Halogen-Substituted Bridged Diphosphine Ligands for Ethylene Tetramerization
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Solution Overview
Problem
Current catalysts for selective tetramerization of ethylene do not efficiently produce octene, which is in high demand for linear low density polyethylene production, as they either reduce hexene production or increase octene production undesirably.
Innovation Solution
A new family of bridged diphosphine ligands with a halogen substituent bonded directly to at least one phosphorus atom, used in conjunction with a chromium source and an activator, to catalyze the selective tetramerization of ethylene, producing octene in at least 25 weight % of the liquid product.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional diphosphine ligands without halogen substituents are used, then hexene production is maintained, but octene production is insufficient for high demand
Solution Approach 1:
The patent introduces halogen substituents (fluorine, chlorine, bromine, or iodine) at specific positions on the diphosphine ligand structure, changing the chemical parameters of the ligand to achieve selective tetramerization. This parameter change enables the catalyst to produce octene in at least 25 weight % of the liquid product while maintaining control over selectivity.
Solution Approach 2:
The invention creates a composite catalyst system combining chromium source with specifically designed halogen-substituted diphosphine ligands. This composite material approach allows optimization of both octene production quantity and selectivity control by leveraging the synergistic effects of the metal center and the modified organic ligand.
2Quantity of substance
If catalysts are modified to increase octene production, then octene yield improves, but internal olefin levels increase
Solution Approach 1:
The patent applies local quality modification by placing halogen substituents at specific positions on the diphosphine ligand structure rather than uniformly modifying the entire ligand. This localized chemical modification enables selective enhancement of tetramerization activity while preserving the ligand's ability to control regioselectivity and minimize internal olefin formation.
3Productivity
If existing alpha olefin production processes are used, then production capacity is maintained, but product distribution is broad requiring extensive distillation
Solution Approach 1:
The invention provides feedback control at the catalytic step by using halogen-substituted diphosphine ligands that inherently promote selective tetramerization. This built-in selectivity feedback reduces the need for subsequent separation processes, as the catalyst itself controls the product distribution to favor octene while minimizing broader carbon number distributions.
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 new catalyst system effectively increases the production of octene while maintaining low levels of internal olefins, making the process more efficient and suitable for integration with existing alpha olefin production processes.
Implementation Method 1
The ligands are useful in ethylene oligomerization reactions... a new family of bridged diphosphine ligands... useful in a process for the selective tetramerization of ethylene
Data Source
AI summary
An ethylene oligomerization catalyst which contains a bridged diphosphine ligand having the formula (R1)m(X1)nP1-bridge-P2(R2)X2 wherein R1 and R2 are independently selected from the group consisting of hydrocarbyl and heterohydrocarbyl; X1 is selected from the group consisting of halogen, hydrocarbyl and heterohydrocarbyl; m is 1 or 2; n is 0 or 1; m+n=2; bridge is a divalent bridging group bonded to P1 and P2; and X2 is halogen. The present ligands differ from prior diphosphine ligands used in olefin oligomerization processes in that at least one halide substituent is directly bonded to at least one P atom of the ligand.