Reducing Alpha-Olefin Isomerization in Copolymerization
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Solution Overview
Problem
The isomerization of alpha-olefins during the polymerization of ethylene reduces the yield of polyethylene copolymers, as only the 1-octene isomer participates in the polymerization reaction, while other isomers formed during heating are inert, leading to undesirable byproducts.
Innovation Solution
A method involving the use of a reactor system where a reaction mixture of hydrogen, ethylene, an alpha-olefin, and a catalyst without dialkyl zinc is heated with additives such as aromatic species, amines, fluoropolymers, phosphates, or fatty acids added upstream of the heat exchanger to reduce isomerization, ensuring the 1-octene isomer is retained.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the product stream is heated in a heat exchanger to increase temperature before the devolatilizer, then the energy efficiency and devolatilization effectiveness are improved, but isomerization of octene occurs forming inert isomers that reduce copolymer yield
Solution Approach 1:
An intermediary substance (inhibitor) is introduced into the system to prevent the harmful isomerization reaction during heating. The inhibitor acts as a mediator between the heat exchanger and the product stream, suppressing the formation of inert isomers while allowing the necessary heating to occur for energy-efficient operation.
Solution Approach 2:
The harmful isomerization reaction is prevented in advance by adding an inhibitor to the product stream before it enters the heat exchanger. This preliminary anti-action counteracts the potential harm of heating by pre-equipping the system with protective chemical agents that will neutralize any isomerization tendency during the heating process.
2Productivity
If the reactor operates at higher temperature to increase polymerization rate, then productivity is improved, but isomerization of alpha-olefin increases reducing copolymer yield
Solution Approach 1:
The system changes the chemical composition parameter by introducing an inhibitor substance that modifies the reaction environment. This parameter change allows the reactor to operate at higher temperatures for increased productivity while the inhibitor compensates for the increased isomerization tendency, maintaining acceptable copolymer yield.
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
This approach reduces alpha-olefin isomerization by 10 to 100% and increases the yield of polyethylene copolymers by minimizing the formation of inert isomers, with the additives effectively reducing isomerization when added between the reactor and heat exchanger.
Implementation Method 1
A heat exchanger (HE) 14 disposed downstream of the reactor increases the temperature of the product stream before entering the devolatilizer 16
Implementation Method 2
A devolatilizer 16 disposed downstream of the heat exchanger 14 removes any unreacted ethylene, solvent or octene
Implementation Method 3
heating the reactor to a first temperature to react the ethylene with the alpha-olefin to form a copolymer
Data Source
Figure 1~2
AI summary
Disclosed herein is a method for reducing isomerization during the copolymerization of ethylene with an α-olefin comprising adding to a reactor a reaction mixture comprising hydrogen, ethylene, an α-olefin, a solvent and a catalyst; where the catalyst does not include a chain shuttling agent that comprises dialkyl zinc; heating the reactor to a first temperature to react the ethylene with the α-olefin to form a copolymer; discharging from the reactor a first product stream to a heat exchanger; where the product stream comprises the copolymer; adding to the product stream prior to the heat exchanger a first additive that is operative to reduce isomerization of the α-olefin; and discharging from the heat exchanger a second product stream.