Exhaust Purification Catalyst With Basic Layer For High Temperature NOx Reduction
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Solution Overview
Problem
The NOx purification rate of internal combustion engine exhaust systems decreases at high temperatures due to the degradation of NOx storage catalysts.
Innovation Solution
An exhaust purification system with a hydrocarbon feed valve and an exhaust purification catalyst, where precious metal catalysts on a basic surface react with hydrocarbons to maintain a high NOx purification rate, and a clogging degree detecting mechanism estimates the NOx purification rate by monitoring the hydrocarbon feed valve's nozzle opening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the temperature of the exhaust purification catalyst becomes high, then the catalytic activity increases, but the NOx purification rate falls
Solution Approach 1:
The patent changes the chemical composition parameters of the catalyst by incorporating a basic component (alkali metal or alkaline earth metal) alongside the precious metal catalyst. This compositional parameter change allows the catalyst to maintain high NOx purification rates even at elevated temperatures where conventional catalysts would degrade in performance.
Solution Approach 2:
The patent uses a composite catalyst structure combining a precious metal (Pt, Pd, or Rh) with a basic component (alkali or alkaline earth metal). This composite material approach creates synergistic effects where the basic component compensates for the temperature-induced deactivation of the precious metal, maintaining purification efficiency across a broader temperature range.
2Quantity of substance
If the feed period of hydrocarbons is lengthened to increase NOx storage amount, then the storage capacity increases, but the purification efficiency during release may be compromised
Solution Approach 1:
The patent implements periodic hydrocarbon injection cycles where the feed period is carefully controlled. During the injection period, hydrocarbons are supplied to reduce NOx; during the non-injection period, the catalyst stores NOx from the exhaust. This periodic action optimizes both storage capacity and purification efficiency by balancing the duration of hydrocarbon supply with the storage and release cycles.
Solution Approach 2:
The system dynamically adjusts the hydrocarbon feed period based on operating conditions to optimize the balance between NOx storage and purification. The control strategy modulates the injection timing and duration to match varying exhaust flow rates and NOx concentrations, ensuring both adequate storage capacity and high purification efficiency during release phases.
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 system maintains a high NOx purification rate even at high catalyst temperatures and allows for the estimation of NOx purification rate drops by detecting clogging in the hydrocarbon feed valve, ensuring efficient NOx reduction.
Implementation Method 1
an exhaust purification catalyst for reacting NOx contained in exhaust gas and referred hydrocarbons
Implementation Method 2
a basic exhaust gas flow surface part is formed around the precious metal catalyst
Data Source
AI summary
Inside of an engine exhaust passage, a hydrocarbon feed valve (15) and an exhaust purification catalyst (13) are arranged. On the exhaust purification catalyst (13), platinum Pt (51) is carried and a basic layer (53) is formed. The concentration of hydrocarbons which flows into the exhaust purification catalyst (13) is made to vibrate within a predetermined range of amplitude and within a predetermined range of period, whereby the NOx which is contained in the exhaust gas is reduced by the exhaust purification catalyst (13). A clogging degree detecting means is provided for detecting a degree of clogging of a nozzle opening of the hydrocarbon feed valve (15). The NOx purification rate is estimated from the degree of clogging of the nozzle opening of the hydrocarbon feed valve (15) which is detected.