Cyclopenta[b]fluorenyl Catalyst for Ethylene Polymerization
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Solution Overview
Problem
Existing catalyst systems for ethylene polymerization, such as Ziegler-Natta and metallocene, face challenges in producing high-molecular weight polymers with uniform molecular weight distribution and composition, especially at high temperatures, and are not economically feasible for commercial use.
Innovation Solution
A transition metal compound with a cyclopenta[b]fluorenyl group linked to a Group 4 transition metal, allowing for easy induction of substituents that enhance solubility and performance, is used in combination with aluminum or boron compounds as cocatalysts to form a catalyst composition for ethylene homopolymerization and copolymerization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Ziegler-Natta catalyst system is used for ethylene polymerization, then high polymerization activity is achieved, but molecular weight distribution becomes broad and composition distribution becomes non-uniform
Solution Approach 1:
The patent changes the chemical structure parameters of the catalyst ligand from conventional metallocene cyclopentadienyl groups to cyclopenta[b]fluorenyl groups with specific substitution patterns. This structural parameter change creates a catalyst with enhanced electronic properties and steric environment, resulting in more uniform polymerization activity and narrower molecular weight distribution while maintaining high productivity
Solution Approach 2:
The patent creates a composite catalyst system combining Group 4 transition metal center with cyclopenta[b]fluorenymine ligand framework and silyl substituents. This composite structure integrates multiple functional elements: the transition metal provides catalytic activity, the fluorenymine framework provides structural rigidity and electronic control, and the silyl groups provide solubility and steric modulation, achieving both high activity and uniform product distribution
2Manufacturing precision
If metallocene catalytic system is used, then narrower molecular weight distribution is obtained, but high-molecular weight polymers cannot be obtained and polymerizing activity decreases at high temperature
Solution Approach 1:
The patent modifies the ligand parameters by introducing cyclopenta[b]fluorenymine structure with silyl substituents, changing the electronic density and steric environment around the metal center. This parameter optimization enables the catalyst to maintain high activity at elevated temperatures while producing narrow molecular weight distribution, overcoming the limitations of conventional metallocenes
Solution Approach 2:
The patent applies local quality modification by placing silyl substituents at specific positions (positions 2 and 7) on the cyclopenta[b]fluorenymine ligand. This localized substitution creates specific electronic and steric environments at the catalyst active site, enhancing temperature stability and molecular weight control without compromising overall catalytic activity
3Stability of the object's composition
If conventional metallocene compounds are used, then homogeneous catalyst activation is achieved, but β-dehydrogenation becomes predominant at high temperature leading to loss of polymerization activity
Solution Approach 1:
The patent changes the ligand parameters by replacing conventional cyclopentadienyl groups with cyclopenta[b]fluorenymine groups containing silyl substituents. This structural modification alters the electronic parameters and thermal stability of the catalyst complex, preventing β-dehydrogenation at high temperatures while maintaining homogeneous activation and reliable polymerization activity
Solution Approach 2:
The patent employs silyl-substituted cyclopenta[b]fluorenymine ligands that are designed to be thermally stable yet readily available through synthetic chemistry. These ligands provide temporary protection against thermal degradation during polymerization, ensuring catalyst reliability without requiring complex stabilization systems
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 high-efficiency and high-molecular weight ethylene-based polymers with narrow molecular weight distribution and improved reactivity, even at high temperatures, making it suitable for commercial production.
Implementation Method 1
a transition metal catalyst composition containing the same and having high catalytic activity for preparing an ethylene homopolymer or a copolymer of ethylene and one α-olefin
Implementation Method 2
having a structure where a Group 4 transition metal in the Periodic Table of Elements as a core metal is linked with a cyclopenta[b]fluorenymine group via an amido group substituted with a silyl group, a transition metal catalyst composition containing the transition metal compound as a primary catalyst and an aluminum compound, a boron compound, or a mixture thereof as cocatalyst
Data Source
AI summary
The present invention relates to a new transition metal compound based on cyclopenta[b]fluorenyl group, a transition metal catalyst composition containing the same and having high catalytic activity for preparing an ethylene homopolymer or a copolymer of ethylene and one α-olefin, a method of preparing an ethylene homopolymer or a copolymer of ethylene and α-olefin using the same, and the prepared ethylene homopolymer or the copolymer of ethylene and α-olefin.