Binuclear Chromium Catalyst for Selective Ethylene Oligomerization
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Solution Overview
Problem
Existing ethylene oligomerization processes using metal-catalyzed methods face challenges in selectivity and purity, producing LAO mixtures that are difficult to separate and do not match market demands, with issues of low selectivity to desired products 1-hexene and 1-octene, wax formation, and high costs due to harsh reaction conditions and catalyst susceptibility to impurities.
Innovation Solution
A catalyst composition comprising a binuclear chromium(II) complex with specific ligands and an activator, allowing for selective ethylene trimerization and tetramerization through a mechanism involving metallocyclopentanes and dinuclear reductive elimination, which suppresses wax and polymer formation and enhances turnover rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If metal-catalyzed ethylene oligomerization processes are used, then LAO production is achieved, but selectivity to desired products (1-hexene and 1-octene) is low and product mixtures are difficult to separate
Solution Approach 1:
The patent changes the chemical parameters of the catalyst system by using binuclear chromium(II) complexes with specific ligands (PNPN or PNPNP structures) and organoaluminum activators. This fundamental parameter change transforms the reaction from producing broad Schulz-Flory distributions to achieving high selectivity for C6 and C8 olefins, making separation feasible and economically viable.
Solution Approach 2:
The invention employs composite catalyst systems combining binuclear chromium complexes with specific ligand structures and organoaluminum activators. This composite approach creates a synergistic effect that achieves high selectivity for target products while suppressing unwanted by-products, thereby simplifying the overall process despite the complexity of the catalyst composition.
2Productivity
If prior art catalysts are used, then ethylene oligomerization occurs, but wax formation and polymer formation occur leading to product yield loss and equipment fouling
Solution Approach 1:
The patent converts the potentially harmful side reactions that lead to wax and polymer formation into beneficial selective oligomerization reactions. By carefully designing the binuclear chromium catalyst system with specific ligands, the reaction pathway is directed toward producing valuable C6 and C8 olefins while suppressing the formation of unwanted heavy products, thereby eliminating equipment fouling issues.
Solution Approach 2:
The invention changes the catalyst parameters from conventional mononuclear systems to binuclear chromium(II) complexes with specific ligand geometries. This parameter change fundamentally alters the reaction mechanism, enabling selective formation of linear alpha-olefins while preventing the uncontrolled polymerization and wax formation that plague prior art processes.
3Productivity
If prior art catalysts are used, then ethylene oligomerization is achieved, but harsh reaction conditions (high temperature and pressure) are required resulting in high invest, maintenance and energy costs
Solution Approach 1:
The patent changes the operational parameters by developing catalysts that are highly active under mild conditions. The binuclear chromium(II) complexes with organoaluminum activators achieve high oligomerization activity at lower temperatures and pressures compared to prior art, directly reducing energy consumption and operational costs while maintaining high productivity.
Solution Approach 2:
The invention employs readily available binuclear chromium(II) complexes and simple organoaluminum activators that can be easily synthesized and handled, replacing complex and expensive catalyst systems. These catalyst components are cost-effective, stable, and require mild reaction conditions, thereby reducing overall process costs and energy requirements.
4Productivity
If prior art catalysts are used, then ethylene oligomerization occurs, but catalyst performance is highly susceptible to trace impurities and components are difficult to handle
Solution Approach 1:
The patent employs composite catalyst systems where the binuclear chromium(II) complex is combined with organoaluminum activators and specific ligands. This composite structure provides mutual stabilization and protection against impurities, enhancing the reliability and handling ease of the catalyst system while maintaining high activity for ethylene oligomerization.
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 composition achieves high selectivity and purity for 1-hexene and 1-octene production with improved turnover rates and reduced costs, allowing for efficient and reproducible oligomerization under mild conditions, avoiding the limitations of prior art processes.
Implementation Method 1
A catalyst composition comprising a binuclear chromium(II) complex with specific ligands and an activator, allowing for selective ethylene trimerization and tetramerization
Implementation Method 2
through a mechanism involving metallocyclopentanes and dinuclear reductive elimination
Data Source
AI summary
The present invention relates to a catalyst composition comprising: (a) a binuclear chromium(II) complex; (b) a ligand of the general structure (A) R1R2P-N(R3)-P(R4)-N(R5)-H or (B) R1R2P-N(R3)-P(R4)-N(R5)-PR6R7, wherein R1, R2, R3, R4, R5, R6 and R7 are independently selected from halogen, amino, trimethylsilyl, C1-C10-alkyl, aryl and substituted aryl, wherein the PNPN- or PNPNP-unit is optionally part of a ring system; and (c) an activator or co-catalyst, as well as to a process for oligomerization of ethylene.