H2-SCR Catalyst Zoning for Low-Temperature NOx Reduction

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Solution Overview

Problem

Current NOx reduction technologies for diesel engine exhausts, such as SCR and LNT, are inefficient at cold start temperatures below 150°C and vulnerable to sulfur poisoning, making it challenging to meet stringent emission regulations as engine exhaust temperatures decrease.

Innovation Solution

An emission treatment system incorporating a hydrogen generator and a catalytic article with a zoned, layered, or intermingled catalytic coating comprising H2-SCR and DOC compositions, along with a low temperature NOx adsorbent, to effectively reduce NOx emissions across a wide temperature range.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional SCR or LNT technologies are used for NOx reduction, then high NOx conversion efficiency is achieved at temperatures of 200°C or higher, but efficiency drops significantly at cold start temperatures below 150°C

Engineering Contradiction:

ImproveNOx conversion efficiencyVSAvoidoperating temperature range

Core Design Contradiction:

ProductivityVSTemperature

Solution Approach 1:

The patent applies local quality by creating zoned catalytic coatings with different compositions in different spatial locations along the exhaust flow path. The upstream zone contains H2-SCR catalyst for low-temperature operation, while downstream zones contain traditional SCR/LNT catalysts for high-temperature operation, allowing the single device to deliver high conversion efficiency across the entire temperature range.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses composite materials by combining H2-SCR catalyst composition with traditional SCR/LNT catalyst compositions in a zoned architecture. This composite approach integrates the low-temperature activity of H2-SCR with the high-temperature performance of conventional catalysts, achieving broad-spectrum effectiveness from cold start through warm-up operations.

Inventive Principle:

Principle #40Composite materials

2Reliability

If conventional SCR or LNT technologies are deployed, then effective NOx control is achieved, but the systems are vulnerable to sulfur poisoning

Engineering Contradiction:

Improvesulfur toleranceVSAvoidsulfur poisoning susceptibility

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by positioning the H2-SCR catalyst in the upstream zone to first treat the exhaust stream and remove sulfur compounds before the exhaust reaches the downstream SCR/LNT catalysts. This protective预处理 prevents sulfur from poisoning the more sensitive downstream catalysts, enhancing overall system reliability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the harmful effect of sulfur by using the H2-SCR catalyst to selectively remove sulfur compounds from the exhaust stream, transforming sulfur from a poison that deactivates catalysts into a removed contaminant. This protects the downstream catalysts and maintains long-term system reliability.

Inventive Principle:

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

3Productivity

If engine exhaust temperatures decrease to meet emission standards, then compliance with stringent regulations is achieved, but NOx reduction efficiency of conventional technologies deteriorates

Engineering Contradiction:

ImproveNOx reduction efficiencyVSAvoidexhaust temperature

Core Design Contradiction:

ProductivityVSTemperature

Solution Approach 1:

The patent applies parameter changes by utilizing the H2-SCR catalyst's ability to operate effectively at lower temperatures where conventional catalysts fail. By changing the catalytic chemistry from traditional ammonia-based SCR to hydrogen-based SCR, the system maintains high NOx reduction efficiency even when exhaust temperatures decrease to meet emission standards.

Inventive Principle:

Principle #35Parameter changes

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 achieves significant NOx reduction, up to 90% or more, even at low temperatures, while being more sulfur tolerant, thus meeting stringent emission standards.

Implementation Method 1

selectively reducing NOx compounds... H2-SCR catalyst composition

Methodology Applied

Scientific EffectCatalytic reduction: Catalysis

Implementation Method 2

diesel oxidation catalyst (DOC) composition... convert certain or all of these exhaust components to innocuous components

Methodology Applied

Scientific EffectCatalytic oxidation: Catalysis

Implementation Method 3

catalysts may adsorb NOx during the warm-up period and thermally desorb NOx at higher exhaust temperatures

Methodology Applied

Scientific EffectAdsorption: Adsorption

Implementation Method 4

thermally desorb NOx at higher exhaust temperatures

Methodology Applied

Scientific EffectThermal desorption: Desorption

Data Source

PatentUS12071882B2Low temperature NOx reduction using H2-SCR for diesel vehicles

Publication Date: 2024.08.27 BASF MOBILE EMISSIONS CATALYSTS LLC

AI summary

Disclosed herein are emission treatment systems, articles, and methods for selectively reducing NOx compounds. The systems include a hydrogen generator, a hydrogen selective catalytic reduction (H2-SCR) article, and one or more of a diesel oxidation catalyst (DOC) and/or a lean NOx trap (LNT) and/or a low temperature NOx adsorber (LTNA). Certain articles may comprise a zone coated substrate and/or a layered coated substrate and/or an intermingled coated substrate of one or more of the H2-SCR and/or DOC and/or LNT and/or LTNA catalytic compositions.