Metallocene Catalyst Flowability via Carboxylate Salt Mediation
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Solution Overview
Problem
Metallocene catalysts, particularly supported metallocene catalysts, face challenges with poor flowability, leading to adherence to surfaces and agglomeration, which complicates storage, transportation, and delivery into polymerization reactors, especially at elevated temperatures above 25°C.
Innovation Solution
A catalyst composition comprising a metallocene catalyst compound and a metal carboxylate salt with improved flow properties, characterized by flowing through a funnel in less than 45 seconds at temperatures above 25°C, and optionally capable of continuous polymerization process operation without cooling the feeding system, utilizing a modified carboxylate metal salt with a hexane extractable fraction having a peak melting point of 60°C or higher.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If metallocene catalysts are used to produce polyolefin polymers, then efficient polymerization processes and improved polymers are achieved, but poor flowability and catalyst particle adherence to surfaces occur
Solution Approach 1:
A carboxylate metal salt is introduced as an intermediary substance to modify the surface properties of metallocene catalyst particles. The salt acts as a mediator that reduces interparticle adhesion and surface adherence, enabling improved flowability while preserving the high polymerization activity of the metallocene catalyst system
Solution Approach 2:
The physical and chemical parameters of the catalyst composition are modified by incorporating carboxylate metal salts, which change the surface energy and electrostatic properties of catalyst particles. This parameter change transforms the catalyst from a poor-flowing state to a free-flowing state suitable for handling and reactor feeding
2Reliability
If carboxylate metal salts are added to address reactor fouling, then reactor operability is improved, but catalyst flowability deteriorates
Solution Approach 1:
Specific parameters of the carboxylate metal salt are optimized, including the carbon chain length of the carboxylate group (14-100 carbon atoms) and the metal identity (Group 2 or 13), to achieve a balance where reactor fouling is prevented while maintaining acceptable catalyst flowability
Solution Approach 2:
The catalyst system is formulated as a composite material combining metallocene catalyst compound, carboxylate metal salt, and optionally alkylalumoxane. This composite approach allows the synergistic combination of high activity (metallocene), fouling prevention (carboxylate salt), and flowability enhancement (alkylalumoxane coating)
3Ease of operation
If catalyst composition is heated to improve flowability, then flow properties are enhanced, but additional energy consumption and process complexity increase
Solution Approach 1:
The catalyst composition is designed to be self-sufficient for flowability without requiring external heating. The carboxylate metal salt and alkylalumoxane coating provide inherent flow improvement through modified interparticle forces and surface properties, eliminating the need for energy-intensive thermal processing
Data Source
AI summary
Catalyst compositions for the polymerization of olefins having improved flowability properties are provided.