Intergrown AEI-CHA Molecular Sieves via Hydroxyphosphono Alkali
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Solution Overview
Problem
The synthesis of molecular sieves with intergrown phases of AEI and CHA topologies faces challenges such as uneven growth, irregular structure, and poor product consistency due to uneven distribution of dual templates, along with harsh synthesis conditions and complex processes, leading to low ion exchange efficiency and long catalyst preparation cycles.
Innovation Solution
The use of a hydroxyphosphono organic alkali compound as both a structure-directing agent and phosphorus source in the hydrothermal synthesis of molecular sieves, allowing for precise control of phosphorus content and avoiding caustic alkali, results in molecular sieves with improved uniformity and regular structure, and a simplified synthesis process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dual templates are used to direct the generation of CHA and AEI topologies, then molecular sieves with intergrown phases can be obtained, but uneven distribution of templates leads to uneven growth, irregular structure, and poor product consistency
Solution Approach 1:
The patent extracts and removes one of the two templates from the synthesis system, keeping only a single template that can direct the formation of both CHA and AEI topologies. This eliminates the distribution problem inherent in using dual templates, as there is now only one template to distribute uniformly throughout the reaction mixture, thereby improving product consistency while still achieving intergrown phase formation.
Solution Approach 2:
The single template used in the patent serves multiple functions: it acts as a structure-directing agent for both CHA and AEI topologies simultaneously, rather than requiring separate templates for each topology. This multi-functional template can direct the formation of different crystal structures within the same reaction system, achieving the intergrown phase structure without the complications of dual-template distribution.
2Productivity
If conventional synthesis methods are used, then molecular sieves can be produced, but harsh synthesis conditions and complex processes result in low ion exchange efficiency and long catalyst preparation cycles
Solution Approach 1:
The patent combines the synthesis of molecular sieves with the ion exchange process into a single integrated step. By incorporating ion-exchangeable cations into the template structure during synthesis, the molecular sieve framework and active metal species are formed simultaneously in one reaction process, eliminating the need for separate synthesis and ion exchange steps, thereby reducing process complexity and preparation time.
Solution Approach 2:
The patent performs the ion exchange action preliminarily during the synthesis stage itself, rather than as a subsequent separate step. The template is designed to include ion-exchangeable cations that will be exchanged for active metal species during or immediately after crystallization, preparing the catalyst in advance and reducing the overall preparation cycle time while simplifying the process flow.
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 approach enables the production of molecular sieves with intergrown AEI and CHA topologies that have enhanced activity and durability, with active ingredients uniformly distributed and tightly bound, suitable for large-scale production and applications in selective catalytic reduction and other catalytic technologies.
Implementation Method 1
H-type molecular sieves with intergrown phases of AEI and CHA topologies can be prepared through hydrothermal synthesis
Implementation Method 2
putting the sol-gel precursor into a closed hydrothermal synthesis reactor for isothermal hydrothermal reaction
Implementation Method 3
putting the sol-gel precursor into a closed hydrothermal synthesis reactor for isothermal hydrothermal reaction at 130°C.-220°C. for 6.5 h-48 h
Data Source
AI summary
The present disclosure provides molecular sieves with intergrown phases of AEI and CHA topologies and a catalyst thereof. A preparation method for the molecular sieves include the following steps: mixing a hydroxyphosphono organic alkali R with an aluminum source and a silicon source to obtain a sol-gel precursor, putting the sol-gel precursor into a closed hydrothermal synthesis reactor for reaction, filtering the reaction solution, washing, drying, and calcination to obtain the molecular sieves with intergrown phases of AEI and CHA topologies. The molecular sieves and the catalyst thereof can be directly synthesized under mild conditions with a hydroxyphosphono organic alkali as a structure-directing agent and a phosphorus source, have a pH value of 6-9 and low requirements for corrosion resistance of production devices, and are suitable for large-scale production.