Catalyst System for HDPE Slurry Polymerization
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Solution Overview
Problem
Current slurry polymerization processes for producing high-density polyethylenes (HDPE) face challenges with the formation of waxes and ethane as by-products, which affect product properties and process efficiency, and existing catalyst systems do not effectively reduce these by-products while maintaining desired properties like MFR, MFR(21.6), and density.
Innovation Solution
A catalyst system comprising a magnesium-containing compound, an organo aluminium halide, and an electron donor, specifically with a molar ratio of magnesium to titanium below 3:1 and a molar ratio of the electron donor to titanium between 0.05 and 0.40, is used to reduce hexane-extractable content and ethane formation in the polymerization process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional catalyst systems are used in slurry polymerization processes, then polyethylene production is achieved, but waxes and ethane are formed as unwanted by-products affecting product properties and process efficiency
Solution Approach 1:
The patent applies parameter changes by optimizing the molar ratio of magnesium to titanium in the catalyst system to be less than 3:1, and the molar ratio of electron donor to titanium to be between 0.05 and 0.40. These specific parameter adjustments modify the catalyst's chemical composition and activity, leading to reduced wax and ethane formation while maintaining high productivity in slurry polymerization processes.
2Object-generated harmful factors
If conventional catalyst systems are used in slurry polymerization processes, then polyethylene production is achieved, but the desired properties like MFR, MFR(21.6), and density are not optimally maintained while reducing by-products
Solution Approach 1:
The patent employs parameter changes by precisely controlling the molar ratios of catalyst components (Mg:Ti < 3:1 and electron donor:Ti = 0.05-0.40) to simultaneously achieve reduced by-product formation and optimal product properties including MFR, MFR(21.6), and density, resolving the contradiction between harm reduction and property control.
Solution Approach 2:
The patent uses a composite catalyst system comprising magnesium-containing compounds, organo aluminium halides, and electron donors in specific ratios. This composite catalyst structure allows for fine-tuned control over polymerization reactions, enabling both reduced wax/ethane formation and precise control of polyethylene properties through the synergistic interaction of different catalyst components.
3Stability of the object's composition
If multi-stage polymerization processes are employed to achieve desired molecular weight distribution, then material properties are improved, but process complexity increases
Solution Approach 1:
The patent applies parameter changes by optimizing the catalyst composition (Mg:Ti ratio < 3:1 and electron donor:Ti ratio = 0.05-0.40) to achieve desired molecular weight distribution and material properties within a single polymerization stage, thereby eliminating the need for complex multi-stage processes and reducing overall process complexity while maintaining composition stability.
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 catalyst system significantly lowers the fraction of waxes and ethane produced, achieving a balance of desired properties such as MFR(5), MFR(21.6), and density in the resulting HDPE, with hexane-extractable content below 2.00% and ethane formation below 0.30% by volume, enhancing process efficiency and product quality.
Implementation Method 1
The process for production of polyethylenes may for example comprise a single polymerisation stage comprising a slurry polymerisation process... Production of polyethylenes in slurry polymerisation processes in general takes place in the presence of a catalyst system... a catalyst system comprising a catalyst, a cocatalyst and an electron donor
Data Source
AI summary
The present invention relates to a catalyst system for the production of polyethylene comprising: I) the reaction product obtained by reacting a) a hydrocarbon solution comprising: i. a magnesium-containing compound selected from an organic oxygen-containing magnesium compound and/or a halogen-containing magnesium compound; and ii. an organic oxygen-containing titanium compound wherein the molar ratio of magnesium: titanium is lower than 3:1; and b) an organo aluminium halide having the formula AlRnX3-n in which R is a hydrocarbon moiety containing 1-10 carbon atoms, X is a halogen and 0 < n < 3; II) an aluminium compound having the formula AlR'3, in which R' is a hydrocarbon moiety containing 1-10 carbon atoms; and III) one or more of an electron donor selected from the group of 1,2-dialkoxy hydrocarbon compounds wherein the molar ratio of supplied organo aluminium halide I)b) to supplied titanium in I) a) in the preparation of I) is between 5.0 and 7.0; and the molar ratio of the electron donor III) to the titanium present in the reaction product I) is between 0.05 and 0.40 The production of polyethylene using said catalyst system results in a reduction of formation of ethane and a reduction of the hexane-extractable content of the polyethylene.