Effects of MgCl₂ Crystallographic Structure on Active Centre Formation in Immobilized Single‐Centre and Ziegler–Natta Catalysts for Ethylene Polymerization

Abstract

The ability of a MgCl2 support to activate a transition metal catalyst has been found to depend both on the crystallographic structure of the support and on the nature of the catalyst. A high degree of crystallographic disorder can be very effective for the immobilization and activation of titanium and vanadium complexes, but is not necessarily effective for zirconocene activation. A highly disordered support prepared by the reaction of MgBu2 with HCl gave high activity with TiCl4 but low activity with (n‐PrCp)2ZrCl2. High polymerization activities with the zirconocene were only obtained with supports of type MgCl2/AlRn(OEt)3−n prepared from the reaction of AlR3 with MgCl2 · 1.1EtOH. These supports are characterized by additional peaks in the X‐ray diffraction pattern, indicating the presence of a crystalline structure which is absent in the other supports and contains highly Lewis acidic sites able to generate the active metallocenium species.magnified image

Preparation of Porous Anhydrous MgCl2 Particles by Spray Drying Process

“…The results shown that higher residual ethanol in particles gave lower crystallographic disorder. In the other hand, lower residual ethanol gave higher crystallographic disorder which consistent with this research [16]. …”

A supported titanium postmetallocene catalyst: Effect of selected conditions on ethylene polymerization

“…A very active catalyst for ethylene polymerization was for example obtained by immobilization of (n-PrCp) 2 ZrCl 2 on magnesium support of type MgCl 2 Á1.1EtOH/AlEt 3 . 19 Its activity results from the presence of the support sites with high Lewis acidity. A similar type of the magnesium support, i.e., MgCl 2 Án(alcohol) (for C 2 H 5 OH n ¼ 3.33 and for CH 3 OH n ¼ 4) modified with an organoaluminium compound (triisobutylaluminium being the best in that group) was also used to immobilize other metallocenes, Cp 2 ZrCl 2 and rac-Et[Ind] 2 ZrCl 2 , which were then utilized in ethylene copolymerization with 1-hexene.…”

Investigation of Alkoxysilanes in the Presence of Hydrogen with Ziegler-Natta Catalysts in Ethylene Polymerization

“…This is because α-MgCl2 turned into the active -MgCl2 resulting in the disappearance of peak at 2θ = 14.4°, 29.7°, 34.3°and 49.5°. This indicated that the -MgCl2 support has a single Cl-Mg-Cl structural layers (monolayers) [22]. Therefore, the modification of α-MgCl2 form into active δ-MgCl2 form led to the increase in the interplanar distance or decrease in 2θ value [23].…”

“…While three peaks at 2θ = 29.7°, 34.3° and 49.5° were found and assigned to be the stacking faults of the triple layers. The peaks at 2θ = 34.3° and 49.5° represented the (104) and (110) plane, respectively [21,22]. Cat-A and Cat-B exhibited the reduction of intensity in all peaks of α-MgCl2.…”