Mixed Oxide NOx Adsorber for Low-Temperature Exhaust Treatment

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Solution Overview

Problem

Current exhaust gas treatment systems for internal combustion engines are inefficient in reducing NOx emissions during the cold start period, as they require high temperatures to operate effectively, leading to increased CO2 emissions and challenges in meeting stringent emission regulations.

Innovation Solution

A mixed oxide composition comprising manganese, aluminum, magnesium, and a rare earth element, specifically designed to adsorb NOx at low temperatures, which is integrated into an NOx adsorber and used in conjunction with catalyst components like SCR catalysts or particulate filters to enhance NOx removal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional SCR catalysts are used for NOx reduction, then high temperature NOx conversion efficiency is improved, but low temperature NOx removal capability deteriorates

Engineering Contradiction:

ImproveNOx conversion efficiencyVSAvoidoperating temperature range

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The exhaust treatment system is divided into two functional segments: a NOx adsorber for low temperature operation and an SCR catalyst for high temperature operation. This segmentation allows each component to optimize its performance in its respective temperature range, resolving the contradiction between low and high temperature NOx removal capabilities.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the operational parameters by introducing a dual-stage system where the NOx adsorber operates at low temperatures (below 200°C) and the SCR catalyst operates at high temperatures (above 200°C). This parameter-based division resolves the temperature range limitation of conventional single-stage SCR systems.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If heating strategies are used to achieve low temperature NOx storage and conversion, then low temperature NOx removal is improved, but CO2 emissions increase

Engineering Contradiction:

Improvelow temperature NOx removalVSAvoidCO2 emissions

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The NOx adsorber uses its own chemical adsorption properties to capture NOx at low temperatures without requiring external heating. The material self-performs the NOx storage function passively, eliminating the need for energy-intensive heating strategies and thereby reducing CO2 emissions.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The invention converts the naturally cold exhaust conditions (which were previously problematic for NOx removal) into a beneficial operating state for the NOx adsorber. The low temperature exhaust directly activates the adsorption mechanism, turning what was a limitation into an advantage and avoiding additional CO2-emitting heating measures.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If precious metals are used in NOx storage catalysts, then catalytic activity is improved, but manufacturing cost increases

Engineering Contradiction:

Improvecatalytic activityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The NOx adsorber uses inexpensive metal oxides (such as alkali metals, alkaline earth metals, or rare earth metals) instead of precious metals. These materials, while having shorter operational lifetimes compared to precious metals, provide sufficient catalytic activity for the adsorption function and significantly reduce manufacturing costs.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The invention employs composite material systems combining metal oxides with support structures (such as alumina, silica, or zeolites). This composite approach enhances the catalytic activity of the inexpensive metal oxide components, providing precious-metal-level performance at a fraction of the cost through synergistic material interactions.

Inventive Principle:

Principle #40Composite materials

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 mixed oxide composition effectively adsorbs and removes NOx at temperatures below 200°C, improving the efficiency of NOx reduction during cold start conditions without increasing CO2 emissions, thus meeting stricter emission standards.

Implementation Method 1

a mixed oxide composition comprising manganese, aluminum and/or magnesium, and a rare earth element... effectively adsorbs and removes NOx at temperatures below 200°C

Methodology Applied

Scientific EffectAdsorption: Adsorption

Data Source

PatentUS11458450B2Mixed oxide and its use as NOx adsorber

Publication Date: 2022.10.04 JOHNSON MATTHEY PLC

AI summary

The present disclosure is directed to a mixed oxide composition comprising manganese, aluminum and/or magnesium, and a rare earth element; a method of making the mixed oxide composition; a NOx adsorber comprising the mixed oxide composition; an exhaust system for internal combustion engines comprising the NOx adsorber; and a method for reducing NOx in an exhaust gas that employs the NOx adsorber.