Abstract: A silica-titania cogel or silica-titania-chromium tergel is first aged at a substantially neutral pH, then aged at an alkaline pH, and then spray dried or azeotrope dried to form a xerogel. Optionally, a pore-preserving agent can be added prior to drying. The cogel can be impregnated with a chromium compound. The chromium-containing catalyst is activated by calcination. The activated catalyst can be used as a polymerization catalyst to polymerize mono-1-olefins.

Abstract: A catalyst system is produced by first forming a chromium catalyst on a predominantly silica support, activating in an oxygen-containing ambient and thereafter subjecting the thus activated composition to carbon monoxide reduction. The resulting reduced supported chromium catalyst composition is then precontacted with a cocatalyst selected from trialkyl boron compounds and dialkyl aluminum alkoxide compounds, preferably triethyl borane and thereafer contacted with ethylene. This results in a catalyst system which produces comonomer in situ so as to give tough, flexible ethylene copolymers from an essentially pure ethylene feed.

Abstract: The catalyst system is produced by first forming a chromium catalyst on a predominantly silica support, activating in an oxygen-containing ambient and thereafter subjecting the thus activated composition to carbon monoxide reduction. The resulting reduced supported chromium catalyst composition is then precontacted with a cocatalyst selected from trialkyl boron compounds and dialkyl aluminum alkoxide compounds, preferably triethyl borane and thereafter contacted with ethylene. This results in a catalyst system which produces comonomer in situ so as to give tough, flexible ethylene copolymers from an essentially pure ethylene feed.

Abstract: Ethylene polymer is particularly suitable for the production of tough film is produced under slurry conditions using a fluorided aluminophosphate support and a reaction temperature within the range of 93.degree. to 107.degree. C. in the presence of hydrogen and a small amount of trialkyl boron cocatalyst wherein said aluminophosphate has a phosphorous to aluminum ratio within the very narrow range of 0.15 to 0.4 and wherein said aluminophosphate carrying chromium catalyst is being activated at a temperature within the range of 482.degree. to 704.degree. C. The resulting film is not only substantially superior to film made from the best of the readily available commercial resins but is also better than film made from polymers using a similar catalyst system without the specific combination of parameters of this invention.