Comparative ethylene polymerization using FI-like zirconium based catalysts

Abstract

Three FI-like Zr-based catalysts, Bis[1-[(phenylimino)methyl]-2-naphtholato]zirconium(IV) dichloride (1), Bis[1-[(mesitylimino)methyl]-2-naphtholato]zirconium(IV) dichloride (2) and Bis[1-[(2,6-diisopropylphenyl)imino] methyl-2-naphtholato]zirconium(IV) dichloride (3) were prepared by changing the ligand from salicylaldehyde imine ligand, which is a well known FI catalysts, to 2-hydroxynaphthalene-1-carbaldehyde imine ligand and used for polymerization of ethylene. Triisobutylaluminum (TIBA) and methylaluminoxane (MAO) were used as scavenger and cocatalyst, respectively. Introduction of the bulky substitution phenyl ring on the N of the phenoxy imine ligand enhanced the viscosity average molecular weight of the obtained polymer strongly. Catalyst 3 produced the highest viscosity average molecular weight (M v ) of the obtained polyethylene, but showed the lowest catalytic activity. The activity of all the catalysts was increased with the increase of [Al]/[Zr] molar ratio to an optimum value followed by a slight decrease at higher [Al]/[Zr] molar ratios. Optimum activity of catalyst 1 was obtained at about 30°C while the highest activity of catalysts 2 and 3 was obtained at about 40°C following a sharp decrease at higher temperatures. The rate/time profile of the polymerization decayed with a short acceleration period for all of the catalysts. The polymerization activity was increased with increasing the hydrogen concentration due to the fast hydrogenation of sterically more hindered and less reactive intermediates such as those resulting from 2,1-insertions. It is noteworthy that the experimental results indicated that the hydrogen does not act as a chain transfer

FI Catalyst for Polymerization of Olefin

“…Catalyst systems based on bis(phenoxy-imine) complexes of Ti(IV), Zr(IV) and MAO are effective catalysts for polymerization of ethylene and propylene [19,33,34,38,50,[51][52][53][54]. Detailed 13 C NMR analysis of end-groups in polypropylene prepared with several catalysts of this type showed unusual chemical and regio-effects [52,55].…”

“…Ahmadjo and coworkers [53] (3) were prepared by changing the ligand from salicylaldehyde imine ligand, to 2-hydroxynaphthalene-1-carbaldehyde imine ligand and used for polymerization of ethylene (Figure 14) [53]. It has been reported that introducing the sterically bulky isopropyl groups enhances molecular weight of the resulting polymer through destabilization of -agostic interaction due to the steric repulsion betweenhydrogen of the growing polymer and isopropyl leading to decrease the -H elimination [34].…”

“…In the catalyst containing bulky isopropyl group phenyl ring on the N (Figure 14), it seems that -carbon of polymer chain is not easily accommodated in the plane because of the steric interaction between naphthoxy-imine ligands of the catalyst and -H of the growing polymer chain (Figure 15). It can be concluded that the sterically bulky substituents on the aniline ring of the naphthoxy-imine ligands cause a strong suppression of the both -hydride elimination and -hydride transfer to monomer leading to increase the molecular weight of the resulted polymer [53].…”

Titanium (IV) and Nickel (II) Catalysts Based on Anilinotropone Ligands

“…Ethylene polymerization behavior using catalysts 3, 4 and 5 were studied under different reaction times (Table 1, entries 20-34) and temperatures (entries [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. The highest activity of catalyst 5 was obtained at 10 °C (31200 Kg PE mol cat -1 h -1 ).…”

“…Therefore, much effort has been directed towards the development of highly active catalysts, following the group 4 metallocene catalysts. In consequence, quite a few highly active catalysts based on both early and late transition metal complexes have been developed [7][8][9][10][11][12][13][14]. There are, however, only a few examples of titanium complexes displaying high ethylene polymerization activities [15][16][17][18][19], though titanium metal is the major player in highly active heterogeneous Ziegler-Natta catalysts.…”