Catalytic tri- and tetramerization of ethylene: a mechanistic overview

ABSTRACT

On purpose, selective oligomerization of ethylene to its linear trimer and tetramer such as 1-hexene and 1-octene has assumed significant commercial interest. Catalytic systems based on chromium and titanium have shown remarkable selectivity and productivity for the tri and tetramerization of ethylene to 1-hexene or 1-octene. Chromium-based catalysts are the most selective and active and show the highest structural diversity. This article discusses the most recent mechanistic approaches regarding active catalytic species that determine the selectivity to either hexene-1 or octene-1 and reaction parameters that control selectivity of byproducts. Isotopic labeling protocols, in-situ spectroscopic investigations and DFT studies on selected chromium-based catalyst systems are reviewed.

KEYWORDS:

• Ethylene trimerization
• chromacycloheptane
• tetramerization
• density functional theory
• P-N-P ligands
• chromacyclononane

Acknowledgments

I am grateful to Dr. Raksh Vir Jasra, Reliance Technology Group, Reliance Industries Ltd. for providing an opportunity to work on the development and commercialization of ethylene oligomerization catalysts during my long tenure at RIL research centre. I am also indebted to my former colleagues in the homogeneous catalysis group at the R&D centre for stimulating discussions. Special appreciation to the pilot plant engineering team at Vadodara for inputs during process scale-up and commercial production of on-purpose alpha olefins.

Disclosure statement

No potential conflict of interest was reported by the author(s).