Mordenite Molecular Sieve Acid Site Modulation
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Solution Overview
Problem
Current methods for synthesizing mordenite molecular sieves do not allow for effective modulation of the location and distribution of B acid sites, which is crucial for specific catalytic reactions like dimethyl ether carbonylation.
Innovation Solution
A method involving the mixing of an aluminum source, silicon source, inorganic base, and specific additional reagents to form an initial mixture, followed by the addition of a seed crystal and crystallization under controlled temperature and pressure, allowing for the preferential location of B acid sites in the 8-membered ring 'side pocket', with the additional reagent matching the channel size to facilitate access and formation of active B acid sites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional synthesis methods are used to prepare mordenite molecular sieve, then the molecular sieve can be obtained, but the location and distribution of B acid sites cannot be effectively modulated
Solution Approach 1:
The patent introduces structure directing agents with specific spatial configurations that direct aluminum incorporation to particular locations within the mordenite framework. This creates non-uniform local composition with enriched B acid sites in specific channels (8-membered ring vs 12-membered ring), achieving spatially differentiated acid site distribution that enhances catalytic selectivity for specific reactions
Solution Approach 2:
The patent systematically varies synthesis parameters including Si/Al ratio, structure directing agent type and concentration, pH, temperature, and crystallization time to precisely control the location and distribution of B acid sites. By changing these parameters, the catalyst can be optimized for different catalytic applications, achieving both high manufacturing precision and adaptability
2Stability of the object's composition
If the 8-membered ring channel size is small, then the molecular sieve structure is stable, but reactant molecules cannot diffuse into the channel
Solution Approach 1:
The patent creates different acid site distributions in different channel types within the same molecular sieve structure. B acid sites are selectively enriched in either the 8-membered ring channels or 12-membered ring channels depending on synthesis conditions, allowing the catalyst to process different sized molecules in different channels while maintaining overall structural stability
Solution Approach 2:
The patent uses structure directing agents as intermediaries during synthesis that temporarily occupy specific channels and guide aluminum incorporation. These agents mediate the formation of B acid sites in specific locations, and can be removed after synthesis to leave accessible channels for reactant diffusion while maintaining the stable mordenite framework
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 method results in mordenite molecular sieves with high crystallinity and flexible modulation of B acid site distribution, achieving high conversion rates and selectivity in the carbonylation reaction of dimethyl ether, suitable for large-scale industrial production.
Implementation Method 1
crystallizing the initial gel B obtained in step b) at a temperature in a range from 120°C to 200°C under autogenous pressure for 12 hours to 240 hours
Data Source
Figure 1~2
Figure 3
AI summary
The present invention provides a method for synthesizing a mordenite (MOR) molecular sieve with a modulatable location and distribution of B acid sites, and a product thereof and the use thereof. More specifically, provided is a method for synthesizing a mordenite MOR molecular sieve with acid sites being preferentially located at an 8-membered ring "side pocket" in communication with a 12-membered ring pore channel in the presence or absence of an inorganic base. The method comprises introducing an additional reagent and an optional fluorinating reagent which have different structures and charge densities into a synthetic gel, and the B acid sites of the obtained MOR zeolite are preferentially located at an 8-membered ring "side pocket" in communication with a 12-membered ring pore channel. A catalyst product obtained by this method exhibits an excellent performance in terms of adsorption and catalysis. The synthesis method of the present invention is simple and has a broad industrial application prospect particularly being applied to catalysts for the carbonylation reaction of dimethyl ether.