FIELD: catalytic chemistry.
SUBSTANCE: method is proposed for activating a chromium catalyst on a substrate, including: a) heating the chromium catalyst on a substrate in an inert atmosphere to a first temperature (T1) at a first temperature change rate (RR1), where this first temperature T1 is from 500 to 1000°C and the indicated first rate of change of temperature (RR1) is more than 1°C/min and less than 5°C/min; b) maintaining the chromium catalyst at a first temperature in an inert atmosphere for a first holding period (tH1), wherein this first holding period (tH1) is less than 15 hours and more than 15 minutes; c) bringing the chromium catalyst to a second temperature (T2) in an inert atmosphere at a second temperature change rate (RR2), where the temperature T2 is in the range of 25°C below T1 to temperature at 500°C is lower than T1 or equal to T1, followed by exposure of the chromium catalyst to an oxidizing atmosphere; d) maintaining the chromium catalyst at a second temperature in an oxidizing atmosphere for a second holding period (tH2), wherein this second holding period (tH2) is less than 1 hour and more than 30 seconds; and e) cooling the chromium catalyst to a temperature below a second temperature in an inert atmosphere, an oxidizing atmosphere, or any sequential combination of an inert atmosphere and an oxidizing atmosphere during a cooling period (tC) to provide an activated chromium catalyst. A method for polymerizing olefins is also proposed.
EFFECT: reduction in the total duration of the activation cycle, a decrease in the activation temperature and the production of catalysts that have the desired activity and provide polymers with the desired properties.
15 cl, 16 dwg, 8 tbl, 30 ex
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Authors
Dates
2024-06-18—Published
2019-09-23—Filed