Solid-Supported PNP-Cr Catalysts for Ethylene Tetramerization
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Solution Overview
Problem
Existing ethylene tetramerization catalysts with amino-biphosphine functional groups, such as PNP—Cr complexes, suffer from high production of polymeric side-products, reactor fouling, reduced reactivity, and low selectivity for 1-octene over 1-hexene.
Innovation Solution
Development of solid-supported PNP—Cr catalysts with surface hydroxyl groups on a solid support, where functional groups are attached through covalent bonds and coordinated with catalytically active transition metals, reducing uncontrolled polymer growth and reactor fouling while maintaining selectivity and reactivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If homogeneous PNP-Cr catalysts are used for ethylene tetramerization, then catalytic activity is achieved, but polymeric side-products are produced causing reactor fouling
Solution Approach 1:
The catalyst system is segmented into homogeneous PNP-Cr catalytic sites dispersed within a heterogeneous porous support matrix. This segmentation allows the catalytic function to be separated from the polymerization side reactions, maintaining high activity while the porous support physically confines and controls the reaction environment to prevent reactor fouling.
Solution Approach 2:
A composite catalyst system is created by combining homogeneous PNP-Cr complexes with a heterogeneous porous support material. The composite structure integrates the high activity of homogeneous catalysts with the structural benefits of heterogeneous supports, enabling selective tetramerization while minimizing unwanted polymer formation and reactor fouling.
2Productivity
If homogeneous PNP-Cr catalysts are used, then ethylene oligomerization proceeds, but selectivity for 1-octene over 1-hexene is low
Solution Approach 1:
The porous support provides a specific local environment with controlled pore sizes and surface properties that favor tetramerization over trimerization. The local confinement effect within the porous structure stabilizes the transition state for 1-octene formation, enhancing selectivity while maintaining overall oligomerization activity.
Solution Approach 2:
The invention changes the physical and chemical parameters of the catalyst system by immobilizing PNP-Cr complexes on porous supports with specific surface areas, pore diameters, and surface chemistries. These parameter changes create a restricted environment that promotes selective ethylene tetramerization to 1-octene over competing trimerization to 1-hexene.
3Productivity
If homogeneous catalysts are used, then catalytic reactivity is maintained, but catalyst recovery is difficult
Solution Approach 1:
The catalyst is segmented into discrete particles by immobilizing PNP-Cr complexes on porous support particles. This segmentation allows the catalyst to be easily separated from the reaction mixture through simple filtration or decantation, while the high surface area of the porous support maintains high catalytic reactivity.
Solution Approach 2:
The porous support acts as an intermediary carrier that holds the homogeneous PNP-Cr catalyst in a fixed, recoverable form. The support mediates between the need for homogeneous catalyst reactivity and the need for heterogeneous catalyst ease of separation, enabling simple catalyst recovery while maintaining high catalytic activity.
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 solid-supported catalysts inhibit polymer generation, reduce reactor fouling, and enhance selectivity for 1-octene production, maintaining reactor cleanliness and reactivity across repeated cycles.
Implementation Method 1
individual functional groups are attached to the solid support as products of condensation reactions of at least one hydrolysable group of precursor ligands with a corresponding surface group of the solid support
Implementation Method 2
Functional groups are attached to the solid support through at least one covalent bond and coordinated with at least one catalytically active transition metal
Data Source
AI summary
Ethylene oligomerization catalysts include a solid support having surface hydroxyl groups on a surface of the solid support. Functional groups attached to the solid support through at least one covalent bond and coordinated with at least one catalytically active transition metal. Individual functional groups are attached to the solid support as products of condensation reactions of at least one hydrolysable group of precursor ligands with a corresponding surface group of the solid support. The precursor ligands have a general formula (Ph2P)2N—R1-A, where R1 is C1-C40 hydrocarbylene or C1-C40 heterohydrocarbylene; and A is a hydrolysable group selected from trialkoxysilyl, halosilyl, carboxylates, esters, phosphonates, amines, imines, thiols, thiocarboxylates, or halides.