Chromium Catalyst Ethylene Oligomerization
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Solution Overview
Problem
Conventional methods for producing 1-hexene or 1-octene through ethylene oligomerization lack catalysts with sufficient high activity, leading to increased production costs and inefficiencies in preparing linear low-density polyethylene (LLDPE) without the need for additional comonomers.
Innovation Solution
A method for ethylene oligomerization using a catalyst system comprising a ligand compound and a chromium source, or a chromium compound, in conjunction with a cocatalyst, which enables highly active ethylene oligomerization reactions, allowing for the production of low-density polyethylene in a single reactor without additional comonomers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional chromium catalysts are used for ethylene oligomerization, then the production cost increases due to low catalyst activity, but using higher catalyst loading to improve activity increases the complexity and cost of the catalyst system
Solution Approach 1:
The patent changes the chemical parameters of the catalyst system by introducing a specific chromium compound with a unique ligand structure (Formula 2) where R1-R6 are specific hydrocarbyl or heterohydrocarbyl groups. This parameter change in the catalyst's molecular structure results in significantly higher ethylene oligomerization activity without requiring increased catalyst loading, thus resolving the contradiction between productivity and system complexity
Solution Approach 2:
The patent employs a composite catalyst system comprising a chromium compound combined with specific ligands (Formula 1) and cocatalysts (Formula 3 or 4). This composite material approach creates a synergistic effect where the combination of components produces higher activity than individual components alone, achieving high productivity without proportionally increasing system complexity
2Manufacturing precision
If comonomers are added to produce LLDPE, then the density control is improved, but the production cost increases
Solution Approach 1:
The patent extracts the density control function from the comonomer addition step by using ethylene oligomerization to produce alpha-olefins (1-hexene, 1-octene) in-situ within the polymerization reactor. These oligomers serve as built-in comonomers that provide density control without requiring external comonomer injection, thereby eliminating the additional production cost while maintaining manufacturing precision
Solution Approach 2:
The catalyst system performs self-service by simultaneously catalyzing both ethylene polymerization and ethylene oligomerization reactions. The oligomerization products (alpha-olefins) generated in-situ automatically function as comonomers for the polymerization reaction, creating a self-sufficient system that achieves density control without external additives, thus reducing production cost
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 method achieves highly active ethylene oligomerization, enabling the production of low-density polyethylene with a Schultz-Flory distribution of alpha-olefin polymers, reducing production costs by eliminating the need for additional comonomers and enhancing catalyst activity.
Implementation Method 1
polymerizing ethylenes in the presence of a catalyst system including i) a ligand compound represented by the following Chemical Formula 1 and a chromium source, or ii) a chromium compound represented by the following Chemical Formula 2; and a cocatalyst
Data Source
AI summary
The present invention relates to a method for ethylene oligomerization. According so the method of the present invention, highly active ethylene oligomerization reaction is possible by using a catalyst system including a novel chromium compound exhibiting high activity for ethylene oligomerization reaction, and therefore, polyethylene can be prepared using a small amount of comonomers or using only ethylene without comonomers.