Supported Hybrid Metallocene Catalyst Preparation via Segmented Cocatalyst Loading
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Solution Overview
Problem
The challenge is to develop a method for preparing a supported hybrid metallocene catalyst that maintains high catalytic activity while improving the bulk density and molecular weight distribution of polyolefins, as existing methods often result in lowered catalytic activity and bulk density due to polymer crystallization and monomer diffusion issues.
Innovation Solution
The method involves supporting at least one first metallocene compound on a silica support, followed by an aluminum-based cocatalyst, and then a second metallocene compound, with the cocatalyst being added in a separate-input method where 50% to 90% is added at 100°C to 150°C and the remainder at -5°C to 40°C, optimizing the distribution of cocatalyst within the support to enhance bulk density and molecular weight distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a highly active metallocene catalyst is used and the amount of aluminoxane cocatalyst supported on the support is increased to increase catalytic activity, then the catalytic activity is improved, but the polymerization occurs first on the surface of the support and the resulting polymer is crystallized, thereby inhibiting monomer diffusion and lowering the bulk density
Solution Approach 1:
The cocatalyst loading process is segmented into multiple temperature stages: initial loading at room temperature, then heating to 80-100°C for further loading, and finally heating to 120-150°C for complete loading. This temporal segmentation of the loading process allows controlled distribution of cocatalyst throughout the support structure, preventing surface-only polymerization while maintaining high catalytic activity.
2Volume of stationary object
If pre-polymerization is carried out in advance at a low temperature and low pressure to control the rate of diffusion of monomer into the inside of the support, then the bulk density can be improved, but an additional polymerization reactor must be installed, increasing device complexity
Solution Approach 1:
The cocatalyst is preliminarily distributed throughout the support structure by controlled thermal loading before the actual polymerization process. By pre-distributing the cocatalyst using temperature-controlled loading steps (room temperature → 80-100°C → 120-150°C), the system prepares the catalyst support to enable uniform polymerization throughout its volume during normal operation, eliminating the need for separate pre-polymerization equipment.
3Ease of manufacture
If hydroxy groups on the surface of the support are treated with aluminum chloride to improve supporting efficiency, then the supporting efficiency is improved, but the catalyst preparation cost increases and uniformity of the catalyst may decrease due to side reactions
Solution Approach 1:
Instead of chemically modifying the support surface with aluminum chloride, the invention changes the physical parameter of temperature during cocatalyst loading. By controlling the temperature progression (room temperature → 80-100°C → 120-150°C), the system achieves uniform cocatalyst distribution and high supporting efficiency without introducing chemical side reactions that would compromise catalyst uniformity or increase preparation costs.
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 effectively increases the bulk density and molecular weight distribution of polyolefins, improving processability and settling efficiency while maintaining high catalytic activity, as demonstrated by increased ethylene load and productivity in slurry loop pilot processes.
Implementation Method 1
supporting an aluminum-based cocatalyst by contacting the silica support on which the first metallocene compound is supported with at least one aluminum-based cocatalyst compound
Data Source
AI summary
The present disclosure relates to a method for preparing a supported hybrid metallocene catalyst, and the catalyst is prepared by supporting a first metallocene compound, supporting a cocatalyst by a separate-input method in which primarily adding a part at 100 °C to 150 °C and secondarily adding the rest at -5 °C to 40 °C, and then supporting a second metallocene compound, thereby improving a supporting rate of the cocatalyst in the supported catalyst and maintaining high catalytic activity. Therefore, the present disclosure can effectively prepare a polyolefin with improved processability which exhibits increased molecular weight distribution while having high morphology (reduced fine powder), high bulk density and improved settling efficiency.