Multi-Catalyst Olefin Polymerization for Multimodal Molecular Weight Control
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Solution Overview
Problem
Existing catalyst systems for olefin polymerization struggle to efficiently produce polymers with adjustable molecular weights, particularly in high-temperature solution processes, limiting the production of multimodal polyethylene resins.
Innovation Solution
A catalyst system combining bis-phenylphenoxy metal-ligand complexes and phosphinimine complexes is used, allowing for the production of multimodal polyethylene resin by adjusting hydrogen levels to tailor molecular weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single catalyst system is used for olefin polymerization, then the process is simple and easy to operate, but the ability to produce polymers with adjustable molecular weights is limited
Solution Approach 1:
The patent combines two different catalyst systems (chromium-based catalyst system and Ziegler-Natta catalyst system) into a single multifunctional catalyst system. This merging allows the system to produce polymers with different molecular weights simultaneously, achieving adjustable molecular weight distribution without requiring separate reactor systems or multiple catalyst systems operating independently.
Solution Approach 2:
The combined catalyst system is designed to perform multiple functions: it can produce both high molecular weight and low molecular weight polymer fractions using the same catalyst system. The chromium-based component provides activity for polymerization while the Ziegler-Natta component enables molecular weight control through hydrogen interaction, making the single system universal for producing multimodal polymer distributions.
2Manufacturing precision
If hydrogen level is increased to control molecular weight of PN catalyst polymer, then molecular weight can be tailored, but the sensitivity of PN catalyst to hydrogen increases
Solution Approach 1:
The patent applies local quality by having different regions of the catalyst system respond differently to hydrogen. The PN catalyst component is highly sensitive to hydrogen and controls molecular weight of its polymer fraction, while the BPP catalyst component remains relatively insensitive and maintains stable polymerization activity. This differential response allows precise molecular weight control without compromising overall catalyst stability.
Solution Approach 2:
The catalyst system is a composite of two different catalyst types (chromium-based and Ziegler-Natta) with different hydrogen sensitivities. This composite structure allows the system to benefit from both the molecular weight control capability of H2-sensitive PN catalysts and the stability of H2-insensitive BPP catalysts, achieving both precision and reliability.
3Productivity
If catalyst system is optimized for high temperature solution processes, then the process efficiency is improved, but the flexibility to produce multimodal polymers is reduced
Solution Approach 1:
The patent merges catalyst systems with different temperature responses into a single multifunctional system. The chromium-based catalyst operates effectively at high temperatures providing good process efficiency, while the Ziegler-Natta catalyst component maintains activity and molecular weight control capability at these temperatures. This combination enables multimodal polymer production without sacrificing process efficiency.
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 system enables precise control over molecular weight distribution, facilitating the production of multimodal polyethylene resin with enhanced flexibility and efficiency.
Implementation Method 1
reacting ethylene and optionally one or more olefin monomers in one reactor or multiple reactors in the presence of a catalyst system
Implementation Method 2
The PN catalysts is much more sensitive to hydrogen than is by BPP catalysts, thus the molecular weight of the polymer produce by the PN catalyst may be altered based on the amount of hydrogen in the reactor system
Data Source
AI summary
A process of polymerizing olefin monomers to produce polyolefin, the process comprising reacting ethylene and optionally one or more olefin monomers in one reactor or multiple reactors in the presence of a catalyst system; the catalyst comprises two or more catalysts, at least one of which is derived from bis-phenylphenoxy procatalysts according to formula (I) and at least one of which is derived from phosphinimine procatalyst according to formula (V).