The Role of the Support in the Performance of Grafted Metallocene Catalysts

Abstract

A series of supports – differing in their textural properties, the nature of their surface sites, and in their crystallinities – were investigated in the sequential grafting reaction of Cp2ZrCl2 and (nBuCp)2ZrCl2 mixtures. The catalyst systems were analyzed by Rutherford backscattering spectrometry, AFM, EXAFS, and nitrogen adsorption. All systems were shown to be active in ethylene polymerization reactions when methylaluminoxane was used as the cocatalyst. Experimental results are discussed in terms of the relationships between the grafted metal content, the catalyst activity, the surface roughness and polarity, the interatomic Zr–C and Zr–O distances of the grafted species and the molecular weights of the resulting polyethylenes.

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

“…[15][16][17][18] Effective immobilization of such systems on a magnesium support became possible much later. 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 .…”

Supported Catalyst (nBuCp)2ZrCl2 on Nano/Micro Domains for High Performance Ethylene Polymerization

“…[21,23] The support acts as a template for the formation of the polymer particle because the support shape is replicated during polymerization. [22,64,88] Thus, controlling the polymer morphology during catalytic reactions is strongly dependent on the characteristics of the support and the catalytic system. [89] Furthermore, the silica particles must be large enough to immobilize sufficient catalyst and produce the necessary polymer weight.…”

“…One of the most commonly used supports for metallocene immobilization is silica, [18,19] in which large pores and high specific surface area facilitate catalyst/MAO dispersion and reduce diffusion effects, therefore improving activity. [18] Common catalyst heterogenization methods include utilizing direct heterogenization of the metallocene onto the support, [4,6,[20][21][22][23][24][25] supported metallocene onto a previously functionalized support, [22,[26][27][28] heterogenization via metallocene direct synthesis, [29,30] catalyst encapsulation, [31,32] and in situ supported metallocene. [33][34][35] However, the environments generated by the routes reported in the literature cannot overcome the deficiencies of the supported metallocene catalysts in terms of reduced catalytic activity, [36][37][38] activation with a high concentration of MAO, inadequate control of molar mass distribution for commonly employed processing conditions, and possibility of catalyst deactivation reactions.…”