EFFECT OF SILICA SUPPORTS ON OLEFIN POLYMERIZATION CATALYST PERFORMANCE

摘要

Transition metal catalysts for the polymerization of olefins are vital to the plastics industry. There are three types of catalysts commercially used in industry. These three types are silica-chromium, Ziegler-Natta, and organometallic (metallocene) catalysts. The first example of a silica-supported catalyst is the silica-chromium type discovered by P. Hogan and R. Banks in 1953. Great strides have been made in developing this catalyst over the years. The current catalyst technology is very versatile and is used in producing high-density polyethylene (HDPE) for large and small blow molding, film, pipe, sheet and wire/cable coating. The surface chemistry and physical properties of the silica play a key role in influencing catalyst performance. This will be illustrated with examples. In the Ziegler-Natta catalyst area the original commercial catalysts are based on magnesium or aluminum supports. In the early 1980's silica supported Ziegler-Natta catalysts were commercialized. Here also the surface chemistry and physical properties of silica play an important role in determining catalyst performance and polymer properties. Silica is the preferred support for organometallic or metallocene catalysts. In this case also, silica is not an inert support and the pore structure of silica greatly influences catalyst performance.