Facile Investigation of Ti3+ State in Ti-based Ziegler-Natta Catalyst with A Combination of Cocatalysts Using Electron Spin Resonance (ESR)

Abstract

This study aims to investigate the influences of a combination of cocatalysts including triethylaluminum (TEA) and tri-n-octylaluminum (TnOA) for activation of a commercial Ti-based Ziegler-Natta catalyst during ethylene polymerization and ethylene/1-hexene copolymerization on the change in Ti3+ during polymerization. Thus, electron spin resonance (ESR) technique was performed to monitor the change in Ti3+ depending on the catalyst activation by a single and combination of cocatalyst. It revealed that the amount of Ti3+ played a crucial role on both ethylene polymerization and ethylene/1-hexene copolymerization. For ethylene polymerization, the activation with TEA apparently resulted in the highest catalytic activity. The activation with TEA+TnOA combination exhibited a moderate activity, whereas TnOA activation gave the lowest activity. In case of ethylene/1-hexene copolymerization, it revealed that the presence of 1-hexene decreased activity. The effect of different cocatalysts tended to be similar to the one in the absence of 1-hexene. The decrease of temperature from 80 to 70 °C in ethylene/1-hexene copolymerization tended to lower catalytic activity for TnOA and TEA+TnOA, whereas only slight effect was observed for TEA system. The effect of different cocatalyst activation on the change of Ti3+ state of catalyst was elucidated by ESR measurement. It appeared that the activation of catalyst with TEA+TnOA combination essentially inhibited the reduction of Ti3+ to Ti2+ leading to lower activity. Furthermore, the polymer properties such as morphology and crystallinity can be altered by different cocatalysts. Copyright © 2020 BCREC Group. All rights reserved

Chemical dealcoholation of MgCl2·EtOH adduct by Al compounds and its effect on the performance of Ziegler–Natta catalysts

“…Also, EDX curves and elemental mappings are shown in Figure 3 and Figure S1. Accordingly, all catalysts demonstrate generally the accepted spherical morphology, 57 arising from admirable…”

“…Also, EDX curves and elemental mappings are shown in Figure 3 and Figure S1. Accordingly, all catalysts demonstrate generally the accepted spherical morphology, 57 arising from admirable mechanical properties of the support and appropriate temperature control during catalyst synthesis. Notably, C‐EADC reveals the highest Ti content, which would be related to its vast surface area and the smallest particle size (D 50 ).…”

Temperature effect on propylene polymerization behavior over Ziegler-Natta catalyst with different cocatalyst systems

“…For each measurement, it was operated at 50°C for 90 min. The relative amount of Ti 3+ as a function of time for each measurement was calculated and compared [15].…”