Chromium PNPNH Catalyst for Ethylene Trimerization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing processes for producing linear alpha olefins, such as comonomer-grade 1-hexene, face challenges including low selectivity to desired products, wax and polymer formation, high catalyst costs, susceptibility to impurities, and narrow operability windows, leading to inefficient and costly production.
Innovation Solution
A catalyst composition comprising a chromium compound, a PNPNH-ligand, a modifier containing organic or inorganic halides, and an activator or co-catalyst, which enhances selectivity and activity while allowing for flexible operation conditions, reducing unwanted by-products and catalyst costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If chromium-based catalyst systems with PNP-ligands and excess MAO are used to achieve high catalytic activity, then productivity is improved, but the system becomes extremely susceptible to catalyst poisons and impurities, requiring huge amounts of scavenger/co-catalyst
Solution Approach 1:
The patent changes the chemical parameters of the catalyst system by replacing MAO with a combination of aluminum alkyl and aluminum halide co-catalysts. This parameter change maintains high catalytic activity while fundamentally altering the system's susceptibility to impurities, allowing operation with much lower co-catalyst ratios (Al/Cr = 1-100) compared to conventional systems
Solution Approach 2:
The patent employs inexpensive aluminum alkyl and aluminum halide compounds as co-catalysts instead of expensive MAO. These simpler, more robust co-catalysts can be used in stoichiometric or near-stoichiometric amounts, eliminating the need for excessive co-catalyst to serve as a scavenger for impurities
2Manufacturing precision
If selective ethylene trimerization processes are used to produce comonomer-grade 1-hexene, then manufacturing precision is improved, but device complexity and process complexity increase
Solution Approach 1:
The patent achieves high 1-hexene selectivity by optimizing specific parameters of the chromium catalyst system, including the use of PNP-ligands with specific structural features (bulky groups at P-aryl ortho positions), chromium oxidation state (Cr(II) or Cr(III)), and the aluminum alkyl/aluminum halide co-catalyst combination. These parameter optimizations enable selective trimerization without requiring complex process designs
Solution Approach 2:
The patent extracts and eliminates unnecessary process complexity by using a well-defined catalyst system with specific ligand structures and co-catalyst combinations. This approach removes the need for complex process control systems, multiple catalyst components, or elaborate reactor configurations that are often required in selective oligomerization processes
3Ease of operation
If conventional oligomerization processes are used, then ease of operation is maintained, but manufacturing precision and product selectivity deteriorate due to Schulz-Flory distribution
Solution Approach 1:
The patent changes the fundamental chemical parameters of the oligomerization process by using chromium catalysts with PNP-ligands and aluminum alkyl/halide co-catalysts. This parameter change transforms the reaction mechanism from conventional radical or coordination oligomerization to a selective cyclization pathway that produces predominantly 1-hexene, maintaining ease of operation while dramatically improving selectivity
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 achieves high 1-hexene selectivity and productivity with improved stability against impurities and flexible operation, reducing costs and simplifying process design, while maintaining high product purity and reducing polymer formation.
Implementation Method 1
A catalyst composition and process for oligomerization of ethylene... chromium compound... achieves high 1-hexene selectivity and productivity
Data Source
AI summary
The present invention relates to a catalyst composition for oligomerization of ethylene, comprising a chromium compound; a ligand of the general structure R1R2P—N(R3)—P(R4)—N(R5)—H, wherein R1, R2, R3, R4 and R5 are independently selected from halogen, amino, trimethylsilyl, C1-C10-alkyl, aryl and substituted aryl; a modifier containing organic or inorganic halide; and an activator or co-catalyst; and a process for oligomerization utilizing that catalyst.