Online Mixed-Catalyst Ratio Adjustment for Olefin Polymerization
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Solution Overview
Problem
Existing polymerization processes face challenges in forming low density polyolefins due to high solids concentration in catalyst slurries, which lead to increased viscosity, foaming, and reactor issues, while conventional trim processes struggle to adjust catalyst ratios in-situ without causing settling and plugging.
Innovation Solution
A method involving a dual catalyst system, where a second catalyst is added to adjust the molecular weight distribution and composition of polyolefins in a reactor by controlling the molar ratio and reactor conditions, such as temperature and hydrogen concentration, to achieve targeted properties like MI, MIR, and density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a high solids concentration is used in the catalyst slurry to reduce the amount of slurry and transportation expenses, then the amount of diluent that must be isolated and recycled is reduced, but the slurry viscosity increases and foaming is increased, causing handling problems, storage problems, and reactor injection problems
Solution Approach 1:
The patent changes the physical-chemical parameters of the slurry by adding a foam control agent and adjusting the diluent composition. This allows the slurry to maintain high solids concentration while reducing foaming and improving flow characteristics, thereby resolving the contradiction between reducing slurry quantity and maintaining ease of operation
Solution Approach 2:
The patent introduces a foam control agent as an intermediary substance that mediates between the high solids concentration requirement and the foaming problem. This agent suppresses foam formation and improves slurry handling without requiring reduction of solids concentration
2Ease of operation
If low viscosity diluents are added to the slurry to reduce the viscosity, then the viscosity is reduced, but settling of the slurry is promoted, resulting in plugging of reactor components and accumulation of solids on the walls of catalyst slurry vessels
Solution Approach 1:
The patent modifies the slurry parameters by adding foam control agents and adjusting diluent composition to achieve optimal viscosity without promoting settling. This resolves the contradiction by finding a viscosity range that ensures ease of operation while maintaining suspension stability and preventing plugging
3Adaptability or versatility
If a second catalyst solution is added to the slurry to adjust polymer properties in-situ, then on-line adjustment of trim rates is achieved, but the low viscosity solution promotes settling of the slurry solution and subsequent gelling and/or plugging of reactor components
Solution Approach 1:
The patent changes the parameters of the trim catalyst solution by adjusting its composition and adding foam control agents. This allows the solution to have sufficient mixing capability for on-line adjustment while maintaining stability and preventing settling and plugging of reactor components
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 allows for efficient on-line adjustment of trim rates, reducing gel formation and reactor issues, enabling the production of polyolefins with controlled molecular weight distribution and composition, including low density polyethylene.
Implementation Method 1
polymerizing olefin(s) using dual catalyst systems... combining a catalyst component slurry with a catalyst component solution to form a third catalyst composition... polymerization reactor
Data Source
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AI summary
In an embodiment, a method for producing a polyolefin is provided. The method includes: contacting a first composition and a second composition in a line to form a third composition, wherein: the first composition comprises a contact product of a first catalyst, a second catalyst, a support, and a diluent, wherein the mol ratio of second catalyst to first catalyst is from 60:40 to 40:60, the second composition comprises a contact product of the second catalyst and a second diluent; introducing the third composition from the line into a gas-phase fluidized bed reactor; exposing the third composition to polymerization conditions; and obtaining a polyolefin.