Supported Vanadium-Chromium Catalyst for Polyethylene Molecular Weight Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current polyethylene catalysts, such as Phillips chromium catalysts, are sensitive to carrier modifications and lack a dual active center configuration, limiting their ability to produce polyethylene with broad molecular weight distribution and optimal comonomer content.
Innovation Solution
A supported metal oxide double active center catalyst is developed, incorporating chromium and vanadium oxides on an inorganic carrier, with titanium dioxide or fluorine modifications to enhance catalyst activity and control molecular weight distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If Phillips chromium catalyst is used, then polyethylene with narrow molecular weight distribution and high molecular weight can be produced, but the catalyst is highly sensitive to carrier modifications and lacks dual active center configuration
Solution Approach 1:
The patent applies composite materials by combining chromium oxide and vanadium oxide as dual active centers on a modified silica gel carrier. This composite catalyst system integrates the advantages of both metal oxides to achieve broad molecular weight distribution while maintaining stability against carrier modifications, resolving the contradiction between precision in molecular weight control and adaptability to carrier changes.
Solution Approach 2:
The patent segments the catalytic function into two distinct active centers: chromium oxide for chain growth and vanadium oxide for chain termination. This segmentation allows independent optimization of each function, enabling precise control over molecular weight distribution while reducing sensitivity to carrier modifications since each center operates semi-independently.
2Productivity
If traditional single active center catalysts are used, then catalyst simplicity is maintained, but the ability to produce polyethylene with broad molecular weight distribution and optimal comonomer content is limited
Solution Approach 1:
The patent merges chromium oxide and vanadium oxide into a single catalytic system on the same carrier. This combination allows the catalyst to simultaneously perform chain growth (Cr) and chain termination (V) functions, achieving broad molecular weight distribution and optimal comonomer content while maintaining a unified catalyst structure rather than separate systems.
Solution Approach 2:
The dual active center catalyst system performs multiple functions: chromium oxide catalyzes ethylene polymerization and comonomer insertion, while vanadium oxide controls chain termination and molecular weight distribution. This multi-functionality within a single catalyst system enhances polyethylene production performance without requiring multiple separate catalysts.
3Productivity
If carrier modification is applied to Phillips catalyst, then catalyst activity and polymerization performance are improved, but the sensitivity to carrier form changes increases
Solution Approach 1:
The patent modifies the carrier parameters by introducing titanium dioxide coating and fluorine treatment to the silica gel carrier. These parameter changes enhance the carrier's acid strength and surface properties, which stabilizes the dual active center configuration and reduces sensitivity to further carrier form changes while maintaining high catalyst activity.
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 catalyst achieves broad molecular weight distribution and improved comonomer content in polyethylene products, leading to higher performance polyethylene with increased tie molecules and enhanced processing properties.
Implementation Method 1
a supported metal oxide double active center catalyst, incorporating chromium and vanadium oxides on an inorganic carrier
Implementation Method 2
with titanium dioxide or fluorine modifications to enhance catalyst activity and control molecular weight distribution
Implementation Method 3
fluorine modifications to enhance catalyst activity and control molecular weight distribution
Data Source
AI summary
The present invention relates to a supported hybrid vanadium-chromium-based catalyst, characterized in the catalyst is supported on a porous inorganic carrier and a V active site and a inorganic Cr active site are present on the porous inorganic carrier at the same time. The present invention further relates to a process for producing a supported hybrid vanadium-chromium-based catalyst. The invention also provides the preparation method of the catalyst, titanium or fluorine compounds, vanadium salt and chromium salt according to the proportion, different methods of sequence and load on the inorganic carrier, after high temperature roasting, still can further add organic metal catalyst promoter prereduction activation treatment on it. The catalyst of the present invention can be used for producing ethylene homopolymers and ethylene/α-olefin copolymers. The hybrid vanadium-chromium-based catalyst can have high activity and produce polyethylene polymers having the properties of broad molecular weight distribution (Part of the products are bimodal distribution) and excellent α-olefin copolymerization characteristic.