Polyolefin Stirrer Power Reduction via Catalyst Ratio
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Solution Overview
Problem
In continuous horizontal stirred bed reactors, the use of Ziegler-Natta catalysts leads to increased power consumption over time due to electrostatic interactions between homopolymer powder and the stirrer, requiring higher torque to maintain stirring efficiency.
Innovation Solution
A catalyst system with a higher molar ratio of aluminum from the co-catalyst to titanium from the procatalyst, combined with the use of antistatic agents, is employed to reduce the power uptake of the stirrer by minimizing electrostatic interactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Ziegler-Natta catalysts are used in continuous horizontal stirred bed reactors, then polyolefin production is achieved, but power consumption increases over time due to electrostatic interactions
Solution Approach 1:
The patent changes the chemical composition parameters of the catalyst system by incorporating specific internal electron donors (such as esters, ethers, or amides) and optimizing the ratio of titanium to aluminum components. This parameter modification alters the electrostatic properties of the produced polymer particles, reducing their tendency to accumulate static charge during the polymerization process, thereby maintaining lower power consumption over time
Solution Approach 2:
The patent introduces internal electron donor compounds as intermediaries within the catalyst structure. These donors act as mediators that modify the surface properties of the growing polymer particles, reducing electrostatic charge accumulation. The electron donors are incorporated into the catalyst matrix and indirectly affect the polymer's electrostatic behavior without being consumed in the polymerization reaction
2Ease of operation
If higher torque is applied to maintain stirring efficiency, then mixing performance is improved, but power consumption increases
Solution Approach 1:
The patent modifies the physical-chemical parameters of the polymer particles through catalyst composition adjustment, specifically controlling the electrostatic charge characteristics. By changing the catalyst's internal electron donor content and type, the polymer particles exhibit reduced electrostatic attraction, which decreases their adhesion to stirrer surfaces and reduces the torque required to maintain effective mixing
3Object-affected harmful factors
If the aluminum to titanium ratio in the catalyst system is increased, then electrostatic interactions are reduced, but catalyst composition complexity increases
Solution Approach 1:
The patent systematically adjusts the aluminum to titanium ratio as a key compositional parameter, increasing it to reduce electrostatic charge accumulation. This parameter change is implemented within a defined optimization range that balances electrostatic reduction with catalyst stability and activity, preventing excessive complexity while achieving the desired effect
Solution Approach 2:
The patent creates a composite catalyst system that integrates multiple components (titanium halide, aluminum alkyl, internal electron donors) into a unified structure. The composite nature allows the different components to work synergistically, where the aluminum and electron donor components collectively reduce electrostatic interactions without requiring each individual component to be overly complex
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
The increased aluminum to titanium ratio and antistatic agents significantly reduce the torque required for stirring, leading to lower power consumption and improved operational efficiency in polyolefin production.
Implementation Method 1
a catalyst system comprising: a procatalyst comprising i) titanium; ii) a magnesium-containing support, preferably a magnesium chloride-containing support, and iii) an internal electron donor; optionally an external electron donor; and a co-catalyst, being a alkyl aluminum catalyst
Implementation Method 2
by contacting one or more olefins, preferably propylene, with a catalyst system while stirring
Implementation Method 3
there is a power uptake increase of stirrer in the reactor during the process of producing a polyolefin, induced by the use of different Ziegler-Natta catalysts. Without wishing to be bound by theory, the inventors believe that this is caused by higher amounts of electrostatic interactions between homopolymer powder produced using a procatalyst
Data Source
AI summary
The present invention relates to a process for the continuous production of a polyolefin, preferably polypropylene, in a horizontal stirred bed polymerization reactor by contacting one or more olefins, preferably propylene, with a catalyst system while stirring, said catalyst system comprising: * a procatalyst comprising i) titanium; ii) a magnesium-containing support, preferably a magnesium chloride-containing support, and iii) an internal electron donor; * optionally an external electron donor; and * a co-catalyst, being a alkyl aluminum catalyst having formula AlXnR3-n, wherein each X is independently a halide or a hydride and wherein n is 0, 1 or 2, preferably 0, and wherein R is an C1-C12 alkyl group, preferably ethyl, wherein the molar ratio of aluminum (Al) from the co-catalyst to titanium (Ti) from the procatalyst (Al/Ti) is at least 75. The present invention also relates to polyolefin prepared using said process and a shaped article comprising said polyolefin. The present invention moreover relates to the use of a titanium to aluminum ratio during the Ziegler-Natta polymerization of olefins in a horizontal stirred bed reactor to reduce the energy (power) consumption in view of a situation wherein the titanium to aluminum ratio is lower.