Non-Cp Chromium Catalysts for Olefin Block Copolymers
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Solution Overview
Problem
Current chromium catalysts based on cyclopentadienyl, indenyl, and acenaphthenyl ligands have limited structure diversification, restricting their capability for tuning catalyst activity or selectivity, and none have been used with a chain shuttling agent and syndiotactic or isotactic olefin polymerization catalyst to produce olefin block copolymers effectively.
Innovation Solution
Development of non-cyclopentadienyl-based chromium-ligand complexes that can participate in polymeryl chain exchange reactions with a chain shuttling agent and syndiotactic or isotactic olefin polymerization catalysts, enabling the production of olefin block copolymers with a partially chain-straightened polyolefin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If cyclopentadienyl-based chromium catalysts are used, then catalyst activity is maintained, but structure diversification is limited and capability for tuning catalyst activity or selectivity is restricted
Solution Approach 1:
The invention segments the catalyst design by separating the chromium center from the cyclopentadienyl ligand system, using alternative ligand types (N-heterocyclic carbenes, phosphines, amines) that can be independently optimized. This segmentation allows structure diversification without compromising catalyst core functionality.
Solution Approach 2:
The invention creates composite catalyst systems by combining chromium with diverse ligand types (NHC, phosphine, amine) and supporting matrices (silica, alumina, organic frameworks). This composite approach enables structure diversification and tunability of both activity and selectivity while maintaining catalytic function.
2Ease of operation
If heterogeneous chromium catalysts are used with chain shuttling agent, then polymerization can proceed, but the metal is not accessible to the polymeryl-chain shuttling agent complex due to pore diffusion limitations
Solution Approach 1:
The invention uses surface-bound ligands and intermediary species on the heterogeneous catalyst surface to mediate the interaction between the chromium center and the polymeryl-chain shuttling agent complex. This intermediary layer allows chain shuttling to occur despite the heterogeneous nature of the catalyst, resolving the accessibility issue.
Solution Approach 2:
The invention employs porous support materials with optimized pore sizes and surface functionalities that allow diffusion of the polymeryl-chain shuttling agent complex to the chromium active sites. The porous structure is designed to balance catalyst stability with reactant accessibility.
3Productivity
If two reactors are used for preparing impact-modified polyolefins, then sequential polymerization can be achieved, but process complexity and time consumption increase
Solution Approach 1:
The invention merges the sequential polymerization steps into a single reactor by using a dual-catalyst system where chromium catalysts and SIOP catalysts coexist and operate in sequence within the same reaction vessel. This eliminates the need for two separate reactors while maintaining the ability to produce impact-modified polyolefins.
Solution Approach 2:
The single reactor system is designed to perform multiple functions: it can accommodate both chromium catalysts for initial polymerization and SIOP catalysts for subsequent impact modification steps. The reactor system achieves multi-functionality, replacing the need for specialized separate reactors.
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 non-cyclopentadienyl-based chromium catalysts facilitate the production of olefin block copolymers with unique properties, such as a lower glass transition temperature and melting point, and allow for the preparation of impact-modified polyolefins in a single reactor, enhancing polymer diversity and efficiency.
Implementation Method 1
participate in polymeryl chain exchange reactions with a chain shuttling agent
Implementation Method 2
chromium catalyst useful for polymerizing an olefin monomer
Data Source
AI summary
Provided is a non-cyclopentadienyl-based chromium-ligand complex, preferably a chromium-ligand complex of formula (J): LCr(RA)m(D)k (J), wherein L is a non-Cp monoanionic ligand; Cr (chromium) is in a formal oxidation state of +3 or +2; when Cr formally is Cr+3, either m is 1 and RA is hydrocarbylene (a hydrocarbylene chromium-ligand complex of formula (J)) or m is 2 and each RA independently is hydrocarbyl (a dihydrocarbyl chromium-ligand complex of formula (J)), wherein each hydrocarbyl or hydrocarbylene of RA independently is unsubstituted or substituted by from 1 to 5 RAS; each RAS independently is a neutral aprotic heteroalkyl, neutral aprotic heterocycloalkyl, neutral aprotic heteroaryl, or neutral aprotic aryl; when Cr formally is Cr+2, m is 1 and RA is hydrocarbyl (a hydrocarbyl chromium-ligand complex of formula (J)); k is an integer of 0 or 1; D is absent when k is 0 or D is a neutral ligand when k is 1; wherein the chromium-ligand complex of formula (J) is overall neutral and lacks a cyclopentadienyl-based (Cp-based) moiety. Also provided is a chromium catalyst comprising or prepared from the complex. Also provided is a process of making the catalyst and a process employing the chromium catalyst for polymerizing the olefin monomer, especially a straight chain 1-alkene, to prepare the polyolefin, especially a partially chain-straightened poly(1-alkene) or olefin block copolymer. Further provided is the partially chain-straightened poly(1-alkene) or olefin block copolymer prepared thereby. Also provided is a high throughput workflow.