Copper-Containing MOZ Zeolite for Low-Temperature SCR
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Solution Overview
Problem
Current SCR catalysts face challenges in achieving high selectivity, activity, and hydrothermal stability, especially at low temperatures and in harsh engine conditions, for the reduction of nitrogen oxides using ammonia.
Innovation Solution
Development of copper-containing MOZ-type zeolites with a specific framework structure and copper content, synthesized using a method involving potassium hydroxide, silica sources, and structure-directing agents like diquat, which enhances low-temperature activity and hydrothermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional SCR catalysts are used, then NOx reduction is achieved, but low-temperature activity and hydrothermal stability are insufficient
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating copper ions into the MOZ-type zeolite framework at specific concentrations (0.1-12.5 wt% CuO), which fundamentally alters the catalyst's temperature-activity profile and hydrothermal stability. This parameter change enables high activity at low temperatures while maintaining stability under hydrothermal conditions.
Solution Approach 2:
The invention creates a composite material system by combining copper ions with the MOZ-type zeolite framework. This composite structure integrates the benefits of both components: the zeolite provides structural stability and hydrothermal resistance, while the copper species provide high low-temperature catalytic activity for NOx reduction.
2Productivity
If copper content is increased to improve low-temperature activity, then N2O formation increases as a harmful side reaction
Solution Approach 1:
The patent optimizes the copper content parameter within a specific range (0.1-12.5 wt% CuO) to achieve the desired balance. By precisely controlling this parameter, the catalyst maintains high low-temperature activity while suppressing the side reaction that produces N2O, thus resolving the contradiction between productivity and harmful emissions.
3Productivity
If zeolite structure is modified to enhance activity, then selectivity and stability may be compromised
Solution Approach 1:
The patent applies local quality modification by introducing copper ions specifically into the MOZ-type zeolite framework at controlled concentrations. This localized modification enhances catalytic activity at the active sites without compromising the overall zeolite structure, thereby maintaining both selectivity for N2 production and hydrothermal stability.
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 copper-containing MOZ-type zeolites demonstrate excellent NH3-SCR performance with high N2 selectivity and stability across a broad temperature range, even after hydrothermal aging, with low N2O formation.
Implementation Method 1
copper-containing MOZ-type catalyst, wherein the zeolite contains 0.1 to 12.5 wt. % copper oxide... the NOx molecules are catalytically reduced to N2 using NH3 reducing agent
Implementation Method 2
Zeolites are highly porous crystalline aluminosilicate materials with uniform pores and channels of molecular dimensions... Zeolites play an important role as catalysts in the NH3—SCR reaction
Data Source
AI summary
The present invention relates to crystalline aluminosilicate comprising a MOZ framework type material. The MOZ framework type material comprises between 0.1 and 12.5 wt-% of copper, calculated as CuO, and one or more alkali and alkaline earth metal cations in an amount of 0.3 to 9 wt.-%, calculated as pure metals. The process for making the copper containing MOZ type zeolites comprises a) preparing a first aqueous reaction mixture comprising a silica source and potassium hydroxide, b) preparing a second reaction mixture comprising an alumina source, potassium hydroxide and a structure-directing agent selected from N,N-1,4-dimethyl-1,4-diazabicyclo-[2.2.2]octane difluoride, dichloride, dibromide, diiodide or dihydroxide, c) combining the two aqueous reaction mixtures, d) aging the combined reaction mixtures, e) heating the combined reaction mixtures, e) recovering, washing and drying the zeolite obtained thereof, g) calcining the zeolite, f) introducing copper, and i) washing and drying the copper containing MOZ type zeolite. Furthermore, the present invention discloses a washcoat comprising the copper containing MOZ framework type material, an SCR catalyst comprising said copper containing MOZ framework type material, and an exhaust gas purification system containing said SCR catalyst.