Modified chromium-based catalysts and polymerization processes for using the same

摘要

Embodiments disclosed herein generally relate to olefin polymerization catalysts, and more specifically to chromium-based catalysts and methods of use of chromium-based catalysts for the production of polyolefins, and even more specifically to methods for controlling or tailoring the flow index response of chromium-based catalysts through the controlled addition of a reducing agent to the catalysts under controlled mixing conditions.

主权项

1. A process for producing a catalyst composition for the polymerization of olefins, the process comprising:
contacting a supported chromium-based catalyst with a reducing agent at a feed rate over an addition time period from about 30 seconds to about 500 minutes, and concurrently, agitating the chromium-based catalyst at an agitation rate in the range of 5 to 200 rpm for a reaction time of from about 5 minutes to about 240 minutes to produce a catalyst composition having a flow index response within a selected range, wherein the feed rate, addition time, and agitation rate are selected to control the flow index response of the catalyst composition within the selected range, and further characterized in that the flow index, I21, measured according to ASTM D-1238 (190° C./21.6 kg), of polymers produced by the catalyst composition ranges from about 0.1 g/10 mint to 1000 g/10 min.