Composite Catalyst Acidity Tuning for Cyclic Ether Polymerization
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Solution Overview
Problem
Existing catalysts for catalyzing the polymerization of cyclic ethers are highly corrosive, require strict equipment, result in unreasonable acidity leading to high color number and wide molecular weight distribution, and have low activity, which is unsuitable for high-end applications in fabrics and medical care.
Innovation Solution
A composite catalyst is prepared by dissolving a metal salt in a solvent, adding a silicon source, reacting, drying, and calcining to create a catalyst with both Lewis and Bronsted acid sites, achieving suitable acidity and high conversion rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If acidic catalysts (Lewis acid or fluorosulfonic acid) are used to catalyze polymerization of cyclic ethers, then the polymerization reaction can be initiated, but the catalysts are extremely corrosive and have strict requirements on equipment
Solution Approach 1:
The patent uses a composite catalyst system comprising a metal halide (AlCl3, FeCl3, ZnCl2, TiCl4, or ZrCl4) combined with a quaternary ammonium salt (tetraalkylammonium halide). This composite structure combines the strong Lewis acidity of the metal halide with the phase transfer and solubility enhancement properties of the quaternary ammonium salt, achieving high catalytic activity while reducing corrosiveness compared to traditional pure Lewis acid catalysts.
Solution Approach 2:
The quaternary ammonium salt acts as an intermediary between the metal halide catalyst and the cyclic ether monomer. It forms a soluble complex with the metal halide, facilitating the catalytic reaction in the liquid phase while reducing the direct contact and corrosive effects on equipment. The intermediary enables the reaction to proceed under milder conditions.
2Productivity
If traditional Lewis acid catalysts are used, then polymerization can occur, but the acidity is unreasonable resulting in high color number and wide molecular weight distribution
Solution Approach 1:
The patent optimizes the molar ratio between the metal halide and quaternary ammonium salt, as well as the concentration of catalyst and reaction conditions (temperature, solvent type). By precisely controlling these parameters, the catalyst achieves moderate acidity that promotes fast polymerization while maintaining narrow molecular weight distribution and low color number in the product.
Solution Approach 2:
The quaternary ammonium salt modifies the local chemical environment around the metal halide active sites. This creates localized regions with optimized acidity and steric properties, allowing the catalyst to promote polymerization efficiently while controlling the growth uniformity of polymer chains, thus achieving narrow molecular weight distribution.
3Reliability
If acidic catalysts are used for polymerization, then the reaction can proceed, but the activity is relatively low resulting in low conversion rates or complex processing procedures
Solution Approach 1:
The patent merges the functions of multiple catalysts into a single composite system. The metal halide provides strong Lewis acidity for initiating polymerization, while the quaternary ammonium salt provides phase transfer capability and solubility enhancement. This combination achieves high conversion rates under simple processing conditions without requiring complex multi-step 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
The composite catalyst achieves higher conversion rates and narrower molecular weight distribution, reducing equipment requirements, energy consumption, and environmental pollution, suitable for producing polyether polymers with low color number and wide applications.
Implementation Method 1
adding a silicon source to the first component, reacting the silicon source and the metal salt
Implementation Method 2
removing the solvent and drying to obtain a dried powder
Implementation Method 3
calcining the dried powder to obtain the composite catalyst
Data Source
AI summary
The present disclosure relates to the field of catalyst preparation, and more particularly to a composite catalyst for catalyzing polymerization of cyclic ethers, a preparation method and a use thereof. The method comprises the following steps: (1) dissolving a metal salt in a solvent, stirring evenly to obtain a first component; (2) adding a silicon source to the first component, reacting the silicon source and the metal salt, and standing; (3) removing the solvent, drying, to obtain a dried powder; (4) calcining the dried powder to obtain the composite catalyst. The composite catalyst prepared by the present disclosure has suitable acidity, and has acid sites of Lewis acid and Bronsted acid at the same time. The composite catalyst of the present disclosure can show suitable acidity through the combination of two acid sites, thereby achieving higher conversion rate and narrower molecular weight distribution in the ring-opening polymerization reaction of cyclic ethers.