STA-18 Zeolite Catalyst for NOx Reduction and Ammonia Oxidation
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Solution Overview
Problem
There is a need for new molecular sieves with minor structural changes that can enhance catalytic properties, particularly for treating exhaust gases from engines to meet regulatory requirements, as existing molecular sieves may not adequately improve catalytic activity despite minor structural modifications.
Innovation Solution
A calcined molecular sieve, STA-18C, with an SFW type framework containing phosphate, is developed using structure directing agents like 1,4-diazabicyclo[2.2.2]octane derivatives and lower alkyl amines, which is calcined to remove templates and form a distinct catalytically active composition suitable for treating exhaust gases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing molecular sieves undergo minor structural modifications, then structural variety is increased, but catalytic activity does not adequately improve
Solution Approach 1:
The patent applies parameter changes by systematically varying the structure directing agent (SDA) chain length (C6, C7, C8 dibromide compounds) and molecular configuration to achieve the desired SFW framework topology. By changing the SDA parameters, the patent successfully created STA-18 with enhanced catalytic properties for NOx reduction and ammonia oxidation, resolving the contradiction between structural variety and catalytic activity.
2Reliability
If new molecular sieve frameworks are developed, then catalytic properties are enhanced, but development complexity increases
Solution Approach 1:
The patent uses structure directing agents (SDAs) as intermediaries to guide the formation of the SFW framework. The SDAs (1,6-(1,4-diazabicyclo[2.2.2]octane)hexyl dibromide, 1,7-(1,4-diazabicyclo[2.2.2]octane)heptyl dibromide, or 1,8-(1,4-diazabicyclo[2.2.2]octane)octyl dibromide combined with lower alkyl amines) act as templates that direct the self-assembly of the molecular sieve framework, simplifying the development process while achieving enhanced catalytic properties.
3Manufacturing precision
If structure directing agents with longer chains are used, then framework formation is improved, but synthesis complexity increases
Solution Approach 1:
The patent systematically varies the SDA chain length parameter (C6, C7, C8 dibromide compounds) to optimize framework formation. By changing this single parameter while maintaining the core DABCO structure, the patent achieves different SFW framework configurations with enhanced catalytic activity, improving manufacturing precision without excessively increasing synthesis complexity.
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
STA-18C exhibits improved catalytic properties, effectively reducing NOx compounds and oxidizing ammonia, making it suitable for use in selective catalytic reduction and ammonia slip catalyst applications, thereby meeting stringent exhaust gas treatment requirements.
Implementation Method 1
STA-18C can be made by calcining STA-18AP (as-prepared) that contains structure directing agents. The structure directing agents are preferably a 1,4-diazabicyclo [2.2.2]octane derivative (SDA1) and a lower alkyl amine (SDA2).
Implementation Method 2
STA-18C can be made by calcining STA-18AP (as-prepared) that contains structure directing agents
Implementation Method 3
STA-18C exhibits improved catalytic properties, effectively reducing NOx compounds and oxidizing ammonia, making it suitable for use in selective catalytic reduction and ammonia slip catalyst applications
Implementation Method 4
STA-18C exhibits improved catalytic properties, effectively reducing NOx compounds and oxidizing ammonia
Data Source
AI summary
STA-18, a molecular sieve having a SFW structure and containing phosphorus in the framework, is described. STA-18AP (as prepared) can have a lower alkyl amine, such as trimethylamine, and one of 1,6-(1,4-diazabicyclo[2.2.2]octane)hexyl cations (from diDABCO-C6) or 1,7-(1,4-diazabicyclo[2.2.2]octane)heptyl cations (from diDABCO-C7) or 1,8-(1,4-diazabicyclo[2.2.2]octane)octyl cations (from diDABCO-C8) as SDAs. A lower alkyl ammonium hydroxide, such as tetrabutylammonium hydroxide, can be used as a pH modifier for making SAPO STA-18. A calcined product, STA-18C, formed from STA-18AP is also described. Methods of preparing STA-18AP, STA-18C and metal containing calcined counterparts of STA-18C are described along with methods of using STA-18C and metal containing calcined counterparts of STA-18C in a variety of processes, such as treating exhaust gases and converting methanol to olefins are described.