Platinum-Cerium Oxide Catalyst for Low-Temperature CO Removal
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Solution Overview
Problem
Lean-burn internal combustion engines, such as diesel engines, face challenges in removing carbon monoxide and hydrocarbons due to low exhaust gas temperatures, which hinder the catalytic activity of existing oxidation catalysts, particularly with saturated and aromatic hydrocarbons, and cerium oxide-based catalysts exhibit increased light-off temperatures and sintering issues.
Innovation Solution
A method involving a catalyst with platinum or palladium supported on refractory materials, including cerium oxide, with a specific weight ratio and additional noble metals, directly connected to the cerium oxide surface, and a regeneration process using rich exhaust gas to maintain catalytic activity, achieving a CO light-off temperature below 130°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxidation catalysts are used to remove CO and HC from diesel exhaust, then harmful gases are converted to CO2 and water vapor, but the catalytic activity is insufficient at low exhaust gas temperatures (100-250°C)
Solution Approach 1:
The patent changes the chemical parameters of the catalyst by using platinum in specific oxidation states (0, +2, +4) supported on cerium oxide, which modifies the catalyst's light-off temperature to achieve sufficient activity at low exhaust gas temperatures
Solution Approach 2:
The patent creates a composite catalyst system combining platinum (in multiple oxidation states) with cerium oxide support material, where the interaction between the precious metal and the oxide support enhances catalytic performance at low temperatures
2Reliability
If the light-off temperature is lowered to ensure catalytic activity at low temperatures, then CO and HC conversion is improved, but saturated and aromatic hydrocarbons become difficult to oxidize
Solution Approach 1:
The patent utilizes multiple oxidation states of platinum (0, +2, +4) on the cerium oxide support, which creates a range of active sites with different oxidation potentials, enabling effective oxidation of both easy-to-oxidize CO and difficult-to-oxidize saturated and aromatic hydrocarbons at low temperatures
3Reliability
If cerium oxide is used as carrier material for precious metals, then catalytic activity is enhanced, but the light-off temperature for CO and HC increases
Solution Approach 1:
The patent optimizes the oxidation state distribution of platinum (states 0, +2, and +4) on the cerium oxide support, which balances the enhancement of catalytic activity with the maintenance of low light-off temperature by creating synergistic interactions between the metal and support
4Stability of the object's composition
If platinum is supported on refractory carrier materials, then catalyst stability is improved, but the amount of precious metal required increases
Solution Approach 1:
The patent uses cerium oxide as a refractory support material with high surface area and porous structure, which provides extensive active sites for platinum dispersion, thereby improving catalyst stability and reducing the total quantity of precious metal required compared to conventional supports
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 effectively lowers the CO light-off temperature and maintains catalytic activity by optimizing the catalyst composition and regeneration process, ensuring efficient conversion of carbon monoxide and hydrocarbons even at low temperatures.
Implementation Method 1
Oxidation catalysts for removing the harmful gases carbon monoxide (CO) and hydrocarbons (HC) from the exhaust gas of diesel and other lean-burn internal combustion engines are well known from the prior art and are based predominantly on platinum and aluminum oxide
Implementation Method 2
They use the oxygen present in large quantities in the diesel exhaust to oxidize the harmful gases mentioned to carbon dioxide (CO2) and water vapor
Implementation Method 3
Under lean exhaust gas conditions, the precious metal can be present in oxidation states > 0, particularly through oxidation with NO2
Implementation Method 4
If the additional noble metal (iii) is deposited on a carrier different from pure cerium oxide according to (ii)
Implementation Method 5
They use the oxygen present in large quantities in the diesel exhaust to oxidize the harmful gases mentioned to carbon dioxide (CO2) and water vapor
Data Source
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AI summary
The invention relates to a method for removing carbon monoxide and hydrocarbons from the exhaust gas of lean-burn internal combustion engines, said exhaust gas being passed over a catalyst which contains platinum supported on one or more refractory supporting materials, pure cerium oxide, and optionally an additional noble metal selected from the group consisting of platinum, palladium, and rhodium, said pure cerium oxide being in close contact with the noble metal. The catalytic activity is regenerated using rich exhaust gas under lean conditions after a threshold temperature load is exceeded.