Ziegler-Natta Catalyst Composition for Xylene Solubles Control
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Solution Overview
Problem
Existing Ziegler-Natta catalyst compositions for polyolefin polymers lack the ability to produce polymers over a broad range of xylene solubles content and require excessive amounts of internal electron donors, limiting their versatility and efficiency.
Innovation Solution
A catalyst composition is developed using a procatalyst subjected to multiple titanation steps with a titanium extractant to remove less active titanium species, incorporating a less bulky titanium extractant and internal electron donor to enhance stereoselectivity and reduce xylene solubles content, allowing production of polyolefin polymers with varied properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional Ziegler-Natta catalyst compositions are used, then catalyst activity is maintained, but the ability to produce polymers over a broad range of xylene solubles content is limited
Solution Approach 1:
The patent applies parameter changes by modifying the procatalyst preparation conditions, specifically using multiple titanation steps with controlled temperatures (e.g., first titanation at 25°C, second titanation at 80°C) and stoichiometries (Ti:Mg ratios from 0.01 to 0.1). These parameter changes enable the catalyst to produce polymers across a broad range of xylene solubles content (5-50%) without requiring excessive internal electron donors, thus resolving the contradiction between versatility and donor quantity.
Solution Approach 2:
The patent implements preliminary action by performing multiple titanation steps during procatalyst preparation to pre-establish the optimal catalyst structure before polymerization. The first titanation step introduces titanium species, followed by a second titanation step that further modifies the catalyst surface. This preliminary structuring enables the catalyst to achieve broad polymer property range with reduced internal electron donor requirements during actual polymerization.
2Manufacturing precision
If internal electron donors are increased to broaden polymer property range, then xylene solubles content control improves, but catalyst composition complexity and cost increase
Solution Approach 1:
The patent resolves this contradiction by changing the preparation parameters of the procatalyst itself rather than adding more complex catalyst components. By controlling titanation temperature, Ti:Mg stoichiometry, and using multiple titanation steps, the patent achieves precise xylene solubles content control (5-50% range) through simplified catalyst compositions with fewer and less bulky internal electron donors.
3Reliability
If less bulky titanium extractants are used, then stereoselectivity is enhanced, but the amount of titanium removed may be reduced
Solution Approach 1:
The patent applies preliminary action by performing multiple titanation steps that progressively build up the titanium content and structure on the magnesium support. The first titanation step establishes a baseline titanium layer, and the second titanation step adds additional titanium species. This staged approach ensures sufficient total titanium removal capability while allowing less bulky extractants to selectively remove specific titanium species that enhance stereoselectivity.
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 catalyst composition achieves increased stereoselectivity and produces polyolefin polymers with a broad range of xylene solubles content, from low to high, while reducing the amount of internal electron donors required, enhancing production flexibility and efficiency.
Implementation Method 1
the procatalyst is contacted with a titanium extractant during at least one titanation step or after the titanation steps
Data Source
AI summary
A Ziegler-Natta catalyst composition is disclosed. The catalyst composition is formed from a procatalyst containing a magnesium moiety and a titanium moiety. At least one internal electron donor is incorporated into the procatalyst. During a titanation procedure in conjunction with the internal electron donor, a titanium extractant is used to remove or deactivate low activity or atactic titanium active sites.