Chromium PNP Catalyst Composition for Selective Ethylene Oligomerization
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Solution Overview
Problem
Conventional methods for producing linear alpha-olefins like 1-hexene and 1-octene are inefficient, leading to high comonomer costs and the need for additional separation processes due to the synthesis of alpha-olefins with varying lengths, and existing catalyst systems lack high selectivity and catalytic activity.
Innovation Solution
A ligand compound with a novel structure, an organic chromium compound, and a catalyst composition that enable high selectivity and efficiency in ethylene oligomerization to produce 1-hexene and 1-octene, utilizing a ligand compound represented by Chemical Formula 1, which forms a stable metal complex with chromium, enhancing catalytic activity and selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If copolymerization is used to control polymer density, then the desired LLDPE product is obtained, but the comonomer cost accounts for a large portion of manufacturing cost
Solution Approach 1:
The patent changes the chemical parameters of the catalyst system by using a chromium complex with a specific PNP ligand structure. This parameter change enables selective oligomerization of ethylene to produce linear alpha-olefins (1-hexene and 1-octene) with high selectivity, which can then be used as comonomers in copolymerization to control polymer density
Solution Approach 2:
The patent performs preliminary oligomerization of ethylene to produce specific linear alpha-olefins (1-hexene and 1-octene) before the copolymerization step. This preliminary action allows for controlled production of comonomers with specific chain lengths, improving both the efficiency of comonomer usage and the precision of polymer density control
2Productivity
If Shell Higher Olefin Process is used to produce linear alpha-olefin, then various alpha-olefins are synthesized, but additional separation process is required
Solution Approach 1:
The patent applies local quality by designing a catalyst with specific ligand structure (PNP type with particular substituents) that creates a localized active site geometry favoring the formation of specific oligomer chain lengths. This local structural control at the catalyst active site enables selective production of 1-hexene and 1-octene, eliminating the need for separation processes
Solution Approach 2:
The patent changes the catalytic parameters by using a chromium complex with a specifically designed PNP ligand. This parameter change shifts the product distribution from the broad Schultz-Flory distribution to a narrow distribution centered on C6 and C8 linear alpha-olefins, thereby eliminating the need for additional separation processes
3Productivity
If existing catalyst systems are used for ethylene oligomerization, then oligomerization occurs, but selectivity and catalytic activity are insufficient
Solution Approach 1:
The patent creates a composite catalyst system by combining chromium metal center with a specifically designed PNP ligand structure. This composite material approach, where the ligand and metal center work synergistically, achieves both high catalytic activity and high selectivity for 1-hexene and 1-octene production, resolving the contradiction between productivity and manufacturing precision
Solution Approach 2:
The patent optimizes the catalytic parameters by modifying the ligand structure with specific substituents (R1-R7 groups) that tune the electronic and steric properties of the chromium active site. This parameter optimization simultaneously enhances both the catalytic activity (productivity) and the selectivity toward desired oligomer products
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 described catalyst system achieves high selectivity and productivity in producing linear alpha-olefins like 1-hexene and 1-octene, reducing by-products and lowering production costs by minimizing polyethylene wax formation.
Implementation Method 1
which forms a stable metal complex with chromium, enhancing catalytic activity and selectivity
Implementation Method 2
enables ethylene oligomerization to produce 1-hexene and 1-octene
Data Source
AI summary
Provided are a ligand compound represented by Chemical Formula 1, which exhibits high 1-hexene and 1-octene selectivity while exhibiting high catalytic activity and enables ethylene oligomerization with excellent efficiency, an organic chromium compound, a catalyst composition containing the organic chromium compound, and a method for ethylene oligomerization using the same:wherein all the variables are described herein.