Ziegler-Natta Catalyst for Broad Polyethylene Molecular Weight
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Solution Overview
Problem
Conventional Ziegler-Natta catalysts fail to produce polyethylene with a broad molecular weight distribution in a single polymerization stage, limiting processibility and requiring multi-stage processes or complex catalyst systems.
Innovation Solution
A main catalyst component for olefin polymerization is prepared by reacting a magnesium compound in nascent state with an alcohol and an alkyl magnesium compound, followed by halogenation and reaction with a titanium compound, using a silica carrier to achieve a catalyst with high polymerization activity and broad molecular weight distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional Ziegler-Natta catalysts are used, then the catalyst system is simple and easy to manufacture, but the molecular weight distribution of polyethylene is narrow (limiting processibility)
Solution Approach 1:
The catalyst preparation is divided into multiple sequential steps: (1) preparing magnesium compound in nascent state, (2) reacting with alcohol, (3) reacting with alkyl magnesium compound, (4) halogenation, and (5) reacting with titanium compound. This segmentation allows each step to be optimized independently to achieve broad molecular weight distribution while maintaining manageable complexity.
Solution Approach 2:
The magnesium compound is prepared in nascent state before the main catalyst formation, and alcohol is pre-reacted with the magnesium compound to form an intermediate complex. These preliminary actions create a reactive intermediate that enables the subsequent formation of catalysts with broad molecular weight distribution.
2Adaptability or versatility
If multi-stage polymerization processes are used to achieve broad molecular weight distribution, then the processibility is improved, but the manufacturing complexity and time consumption increase
Solution Approach 1:
The main catalyst component prepared according to the invention performs multiple functions simultaneously: it provides high polymerization activity while also producing polyethylene with broad molecular weight distribution (Mw/Mn = 6-10) in a single polymerization stage. This eliminates the need for multiple polymerization stages, thereby improving productivity while maintaining processibility.
3Productivity
If conventional catalysts are used, then the manufacturing process is simple, but the polymerization activity and hydrogen response are insufficient
Solution Approach 1:
The invention changes the chemical parameters of the catalyst system by using magnesium compound in nascent state (with specific composition (RMgX)y(MgX2) where y = 0.02-1) and reacting it with alcohol and alkyl magnesium compound to form a unique intermediate complex. This parameter change in the magnesium compound's chemical state and composition leads to enhanced polymerization activity and hydrogen response.
Solution Approach 2:
Alcohol acts as an intermediary in the reaction between magnesium compound in nascent state and alkyl magnesium compound. The alcohol forms an intermediate complex that mediates the formation of the final catalyst structure, enabling the achievement of high polymerization activity through a controlled reaction pathway.
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 exhibits high polymerization activity, good hydrogen response, and produces polyethylene with a molecular weight distribution of 6 to 10, enhancing processibility and reducing the need for multi-stage polymerization.
Implementation Method 1
reacting a magnesium compound in nascent state with an alcohol and an alkyl magnesium compound, followed by halogenation and reaction with a titanium compound
Implementation Method 2
Main catalyst component for olefin polymerization, a process for preparing the same and a catalyst comprising the same. The olefin polymerization catalyst is useful in homopolymerization and copolymerization of ethylene
Data Source
AI summary
The present invention provides a main catalyst component for olefin polymerization, which is prepared by a process comprising the steps of: (i) reacting a magnesium compound in nascent state having a rational formula (RMgX)y(MgX2), in which R is an alkyl having from 3 to 12 carbon atoms, X is a halogen, and y is a value of from 0.02 to 1, with an alcohol having a formula R1OH, in which R1 is an alkyl having from 2 to 12 carbon atoms, to form a homogeneous solution; (ii) reacting an alkyl magnesium compound having a formula R′MgR″, in which R′ and R″ are independently an alkyl having from 1 to 20 carbon atoms, with the homogeneous solution formed in the step (i) to form a magnesium complex; (iii) reacting the magnesium complex with a halogenating agent in the presence of a silica, to form a magnesium halide-containing intermediate product; and (iv) reacting the magnesium halide-containing intermediate product from the step (iii) with a titanium compound having a formula Ti(OR2)mCl4-m, in which R2 is an alkyl having from 1 to 10 carbon atoms and m is an integer of from 0 to 4, to form a titanium-containing main catalyst component. The main catalyst component of the invention, when used together with an orgaoaluminium cocatalyst component in a single polymerization stage in one reactor to catalyze the polymerization of ethylene to polyethylene, gives a polyethylene having a molecular weight distribution of from 6 to 10.