Chromium Catalyst Ligand Design for Olefin Trimerization Selectivity
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Solution Overview
Problem
Current olefin oligomerization catalysts lack high activity and selectivity for producing specific oligomers like 1-hexene or 1-octene, necessitating the development of a more effective catalyst system.
Innovation Solution
A catalyst system comprising a ligand characterized by specific formulas, a chromium metal precursor, and optional activators is used for the oligomerization of olefins, achieving selectivity of at least 70 mole percent for the desired oligomer, particularly trimerization or tetramerization of ethylene to produce 1-hexene or 1-octene.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional chromium catalysts are used for olefin oligomerization, then the catalyst can perform basic oligomerization function, but the selectivity for specific oligomers (1-hexene or 1-octene) is low and activity is insufficient
Solution Approach 1:
The patent applies parameter changes by modifying the ligand structure parameters (introducing specific heteroaryl groups, adjusting donor atom types and positions) to optimize the catalyst's electronic and steric properties. This enables the catalyst to achieve both high activity and high selectivity for specific oligomers like 1-hexene and 1-octene, resolving the contradiction between productivity and manufacturing precision.
Solution Approach 2:
The patent employs composite materials by creating a sophisticated catalyst system that combines chromium metal center with complex multi-donor ligands containing heteroaryl groups (pyridine, pyrimidine, triazine, etc.). This composite catalyst structure integrates multiple functional components that work synergistically to achieve both high oligomerization activity and high selectivity for desired products.
2Ease of manufacture
If chromium catalysts with simple ligands are used, then the catalyst preparation is simple, but the selectivity for desired oligomers remains low
Solution Approach 1:
The patent modifies ligand parameters by incorporating heteroaryl groups with specific donor atoms (N, O, S) at controlled positions and ratios. These parameter changes enhance the catalyst's ability to discriminate between different oligomerization pathways, achieving high selectivity for 1-hexene or 1-octene while maintaining reasonable preparation complexity through systematic ligand design.
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 high activity and selectivity in producing desired oligomers, with selectivity of at least 70 mole percent, effectively addressing the limitations of existing catalysts in olefin oligomerization.
Implementation Method 1
The oligomerization of ethylene typically returns a broad distribution of 1-olefins having an even number of carbon atoms (C4, C6, C8, C10, etc.). Several catalysts useful for the oligomerization of olefin monomers have been developed, including the trimerization of ethylene. Several of these catalysts use chromium as a metal center.
Data Source
AI summary
The present invention provides a method of producing oligomers of olefins, comprising reacting olefins with a catalyst under oligomerization conditions. The catalyst can be the product of the combination of a chromium compound and a heteroaryl-amine compound. In particular embodiments, the catalyst compound can be used to trimerize or tetramerize ethylene to 1-hexene, 1-octene, or mixtures of 1-hexene and 1-octene.