Fluorided Silica Catalyst for Olefin Polymerization
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Solution Overview
Problem
There is a need for new and improved catalyst systems for olefin polymerization to achieve increased activity, specific polymer properties such as high melting point, high molecular weights, and altered comonomer distribution without compromising polymer properties.
Innovation Solution
A catalyst system comprising a fluorided silica support, an alkylalumoxane activator, and a bridged monocyclopentadienyl group 4 transition metal compound, where the fluorided support has not been calcined at temperatures of 400° C. or more, is used for ethylene polymerization, along with a metallocene catalyst represented by the formula TyCpmMGnXq, where Cp is a cyclopentadienyl group, M is a group 4 transition metal, and X is a leaving group.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the fluorided support is calcined at high temperatures (400°C or more), then the catalyst activity increases, but the polymer molecular weight decreases and molecular weight distribution worsens
Solution Approach 1:
The patent applies parameter changes by controlling the calcination temperature of the fluorided support to be below 400°C, specifically within the range of 20-350°C. This temperature parameter modification allows the catalyst to maintain adequate activity while preserving the integrity of polymer chains, thereby achieving both good catalyst activity and high molecular weight polymers with narrow molecular weight distribution.
2Productivity
If conventional metallocene catalysts are used, then polymerization activity is achieved, but specific polymer properties such as high melting point and high molecular weight cannot be simultaneously obtained
Solution Approach 1:
The patent employs composite materials by combining a fluorided support (silica modified with fluorine compounds) with a bridged monocyclopentadienyl group 4 transition metal compound. This composite catalyst system integrates the high surface area and fluorine-modified properties of the support with the specific catalytic activity of the metallocene, enabling simultaneous achievement of high polymerization activity and superior polymer properties including high melting point and high molecular weight.
Solution Approach 2:
The patent applies local quality by using a bridged monocyclopentadienyl structure with specific ligand arrangements on the group 4 transition metal. The localized structural features of the metallocene catalyst, including the bridging group and cyclopentadienyl substituents, create specific active sites that control polymerization stereochemistry and chain growth, thereby achieving specific polymer properties such as high isotacticity and high molecular weight alongside high activity.
3Quantity of substance
If the catalyst system is modified to achieve high molecular weight polymers, then molecular weight increases, but comonomer incorporation and melting point are compromised
Solution Approach 1:
The patent applies parameter changes by optimizing the fluorine content on the support (0.1-5.0 mmol F/g support), the type of bridging group, and the cyclopentadienyl substituents. These parameter modifications create a catalyst system that maintains high molecular weight polymer production while simultaneously achieving good comonomer incorporation and high melting points through controlled chain growth and stereoregularity.
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 catalyst system produces polymers with improved molecular weight distribution and comonomer incorporation, achieving high melting points and specific properties while maintaining polymer quality.
Implementation Method 1
A catalyst system comprising a fluorided silica support, an alkylalumoxane activator, and a bridged monocyclopentadienyl group 4 transition metal compound is used for ethylene polymerization
Data Source
AI summary
This invention relates to a catalyst system including fluorided silica, alkylalumoxane activator and a bridged monocyclopentadienyl group 4 transition metal compound, where the fluorided support has not been calcined at a temperature of 400° C. or more, and is preferably, produced using a wet mix method, particularly an aqueous method.