Influence of Hydrogen on Catalytic Properties of Ziegler‐Natta Catalysts Prepared by Different Methods in Ethylene Polymerization

Abstract

Ethylene homopolymerization by two types of Ziegler-Natta catalyst including ZN-THF and ZN-EtOH catalysts was compared. The influences of hydrogen pressure and reaction time on catalytic activity using different types of catalyst were investigated. The EDX analysis and surface area measurement confirmed that ZN-EtOH catalyst had better active center distribution than that of ZN-THF. Thus, the ZN-EtOH catalyst could retard the effect of hydrogen and show higher activity with increased hydrogen pressures. However, catalytic activity was lower with high hydrogen pressure. Moreover, polymerization time also has an influence on activity. Both catalysts showed the similar result where an increase in polymerization time can improve yield of polymer, but it decreased activity. In addition, it is seen that the increase in hydrogen pressure leads to decrease the melting temperature for polyethylenes, but it increases the crystallinity.

Geometry and Local Environment of Surface Sites in Vanadium-Based Ziegler–Natta Catalysts from 51V Solid-State NMR Spectroscopy

“…X-ray powder diffraction analysis exhibited a significant broadening of the features upon treatment of MgCl 2 (thf) 1.5 with VOCl 3 , which is consistent with the observed increase of the surface area from 5.2 m 2 /g to 50 m 2 /g, both indicating a loss of long-range order (>2 nm) compared to its pristine state, also paralleling what is observed for the corresponding Ti-based systems (Supporting Information). The solid displays a catalytic activity of 4.7 kg PE ·g V –1 ·h –1 in the ethylene polymerization reaction under standard conditions (20 bar of ethylene, 30 °C, n -heptane as solvent) upon activation with AlEt 3 , paralleling the reactivity of the Ti-based systems. Coming back to characterization, the solid-state 13 C NMR spectrum is dominated by two features at 70 and 28 ppm corresponding to residual THF coordinated to the surface of MgCl 2 , while the IR spectrum shows the emergence of a peak at ca.…”

“…X-ray powder diffraction analysis exhibited a significant broadening of the features upon treatment of MgCl 2 (thf) 1.5 with VOCl 3 , which is consistent with the observed increase of the surface area from 5.2 m 2 /g to 50 m 2 /g, both indicating a loss of long-range order (>2 nm) compared to its pristine state, also paralleling what is observed for the corresponding Ti-based systems (Supporting Information). 33 The solid displays a catalytic activity of 4.7 kg PE •g V −1…”

Impact of AlCl3 and FeCl2 Addition on Catalytic Behaviors of TiCl4/MgCl2/THF Catalysts for Ethylene Polymerization and Ethylene/1-Hexene Copolymerization

“…In case of hydrogen addition during polymerization, effect of hydrogen on catalytic activity for ethylene polymerization behaviors is summarized as seen in Table 3. Activity of all catalysts decreased with hydrogen addition, which is common for ethylene polymerization with ZN catalysts [30,31]. In this study, Lewis acid doped catalysts exhibited higher activity than the one with the absence of Lewis acid (Cat.…”

Effect of adduct synthesis parameters on the ethylene polymerization kinetics of Ziegler Natta catalysts

“…Since cocatalyst type and amount has a significant effect on the polymerization kinetic and the final properties of polyethylene, 44,45 the amount of TEA was constant in all experiments. In the polymerization experiments, beside ethylene monomer, H 2 is also employed as the chain transfer agent 46,47 to assess H 2 response of the catalysts. According to the flow (MFR2.16) and molar mass characteristics, Table 4, Cat-10, Cat-1, and Cat-4 exhibit better H 2 response, with lower MFR2.16 and M w .…”