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Heterogeneous Catalysis

Heterogeneous Catalysis

Heterogeneous catalysis involves a catalyst in a different phase from the reactants. It is a process where the catalyst and the reactants are in distinct phases, typically solid and gas or liquid.Most heterogeneous catalysts are metals, metal oxides, or acids. The list includes transition metals like iron (Fe), cobalt (Co), nickel (Ni), palladium (Pd), platinum (Pt), chromium (Cr), manganese (Mn), tungsten (W), silver (Ag), and copper (Cu). These metals possess partially vacant d orbitals that...

Olefin Metathesis Polymerization: Overview

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Recently, the development of olefin metathesis polymerization advanced the field of polymer synthesis. Simply put, the reorganization of substituents on their double bonds between two olefins in the presence of a catalyst is known as the olefin metathesis reaction. The use of metathesis reaction for polymer synthesis is called olefin metathesis polymerization.
Ruthenium-based Grubbs catalyst is the most commonly used catalyst for olefin metathesis polymerization. Grubbs catalyst consists of a...

Ziegler–Natta Chain-Growth Polymerization: Overview

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Ziegler–Natta polymerization is another form of addition or chain‐growth polymerization used for synthesizing linear polymers over branched polymers. The catalyst used for polymerization is the Ziegler–Natta catalyst, named after Karl Ziegler and Giulio Natta, who developed it in 1953. This catalyst is an organometallic complex of titanium tetrachloride and triethyl aluminum, with the active form of the catalyst being an alkyl titanium compound. Using the Ziegler–Natta catalyst, high molecular...

Catalysis

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Catalysis influences the rate of chemical reactions by providing an alternative reaction pathway with lower activation energy. A catalyst speeds up a reaction, but it is not consumed during the process. The fundamental principle of catalysis is the ability of a catalyst to alter the reaction mechanism, often introducing a more efficient pathway than the uncatalyzed process.In a catalyzed reaction, the catalyst participates directly in the reaction mechanism. It interacts with reactants to form...

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Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
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Fluid-mediated nuclearity control in heterogeneous polyolefin catalysis.

Zaitian He^1,2, Jingyuan Sun^1,2, Qingyuan Zheng^3,4

¹State Key Laboratory of Chemical Engineering, Zhejiang Provincial Key Laboratory of Advanced Chemical Engineering Manufacture Technology, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, P.R. China.

Nature Communications

|July 2, 2026

Summary

Researchers developed a liquid-phase polymerization method to control active sites in Ziegler-Natta catalysts. This strategy enhances comonomer incorporation, leading to polyethylene with uniform short-chain branching (SCB) distribution.

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Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization

Ethylene Polymerizations Using Parallel Pressure Reactors and a Kinetic Analysis of Chain Transfer Polymerization

Published on: November 27, 2015

Area of Science:

Polymer Chemistry
Catalysis
Materials Science

Background:

The structure of active sites in heterogeneous Ziegler-Natta catalysts is crucial for polyolefin microstructure.
Dynamically regulating active site nuclearity during polymerization is a significant challenge.
Conventional gas- or slurry-phase polymerization typically favors monomeric active species.

Purpose of the Study:

To investigate a liquid-containing polymerization strategy for controlling Ziegler-Natta catalyst active site nuclearity.
To understand how fluid dynamics influence active site formation and polymerization outcomes.
To enhance comonomer incorporation and control short-chain branching (SCB) distribution in polyethylene.

Main Methods:

Developed a liquid-containing polymerization strategy involving periodic wetting-drying of inert n-hexane.
Utilized operando spectroscopy to characterize active site formation (dinuclear vs. monomeric species).
Employed diffusion-ordered NMR spectroscopy to analyze comonomer concentration within catalyst pores.

Main Results:

The liquid-containing environment promoted the formation of dinuclear titanium species, unlike conventional methods.
Dinuclear sites significantly improved comonomer incorporation efficiency.
Polyethylene synthesized exhibited a more uniform short-chain branching (SCB) distribution.
Capillary condensation of n-hexane enriched 1-octene concentration in catalyst pores, boosting SCB content.

Conclusions:

Reactor fluid dynamics can be leveraged for in-situ active-site engineering in Ziegler-Natta catalysis.
This approach allows for selective control over polymer microstructure, specifically SCB distribution.
The strategy offers a pathway to tailor polyethylene properties without altering catalyst composition.