Silicate-Free Ceramic Substrate for Diesel NOx Adsorber
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Solution Overview
Problem
Current ceramic substrates used in diesel exhaust after-treatment systems, particularly cordierite, are incompatible with potassium-based NOx adsorber systems due to leaching and reaction issues, leading to durability and thermal stability concerns, and require high porosity which reduces heat capacity and increases the risk of temperature excursions.
Innovation Solution
Development of a porous non-silicate ceramic oxide composition comprising a sintered phase of aluminum titanate, zirconium titanate, yttrium oxide, and yttrium phosphate, which supports potassium-based catalyst formulations and exhibits high heat capacity, thermal shock resistance, and low thermal expansion coefficients, preventing potassium migration and maintaining durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cordierite ceramic substrate is used with high porosity (at least 50%), then NOx adsorption function and particulate matter oxidation are improved, but heat capacity is reduced and thermal shock resistance deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the ceramic substrate from conventional cordierite to a silicate-free composition containing alumina (40-70 wt%), titania (10-30 wt%), zirconia (5-20 wt%), and magnesia (5-20 wt%). This compositional parameter change enables the substrate to achieve both high porosity (40-60%) and high heat capacity, resolving the contradiction between NOx adsorption function and thermal stability.
2Strength
If cordierite ceramic substrate is used, then structural support is provided, but silicate phases leach and react with potassium-based catalysts causing durability issues
Solution Approach 1:
The patent extracts and removes the harmful silicate phase from the ceramic substrate composition. By formulating a silicate-free ceramic comprising alumina, titania, zirconia, and magnesia, the substrate eliminates the leaching and reaction problems with potassium-based catalysts while maintaining structural support strength.
Solution Approach 2:
The patent creates a composite ceramic material combining multiple oxide phases (alumina, titania, zirconia, magnesia) in specific proportions. This composite structure provides both mechanical strength for structural support and chemical inertness toward potassium catalysts, resolving the durability contradiction.
3Productivity
If high porosity (at least 50%) is used in ceramic substrate, then catalytic activity and exhaust flow are improved, but thermal mass is reduced increasing temperature excursion risk
Solution Approach 1:
The patent changes the material density and specific heat parameters by using a silicate-free oxide composition. This enables the substrate to achieve high porosity (40-60%) for catalytic activity while simultaneously maintaining high heat capacity and thermal mass to prevent temperature excursions.
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 ceramic articles demonstrate enhanced durability, thermal shock resistance, and high heat capacity, ensuring effective NOx reduction and stability across a broader temperature range without potassium migration, making them suitable for 4-way diesel exhaust treatment applications.
Implementation Method 1
a sintered phase ceramic composition containing, as expressed on a weight percent oxide basis: a(Al2TiO5)+b(ZrTiO4)+c(Y2O3)+d(YPO4)
Data Source
AI summary
Disclosed are ceramic articles comprising a sintered phase ceramic composition containing, as expressed on a weight percent oxide basis: a(Al2TiO5)+b(ZrTiO4)+c(Y2O3)+d(YPO4) wherein “a, b, c, and d” represent weight fractions of each component such that (a+b+c+d)=1.00 and wherein 0.5<a≦0.95; 0≦b≦0.5, 0.0≦c≦0.10, and 0≦d≦0.5. Also disclosed are precursor batch compositions and methods for manufacturing the ceramic articles disclosed herein.