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

Patent metadata

Field	Value
Publication number	US-9303103-B2
Application number	US-91997908-A
Country	US
Kind code	B2
Filing date	Dec 10, 2008
Priority date	Feb 27, 2008
Publication date	Apr 5, 2016
Grant date	Apr 5, 2016

Abstract

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.

First claim

What is claimed:

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, I 21 , 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.

2. The process of claim 1 , wherein the selected reaction time is in the range from about 30 minutes to about 180 minutes.

3. The process of claim 1 , wherein the supported chromium-based catalyst comprises a supported chromium oxide catalyst.

4. The process of claim 3 , further comprising activating at least one of a supported chromic acetyl acetonate, chromic halide, chromic nitrate, chromic acetate, chromic sulfate, ammonium chromate, and ammonium dichromate by heating to a temperature ranging from about 300° C. to about 900° C. under oxidizing conditions to form the supported chromium oxide catalyst.

5. The process of claim 1 , wherein the supported chromium-based catalyst comprises a supported silyl chromate catalyst.

6. The process of claim 5 , further comprising:
calcining a silica support at a temperature ranging from about 400° C. to about 850° C.; and
contacting a silyl chromate compound with the calcined silica support to form the supported silyl chromate catalyst.

7. The process of claim 5 , wherein the silyl chromate compound comprises at least one of a bis-triethylsilyl chromate, a bis-tributylsilyl chromate, a bis-triisopentylsilyl chromate, a bis-tri-2-ethylhexylsilyl chromate, a bis-tridecylsilyl chromate, a bis-tri(tetradecyl)silyl chromate, a bis-tribenzylsilyl chromate, a bis-triphenylethylsilyl chromate, a bis-triphenylsilyl chromate, a bis-tritolylsilyl chromate, a bis-trixylylsilyl chromate, a bis-trinaphthylsilyl chromate, a bis-triethylphenylsilyl chromate, a bis-trimethylnaphthylsilyl chromate, a polydiphenylsilyl chromate, and a polydiethylsilyl chromate.

8. The process of claim 1 , wherein the reducing agent comprises at least one of an alkyl aluminum and an alkyl aluminum alkoxide.

9. The process of claim 8 , wherein the alkyl aluminum alkoxide comprises at least one of diethyl aluminum methoxide, diethyl aluminum ethoxide, diethyl aluminum propoxide, dimethyl aluminum ethoxide, di-isopropyl aluminum ethoxide, di-isobutyl aluminum ethoxide, methyl ethyl aluminum ethoxide, and mixtures thereof.

10. The process of claim 1 , wherein the agitating is performed with at least one of a helical ribbon agitator, a conical agitator, or a combination of a helical ribbon agitator or a conical agitator with an impeller.

11. The process of claim 1 , wherein at an agitation rate of less than about 70 rpm the selected time period for adding the reducing agent is decreased in order to lower the flow index response.

12. The process of claim 1 , wherein the selected agitation rate is less than 70 rpm and the selected addition time is less than 20 minutes.

13. The process of claim 1 , wherein the selected agitation rate is less than 70 rpm and the selected addition time is greater than 20 minutes.

14. The process of claim 1 , wherein the selected agitation rate is greater than 70 rpm and the selected addition time is greater than 20 minutes.

15. The process of claim 1 , wherein the resulting catalyst composition has a molar ratio of reducing agent to chromium ranging from about 0.5 to about 8.

16. The process of claim 1 , wherein the supported chromium-based catalyst comprises a silica-containing support selected from the group consisting of silica having: (a) a pore volume of about 1.1 to about 1.8 cm 3 /g and a surface area of about 245 to about 375 m 2 /g, (b) a pore volume of about 2.4 to about 3.7 cm 3 /g and a surface area of about 410 to about 620 m 2 /g, and (c) a pore volume of about 0.9 to about 1.4 cm 3 /g and a surface area of about 390 to about 590 m 2 /g.

17. The process of claim 3 , wherein the process further comprises:
activating a supported chromic acetate compound by heating to a temperature in the range from about 500° C. to about 850° C. under oxidizing conditions to produce the chromium oxide catalyst.

18. The process of claim 5 , wherein the process further comprises:
calcining a silica support at a temperature of about 600° C.; and
contacting a bis(triphenylsilyl) chromate compound with the calcined silica to form the supported silyl chromate catalyst.

19. The process of claim 18 , wherein the selected addition time period is in the range from 0.5 to 10 minutes.

20. A process for producing a polyolefin, the process comprising:
producing a catalyst composition by contacting a supported chromium-based catalyst with a reducing agent fed at a selected feed rate over a selected addition time period, wherein the selected addition time period is within the range of from about 30 seconds to about 500 minutes, and concurrently, agitating the chromium-based catalyst at a selected agitation rate in the range of 5 to 200 rpm for a selected reaction time, wherein the selected reaction time is in the range of from about 5 minutes to about 240 minutes; and
contacting the catalyst composition with olefins under polymerization conditions; and further characterized in that the flow index, I 21 , 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 min to 1000 g/10 min.

21. The process of claim 20 , wherein the catalyst composition is contacted with olefins in a gas-phase polymerization reactor.

22. The process of claim 20 , wherein the olefins comprise at least one of ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene and 1-octene.

23. The process of claim 20 , wherein the polyolefin is an ethylene-based polymer having a density in the range from about 0.915 to about 0.965 g/cc.

24. The process of claim 20 , wherein the reactor is operated in condensing mode.

25. The process of claim 1 , wherein at a selected agitation rate of less than about 70 rpm, the time period for adding the reducing agent is increased in order to increase the flow index response.

26. The process of claim 1 , wherein the selected agitation rate is greater than 70 rpm and the selected addition time is less than 20 minutes.

Assignees

• Moorhouse John H
• Cann Kevin J
• Goode Mark G
• Eisinger Ronald S
• Univation Tech Llc

Inventors

• Moorhouse John H
• Cann Kevin J
• Goode Mark G
• Eisinger Ronald S

Classifications

• C08F210/16

  Copolymers of ethene with alpha-alkenes, e.g. EP rubbers · CPC title

• C08F10/00 Primary

  Homopolymers and copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond · CPC title

• Y10T29/49345

  Catalytic device making · CPC title