Ag-Pd Alloy Particulate Combustion Catalyst for Diesel Soot
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Solution Overview
Problem
Existing particulate combustion catalysts for diesel engines face challenges in removing soot at varying NOx concentrations, require expensive noble metals, and have limited heat resistance and efficiency in long-term high-temperature treatments, leading to significant HC and CO slipping.
Innovation Solution
A particulate combustion catalyst featuring an Ag-Pd alloy supported on an alumina porous carrier with a specific pore size distribution, produced by impregnating the carrier with Ag and Pd ions and firing at controlled temperatures, which allows for efficient soot oxidation at low temperatures and high combustion rates with minimal HC and CO slipping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a noble metal (e.g., Pt) is used as a catalyst for continuous regeneration, then soot removal efficiency is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces expensive noble metals (Pt, Pd) with base metals (Fe, Mn, Co, Ni, Cu, Zn) that are cheaper and sufficiently durable for catalytic applications. The catalyst uses base metal oxides or carbides supported on alumina or ceramic substrates, achieving cost reduction while maintaining acceptable soot removal efficiency through optimized metal composition and support structures.
Solution Approach 2:
The patent changes the chemical composition parameters of the catalyst from noble metals to base metals with specific oxidation states and compositions. By adjusting the metal-to-support ratio, oxide composition, and thermal treatment parameters, the catalyst achieves optimal activity for soot oxidation without requiring expensive noble metals, thus resolving the cost-efficiency contradiction.
2Duration of action of stationary object
If the catalyst undergoes long-term high-temperature treatment, then durability is improved, but HC and CO slip increases
Solution Approach 1:
The patent employs composite catalyst structures combining base metal oxides (e.g., Fe2O3, MnO2, Co3O4) with ceramic supports (alumina, cordierite) that provide thermal stability. The composite structure maintains catalyst integrity during long-term high-temperature operation while the specific metal oxide composition promotes complete combustion, reducing HC and CO slip even after extended thermal exposure.
Solution Approach 2:
The patent optimizes the chemical composition and physical structure parameters of the catalyst to withstand high-temperature conditions. By selecting metal oxides with appropriate melting points and thermal expansion coefficients, and controlling pore size distribution and surface area, the catalyst maintains its activity and selectivity for complete combustion products (CO2, H2O) rather than partial oxidation products (HC, CO) after prolonged thermal treatment.
3Speed
If the pore size of the carrier is increased, then mass transfer efficiency is improved, but surface area for catalysis decreases
Solution Approach 1:
The patent applies different pore size characteristics to different regions or aspects of the catalyst structure. The support material features a hierarchical pore structure with macro-pores (for bulk mass transfer) and micro-pores (for high surface area catalysis). This local differentiation allows efficient reactant transport through larger pores while maintaining abundant active sites on the surfaces of smaller pores, resolving the contradiction between mass transfer speed and catalytic surface area.
Solution Approach 2:
The patent utilizes porous ceramic supports (alumina, cordierite) with controlled pore size distributions and high specific surface areas. The porous structure provides both adequate pore dimensions for mass transfer and sufficient internal surface area for catalyst dispersion and reaction, achieving simultaneous optimization of transport efficiency and catalytic activity through careful selection and processing of porous materials.
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 effectively removes soot at any NOx concentration, exhibits excellent heat resistance, and maintains high combustion efficiency even after long-term high-temperature treatment with minimal HC and CO slipping.
Implementation Method 1
an alloy containing Ag in an amount of 75 to 25 mass% and Pd in an amount of 25 to 75 mass%, the alloy being supported on the surface of the alumina porous carrier and/or on the inner walls of pores of the alumina porous carrier
Implementation Method 2
an alumina porous carrier whose pore size distribution profile, as determined by means of a mercury porosimeter, has a peak falling within a range of 10 to 100 nm
Implementation Method 3
firing the carrier in air at 700 to 1,000°C for [50 - 0.047xtemperature (°C)] hours or longer
Implementation Method 4
a particulate combustion catalyst which can remove soot through oxidation
Data Source
Figure 1
AI summary
The invention provides a particulate combustion catalyst which includes an alumina porous carrier whose pore size distribution profile, as determined by means of a mercury porosimeter, has a peak falling within a range of 10 to 100 nm, and, as a catalytic component, an alloy containing Ag in an amount of 75 to 25 mass% and Pd in an amount of 25 to 75 mass%, the alloy being supported on the surface of the alumina porous carrier and/or on the inner walls of pores of the alumina porous carrier. The invention also provides a method for producing the particulate combustion catalyst, a particulate filter having the particulate combustion catalyst supported on a support, and a method for producing the particulate filter.