Chromium Catalyst System for Selective Ethylene Oligomerization
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Solution Overview
Problem
Conventional methods for producing linear low-density polyethylene (LLDPE) face challenges in efficiently synthesizing high comonomer content, particularly due to the high cost of comonomers like 1-hexene and 1-octene, and the inconvenience of separating specific alpha-olefins in the polymerization process.
Innovation Solution
A novel organochromium compound with a specific ligand structure, represented by Formula 1, is used to form a catalyst system that selectively oligomerizes ethylene, producing linear alpha-olefins like 1-hexene and 1-octene with high efficiency and selectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If copolymerization with alpha-olefin comonomers is performed to adjust polymer density, then the desired polymer properties are achieved, but the manufacturing cost increases significantly due to high comonomer costs
Solution Approach 1:
The invention changes the chemical parameters of the catalyst system by using a specific chromium-based catalyst with particular ligand structures (Formula 1) and cocatalysts (Formula 2-5), which fundamentally alters the polymerization mechanism to enable comonomer-free or low-comonomer production while maintaining density control through process parameters
2Productivity
If the shell higher olefin process is used to produce LLDPE, then polymer production is achieved, but a separate separation process is required to obtain specific alpha-olefins due to Schultz-Flory distribution
Solution Approach 1:
The invention extracts the separation step entirely from the process by using a selective catalyst that produces only the desired alpha-olefin product (1-hexene or 1-octene) directly through oligomerization, eliminating the need for downstream separation units and simplifying the overall process flow
3Productivity
If conventional catalysts are used for ethylene oligomerization, then some alpha-olefin production is achieved, but catalyst activity and selectivity are insufficient leading to by-product formation
Solution Approach 1:
The invention creates a composite catalyst system combining chromium compound (Formula 6-8) with specifically designed ligand compounds (Formula 1) and cocatalysts (Formula 2-5), where the synergistic interaction between components enhances both activity and selectivity, reducing by-product formation while increasing desired alpha-olefin production
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 catalyst system demonstrates enhanced catalyst activity and selectivity for 1-hexene and 1-octene, reducing the production of by-products and improving the efficiency of LLDPE synthesis, thereby addressing the cost and separation challenges in conventional methods.
Implementation Method 1
an organochromium compound including the ligand compound represented by Formula 1; and chromium (Cr) coordinated with the ligand compound
Implementation Method 2
selectively synthesizing 1-hexene through the trimerization reaction of ethylene, or selectively synthesizing 1-octene through the tetramerization reaction of ethylene
Data Source
AI summary
The present invention relates to a ligand compound represented by the following Formula 1, an organochromium compound, a catalyst system including the organochromium compound and a method for oligomerizing ethylene using the same:wherein Cy, and R1 to R4 are described herein.