This intermediary role enhances the overall catalytic activity for NOx purification at low to medium temperatures without complicating the manufacturing process.
3Reliability
If cerium-based oxygen storage materials are used, then oxygen storage capacity is improved, but the NOx purifying performance at low to medium temperatures remains insufficient
Solution Approach 1:
The patent extracts cerium from the catalyst composition and replaces it with rare earth elements other than cerium (such as lanthanum, neodymium, or yttrium). This extraction and replacement maintains oxygen storage capacity while significantly improving NOx purifying performance at low to medium temperatures, resolving the technical contradiction.
Solution Approach 2:
Instead of using cerium-based materials for oxygen storage, the patent inverts the approach by using non-cerium rare earth elements combined with phosphorus and rhodium. This inversion achieves superior NOx purification at low to medium temperatures while maintaining the necessary oxygen storage functionality.
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 NOx purifying performance at low to medium temperatures, with the catalyst layer containing rhodium, phosphorus, and a rare earth element other than cerium, enhancing the exhaust gas purifying performance.
Implementation Method 1
a catalyst layer formed on the substrate, wherein the catalyst layer contains rhodium element, phosphorus element and a rare earth element other than cerium element
Implementation Method 2
a ratio of a mass of the phosphorus element contained in the catalyst layer to a mass of the rhodium element contained in the catalyst layer is from 1.0 to 10, and wherein a ratio of a mass of the rare earth element other than cerium element in terms of an oxide thereof contained in the catalyst layer to the mass of the rhodium element contained in the catalyst layer is from 1.0 to 5.0
Data Source
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AI summary
An object of the present invention is to provide an exhaust gas purification catalyst having improved exhaust gas purifying performance (in particular, improved NOx purifying performance) at low to medium temperature, and, in order to achieve the object, the present invention provides an exhaust gas purification catalyst (10A) including: a substrate (20); and a catalyst layer (30 or 40) formed on the substrate (20), wherein the catalyst layer (30 or 40) contains rhodium element, phosphorus element and a rare earth element other than cerium element, wherein a ratio of a mass of the phosphorus element contained in the catalyst layer (30 or 40) to the mass of the rhodium element contained in the catalyst layer (30 or 40) is from 1 to 10, and wherein a ratio of a mass of the rare earth element other than cerium element in terms of an oxide thereof contained in the catalyst layer (30 or 40) to the mass of the rhodium element contained in the catalyst layer (30 or 40) is from 1 to 5.