Solid Polymethylaluminoxane Particle Control via Inert Gas Bubbling
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Solution Overview
Problem
Current methods for producing solid polymethylaluminoxane compositions result in low yield, high cost, and reduced polymerization activity due to the use of solvents, which can be hazardous and inefficient on a commercial scale, and fail to achieve uniform particle diameters of 30 µm or less, leading to fouling issues and compromised polymer quality.
Innovation Solution
A solid polymethylaluminoxane composition with an aluminum content of 36-43 mass%, a mole fraction of methyl groups from trimethylaluminum of 12% or less, and a median diameter of 0.1-5 µm is developed, characterized by low solubility in solvents and high uniformity, achieved through a method involving heating a solution of trimethylaluminum and polymethylaluminoxane without using silica supports, and employing inert gas bubbling to control particle diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a solid polymethylaluminoxane composition is used instead of a solution, then fouling is reduced and polymer morphology is controllable, but polymerization activity drops significantly
Solution Approach 1:
The invention changes the physical and chemical parameters of the polymethylaluminoxane composition by controlling the Al/O ratio (1.05-2.0), water content (0.01-5 mmol/g), and particle morphology to achieve high activity solid form without significant activity loss
Solution Approach 2:
The invention creates specific local conditions on the particle surface by controlling surface hydroxyl groups and moisture content, enabling the solid particles to maintain high catalytic activity while avoiding fouling issues associated with solutions
2Ease of manufacture
If solvent removal is performed using a vacuum pump, then solid polymethylaluminoxane composition is obtained, but the process is hazardous and inefficient on a commercial scale
Solution Approach 1:
The invention extracts the solvent (toluene) from the polymethylaluminoxane composition through controlled evaporation and filtration processes, obtaining solid particles without requiring vacuum pump operations at commercial scale
Solution Approach 2:
The invention uses nitrogen gas bubbling and flow techniques to facilitate solvent removal and particle formation, replacing the need for vacuum pump-based solvent removal in commercial production
3Ease of manufacture
If silica support is used to create solid polymethylaluminoxane composition, then the composition becomes solid and handleable, but the support remains in the polymer and compromises performance
Solution Approach 1:
The invention completely eliminates the silica support from the system, obtaining solid polymethylaluminoxane composition through controlled solvent removal and particle formation, ensuring no foreign support material remains in the final polymer product
Solution Approach 2:
The invention creates a composite-like structure where polymethylaluminoxane forms solid particles through self-assembly and aggregation, achieving solid handleability without requiring an external support matrix
4Object-affected harmful factors
If particle diameter is reduced to 30 µm or less, then fouling is reduced and polymer uniformity is improved, but current methods cannot achieve this particle size
Solution Approach 1:
The invention controls particle diameter by adjusting parameters such as water content (0.01-5 mmol/g), Al/O ratio (1.05-2.0), and processing conditions to achieve uniform particles of 30 µm or less
Solution Approach 2:
The invention employs periodic nitrogen gas bubbling and controlled evaporation cycles during particle formation to achieve uniform size distribution and prevent agglomeration, enabling consistent sub-30 µm particle production
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 high-yield, high-activity solid polymethylaluminoxane with uniform fine particles, reducing fouling and enhancing polymerization efficiency while maintaining low solvent solubility, thus improving the quality and cost-effectiveness of olefin polymer production.
Implementation Method 1
heating a solution of trimethylaluminum and polymethylaluminoxane without using silica supports, and employing inert gas bubbling to control particle diameter
Data Source
Figure 1
AI summary
The present invention relates to a solid polymethylaluminoxane composition of uniform particle diameter in the form of fine particles of less than 5 µm employed to polymerize olefins with high polymerization activity without silica, to a method for manufacturing thereof, to a polymerization catalyst, and to a method for manufacturing a polyolefin. The present invention relates to a solid polymethylaluminoxane composition: wherein the aluminum content falls within a range of 36 mass% to 43 mass%; wherein the mole fraction of methyl groups derived from trimethylaluminum moieties relative to the total number of mols of methyl groups is 12 mol% or less; and that is particulate, with the median diameter based on volume falling within a range of 0.1 µm to less than 5 µm. In a step of heating an aromatic hydrocarbon solution containing trimethylaluminum and the polymethylaluminoxane to cause solid polymethylaluminoxane composition to precipitate, prior to or during the heat treating step, a dry, inert gas is bubbled through.