Alumina-Supported Perovskite Oxide for Low-Temperature NOx Storage
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Solution Overview
Problem
Existing NOx trap catalysts for lean-burn engines face challenges in storing NOx in the low- to medium-temperature range without being redox active, and perovskite materials lack sufficient surface area for effective NOx reaction in the bulk state, necessitating improved alumina-supported perovskite composites with enhanced characteristics.
Innovation Solution
A method involving the preparation of doped alumina by combining boehmite suspension with aqueous salt solutions, followed by impregnation and calcination, results in a homogeneously dispersed alumina-supported perovskite type oxide composition with controlled crystallite size and improved catalytic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If CeO2 is used as a storage component for NOx, then NOx storage capability is improved in the low to medium temperature range, but fuel consumption increases due to redox activity and reducing agent consumption during regeneration
Solution Approach 1:
The patent changes the chemical composition parameters by replacing redox-active CeO2 with non-redox-active perovskite materials (ABO3) where A is a rare-earth element and B is a transition metal. This parameter change eliminates the redox activity that causes fuel consumption during regeneration, while maintaining NOx storage capability through the perovskite structure's ability to adsorb and store NOx without requiring reduction to N2.
Solution Approach 2:
The patent uses composite materials by combining perovskite-type oxide particles with a porous support material (such as alumina, silica, or titania). This composite structure provides both the NOx storage function of the perovskite and the high surface area and structural stability of the support, while eliminating the fuel penalty associated with redox-active ceria-based systems.
2Reliability
If perovskite materials are used for NOx storage, then redox activity is reduced, but surface area is insufficient for effective NOx reaction in the bulk state
Solution Approach 1:
The patent employs porous materials by using a porous support structure (such as gamma-alumina, silica, or titania) with high surface area to disperse and hold the perovskite-type oxide particles. The porous support provides extensive surface area for NOx reaction while the perovskite particles maintain their non-redox-active storage function, effectively resolving the surface area deficiency of bulk perovskite materials.
Solution Approach 2:
The patent creates a composite material system where perovskite-type oxide particles are distributed on a porous support. This composite structure combines the non-redox-active NOx storage property of perovskites with the high surface area and catalytic activity of the porous support, achieving both reduced redox activity and sufficient surface area for effective NOx conversion.
3Productivity
If perovskite crystallites are made finer to increase surface area, then catalytic performance is improved, but manufacturing precision becomes more difficult to control
Solution Approach 1:
The patent applies preliminary action by performing impregnation of the perovskite precursor compounds onto the porous support before calcination. This preliminary impregnation step ensures uniform distribution and controlled nucleation sites, which during subsequent calcination produces uniformly dispersed fine perovskite crystallites with controlled size and high surface area, thereby achieving both fine crystallite structure and manufacturing precision.
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 method produces a perovskite composite with fine crystallites (<5 nm) and high surface area, enabling efficient NOx storage and conversion without redox activity, reducing fuel consumption and enhancing catalytic performance.
Implementation Method 1
a material that is able to store NOx, e.g. as a nitrate/nitrite under lean conditions
Implementation Method 2
By applying short stoichiometric or rich operation conditions the stored NOx can then be converted to nitrogen
Data Source
AI summary
The present invention relates to a method for preparing an alumina supported perovskite type oxide composition, to an alumina supported perovskite type oxide composition and to the use of such an alumina supported perovskite type oxide composition in catalytic systems in emission control applications.