Study on the micro-mechanism for the thermal stability of α-diimine nickel catalysts and active centers

Abstract

The thermal stability of α-diimine nickel catalysts has always been a hot research topic, and its thermal deactivation mechanism has not been determined for the time being. In this work, three model α-diimine nickel catalysts with simple backbone structures and only one or two –CH₃ differences were synthesized to catalyze ethylene polymerization at different temperatures. For the first time, the focus of catalyst thermal stability was related to the internal essence (active centers) from the external manifestation (thermal stability of catalyst structure, catalytic activity), and the quenching method of thiophene-2-carbonyl chloride (TPCC) was adopted to further elucidate the essence of catalyst thermal stability from the perspectives of the quantity (quantity of active centers at low/high temperature) and quality (insertion rate constant) of active centers. In this study, it is proposed that the thermal stability of catalysts is a result of the combined effect of the quantity and quality of active centers, while increasing the steric effect by means of increasing –CH₃, etc., essentially affects the balance between the quantity and the quality of active centers. Designing suitable steric effects and finding the optimum point between the above influencing factors is one of the effective ways to improve the thermal stability of catalysts.