P-N-P Ligand Selective Ethylene Oligomerization
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Solution Overview
Problem
Current ethylene oligomerization processes produce a mixture of alpha olefins with high levels of internal olefins, which are difficult to separate and not readily incorporated into linear low density polyethylene (LLDPE), leading to contamination and inefficiencies in production.
Innovation Solution
A new family of P-N-P ligands with an aromatic fluorocarbyl oxide group bonded to a P atom is used in conjunction with a chromium source and an activator to selectively oligomerize ethylene, producing high levels of octene-1 with low internal olefin contamination, thereby improving the separation and utilization of hexene-1 and octene-1 in LLDPE production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional oligomerization processes are used to produce alpha olefins, then a broad distribution of alpha olefins is obtained, but the product contains high levels of internal olefins that are difficult to separate and contaminate LLDPE production
Solution Approach 1:
The patent modifies the chemical parameters of the ligand structure by introducing specific substituents (aromatic groups with electron-withdrawing groups, bulky groups) at defined positions. These parameter changes in ligand structure directly affect the catalyst's selectivity, transforming the product distribution to favor terminal olefins over internal olefins, thereby resolving the contamination issue while maintaining productivity
Solution Approach 2:
The patent applies local quality by introducing specific functional groups at particular positions on the ligand structure (ortho, meta, para positions of phenyl rings). These localized modifications create specific steric and electronic environments at the catalyst active site, which control the oligomerization pathway to selectively produce terminal olefins and minimize internal olefin formation
2Manufacturing precision
If distillation is used to separate hexene-1 from internal hexenes, then separation is achieved, but the process becomes complex and inefficient due to close boiling points
Solution Approach 1:
The patent performs preliminary action by designing the catalyst system to selectively produce hexene-1 with minimal internal hexene formation from the outset. This prevents the formation of difficult-to-separate isomers before the separation step, eliminating the need for complex distillation processes and multiple columns, thereby simplifying the overall manufacturing process while achieving high purity
3Quantity of substance
If ligands without ortho substituents are used, then the catalyst produces more octene, but the hexene fraction contains a large portion of internal hexenes which is undesirable
Solution Approach 1:
The patent systematically varies ligand structure parameters, specifically introducing ortho-substituted phenyl groups with electron-withdrawing substituents. This parameter change simultaneously achieves two objectives: maintaining high octene production levels while dramatically reducing internal hexene formation, a dual benefit not achieved by previous ligand structures
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 process achieves selective production of octene-1 with very low levels of internal olefins, enhancing the separation of hexene-1 and octene-1 in existing distillation columns and reducing polymer by-product formation, making the process more efficient and suitable for LLDPE production.
Implementation Method 1
a catalyst system comprising i) a source of chromium; ii) a ligand defined by the formula (I)
Implementation Method 2
The ligands are characterized by having at least one aromatic fluorocarbyl oxide group bonded to a P atom
Data Source
AI summary
A new P-N-P ligand is useful in ethylene oliogomenzation. The ligand is characterized by having at least one aromatic fiuorocarbyl alkoxide group bonded to a P atom, hi combination with 1) a source of chromium and 11) an activator such as methylalumoxane, the ligand of this invention may be used to prepare an oligomer product that contains a mixture of high purity alpha olefins, hi a preferred emobidment, the ligand of this invention enables a selective oligomerization in which the majority of the liquid product is a mixture of hexene and octene. The amount of byproduct polymer that is produced in preferred oligomerization reactions is advantegeously low.