Investigation of silica particle structure containing metallocene immobilized by a sol-gel method

A series of homogeneous metallocenes (Cp2ZrCl2, (nBuCp)(2)ZrCl2, (iBuCp)(2)ZrCl2, (tBuCp)(2)ZrCl2, Cp2TiCl2, Cp2HfCl2, Etlnd(2)ZrCl(2) and Et(lndH(4))(2)ZrCl2) Were immobilized within a silica matrix during its preparation using a non-hydrolytic sol-gel method. Supported metallocenes were characterized by small angle X-ray scattering (SAXS) and nitrogen adsorption. The results show that the silica particle was formed by the aggregation of primary structures having a diameter of about 160 nm. This was a result of the aggregation process, which was affected by the metallocene. This result suggests that the metallocene is surrounded by primary particles deep inside the silica matrix. The low polymer productivity exhibited by the less active metallocene catalysts could be related to the problems of particle fragmentation due to monomer mass transfer limitations along the partially fragmented particle. which would subsequently affect catalytic activity. (C) 2008 Elsevier B.V. All rights reserved.