Abstract: A transition metal containing catalyst having a silica-support is provided for the production of polyolefins from .alpha.-olefins that can be converted to polymer films, preferably thin films of polyolefin, which have lower defects resulting from a decreased presence of silica-containing residues from the catalyst. The catalyst has a porous silica support component and a catalytic component which may include, but is not limited to, such materials as chromium, magnesium-titanium (Ziegler-Natta type) or metallocene compounds (Metallocene catalyst type). The porous silica component of the catalyst has an average pore volume of from about 2.5 to about 3.5 ml/g and a surface area of 200 to 400 m.sup.2 /g and preferably 250 to 350 m.sup.2 /g. The average pore diameter ranges from about 285 to about 700 Angstroms and preferably 500-700 Angstroms for porous silica components having surface areas of 200 m.sup.2 /g and preferably 285-400 Angstroms for porous silica components having surface areas of 350 m.sup.2 /g.

Abstract: A process of producing supported olefin polymerization catalysts in which the support is a porous silica material containing specified amounts of alkali and alkaline metal cations, and olefin polymerization catalysts produced thereby.