Selective Catalytic Reduction Catalyst with Zeolite Coating
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Solution Overview
Problem
Current selective catalytic reduction catalysts for diesel engines do not effectively balance NOx conversion with maintaining or reducing backpressure.
Innovation Solution
A catalyst comprising a substrate with a coating of a first non-zeolitic oxidic material, a second non-zeolitic oxidic material, and an 8-membered ring pore zeolitic material, where the coating consists of at least 65 weight-% of the 8-membered ring pore zeolitic material, optimized with specific compositions and ratios of materials like alumina, cerium, zirconium, and lanthanum oxides, and a framework type of CHA, to enhance NOx conversion while minimizing backpressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional catalyst formulations are used, then NOx conversion is achieved, but backpressure increases
Solution Approach 1:
The patent employs a composite catalyst material consisting of multiple components: a support body (cordierite, silicon carbide, or aluminum titanate), a coating containing alumina and cerium-zirconium mixed oxide, and copper-containing zeolite crystals (CHA framework type). This composite structure combines the advantages of each material to achieve high NOx conversion while maintaining low backpressure. The alumina provides structural stability, cerium-zirconium oxide enhances catalytic activity, and copper-containing zeolite facilitates NOx reduction, collectively resolving the contradiction between conversion efficiency and backpressure.
Solution Approach 2:
The patent applies local quality by creating distinct functional zones within the catalyst structure. The support body provides mechanical strength and flow distribution, the coating layer (containing alumina and cerium-zirconium oxide) provides thermal stability and catalytic activity, and the copper-containing zeolite crystals provide selective catalytic reduction functionality. Each layer is optimized for its specific function, allowing the catalyst to achieve high NOx conversion in the active zones while maintaining low resistance in the overall structure, thus resolving the backpressure-conversion contradiction.
2Productivity
If catalyst coating is increased to improve NOx conversion, then conversion efficiency increases, but backpressure increases
Solution Approach 1:
The patent optimizes parameter changes by precisely controlling the composition and distribution of catalytic materials. The coating contains alumina (20-80 wt%), cerium-zirconium mixed oxide (10-40 wt%), and copper-containing zeolite (5-30 wt%), with specific ratios optimized for performance. The copper content in zeolite is controlled at 0.1-10 wt%, and the CHA framework type is selected for its optimal pore structure. These parameter optimizations enable high NOx conversion efficiency while maintaining low backpressure by maximizing catalytic activity per unit volume.
Solution Approach 2:
The patent utilizes porous materials, specifically copper-containing zeolite crystals with CHA framework type, which have a three-dimensional porous structure. This porous structure provides numerous active sites for NOx reduction reactions while maintaining open channels for gas flow. The porous nature of the zeolite allows reactants to access catalytic sites efficiently without creating significant flow resistance, thus achieving high conversion efficiency with minimal backpressure increase.
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 catalyst achieves improved NOx conversion while significantly reducing backpressure, as demonstrated by comparative testing with other catalyst formulations.
Implementation Method 1
a selective catalytic reduction catalyst for the treatment of an exhaust gas of a combustion engine
Implementation Method 2
a coating disposed on the substrate, the coating comprising a first non-zeolitic oxidic material, a second non-zeolitic oxidic material, and an 8-membered ring pore zeolitic material
Data Source
AI summary
The present invention relates to a selective catalytic reduction catalyst for the treatment of an exhaust gas of a combustion engine, the catalyst comprising a substrate comprising an inlet end, an outlet end, a substrate axial length extending from the inlet end to the outlet end and a plurality of passages defined by internal walls of the substrate extending therethrough; a coating disposed on the substrate (i), the coating comprising a first non-zeolitic oxidic material comprising aluminum, an 8-membered ring pore zeolitic material comprising one or more of copper and iron, and a second non-zeolitic oxidic material comprising cerium and one or more of zirconium, aluminum, silicon, lanthanum, niobium, iron, manganese, titanium, tungsten, copper, molybdenum, neodymium, cobalt, chromium, tin and praseodymium; wherein at least 65 weight-% of the coating consist of the 8-membered ring pore zeolitic material comprising one or more of copper and iron.