Abstract: Silica xerogels having pore volumes greater than about 2.0 cc/g., the major portion of which volumes are provided by pores having pore diameters ranging from 300 to 600 A, and surface areas ranging from 200 to 500 m.sup.2 /g. Xerogels having such cumulative pore volume, pore diameter distribution, and surface area characteristics are useful as supports for stereospecific catalysts for particle form olefin polymerization reactions effecting the production of low molecular weight, high melt index polyolefins.

Abstract: An olefin polymerization catalyst comprising a silica xerogel support having a pore volume greater than about 2.0 cc/g, the major portion of which volume is provided by pores having pore diameters ranging from 300 to 600 A and a surface area ranging from 200 to 500 m.sup.2 /g, and having deposited thereon a metal-containing catalytic material, such as chromium oxide, or other metal oxide. Further, a polymerization process utilizing such a catalyst for the preparation of polyolefins having relatively low molecular weights and high melt indexes without loss of catalyst activity, especially a process for the preparation of polymers and copolymers of 1-olefins having a maximum of 8 carbon atoms in the chain and having no branching nearer the double bond than the 4-position, e.g., ethylene polymers.

Abstract: An olefin polymerization process for the preparation of polyolefins having relatively low molecular weights and high melt indexes without loss of catalyst activity, utilizing a catalyst comprising a silica xerogel support having a pore volume greater than about 2.0 cc/g, the major portion of which volume is provided by pores having pore diameters ranging from 300 to 600 A and a surface area ranging from 200 to 500 m.sup.2 /g, and having deposited thereon a metal-containing catalytic material, such as chromium oxide, or other metal oxide. The process is designed for the preparation of polymers and copolymers of 1-olefins having a maximum of 8 carbon atoms in the chain and having no branching nearer the double bond than the 4-position, e.g., ethylene polymers.