초록 ▼

High melt flow olefin polymers suitable for such applications as injection molding, and the like requiring a narrow molecular weight distribution are produced using a catalyst made by reducing and reoxidizing a chromium catalyst on either a titanium-silica cogel or a self-reduced silica-containing c

High melt flow olefin polymers suitable for such applications as injection molding, and the like requiring a narrow molecular weight distribution are produced using a catalyst made by reducing and reoxidizing a chromium catalyst on either a titanium-silica cogel or a self-reduced silica-containing composition. In the first embodiment, a cogel formed by coprecipitating silica and titania, and containing a chromium compound, is treated in a nonoxidizing atmosphere, such as CO, hydrogen, N2 or a material decomposable to these materials, and thereafter reoxidized. In the second embodiment, a titanium-free chromium containing catalyst is first heated in air or the like to dry the catalyst and oxidize the chromium after which it is heated in an inert atmosphere wherein the composition is self-reduced to give chromium in a lower valence state. The resulting self-reduced composition is then heated in a reducing ambient and then reoxidized as in the first embodiment.

대표청구항 ▼

A process for activating a chromium-containing catalyst prepared by coprecipitating a titanium compound and silica to form a cogel comprising a first step wherein said catalyst is contacted with a nonoxidizing ambient at a temperature of at least 600°C. and a subsequent second step where it is conta

A process for activating a chromium-containing catalyst prepared by coprecipitating a titanium compound and silica to form a cogel comprising a first step wherein said catalyst is contacted with a nonoxidizing ambient at a temperature of at least 600°C. and a subsequent second step where it is contacted with an oxygen-containing oxidizing ambient at a temperature within the range of 450°-1000°C. A process for producing a catalyst active for olefin polymerization comprising subjecting a titanium-free silica composition containing chromium wherein at least a portion of said chromium is in the form of CrO3 to an inert ambient for a time and at a temperature sufficient to self-reduce at least a portion of said CrO3 to a lower valence state, and thereafter subjecting the thus self-reduced composition to a reducing ambient at a temperature sufficient to further reduce at least a portion of said chromium, and thereafter reoxidizing the thus reduced composition.