Effects of Silica Support Properties on the Performance of Immobilized Metallocene Catalysts for Ethylene Polymerization

The choice of the silica support for α‐olefin polymerization catalysts has overwhelming ramifications on the overall metal loading, catalyst performance, and properties of the resulting polymer. There are several physical properties of a silica support to consider but the pore volume and pore diameter are the two of the most important support properties in such considerations. During the catalyst immobilization process and the subsequent polymerization reaction, the change in the pore volume can either facilitate or inhibit the mass transfer of catalytic compounds and monomers within and throughout the catalyst particle. This work presents the experimental study on the effects of pore diameter and pore volume in porous silica particles used to support rac‐Et(ind)2ZrCl2 catalyst on ethylene polymerization. The amount of immobilized methylaluminoxane (MAO) is varied for three commercially available silica micro‐particles with similar surface areas and particle sizes. It has been observed that each type of silica exhibits different effects of the immobilized MAO on their pore characteristics, although a general trend is observed. Ethylene polymerization in slurry phase with the prepared supported catalysts also shows that the polymerization activities can be correlated with pore diameter and surface area for the three silica supports. The effects of immobilizing different amounts of methylaluminoxane (MAO) onto three different commercially available amorphous silica particles with similar physical characteristics are presented. The pore structure of each silica support is changed differently with a strong correlation shown between the polymerization activity and the pore diameter of the support after immobilization. The effects of interstitial voids are also investigated.