Segmented Catalytic Wall-Flow Filter for NOx Conversion and Ammonia Slip Control

Solution Overview

Problem

Conventional emission treatment systems face challenges in achieving high NOx conversion and minimizing N2O formation across a wide temperature window while effectively removing ammonia slip, which is essential for reducing environmental impact and maintaining system integrity.

Innovation Solution

A catalytic wall-flow monolith design incorporating a first zone with a distributed SCR catalyst and a second zone with an ammonia oxidation catalyst, where the second SCR catalyst is either present as a coating or distributed throughout the porous substrate, enhancing NOx conversion and reducing N2O formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If an SCR catalyst is used to reduce NOx, then NOx conversion is improved, but ammonia slip increases which is harmful to the environment and can cause corrosion

Engineering Contradiction:

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The monolith is divided into two distinct zones: a first zone containing SCR catalyst for NOx reduction, and a second zone containing ammonia oxidation catalyst for ammonia removal. This segmentation allows each zone to perform its specific function optimally, achieving high NOx conversion while preventing ammonia slip.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The ammonia oxidation catalyst acts as an intermediary component that treats the excess ammonia produced by the SCR catalyst. By positioning this catalyst in the second zone, the system mediates the harmful effect of ammonia slip by converting it to nitrogen and water before discharge.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If more ammonia is added to maximize NOx conversion, then NOx reduction efficiency is improved, but ammonia slip and potential corrosion increase

Engineering Contradiction:

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The system converts the harmful ammonia slip into a beneficial outcome by using the ammonia oxidation catalyst to transform excess ammonia into nitrogen and water. This allows the system to use excess ammonia for complete NOx conversion while eliminating the harmful effects through the second zone's oxidation catalyst.

Inventive Principle:

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

3Device complexity

If a single-zone monolith design is used, then device complexity is reduced, but the ability to achieve high NOx conversion and minimize ammonia slip simultaneously is compromised

Engineering Contradiction:

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent merges two functional zones (SCR catalyst zone and ammonia oxidation catalyst zone) into a single integrated monolith structure. This combination achieves the performance benefits of separate systems while maintaining a compact, unified design that does not significantly increase overall complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The monolith serves multiple functions within a single component: the first zone performs NOx reduction via SCR catalysis, while the second zone performs ammonia oxidation. This multi-functionality allows the system to achieve both high NOx conversion and ammonia slip control in one integrated device.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 design improves NOx conversion and reduces N2O formation across a wide temperature range, maintaining similar ammonia conversion efficiency and minimizing ammonia slip, thus addressing environmental concerns and system durability.

Implementation Method 1

a first SCR catalyst distributed throughout the porous substrate

Methodology Applied

Scientific EffectSelective catalytic reduction: Catalysis

Implementation Method 2

an ammonia oxidation catalyst distributed throughout the porous substrate

Methodology Applied

Scientific EffectCatalytic oxidation: Catalysis

Data Source

PatentUS10369555B2Catalytic wall-flow filter with an ammonia slip catalyst

Publication Date: 2019.08.06

AI summary

A catalytic wall-flow monolith filter for use in an emission treatment system comprises a wall flow monolith comprising a porous substrate having surfaces that define the channels and having a first zone extending in the longitudinal direction from a first end face towards a second end face for a distance less than the filter length and a second zone extending in the longitudinal direction from the second end face towards the first end face and extending in the longitudinal direction for a distance less than the filter length, wherein a first SCR catalyst is distributed throughout the first zone of the porous substrate, an ammonia oxidation catalyst is distributed throughout the second zone of the porous substrate and a second SCR catalyst is located in a layer that covers the surfaces in the second zone of the porous substrate.