Phosphorus-Modified AEI Zeolite Catalyst for NOx Reduction
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Solution Overview
Problem
AEI zeolites reported in the literature have unmodified acid sites with excessively high acid strength, leading to side reactions in hydrocarbon conversion catalysts, and require cyclic quaternary ammonium cations as structure-directing agents, which are not industrially distributed and result in low yield and productivity.
Innovation Solution
Incorporating phosphorus uniformly outside the AEI framework in AEI aluminosilicate zeolites, eliminating the need for cyclic quaternary ammonium cations and achieving appropriate acid strength, thereby enabling the production of AEI zeolites with improved catalytic applications and industrial viability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If AEI zeolite is used as a catalyst, then catalytic activity is achieved, but side reactions occur due to excessively high acid strength
Solution Approach 1:
The patent modifies the acid strength parameter of AEI zeolite by incorporating phosphorus elements and adjusting the SiO2/Al2O3 ratio to fall within specific ranges (10-35). This parameter optimization reduces excessive acid strength that causes side reactions while preserving sufficient catalytic activity for main reactions.
Solution Approach 2:
Phosphorus compounds are introduced as intermediary substances that modify the acid sites on the zeolite surface. These phosphorus species act as mediators between the highly acidic zeolite framework and the reactants, reducing the harmful acid strength while maintaining catalytic functionality.
2Shape
If cyclic quaternary ammonium cations are used as structure-directing agents, then AEI zeolite structure is formed, but industrial application becomes difficult due to limited availability
Solution Approach 1:
The patent uses conventional, readily available quaternary ammonium cations (such as tetraethylammonium, tetramethylammonium) as substitutes for the specialized cyclic quaternary ammonium cations. These alternative cations copy the structure-directing function while being commercially accessible and suitable for industrial production.
Solution Approach 2:
The invention replaces expensive, specialized cyclic quaternary ammonium cations with inexpensive, commonly available quaternary ammonium salts. These substitute cations perform the necessary structure-directing role temporarily during synthesis and can be easily removed, making the process economically viable for industrial application.
3Quantity of substance
If conventional AEI zeolite production methods are used, then zeolite is obtained, but yield and productivity remain low
Solution Approach 1:
The patent optimizes synthesis parameters including SiO2/Al2O3 ratio (10-35), phosphorus content (0.01-0.10 mol ratio to T-atoms), and crystallization conditions to significantly improve yield and productivity. These parameter adjustments enhance crystallization efficiency and reduce formation of by-products.
Solution Approach 2:
Phosphorus compounds serve as intermediaries that facilitate the crystallization process and improve yield. The phosphorus species promote orderly arrangement of framework atoms during crystallization, leading to higher productivity and reduced synthesis time.
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 modified AEI zeolites exhibit suitable acid strength for applications like lower olefin production, cracking, dewaxing, isomerization, and nitrogen oxide reduction, with increased yield and industrial feasibility, particularly as high-temperature nitrogen oxide reduction catalysts.
Implementation Method 1
uniformly including phosphorus outside the AEI framework in pores in AEI aluminosilicate zeolite is effective for changing the acid strength of the AEI aluminosilicate zeolite
Implementation Method 2
a method for reducing nitrogen oxide using the AEI aluminosilicate zeolite
Data Source
Figure 1(a)~2
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AI summary
Provided is AEI zeolite having a uniform acid strength of an appropriate degree. AEI zeolite comprising phosphorus, preferably AEI zeolite comprising phosphorus in the pores, and a method for producing AEI zeolite comprising a crystallization step of crystallizing a raw material mixture containing a tetraethylphosphonium cation.