A chromium precursor for the Phillips ethylene trimerization catalyst: (2-ethylhexanoate)2CrOH.

Area of Science:

• Organometallic Chemistry
• Catalysis
• Polymer Science

Background:

• The Phillips ethylene trimerization catalyst, based on chromium(III) 2-ethylhexanoate (Cr(EH)3), exhibits variable performance.
• The ill-defined nature of the Cr(EH)3 precursor contributes to inconsistent catalytic activity.

Purpose of the Study:

• To develop an improved Phillips catalyst system with enhanced stability and activity.
• To synthesize and characterize new chromium precursors for ethylene trimerization.

Main Methods:

• Synthesis of a novel chromium precursor, (EH)2CrOH, via reaction of CrCl3 with sodium 2-ethylhexanoate.
• Preparation of a dimeric Cr(II)-complex coordinated by specific ligands.
• Activation of the Cr(II)-complex with a co-catalyst (Et3Al·ClAlEt2) for ethylene trimerization.

Main Results:

• The new precursor (EH)2CrOH was successfully synthesized and characterized.
• The improved catalyst system demonstrated consistently high activity (54 × 10^6 g per mol-Cr h), significantly outperforming the conventional Phillips system.
• The dimeric Cr(II)-complex, when activated, yielded highly active catalytic species.

Conclusions:

• The novel chromium precursor and associated catalytic system provide a more reliable and active route for ethylene trimerization.
• This advancement offers a more robust alternative to the conventional Phillips catalyst for industrial applications.