Cu-CHA Zeolite Direct Synthesis via Cu-Polyamine OSDA
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Solution Overview
Problem
Commercial Cu containing CHA zeolites for NOx abatement in automotive applications require high SCR activity at low exhaust temperatures, but existing direct synthesis methods are costly and inefficient due to the need for ammonium and Cu exchange steps, and often rely on expensive organic structure-directing agents or alkali in the synthesis process.
Innovation Solution
A direct synthesis method for Cu containing CHA zeolites is developed, which avoids alkali metal cations and uses a Cu-polyamine complex as the first organic structure-directing agent, along with N,N,N-trimethyl-1-adamantyl ammonium or trimethylbenzylammonium as the second OSDA, and tetramethyl ammonium or tetraethyl ammonium as the third OSDA, to produce a microporous crystalline material with a CHA structure and high SCR activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional ion exchange steps (ammonium exchange and Cu exchange) are used to produce Cu containing CHA zeolites, then the catalyst achieves required Cu content and structure, but the synthesis cost increases and efficiency decreases
Solution Approach 1:
The patent applies preliminary action by incorporating Cu ions into the zeolite framework during the synthesis stage rather than through subsequent ion exchange steps. The synthesis gel is formulated with Cu sources (CuCl2, Cu(NO3)2, or CuSO4) and alkali metal hydroxides to pre-establish Cu-containing CHA zeolite structure directly, eliminating the need for separate ammonium exchange and Cu exchange operations.
Solution Approach 2:
The patent merges multiple steps into one by combining the zeolite synthesis and Cu incorporation into a single hydrothermal treatment process. The reaction gel contains all necessary components (silica source, alumina source, Cu sources, alkali metal hydroxides, and water) that simultaneously form the CHA zeolite structure and incorporate Cu ions, replacing the traditional multi-step sequence of zeolite synthesis, ammonium exchange, and Cu exchange.
2Manufacturing precision
If traditional ion exchange steps are used to produce Cu containing CHA zeolites, then the catalyst achieves required Cu content and structure, but the synthesis cost increases
Solution Approach 1:
The patent applies preliminary action by incorporating Cu ions into the zeolite framework during the synthesis stage rather than through subsequent ion exchange steps. The synthesis gel is formulated with Cu sources (CuCl2, Cu(NO3)2, or CuSO4) and alkali metal hydroxides to pre-establish Cu-containing CHA zeolite structure directly, eliminating the need for separate ammonium exchange and Cu exchange operations.
Solution Approach 2:
The patent merges multiple steps into one by combining the zeolite synthesis and Cu incorporation into a single hydrothermal treatment process. The reaction gel contains all necessary components (silica source, alumina source, Cu sources, alkali metal hydroxides, and water) that simultaneously form the CHA zeolite structure and incorporate Cu ions, replacing the traditional multi-step sequence of zeolite synthesis, ammonium exchange, and Cu exchange.
3Productivity
If expensive organic structure-directing agents are used in direct synthesis methods, then Cu containing CHA zeolites can be produced directly, but the synthesis cost increases
Solution Approach 1:
The patent applies parameter changes by substituting expensive organic structure-directing agents with inorganic alkali metal hydroxides (KOH, NaOH, or LiOH) as the structure-directing component. This chemical parameter substitution maintains the ability to direct CHA zeolite formation while dramatically reducing material costs. The alkali metal hydroxides provide both the structural direction and the Cu incorporation function through a single additive.
4Manufacturing precision
If alkali is used in the synthesis process, then Cu containing CHA zeolites can be formed, but extra ion exchange steps are required to remove alkali
Solution Approach 1:
The patent applies the taking out principle by selectively removing only the alkali metal cations that remain after synthesis, while retaining the Cu ions that are incorporated into the zeolite framework. The synthesis uses alkali metal hydroxides to direct structure formation and incorporate Cu, then a selective ion exchange step removes excess alkali cations, preserving the Cu-containing active sites.
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 method results in Cu containing CHA zeolites with high SCR activity at low reaction temperatures, eliminating the need for additional exchange steps and reducing synthesis costs, while maintaining high catalytic performance comparable to or exceeding that of zeolites produced by prior art methods.
Implementation Method 1
heating the gel in a vessel at a temperature ranging from 80° C. to 250° C. to form a crystalline chabazite product
Implementation Method 2
contain Cu-polyamine complex (e.g. Cu-TEPA) as the first OSDA and Copper source
Implementation Method 3
contain N,N,N-trimethyl-1-adamantyl ammonium (TMAda+) or trimethylbenzylammonium (TMBA+) or N,N,N-dimethylethylcyclohexyl ammonium (DMECHA+) organic as the second OSDA
Implementation Method 4
heating the gel in a vessel at a temperature ranging from 80° C. to 250° C. to form a crystalline chabazite product
Implementation Method 5
heating the gel in a vessel at a temperature ranging from 80° C. to 250° C. to form a crystalline chabazite product
Implementation Method 6
calcining the product to produce an aluminosilicate zeolite having a CHA structure
Implementation Method 7
contacting exhaust gas, such as in the presence of ammonia or urea, with a zeolitic material comprising a copper containing CHA-type zeolite
Data Source
AI summary
A metal-containing chabazite zeolite, which has an FTIR peak area ratio between the peak at 900-1300 cm−1 (Si—O—Si asymmetric stretch) and the peak at 765-845 cm−1 (˜805 cm−1 is Si—O—Si symmetric stretch) of at least 55. A method for preparing metal-containing CHA zeolites with high SCR activity at low reaction temperatures from alkali cation-free reaction mixtures that contain the three OSDA structures: metal-polyamine, N,N,N-trimethyl-1-adamantyl ammonium (TMAda+) and TMAOH. The metal-containing CHA zeolites produced by the disclosed method can be identified by XRD, FTIR spectroscopy, FT-VIS spectroscopy, and scanning electron microscopy. A method of selective catalytic reduction of NOx in exhaust gas using the material described herein is also disclosed.