Purified Propane Feed Stabilizes Catalyst Activity in Ethylene Polymerization
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Solution Overview
Problem
Gas-phase polymerization processes for ethylene face challenges due to impurities in the propane feed stream, leading to fluctuations in organometallic compound concentrations and catalyst properties, which affect reactor yields and polymer quality, particularly when multiple reactors are operated in series.
Innovation Solution
A process involving the use of a purified propane feed stream with at least 99% mol propane and minimal impurities, purified through hydrocarbon purification units, is fed to the gas-phase polymerization unit, and the polymerization catalyst is pre-activated in liquid propane to maintain consistent catalyst activity and polymerization conditions across reactors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard propane feed stream is used without purification, then the process is simple and costs are low, but impurities in the propane cause fluctuations in organometallic compound concentrations and catalyst properties, affecting reactor yields and polymer quality
Solution Approach 1:
The propane feed stream is purified in advance before entering the polymerization reactors. The purification system removes impurities such as propylene, acetylene, carbon monoxide, carbon dioxide, oxygen, and water from the propane stream before it contacts the catalyst system, preventing catalyst deactivation and ensuring stable organometallic compound concentrations throughout the polymerization process.
2Productivity
If multiple polymerization reactors are operated in series, then productivity is increased, but impurities in the feed stream cause varying catalyst activity across reactors, leading to inconsistent polymer properties
Solution Approach 1:
The purification system provides locally optimized feed quality to each reactor in the series. By ensuring that each reactor receives highly purified propane with controlled impurity levels, the catalyst activity and organometallic compound concentrations are maintained within narrow ranges in each reactor, resulting in consistent polymer properties across the entire production line despite the multi-reactor configuration.
3Productivity
If organometallic compounds are used as cocatalysts, then polymerization activity is enhanced, but they are sensitive to impurities and act as catalyst poisons, requiring strict feed purification
Solution Approach 1:
The purification system creates an inert feed environment by removing all impurities that could react with or deactivate the organometallic cocatalysts. The propane feed is purified to eliminate propylene, acetylene, carbon monoxide, carbon dioxide, oxygen, and water, creating a chemically inert atmosphere that protects the sensitive organometallic compounds from deactivation while allowing them to function effectively as cocatalysts for high polymerization 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
This approach stabilizes catalyst activity and reactor yields, improving the quality of the ethylene polymer by reducing impurity-related issues and maintaining consistent polymer properties across a reactor cascade, resulting in high-density polyethylene with desired properties.
Implementation Method 1
passing a hydrocarbon stream through hydrocarbon purification units which reduce at least the concentration of propylene, acetylene, carbon monoxide, carbon dioxide, oxygen and water contained in the hydrocarbon stream
Implementation Method 2
The reaction of the organometallic compounds with polar compounds changes the availability of the organometallic compounds as cocatalyst
Implementation Method 3
Gas-phase polymerization processes are processes for the polymerization of ethylene, such as homopolymerizing ethylene or copolymerizing ethylene with other olefins
Implementation Method 4
forming an ethylene polymer in particle form in a gas-phase polymerization unit
Data Source
AI summary
A process for preparation of an ethylene polymer in a gas-phase polymerization unit comprising a gas-phase polymerization reactor by homopolymerizing ethylene or copolymerizing ethylene and one or more C4-C12-1-alkenes in a reaction gas made from or containing propane as polymerization diluent in the presence of a pre-activated polymerization catalyst, wherein a purified propane feed stream made from or containing at least 99 mol % propane and from 0.1 to 100 ppm mol propylene is fed to the gas-phase polymerization unit.