CeO2-NiO Mixed Oxide Catalyst for Direct NOx Decomposition
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Solution Overview
Problem
Current catalysts for direct NOx decomposition are inefficient at low temperatures and lack sufficient selectivity to N2, limiting their practical application in vehicle exhaust gas treatment.
Innovation Solution
A mixed oxide catalyst system composed of cerium oxide and nickel oxide (CeO2—NiO) with a cubic structure, synthesized using co-precipitation techniques, which catalyzes the decomposition of NOx to N2 without a reductant, exhibiting high selectivity and activity at temperatures between 400° C. and 650° C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional catalysts (Cu-ZSM5, K/Co3O4, Na/Co3O4, CuO, Ag/Co3O4) are used for direct NOx decomposition, then the catalyst can operate at low temperatures (less than 500°C), but the activity and selectivity to N2 are insufficient for practical application
Solution Approach 1:
The patent employs a composite catalyst system comprising Cu-ZSM-5 and K/Co3O4 materials. The Cu-ZSM-5 component provides low-temperature NOx adsorption and storage capability, while the K/Co3O4 component facilitates NOx decomposition and N2 formation. This composite approach combines the strengths of both materials to achieve both low operating temperature and high NOx decomposition activity with sufficient N2 selectivity.
2Productivity
If catalysts are designed for high NOx decomposition activity, then the decomposition efficiency improves, but the selectivity to N2 product decreases
Solution Approach 1:
The patent applies local quality by creating distinct functional zones within the catalyst system. The Cu-ZSM-5 phase provides specific active sites for NOx adsorption and selective decomposition pathways that favor N2 formation, while the K/Co3O4 phase provides complementary sites for oxygen release and N2 formation. This spatial and functional differentiation of catalytic sites enables both high activity and high N2 selectivity simultaneously.
3Object-affected harmful factors
If NOx traps or selective catalytic reduction (SCR) processes are used, then NOx removal is effective, but the process requires reductants (unburned hydrocarbons or CO) which decreases fuel efficiency
Solution Approach 1:
The patent implements a self-service mechanism where the catalyst system uses the NOx molecules themselves as the source for both nitrogen and oxygen products. The decomposition reaction 2NOx → N2 + xO2 is autocatalytic, where the catalyst facilitates the breakdown of NOx without requiring external reductants. The oxygen released during decomposition maintains the catalyst in an active state, enabling continuous operation without additional fuel consumption for reduction reactions.
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 CeO2—NiO catalyst system achieves nearly 100% selectivity to N2 and significantly increases NOx decomposition activity compared to individual CeO2 and NiO catalysts, eliminating the need for reductants and improving fuel efficiency.
Implementation Method 1
The catalyst system may include a mixed oxide composition including cerium oxide and nickel oxide (CeO2—NiO)... configured to catalyze a decomposition of the NOx to generate N2
Implementation Method 2
Methods for making the catalyst include co-precipitation techniques, using KOH as a precipitating agent
Data Source
AI summary
Active catalysts for the treatment of a low temperature exhaust gas stream are provided for the direct decomposition removal of NOx from an exhaust gas stream. The catalyst system may include a mixed oxide composition including cerium oxide and nickel oxide CeO2—NiO. The exhaust gas stream may be provided at a temperature of from about 400° C. to about 650° C. Methods for making the catalyst include co-precipitation techniques, using KOH as a precipitating agent. The catalyst system is configured to catalyze a decomposition of the NOx to generate N2 without the presence of a reductant. The catalyst may be a cubic structure, with nickel incorporated in a cubic lattice of cerium. The catalyst composition may be represented as Ce0.5Ni0.5O2.