Methods for making fluorided chromium (VI) catalysts, and polymerization processes using the same

• US 9,505,856 B1
• Filed: 01/13/2016
• Issued: 11/29/2016
• Est. Priority Date: 01/13/2016
• Status: Active Grant

• Current Assignee: Chevron Phillips Chemical Company LP (Chevron Corp.)
• Original Assignee: Chevron Phillips Chemical Company LP (Chevron Corp.)
• Inventors: Schwerdtfeger, Eric D., Clear, Kathy S., McDaniel, Max P.
• Primary Examiner(s): Neckel, Alexa
• Assistant Examiner(s): Eng, Elizabeth
• Application Number:
  US14/994,189
• Time in Patent Office: 321 Days
• Field of Search: 502/224, 502/256, 502/319, 526/98, 526/106
• US Class Current: 1/1
• CPC Class Codes: B01J 23/26 Chromium
• CPC Class Codes: B01J 27/132 with chromium, molybdenum, tungsten or polonium
• CPC Class Codes: B01J 27/135 with titanium, zirconium, hafnium, germanium, tin or lead
• CPC Class Codes: B01J 35/615 100-500 m2/g
• CPC Class Codes: B01J 35/617 500-1000 m2/g
• CPC Class Codes: B01J 35/638 more than 1.0 ml/g
• CPC Class Codes: B01J 37/08 Heat treatment B01J37/0009, B01J37/0018 take precedence
• CPC Class Codes: B01J 37/26 Fluorinating
• CPC Class Codes: C08F 10/02 Ethene
• CPC Class Codes: C08F 110/02 Ethene
• CPC Class Codes: C08F 110/06 Propene
• CPC Class Codes: C08F 210/14 Monomers containing five or more carbon atoms
• CPC Class Codes: C08F 210/16 Copolymers of ethene with alpha-alkenes, e.g. EP rubbers
• CPC Class Codes: C08F 2410/01 Additive used together with the catalyst, excluding compounds containing Al or B
• CPC Class Codes: C08F 2410/06 Catalyst characterized by its size
• CPC Class Codes: C08F 2500/04 Broad molecular weight distribution, i.e. Mw/Mn > 6
• CPC Class Codes: C08F 2500/09 Long chain branches
• CPC Class Codes: C08F 2500/12 Melt flow index or melt flow ratio
• CPC Class Codes: C08F 4/025 Metal oxides
• CPC Class Codes: C08F 4/24 Oxides

Abstract

Methods for preparing a fluorided chromium catalyst can include a step of calcining a supported chromium catalyst at a peak calcining temperature to produce a calcined supported chromium catalyst, followed by contacting the calcined supported chromium catalyst at a peak fluoriding temperature with a vapor comprising a fluorine-containing compound to produce the fluorided chromium catalyst. The peak fluoriding temperature can be at least 50° C. less, and often from 200° C. to 500° C. less, than the peak calcining temperature. Polymers produced using the fluorided chromium catalyst can have a beneficial combination of higher melt index, narrower molecular weight distribution, and lower long chain branch content.

Claims

1. A process to produce a fluorided chromium catalyst, the process comprising:

(a) calcining a supported chromium catalyst at a peak calcining temperature to produce a calcined supported chromium catalyst; and

(b) contacting the calcined supported chromium catalyst at a peak fluoriding temperature with a vapor comprising a fluorine-containing compound to produce the fluorided chromium catalyst;

wherein the peak fluoriding temperature is at least about 50°

C. less than the peak calcining temperature.

2. The process of claim 1, wherein:

the peak calcining temperature is in a range from about 725°

C. to about 900°

C.;

the peak fluoriding temperature is in a range from about 300°

C. to about 675°

C.;

the peak fluoriding temperature is from about 100°

C. to about 600°

C. less than the peak calcining temperature;

or

any combination thereof.

3. The process of claim 1, wherein:

the peak calcining temperature is in a range from about 600°

C. to about 871°

C.;

the peak fluoriding temperature is in a range from about 300°

C. to about 500°

C.;

the peak fluoriding temperature is from about 200°

C. to about 500°

C. less than the peak calcining temperature;

or

any combination thereof.

4. The process of claim 1, wherein the fluorided chromium catalyst comprises fluorided chromium/silica, fluorided chromium/silica-titania, fluorided chromium/silica-titania-magnesia, fluorided chromium/silica-alumina, fluorided chromium/alumina, fluorided chromium/phosphated alumina, or a combination thereof.

5. The process of claim 1, wherein the fluorine-containing compound comprises a fluorocarbon.

6. The process of claim 1, wherein the fluorine-containing compound comprises perfluorohexane, perfluoroacetic anhydride, tetrafluoroethane, or a combination thereof.

7. The process of claim 1, wherein the fluorided chromium catalyst comprises:

from about 0.1 to about 10 wt. % chromium; and

from about 0.25 to about 8 wt. % fluorine.

8. The process of claim 1, wherein step (a) and step (b) are performed in an oxidizing atmosphere.

9. The process of claim 1, wherein:

the contacting in step (b) is performed for a time period ranging from about 10 minutes to about 6 hours; and

the fluorine-containing compound is present in the vapor for less than about 25% of the contacting time period in step (b).

10. The process of claim 1, wherein the fluorided chromium catalyst has:

a pore volume in a range from about 1 to about 5 mL/g; and

a surface area in a range from about 200 to about 550 m²/g.

11. The process of claim 1, wherein the surface area of the fluorided chromium catalyst produced by the process is at least about 10% greater than a surface area of a fluorided chromium catalyst obtained by performing the contacting step at the peak calcining temperature.

12. The process of claim 1, wherein a catalyst activity of the fluorided chromium catalyst produced by the process is at least about 10% greater than that of a fluorided chromium catalyst obtained by performing the contacting step at the peak calcining temperature, under the same polymerization conditions.

13. An olefin polymerization process, the olefin polymerization process comprising:

(i) calcining a supported chromium catalyst at a peak calcining temperature to produce a calcined supported chromium catalyst;

(ii) contacting the calcined supported chromium catalyst at a peak fluoriding temperature with a vapor comprising a fluorine-containing compound to produce a fluorided chromium catalyst, wherein the peak fluoriding temperature is from about 100°

C. to about 600°

C. less than the peak calcining temperature; and

(iii) contacting the fluorided chromium catalyst and an optional co-catalyst with an olefin monomer and an optional olefin comonomer in a polymerization reactor system under polymerization conditions to produce an olefin polymer.

14. The olefin polymerization process of claim 13, wherein:

the olefin monomer comprises ethylene or propylene; and

the polymerization reactor system comprises a slurry reactor, a gas-phase reactor, a solution reactor, or a combination thereof.

15. The olefin polymerization process of claim 13, wherein:

the fluorided chromium catalyst and a co-catalyst are contacted with ethylene and an olefin comonomer comprising a C₃-C₁₀ alpha-olefin; and

the polymerization reactor system comprises a loop slurry reactor.

16. The olefin polymerization process of claim 13, wherein:

a number of long chain branches per 1,000,000 total carbon atoms of the olefin polymer is less than that of an olefin polymer obtained without using step (ii) of the process, under the same polymerization conditions;

a HLMI of the olefin polymer is less than that of an olefin polymer obtained without using step (ii) of the process, under the same polymerization conditions;

a ratio of Mw/Mn of the olefin polymer is greater than that of an olefin polymer obtained without using step (ii) of the process, under the same polymerization conditions;

a ratio of I₂₁/I₁₀ of the olefin polymer is greater than that of an olefin polymer obtained without using step (ii) of the process, under the same polymerization conditions;

or

any combination thereof.

17. The olefin polymerization process of claim 13, wherein:

a HLMI of the olefin polymer is greater than that of an olefin polymer obtained by using a fluorided chromium catalyst activated at a temperature of about 650-700°

C., under the same polymerization conditions;

a ratio of Mw/Mn of the olefin polymer is less than that of an olefin polymer obtained by using a fluorided chromium catalyst activated at a temperature of about 650-700°

C., under the same polymerization conditions;

a number of long chain branches (LCB'"'"'s) per 1,000,000 total carbon atoms of the olefin polymer is less than that of an olefin polymer obtained by using a fluorided chromium catalyst activated at a temperature of about 650-700°

C., under the same polymerization conditions;

or

any combination thereof.

18. The olefin polymerization process of claim 13, wherein the olefin polymer is an ethylene homopolymer, an ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, or an ethylene/1-octene copolymer.

19. The olefin polymerization process of claim 18, wherein the olefin polymer is characterized by:

a HLMI in a range from about 2 to about 70 g/10 min;

a density in a range from about 0.92 to about 0.96 g/cm³;

a ratio of Mw/Mn in a range about 6 to about 25;

a ratio of Mz/Mw in a range from about 6 to about 12; and

less than or equal to about 10 LCB'"'"'s per 1,000,000 total carbon atoms.