Bis-Indenyl Metallocene Catalysts for High-Temperature Polypropylene
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Metallocene catalysts used for polypropylene production typically fail to achieve high molecular weights and melting points at industrially relevant temperatures, resulting in polymers with lower properties compared to Ziegler-Natta catalysts.
Innovation Solution
Development of a new family of bis-indenyl metallocene catalysts with specific aryl and alkyl substitutions, used in solid particulate form without external carriers, to enhance polymerization efficiency and produce isotactic polypropylene with high melting points and molecular weights.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional metallocene catalysts are used at industrially relevant temperatures (60-70°C), then catalyst activity and ease of operation are improved, but molecular weight and melting point of the polypropylene decrease
Solution Approach 1:
The patent changes the chemical parameters of the metallocene catalyst by introducing specific substitution patterns (2,4,7-trisubstituted indenyl ligands with bulky aryl groups and electron-withdrawing substituents). This modifies the electronic and steric properties of the catalyst, enabling it to maintain high melting point polymers at industrially relevant temperatures. The parameter change is in the molecular structure of the catalyst ligands, which alters the catalytic activity and polymerization mechanism.
Solution Approach 2:
The patent creates a composite catalyst system combining metallocene complex with specific ligand structures (2,4,7-trisubstituted indenyl) and activating agents (MAO or borate cocatalysts). This composite structure integrates multiple functional components that work synergistically to achieve both high catalyst activity and high polymer melting point at elevated temperatures, resolving the contradiction between operational temperature and polymer quality.
2Productivity
If polymerization temperature is increased to industrially useful levels (70°C), then productivity and ease of operation improve, but molecular weight and melting point decrease significantly
Solution Approach 1:
The patent modifies the catalytic system parameters by incorporating electron-withdrawing substituents (such as CF3, Cl, or Br) at the 7-position of the indenyl ligand. This parameter change in the ligand structure adjusts the electron density at the metal center, optimizing the catalyst's ability to control polymerization at high temperatures while maintaining high molecular weight and melting point polymers.
Solution Approach 2:
The patent applies local quality modification by placing specific substituents at particular positions (2, 4, and 7) on the indenyl ligand structure. The bulky aryl groups at positions 2 and 4 provide steric control, while the electron-withdrawing substituent at position 7 provides electronic control. This localized modification of the ligand structure enables the catalyst to simultaneously achieve high productivity and high polymer melting point at elevated temperatures.
3Strength
If conventional metallocenes are used to achieve high molecular weight at low temperature (-30°C), then melting point and molecular weight improve, but energy consumption increases and productivity decreases
Solution Approach 1:
The patent fundamentally changes the operational temperature parameter from -30°C to 60-70°C by modifying the catalyst structure. This parameter change eliminates the need for expensive cooling infrastructure and energy consumption, while the modified metallocene catalyst with 2,4,7-trisubstituted indenyl ligands maintains the capability to produce high molecular weight, high melting point polypropylene at the higher temperature.
4Reliability
If supported metallocenes are used to improve catalyst stability and ease of operation, then catalyst activity is improved, but polymer melting point decreases
Solution Approach 1:
The patent changes the chemical parameters of the ligand structure by introducing bulky aryl groups (such as 3,5-di-tert-butylphenyl) at the 4-position of the indenyl ring. This parameter change in steric bulk and electronic properties creates a catalyst that produces high melting point polymers even when supported, resolving the contradiction between catalyst stability and polymer quality.
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
The new catalysts produce polypropylene with melting points above 152°C and molecular weights exceeding 300,000 g/mol at commercially relevant temperatures, maintaining high catalyst activity and improving polymer morphology.
Implementation Method 1
a homogeneous catalyst system containing an organometallic compound of a transition metal can be converted, in a controlled way, to solid, uniform catalyst particles
Data Source
AI summary
A catalyst in solid particulate form free from an external carrier material comprising (i) a complex of formula (I) wherein M is zirconium or hafnium; each X is a sigma ligand; L is a divalent bridge selected from -R'2C-, -R'2C-CR'2-, -R'2Si-, -R'2Si-SiR'2-,-R'2Ge-, wherein each R' is independently a hydrogen atom, C1-20-alkyl, tri(C1-20-alkyl)silyl, C6-20-aryl, C7-20-arylalkyl or C7-20-alkylaryl; R2 is a C1-20-hydrocarbyl radical; R2' is a C1-20-hydrocarbyl radical; R5 is a linear or branched aliphatic C1-20-hydrocarbyl group, SR9 or OR9; R6' is a linear or branched aliphatic C1-20-hydrocarbyl group, SR9' or OR9'; with the proviso that neither R6 or R6' represents a group having a quaternary carbon atom directly attached to the indenyl ring; R9 is a C1-20-hydrocarbyl group; R9' is a C1-20-hydrocarbyl group; Ar is a C6-12-aryl or C5-12-heteroaryl group optionally carrying one or more substituents R8; Ar' is a C6-12-aryl or C5-12-heteroaryl group optionally carrying one or more substituents R8'; each R8 is a C1-20-hydrocarbyl group; each R8' is a C1-20-hydrocarbyl group; wherein at least two of R2 and R2'; R6 and R6'; or Ar and Ar' are the same; and (ii) a cocatalyst comprising a compound of a group 13 metal, e.g. A1 or boron.