Group iii-halide or lanthanide-halide bis(phenylphenoxy) metal-ligand complexes
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Solution Overview
Problem
Existing catalyst systems for olefin polymerization, such as Group III bis-phenylphenoxy metal-ligand catalysts, react prematurely in feedlines due to their reactivity with ethylene, leading to fouling and inefficiencies in producing polymers with high molecular weights and narrow molecular weight distribution.
Innovation Solution
A chloro-scandium-bis(phenylphenoxyl) metal-ligand complex that becomes active only after replacing the chlorine atom with an alkyl group, allowing for high selectivity and efficiency in ethylene and α-olefin copolymerization reactions at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If Group III bis-phenylphenoxy metal-ligand catalysts are used for olefin polymerization, then high molecular weight polymers with narrow molecular weight distribution can be produced, but the catalyst reacts prematurely in feedlines causing fouling and inefficiencies
Solution Approach 1:
The catalyst is designed with a preliminary protective chlorine atom attached to the metal center that prevents premature activation. This preliminary action blocks the catalytic site during transport and storage, and only upon intentional activation (e.g., by adding an alkyl aluminum co-catalyst) does the chlorine leave and enable polymerization. This resolves the contradiction by maintaining stability during feedline transport while preserving the ability to produce high molecular weight polymers with narrow distribution when activated.
2Productivity
If the catalyst reactivity is increased to improve polymerization efficiency, then catalyst efficiency improves, but the catalyst reacts too early and causes fouling in the feedline
Solution Approach 1:
The catalyst employs parameter changes through the use of a chlorine atom with specific electronic and steric properties that modulate the metal center's reactivity. The chlorine atom acts as a temporary modifier that reduces reactivity during transport. When activated by alkyl aluminum compounds, the chlorine is displaced and the metal center's reactivity parameter increases to optimal levels for high-efficiency polymerization, thus resolving the contradiction between efficiency and fouling.
Solution Approach 2:
The chlorine atom serves as an intermediary that mediates between the stable precursor form and the active catalytic form. It temporarily occupies the coordination site, preventing premature reaction with ethylene in the feedline. Upon addition of alkyl aluminum co-catalyst, the chlorine is replaced and the true active species is generated, enabling high productivity without feedline fouling.
3Reliability
If a co-catalyst or activator is required to activate the catalyst, then premature reaction is prevented, but the catalyst system complexity increases
Solution Approach 1:
The stabilizing function traditionally performed by a separate co-catalyst or activator is merged into the catalyst structure itself through the chlorine atom attachment. The chlorine-modified metal complex is a single molecular entity that contains both the precursor and the protective element. This merging reduces system complexity while maintaining reliability, as the protection is intrinsic rather than requiring separate components.
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 metal-ligand complex achieves high catalyst efficiency and versatility in producing polymers with varying molecular weights, addressing the reactivity issues of previous catalysts and enhancing polymer production efficiency.
Implementation Method 1
a catalyst system comprising a metal-ligand complex according to formula (I) wherein M is scandium, yttrium, a lanthanide metal or an actinide metal having an oxidation state of +3
Data Source
AI summary
Embodiments of this disclosure are directed to catalyst systems comprising a metal-ligand complex according to formula (I).