Metallocene-Alkyl Catalyst Flowability and Fouling
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Solution Overview
Problem
Supported metallocene catalysts face issues with flowability and reactor fouling, which complicates storage, transportation, and injection into polymerization reactors, and existing solutions either require complex processes or increase costs.
Innovation Solution
The use of metallocene-alkyls in conjunction with an inorganic oxide support calcined at high temperatures (above 750°C) and an antifoulant agent improves flowability and reactor operability, enhancing polymerization activity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If metallocene catalysts are used in olefin polymerization, then polymerization activity is improved, but flowability deteriorates and reactor fouling increases
Solution Approach 1:
The patent changes the chemical composition parameters by using metallocene-alkyl instead of metallocene-halide, and adjusts the support calcination temperature to above 750°C. These parameter changes resolve the contradiction by improving flowability while maintaining high polymerization activity, eliminating the need for prepolymerization steps.
Solution Approach 2:
The patent creates a composite catalyst system combining metallocene-alkyl with specific support materials (calcined at >750°C) and antifoulant agents. This composite approach simultaneously addresses flowability issues and reactor fouling while preserving high catalytic activity, avoiding the complexity of multiple processing steps.
2Object-affected harmful factors
If antifoulant agents are added to address reactor fouling, then reactor operability is improved, but flowability deteriorates
Solution Approach 1:
The patent changes the chemical nature of the catalyst from metallocene-halide to metallocene-alkyl, which fundamentally alters how the catalyst interacts with antifoulant agents. This parameter change allows the use of antifoulants to control reactor fouling without the severe flowability penalties observed with traditional metallocene-halide systems.
Solution Approach 2:
The metallocene-alkyl acts as an intermediary that mediates between the antifoulant agent and the catalyst activity. This intermediary approach allows the antifoulant to effectively reduce reactor fouling while the metallocene-alkyl maintains catalyst flowability and activity, avoiding the trade-off present in conventional systems.
3Productivity
If metallocene-halides are used, then catalyst activity is high, but flowability and reactor operability deteriorate
Solution Approach 1:
The patent fundamentally changes the catalyst composition parameter by replacing the halide ligand with an alkyl ligand on the metallocene. This parameter change transforms the catalyst's physical and chemical properties, achieving high activity while simultaneously improving flowability and reactor operability without requiring complex processing steps.
Solution Approach 2:
The patent extracts the problematic halide component from the metallocene structure and replaces it with an alkyl group. This extraction of the harmful element (halide) while retaining the core metallocene structure allows the catalyst to maintain high activity while eliminating the flowability and reactor fouling issues associated with metallocene-halides.
4Ease of operation
If prepolymerization is performed to improve flowability, then flow properties are improved, but process complexity increases
Solution Approach 1:
Instead of performing prepolymerization as a preliminary action to improve flowability, the patent uses a different preliminary approach: selecting metallocene-alkyl and calcining the support at high temperature (>750°C) during catalyst preparation. This alternative preliminary action achieves improved flow properties without requiring the complex prepolymerization step.
Solution Approach 2:
The patent adopts a simpler, more direct catalyst composition (metallocene-alkyl with calcined support) that provides adequate flowability without the need for elaborate prepolymerization treatments. This approach uses a straightforward catalyst formulation that eliminates complex processing steps while achieving the desired flow properties.
Data Source
AI summary
A supported catalyst composition having improved flow properties is disclosed comprising an alkylalumoxane, a metallocene-alkyl an inorganic oxide support having an average particle size of from 0.1 to 100 µm and calcined at a temperature of 600°C or greater, and optionally an antifoulant agent. In one embodiment, the metallocene-alkyl is a Group 4, 5 or 6 metallocene-alkyl, and in another embodiment is a hafnocene-alkyl. Also disclosed is a method of polymerization using such a supported catalyst compositions.