Supported Three-Center Catalyst for Trimodal Polyethylene
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Solution Overview
Problem
Current polyethylene catalysts lack the capability to produce high-performance trimodal polyethylene with a wide molecular weight distribution using a single reactor, as existing three-center catalysts have not been reported in the prior art.
Innovation Solution
A supported three-center catalyst comprising a porous inorganic carrier and three catalyst active centers: organic chromium, inorganic chromium, and inorganic vanadium active components, which are activated through specific precursor preparation and calcination processes, enabling homopolymerization and copolymerization of ethylene and α-olefins with trimodal molecular weight distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single-metal catalyst or two-center catalyst is used, then the catalytic activity is improved, but the molecular weight distribution is limited and cannot achieve trimodal distribution
Solution Approach 1:
The patent combines three different metal centers (chromium, vanadium, and zinc) into a single catalyst system, where each metal center contributes different catalytic functions. This merging of multiple active centers enables the catalyst to produce polymers with trimodal molecular weight distribution while maintaining high catalytic activity, resolving the contradiction between activity and distribution capability.
Solution Approach 2:
The catalyst uses a composite structure with multiple metal components supported on a carrier. The composite nature of the catalyst, containing chromium, vanadium, and zinc in specific ratios, allows it to simultaneously provide high activity and produce trimodal molecular weight distribution, overcoming the limitations of single-metal or two-center catalysts.
2Adaptability or versatility
If a three-stage process with single metal center catalyst is used, then trimodal polyethylene can be produced, but the device complexity and operation difficulty increase
Solution Approach 1:
The patent merges the functions of three separate catalysts (each producing different molecular weight components) into a single three-center catalyst system. This allows trimodal polyethylene to be produced in a single reactor instead of requiring three sequential reactors, significantly reducing device complexity and operational difficulty while maintaining the ability to produce trimodal distribution.
Solution Approach 2:
The three-center catalyst exhibits multi-functionality by simultaneously catalyzing the formation of three different molecular weight components in one reactor. This universal catalyst can replace multiple specialized catalysts and reactors, simplifying the overall process while achieving the same trimodal product distribution.
3Reliability
If two-pot series process is used to synthesize bimodal polyethylene, then the product performance is improved, but the investment and energy consumption increase
Solution Approach 1:
The patent combines two separate polymerization processes into one by using a dual-functional catalyst system. The catalyst contains both chromium centers (for high molecular weight) and vanadium centers (for low molecular weight), allowing bimodal polyethylene to be synthesized in a single reactor, thereby reducing energy consumption and equipment investment while maintaining product performance.
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 a wide molecular weight distribution with trimodal or multimodal polyethylene products, allowing for the synthesis of ethylene homopolymers and copolymers with adjustable molecular weights and comonomer distributions, offering economic, green, and efficient production compared to traditional multi-stage processes.
Implementation Method 1
activated through specific precursor preparation and calcination processes
Implementation Method 2
three catalyst active centers: organic chromium, inorganic chromium, and inorganic vanadium active components
Data Source
AI summary
A supported three-center catalyst, a preparation method and the use are provided. The catalyst comprises a porous inorganic carrier, an organic chromium active component, an inorganic chromium active component and an inorganic vanadium active component, and may further comprise a catalyst modifying component. A method involves, by means of one or more steps of dipping and drying or dipping, drying and high-temperature roasting procedures, respectively converting an organic chromium source, a chromium source, a vanadium source and a Q component into an organic chromium active component precursor, an inorganic chromium active component precursor, an inorganic vanadium active component precursor and a catalyst modifying component that are supported on the surface of the porous inorganic carrier, and then activating same with an organometallic cocatalyst or a polymerization monomer, so as to obtain the supported three-center catalyst.