Polyolefin Catalyst Productivity via Induced Condensing Agent Control
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Solution Overview
Problem
Existing polyolefin polymerization methods face challenges in increasing catalyst productivity while maintaining the desired melt index, as higher concentrations of induced condensing agents (ICAs) can decrease the melt index, affecting the processability of polyolefins for downstream applications.
Innovation Solution
The method involves contacting olefin monomers with a metallocene catalyst and increasing the partial pressure of ICAs in a fluidized bed reactor to enhance catalyst productivity, while adjusting the partial pressures of hydrogen, olefin monomer, or comonomer to maintain the desired melt index within 10% of the initial value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the concentration of induced condensing agents (ICAs) is increased to enhance catalyst productivity, then the productivity increases, but the melt index of the polyolefin decreases
Solution Approach 1:
The patent applies parameter changes by adjusting the partial pressures of multiple components (ICA, hydrogen, olefin monomer, comonomer) simultaneously. Specifically, it increases ICA partial pressure to enhance productivity while compensating for melt index changes by adjusting hydrogen to monomer ratio and modifying monomer/comonomer partial pressures, thereby maintaining melt index within the desired range
Solution Approach 2:
The patent implements dynamic control by continuously adjusting the ratios and partial pressures of reactor components during the polymerization process. The method dynamically balances the competing effects of ICA concentration changes on productivity and melt index through real-time modification of hydrogen, monomer, and comonomer proportions
2Productivity
If the recycle stream temperature is lowered below the dew point to increase polymer production, then the production rate increases, but the polymerization process becomes more complex due to two-phase gas/liquid mixture
Solution Approach 1:
The patent utilizes phase transitions by operating the recycle stream below its dew point temperature, intentionally condensing a portion of the recycle gas stream to create a two-phase gas/liquid mixture. This condensation mode operation enables enhanced heat transfer and increased polymer production by leveraging the phase change of the recycle stream components
Solution Approach 2:
The patent introduces induced condensing agents (ICAs) as intermediaries that facilitate controlled condensation in the recycle stream. These ICAs act as mediators that enable the two-phase operation by lowering the dew point temperature and promoting controlled liquid formation, which enhances heat transfer without causing uncontrolled aggregation or plugging
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 achieves a higher catalyst productivity, with productivity increases of at least 5%, 10%, 15%, or 20%, while keeping the melt index within the desired range, thus optimizing polyolefin production for specific applications.
Implementation Method 1
contacting olefin monomers with a metallocene catalyst to produce a polyolefin
Implementation Method 2
The liquid phase of this two-phase gas/liquid mixture in condensed mode operation is generally entrained in the gas phase of the mixture. Vaporization of the liquid occurs only when heat is added or pressure is reduced.
Implementation Method 3
In a typical gas-phase fluidized bed polymerization process, a gaseous stream containing one or more monomers is continuously passed through the fluidized bed under reactive conditions
Implementation Method 4
since the polymerization reaction is exothermic, the amount of polymer produced in a fluidized bed polymerization process is related to the amount of heat that can be withdrawn from the reaction zone
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
The catalyst productivity of a polyolefin catalyst in the methods disclosed herein may be increased by increasing the concentration of an induced condensing agent (ICA) in the reactor system. The effect the increased ICA concentration may have on a melt index may be counteracted, if necessary, in various ways.