Effect of Phosphine‐Containing Modifiers on the Performance of Chromium/Silicon‐Bridged Diphosphine/Methylaluminium Catalytic System for Ethylene Tri‐/Tetramerization

ABSTRACT In recent years, many researchers have studied the influence of modifying components on catalytic performance by adding them to ethylene oligomerization systems. This paper studied the effect of eight phosphine‐containing modifiers on the catalytic performance of the chromium‐based silicon‐bridged diphosphine (PNSiP)/methylaluminium system. Modifiers like diethylchlorophosphine oxide, diphenylchlorophosphine oxide, triphenylphosphine, trimethylphosphine, triethylphosphine, phosphorus trichloride, diphenylphosphine chloride, and diisopropyl phosphorus chloride showed a significant influence on the catalytic activity of the catalytic system and the selectivity of 1‐octene. When the molar ratio of diethylchlorophosphine oxide to chromium increased to 0.6, the catalytic activity increased from 7.39 × 10 6 to 11.75 × 10 6 g/ (mol Cr·h), exhibiting the most remarkable promotional effect. When the molar ratio of diphenylphosphine chloride to chromium increased to 0.6, the selectivity of 1‐octene increased by 11.89%. Based on the results of electron paramagnetic resonance (EPR) and ultraviolet–visible spectrum (UV–Visible) analysis, we inferred that diethylchlorophosphine oxide was coordinated with the chromium active center through a phosphine‐oxygen bond, which improved the catalytic activity of the reaction system. Furthermore, a possible reaction path between diethylchlorophosphine oxide and the chromium active center has been proposed, which is expected to provide a more economical and feasible strategy for the optimization of selective ethylene tetramerization systems.