Exhaust Gas Purification Catalyst Dummy Coating Layer
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Solution Overview
Problem
Exhaust gas purification catalysts degrade due to poisoning substances like phosphorus, calcium, and other additives from engine oil, which adhere to the catalyst coating layer, reducing the number of active centers and degrading purification performance.
Innovation Solution
A porous substrate with a catalyst coating layer and a dummy coating layer containing alumina, which acts as a trapping mechanism for poisoning substances, preventing them from adhering to the catalyst coating layer and maintaining the active centers' integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a catalyst coating layer with noble metal catalyst is used for exhaust gas purification, then the purification performance is improved, but the catalyst degrades due to poisoning substances adhering to the coating layer
Solution Approach 1:
The patent introduces a dummy coating layer as an intermediary between the exhaust gas and the catalyst coating layer. This dummy layer, containing alumina and/or OSC material but no noble metal catalyst, preferentially adsorbs poisoning substances (P, Ca, Pb, Zn, Mg) from the exhaust gas, preventing them from reaching and adhering to the catalyst coating layer. This mediator approach protects the noble metal catalyst while maintaining purification performance.
Solution Approach 2:
The patent segments the coating structure into two distinct functional layers: a catalyst coating layer containing noble metal catalyst for purification, and a dummy coating layer containing alumina and/or OSC material for poisoning substance trapping. This segmentation allows each layer to perform its specific function independently, with the dummy layer protecting the catalyst layer from degradation.
2Object-generated harmful factors
If the catalyst coating layer is made thinner to reduce pressure loss, then the flow resistance is reduced, but the catalyst has less capacity to resist poisoning substances
Solution Approach 1:
By segmenting the coating into catalyst layer and dummy layer, the patent allows the catalyst layer to remain thin for low pressure loss while the dummy layer provides the trapping function. The dummy coating layer occupies at least 10% of the total coating layer length, providing sufficient capacity to trap poisoning substances even when the catalyst layer is thin.
Solution Approach 2:
The dummy coating layer acts as an intermediary that absorbs the harmful effect of poisoning substances, allowing the thin catalyst layer to maintain its purification function without being overwhelmed by poisoning substances. The dummy layer's alumina and OSC materials provide the necessary trapping capacity.
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 dummy coating layer effectively prevents the adhesion of poisoning substances to the catalyst coating layer, maintaining the purification performance and improving the durability of the exhaust gas purification catalyst against exhaust gases containing these substances.
Implementation Method 1
the dummy coating layer can act as a trapping and removing mechanism for a poisoning substance contained in the exhaust gas. Thus, when the exhaust gas including a poisoning substance such as P and Ca, which is contained in an engine oil or other additives, reaches the exhaust gas purification catalyst, the poisoning substance is caused to adhere preferentially to the dummy coating layer.
Data Source
AI summary
Provided is an exhaust gas purification catalyst with excellent durability against exhaust gas including a poisoning substance. The exhaust gas purification catalyst includes a porous substrate, a catalyst coating layer formed on the porous substrate, and a dummy coating layer formed on the outermost surface of the catalyst coating layer. The catalyst coating layer has a carrier and a noble metal catalyst supported on the carrier. The dummy coating layer includes a carrier having at least alumina and does not include a noble metal catalyst. The dummy coating layer is formed to have a length which, from the end on the exhaust gas inlet side, is 10% to 70% of the entire length of the catalyst coating layer along the exhaust gas flow direction.