Zinc-Modified MgTi Catalyst for Propylene Stereospecificity
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Solution Overview
Problem
Current catalysts for propylene polymerization, particularly those based on Mg, Ti, and internal electron donors, face challenges in achieving high stereospecificity without compromising activity, and alternatives to phthalates are needed due to health concerns and reduced performance.
Innovation Solution
A solid catalyst component comprising Ti, Mg, Zn, Cl, and an electron donor, with more than 50% of titanium atoms in the +4 valence state, and a Zn/Mg molar ratio ranging from 0.001 to 0.05, using specific Zn compounds and electron donors to enhance stereospecificity and activity balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the amount of electron donor compound in the catalyst is increased to improve stereospecificity, then the stereospecificity increases, but the polymerization activity decreases
Solution Approach 1:
The patent introduces zinc compounds as a new parameter (zinc content 0.1-3.0 wt%, Zn/Mg molar ratio 0.001-0.05) to modify the catalyst system. This parameter change allows achieving high stereosspecificity without the negative effect of reduced activity that occurs when simply increasing electron donor amount. The zinc compound acts as a modifier that changes the catalyst's electronic and geometric properties.
Solution Approach 2:
The patent creates a composite catalyst system combining MgCl2 support, titanium compounds, electron donor compounds, and zinc compounds. This composite approach (Mg-Zn-Ti system) synergistically combines the functions of each component: MgCl2 as support, Ti as active center, electron donor for stereosspecificity control, and Zn compound as activity-enhancing modifier, resolving the contradiction between stereosspecificity and activity.
2Object-affected harmful factors
If alternative electron donor compounds to phthalates are used to address health concerns, then health safety improves, but stereosspecificity and xylene insolubility decrease
Solution Approach 1:
The patent introduces zinc compounds as a new parameter to compensate for the loss of stereosspecificity when using safer alternative electron donors. By optimizing zinc content (0.1-3.0 wt%) and Zn/Mg molar ratio (0.001-0.05), the catalyst achieves high stereosspecificity with non-phthalate donors like esters, ethers, amines, silanes, or ketones.
Solution Approach 2:
The zinc compound acts as an intermediary that mediates between the electron donor compound and the titanium active center. It enhances the interaction between the alternative electron donor and Ti, compensating for the weaker stereosspecificity-inducing effect of non-phthalate donors while maintaining health safety.
3Productivity
If zinc content in the catalyst is increased to improve activity, then polymerization activity increases up to a point, but stereosspecificity dramatically decreases
Solution Approach 1:
The patent establishes optimal parameter ranges for zinc content (0.1-3.0 wt%) and Zn/Mg molar ratio (0.001-0.05) to simultaneously achieve high activity and stereosspecificity. This precise parameter control prevents the dramatic drop in stereosspecificity that occurs at higher zinc levels while maintaining the activity enhancement benefit.
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 catalysts exhibit improved stereospecificity and activity balance, producing propylene polymers with increased xylene insolubility and enhanced comonomer incorporation, while minimizing the xylene soluble fraction, suitable for various applications.
Implementation Method 1
Catalyst components for the polymerization of olefins, in particular propylene, comprising a Mg, Zn, Ti and halogen elements and at least an electron donor compound
Data Source
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AI summary
Catalyst components component for the (co)polymerization of olefins CH2=CHR, in which R is a hydrocarbyl radical with 1-12 carbon atoms, optionally in mixture with ethylene, comprising Ti, Mg, Zn, CI, and an electron donor compound characterized by the fact that more than 50% of the titanium atoms are in the +4 valence state, and that the amount of Zn ranges from 0.1 to 4% by weight based on then total weight of said solid catalyst component.