Copper Chabazite Molecular Sieve Preparation Process
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Solution Overview
Problem
The preparation of copper containing molecular sieves with the CHA structure for NOx conversion in SCR processes faces fluctuations in NOx conversion activity due to variations in synthesis conditions, leading to inconsistent catalytic performance across different experiments.
Innovation Solution
A process involving copper exchange via a wet state exchange method using a copper acetate solution with an initial concentration of 0.15 to 0.225 molar, a liquid to solid ratio of 4 to 8, and specific reaction conditions such as temperature, pH, and stirring, followed by washing and calcination, to stabilize the copper content and enhance NOx conversion activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper exchange is conducted via conventional wet state exchange methods, then copper loading is achieved, but NOx conversion activity fluctuates strongly due to variations in synthesis conditions
Solution Approach 1:
The patent applies parameter changes by optimizing the copper salt concentration to a specific range (0.15-0.225 M) and controlling the liquid-to-solid ratio (4-8), along with pH adjustment (3-5.5) and temperature (40-75°C) to achieve consistent copper loading and reliable NOx conversion activity across different batches
Solution Approach 2:
The patent implements feedback control by monitoring and adjusting synthesis parameters based on their influence on copper exchange efficiency, using the identified critical parameters (concentration, liquid-to-solid ratio, pH, temperature) to maintain consistent catalytic performance
2Quantity of substance
If multiple aqueous ion-exchanges are carried out to target 3 wt% Cu, then copper loading is achieved, but reaction conditions and details are not provided leading to reproducibility issues
Solution Approach 1:
The patent applies preliminary action by pre-defining and optimizing all critical synthesis parameters before conducting the copper exchange, including copper salt concentration (0.15-0.225 M), liquid-to-solid ratio (4-8), pH (3-5.5), and temperature (40-75°C), making the process easily reproducible without requiring iterative optimization
Solution Approach 2:
The patent changes the approach from multiple ion-exchanges to a single optimized exchange step with precisely controlled parameters, simplifying the manufacturing process while achieving the target copper content of 3 wt% with high reproducibility
3Ease of manufacture
If copper concentration in exchange solution is not controlled, then exchange process is simple, but NOx conversion activity fluctuates strongly from one experiment to another
Solution Approach 1:
The patent identifies copper salt concentration as a critical parameter and optimizes it to a specific range (0.15-0.225 M), along with other parameters like liquid-to-solid ratio (4-8) and pH (3-5.5), maintaining process simplicity while achieving reliable and consistent NOx conversion activity
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
This process minimizes fluctuations in NOx conversion activity and achieves an overall increase in NOx conversion efficiency, maintaining high activity at both low and high temperatures, as demonstrated by the presence of a peak in diffuse reflectance FT-IR spectroscopy at 1948 cm^-1 and stable SCR activity.
Implementation Method 1
copper exchange is conducted via wet state exchange and prior to potential coating
Implementation Method 2
a liquid copper solution is used wherein the initial concentration of copper is in the range of 0.15 to 0.225 molar using copper acetate as copper source
Implementation Method 3
followed by washing and calcination
Data Source
AI summary
Disclosed are processes for the preparation of copper containing molecular sieves with the CHA structure having a silica to alumina mole ratio greater than about 10, wherein the copper exchange step is conducted via wet state exchanged and prior to the coating step and wherein in the copper exchange step a liquid copper solution is used wherein the concentration of copper is in the range of about 0.001 to about 0.25 molar using copper acetate and/or an ammoniacal solution of copper ions as copper source. Catalysts made by the processes, catalyst systems and methods of treating exhaust gas with the molecular sieves and catalysts are also disclosed.