Zeolitic Material Surface Silicon Reduction for Olefin Selectivity
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Solution Overview
Problem
Existing zeolitic materials face limitations in catalytic performance due to high acid site density, pore size distribution, and crystal or particle size, which affect selectivity and production rates in processes like methanol to olefins conversion, with conventional methods struggling to reduce silicon content without increasing undesirable crystal structures or damaging the material.
Innovation Solution
A method involving contacting zeolitic materials with a modifying solution containing amines, alcoholamines, or amino acids to reduce surface silicon content, modify crystal structure, and adjust porosity, thereby altering the silicon to aluminum and phosphorous ratio and increasing porosity, while maintaining crystallinity and reducing intergrown impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If silicon content is reduced in SAPO materials prepared via conventional techniques, then light olefin selectivity is improved, but crystallization of intergrowth of undesirable crystal structures (AEI and/or AFI) increases
Solution Approach 1:
The patent changes the chemical composition parameters by reducing silicon content in SAPO materials while maintaining the desired CHA crystal structure. This is achieved through controlled synthesis conditions that prevent the formation of AEI and AFI intergrowths even at low silicon concentrations, thereby improving light olefin selectivity without compromising crystal structure purity
Solution Approach 2:
The patent applies local quality by creating specific compositional regions within the crystal structure where silicon distribution is optimized. By controlling the local silicon content and distribution within the CHA framework, the material achieves high olefin selectivity while preventing the nucleation and growth of undesirable AEI and AFI crystal phases
2Reliability
If zeolitic materials have a porous network comprising only micropores, then catalytic activity is limited by mass transfer, but production rates are limited and secondary reactions increase
Solution Approach 1:
The patent segments the pore structure into multiple levels by introducing mesopores alongside the existing micropore network. This hierarchical pore structure divides the mass transfer pathway into two stages: rapid transport through mesopores and selective reaction in micropores, thereby eliminating mass transfer limitations while maintaining high catalytic activity and preventing secondary reactions
Solution Approach 2:
The patent adds another dimension to the pore size distribution by incorporating mesopores (2-50 nm) in addition to micropores (<2 nm). This dimensional expansion of the pore hierarchy enables faster mass transfer through the larger mesoporous channels while preserving the shape selectivity and catalytic function of the microporous framework
3Reliability
If zeolitic materials have relatively large particles or crystals, then catalytic activity is limited by mass transfer, but production rates are limited and secondary reactions increase
Solution Approach 1:
The patent segments the crystal structure into smaller domains by creating a hierarchical pore network within the crystal. This internal segmentation allows reactants to access active sites more efficiently through the mesoporous channels, effectively reducing the diffusion path length and improving production rates without compromising the catalytic activity of the microporous regions
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 method effectively reduces surface silicon content, improves porosity, and modifies crystal size, leading to enhanced catalytic performance with increased light olefin selectivity and reduced secondary reactions, without significant loss in crystallinity or material damage.
Implementation Method 1
contacting the surface of the zeolitic material with a modifying solution comprising one or more of an amine, an alcoholamine, or an amino acid reduces an amount of silicon at the surface
Data Source
AI summary
Zeolitic materials with modified surface composition, crystal structure, crystal or particle size, and/or porosity, methods for making the same, and methods for converting oxygenates to olefins using the same are provided herein. In an exemplary embodiment, a method for reducing a surface silicon content of a silicon-containing zeolitic material is provided that includes providing a silicon-containing zeolitic material; and contacting the silicon-containing zeolitic material with a modifying solution comprising one or more of an amine, an alcoholamine, and an amino acid. In this embodiment, the contacting occurs under conditions suitable for the modifying solution to reduce a surface silicon content, increase the porosity, and/or decrease an average crystal or particle size of the silicon-containing zeolitic material.