Multi-Catalyst Olefin Polymerization for Multimodal Molecular Weight Control
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Solution Overview
Problem
Existing catalyst systems for olefin polymerization struggle to produce polymers with high molecular weights and narrow molecular weight distribution efficiently.
Innovation Solution
A catalyst system combining constrained geometry metal-ligand complexes (CGC) and phosphinimine complexes (PN) is used to tailor the molecular weight of polyethylene resin production by adjusting hydrogen levels, leveraging the sensitivity of PN catalysts to hydrogen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single catalyst system is used for olefin polymerization, then the process is simple, but the molecular weight distribution is broad and efficiency is limited
Solution Approach 1:
The patent divides the polymerization process into multiple segments by using separate catalyst systems (CGC catalyst and PN catalyst) that each produce polymer with distinct molecular weight characteristics. The CGC catalyst produces high molecular weight polymer while the PN catalyst produces lower molecular weight polymer, creating a multimodal distribution that combines the advantages of both segments.
Solution Approach 2:
The patent merges two different catalyst systems (CGC and PN catalysts) into a single polymerization process to achieve combined benefits. By combining these catalysts in one reactor or in series, the system produces a multimodal polymer distribution that achieves both high productivity and improved molecular weight characteristics that neither catalyst could achieve alone.
2Manufacturing precision
If high molecular weight polymer is produced, then the polymer quality is improved, but the polymerization efficiency decreases
Solution Approach 1:
The patent segments the molecular weight production by assigning different catalysts to different molecular weight ranges. The CGC catalyst is optimized for high molecular weight polymer production while the PN catalyst produces lower molecular weight polymer, allowing both high quality and high efficiency to be achieved in the same process.
Solution Approach 2:
The patent changes the parameter of molecular weight by adjusting hydrogen levels, which differentially affect the two catalyst systems. Since PN catalyst molecular weight is more sensitive to hydrogen than CGC catalyst, varying hydrogen concentration allows dynamic control over the molecular weight split and overall polymerization efficiency.
3Manufacturing precision
If hydrogen levels are increased to control molecular weight, then molecular weight is reduced, but the effect on PN catalyst is too significant causing loss of control
Solution Approach 1:
The patent utilizes parameter changes (hydrogen concentration) to control molecular weight while leveraging the differential sensitivity of the two catalysts. By adjusting hydrogen levels, the system can fine-tune the molecular weight of PN-catalyzed polymer without completely dominating the CGC catalyst response, maintaining process flexibility and control.
Solution Approach 2:
The patent applies local quality by having different catalysts respond differently to the same hydrogen concentration. The CGC catalyst maintains relatively stable molecular weight across a range of hydrogen levels while the PN catalyst responds more sensitively, allowing localized control over different portions of the molecular weight distribution through a single parameter adjustment.
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
This approach allows for the production of multimodal polyethylene resin with tailored molecular weights, enhancing the efficiency and flexibility of polymerization processes.
Implementation Method 1
The catalyst comprises two or more catalysts, at least one of which is derived from constrained geometry procatalyst according to formula (I) and at least one of which is derived from phosphinimine procatalyst according to formula (V)
Implementation Method 2
The amount of hydrogen gas may be adjusted to tailor the molecular weight of the polyolefin
Data Source
AI summary
This disclosure is directed to processes of polymerizing olefin monomers to produce polyolefin. The processes include reacting ethylene and optionally one or more olefin monomers in one or multiple reactors in the presence of a catalyst system. The catalyst system includes two or more catalysts, at least one of which is derived from constrained geometry procatalyst according to formula (I) and at least one of which is derived from phosphinimine procatalyst according to formula (V): (I) (V).