Fluoride-Free CHA Zeolite Synthesis for Scalable Olefin Production
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Solution Overview
Problem
Current methods for synthesizing high silica aluminosilicates with the CHA framework type face challenges such as the use of corrosive materials like hydrofluoric acid, expensive directing agents, and low water content, which are obstacles for commercial-scale production and process scalability.
Innovation Solution
A method for synthesizing crystalline materials with a CHA framework type molecular sieve using a reaction mixture free of fluoride ions, employing an inexpensive organic directing agent and high water content, allowing for the substitution of silicon with other tetravalent elements and aluminum with trivalent elements, and potentially including stacking faults or intergrown phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional methods are used to synthesize high silica aluminosilicates with CHA framework type, then the catalytic activity and selectivity are improved, but the use of corrosive materials like hydrofluoric acid and expensive directing agents increases manufacturing complexity and cost
Solution Approach 1:
The patent removes harmful fluoride ions from the synthesis process by using a fluoride-free reaction mixture. This extraction of the harmful component eliminates the need for corrosive hydrofluoric acid while maintaining the ability to produce high silica CHA framework molecular sieves with the required catalytic activity for OTO reactions.
Solution Approach 2:
The patent replaces expensive organic directing agents with inexpensive inorganic base catalysts such as sodium hydroxide, potassium hydroxide, or cesium hydroxide. These simple, cheap catalysts can be easily handled and disposed of, dramatically reducing manufacturing costs while still enabling the formation of the CHA framework structure.
2Manufacturing precision
If conventional synthesis methods with low water content are used, then the crystallization process is controlled, but the scalability and cost-effectiveness for commercial production are reduced
Solution Approach 1:
The patent fundamentally changes the water content parameter in the reaction mixture from low (conventional) to high (at least 20 mole ratios of H2O:YO2). This parameter change enables better heat and mass transfer, improves scalability for commercial production, and maintains crystallization control through the use of inorganic base catalysts that function effectively in high water content environments.
3Reliability
If high silica to alumina ratios are achieved through conventional methods, then the catalyst performance for OTO reactions is improved, but the synthesis becomes more complex and expensive
Solution Approach 1:
The patent uses inexpensive inorganic base catalysts (sodium hydroxide, potassium hydroxide, cesium hydroxide) instead of expensive organic directing agents to achieve high silica to alumina ratios (greater than 100:1). These simple, cheap catalysts enable the formation of the desired CHA framework structure with high silica content without requiring complex synthesis procedures.
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 high silica zeolites with improved scalability and cost-effectiveness, maintaining catalytic activity without the need for preliminary ion-exchange steps, and can produce olefins like ethylene and propylene efficiently.
Implementation Method 1
maintaining the reaction mixture under conditions sufficient to form crystals of the crystalline material
Implementation Method 2
an organic directing agent for directing the formation of a CHA framework type molecular sieve
Implementation Method 3
preparing a reaction mixture capable of forming the material, the reaction mixture comprising a source of water and a source of an oxide of a tetravalent element
Implementation Method 4
maintaining the reaction mixture under conditions sufficient to form crystals of the crystalline material
Implementation Method 5
their use in the conversion of oxygenates, particularly methanol, to olefins, particularly ethylene and propylene
Data Source
AI summary
A method is disclosed of synthesizing a crystalline material comprising a CHA framework type molecular sieve and having a composition involving the molar relationship:(n)X2O3:YO2,wherein X is a trivalent element; Y is a tetravalent element; and n is from 0 to less than 0.01. The method comprises preparing a reaction mixture capable of forming said material, said mixture comprising a source of water, a source of an oxide of a tetravalent element Y and optionally a source of an oxide of a trivalent element X, wherein the reaction mixture is substantially free of fluoride ions added as HF; maintaining the reaction mixture under conditions sufficient to form crystals of the crystalline material; and than recovering the crystalline material. The reaction mixture comprises either a specific directing agent for directing the formation of a CHA framework type molecular sieve and/or a H2O:YO2 molar ratio of greater than 20. In one embodiment, the resultant crystalline material is free of stacking faults and/or any intergrown phase with an AEI framework type molecular sieve.