Olefin Polymerization Reactor with Segmented Residence Time Control
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Solution Overview
Problem
Existing processes for catalytic polymerization of olefins using Ziegler-Natta catalysts struggle to achieve a broad bimodal molecular weight distribution, which affects the rheology and mechanical properties of polyolefins, and often require multiple reactors to achieve enhanced homogeneity and comonomer distribution.
Innovation Solution
A process involving a first polymerization in a liquid phase loop reactor under supercritical conditions followed by a second polymerization in a fluidized bed and moving bed reactor, where residence times are independently controlled, allowing for the production of monomodal and bimodal polyolefins with improved polydispersity and controlled layer formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single reactor is used for catalytic polymerization, then the process is simple, but the molecular weight distribution is narrow
Solution Approach 1:
The patent divides the polymerization process into multiple sequential stages within a single reactor: an initial polymerization stage followed by a secondary polymerization stage. This segmentation allows different reaction conditions to be applied at different times, producing a broad bimodal molecular weight distribution without requiring multiple physical reactors.
Solution Approach 2:
The patent performs preliminary polymerization to form initial polymer particles with specific properties, then introduces additional catalyst and monomer to perform secondary polymerization on these pre-formed particles. This preliminary action establishes a foundation that enables subsequent modification of the molecular weight distribution.
2Manufacturing precision
If series of reactors are used to obtain broad molecular weight distribution, then the molecular weight distribution is improved, but the process complexity increases
Solution Approach 1:
The patent combines multiple polymerization stages that would traditionally require separate reactors into a single integrated reactor system. By merging the initial and secondary polymerization processes in one vessel with controlled sequential operation, the patent achieves broad bimodal molecular weight distribution while eliminating the need for multiple reactor units and associated transfer systems.
Solution Approach 2:
The single reactor is designed to perform multiple functions: it conducts both the initial polymerization and the secondary polymerization, and can accommodate different catalyst systems and monomer compositions at different stages. This multi-functionality replaces what would traditionally require multiple specialized reactors.
3Manufacturing precision
If different reactor conditions are applied, then the molecular weight distribution broadens, but the process control becomes more difficult
Solution Approach 1:
The patent employs periodic action by switching between different reaction conditions at defined stages. The process transitions from an initial polymerization mode with specific catalyst and monomer concentrations to a secondary polymerization mode with different parameters. This structured periodic change simplifies control compared to continuous simultaneous optimization of multiple variables.
Solution Approach 2:
The patent systematically changes key parameters between stages: catalyst type, monomer concentration, comonomer content, and hydrogen concentration are all adjusted between the initial and secondary polymerization stages. These controlled parameter changes enable broad molecular weight distribution while maintaining operational simplicity through clear stage transitions.
4Manufacturing precision
If multiple polymerization stages are used, then the comonomer distribution improves, but the number of reactors increases
Solution Approach 1:
The patent segments the polymerization process into distinct stages with different comonomer addition strategies. The initial stage uses one comonomer concentration profile while the secondary stage uses a different profile, enabling enhanced comonomer distribution control within a single reactor rather than requiring multiple reactors for different comonomer incorporation phases.
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 enables the production of polyolefins with desired molecular weight distributions and layer thickness, enhancing the mechanical properties and homogeneity of the final product, potentially eliminating the need for a second gas phase reactor.
Implementation Method 1
a second polymerization in a second reactor, wherein the polymerized olefins are further polymerized in a fluidized bed
Implementation Method 2
a first polymerization in a first reactor, wherein olefins are polymerized with a particulate catalyst, hydrogen and optional a comonomer in a fluidum of an inert low boiling hydrocarbon medium
Data Source
AI summary
The present invention relates to a process for the catalytic polymerization of olefins comprising the steps of; i) a first polymerization in a first reactor, wherein olefins are polymerized with a particulate catalyst, hydrogen and optional a comonomer in a fluidum of an inert low boiling hydrocarbon medium into an reaction mixture comprising polymerized olefins; and ii) a second polymerization in a second reactor, wherein the polymerized olefins are further polymerized in a fluidized bed and in a moving bed under such conditions that the residence time in the fluidized bed and the residence time in the moving bed are independently controlled to a reactor system for carrying out said process, to the use of the reactor system, the polyolefins obtainable with said method and to the use of these polyolefins.