Dry Catalyst Feed Trimming for Polyolefin Composition Control
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Solution Overview
Problem
Current polymerization processes face challenges in efficiently producing low density polyolefins with controlled molecular weight distribution and composition, particularly due to issues such as gel formation and the need for additional components like catalyst slurry, which can be uneconomical.
Innovation Solution
The process involves combining a dry-feed composition of a supported catalyst system with a solution composition to form a slurry catalyst, which is then introduced into a gas-phase fluidized bed reactor, allowing for in-line adjustment of catalyst ratios and other process conditions to achieve desired polymer properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a supported catalyst system with trim technology is used to adjust catalyst ratios, then the polymer composition and molecular weight distribution can be controlled, but additional components like catalyst slurry and large amounts of solvent are required, increasing process complexity and cost
Solution Approach 1:
The invention extracts and eliminates the solvent component from the traditional slurry-based trim system. By using a gas-phase fluidized bed reactor without solvent, the process simplifies the system while maintaining the ability to control polymer composition and molecular weight distribution through catalyst ratio adjustment. The solvent removal eliminates the need for large amounts of hydrocarbon solvent and associated handling infrastructure.
Solution Approach 2:
The invention employs gas-phase fluidization technology to transport and distribute the supported catalyst system uniformly throughout the reactor. The gas flow serves both as the fluidizing medium and as the carrier for the catalyst particles, eliminating the need for liquid slurry systems while maintaining effective catalyst distribution and contact with monomers.
2Adaptability or versatility
If catalyst slurry with large amounts of solvent is used for trim operations, then catalyst ratio adjustment is achievable, but the process becomes uneconomical due to solvent consumption and additional equipment requirements
Solution Approach 1:
The invention extracts and removes the solvent from the trim operation system. By conducting catalyst ratio adjustment directly in the gas-phase fluidized bed reactor without using hydrocarbon solvents, the process eliminates solvent consumption costs, solvent recovery equipment, and associated operational expenses, thereby improving economic viability while maintaining catalyst ratio adaptability.
Solution Approach 2:
The invention changes the physical state parameter of the reaction medium from liquid (slurry) to gas (fluidized bed). This parameter change enables catalyst ratio adjustment through gas-phase mixing and distribution, eliminating the need for solvent-based trim operations and associated economic burdens while preserving process flexibility.
3Strength
If gel formation occurs during polymerization, then crosslinked high molecular weight structures are formed, but this leads to fisheye defects in extruded film and extrusion difficulties
Solution Approach 1:
The gas-phase fluidized bed reactor provides excellent mixing and heat transfer characteristics that create uniform reaction conditions throughout the reactor volume. This uniform environment prevents localized overheating and excessive crosslinking that lead to gel formation. The continuous gas circulation acts as a feedback mechanism to maintain consistent temperature and monomer distribution, thereby preventing fisheye defects while still achieving desired molecular weights.
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 tailored molecular weight distribution and composition, improving process efficiency and reducing the need for additional components, thus enhancing economic viability.
Implementation Method 1
Gas-phase polymerization processes are today among the preferred processes for polymerizing ethylenically unsaturated monomers, in particular for the polymerization of ethylene, if desired in the presence of further unsaturated monomers. Polymerization processes in fluidized beds are moreover particularly economical.
Implementation Method 2
Polymerization takes place in the presence of catalyst systems such as those employing, for example, a Ziegler-Natta catalyst, a metallocene catalyst, or combinations thereof.
Data Source
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AI summary
A process for polymerizing polyethylene is disclosed. The process comprises contacting ethylene and at least one co-monomer with a catalyst system to produce a polyolefin. The first catalyst and at least a portion of the second catalyst are co- supported to form a commonly- supported catalyst system. The catalyst system is introduced to a line as a dry-feed. The line is coupled with a polymerization reactor. A carrier fluid is added to the line to form a slurry. The slurry is introduced to the polymerization reactor.