Methods for increasing polymer production rates with halogenated hydrocarbon compounds

1. A method of controlling a polymerization reaction in a polymerization reactor system, the method comprising:

(i) contacting a transition metal-based catalyst system with an olefin monomer and an optional olefin comonomer in the polymerization reactor system under polymerization conditions to produce an olefin polymer; and

(ii) introducing an amount of a halogenated hydrocarbon compound into the polymerization reactor system to increase a productivity of the olefin polymer; wherein:

the polymerization reactor system comprises a single reactor or two reactors;

the halogenated hydrocarbon compound comprises perfluorohexane, hexafluorobenzene, or both; and

the transition metal-based catalyst system is a chromium-based catalyst system, a metallocene-based catalyst system, or a combination thereof.

2. The method of claim 1 , wherein the amount of the halogenated hydrocarbon compound introduced into the polymerization reactor system is in a range from about 5 ppm to about 2000 ppm, based on the weight of the halogenated hydrocarbon compound to the weight of contents of the polymerization reactor system.

3. The method of claim 1 , wherein the polymerization reactor system comprises a slurry reactor, a gas-phase reactor, a solution reactor, or a combination thereof.

4. The method of claim 1 , wherein the transition metal-based catalyst system is contacted with ethylene and an olefin comonomer comprising a C 3 -C 10 alpha-olefin.

5. The method of claim 1 , further comprising measuring the productivity, and adjusting the amount of the halogenated hydrocarbon compound introduced into the polymerization reactor system based on a difference between the measured productivity and a target productivity.

6. The method of claim 1 , wherein the amount of the halogenated hydrocarbon compound introduced into the polymerization reactor system is in a range from about 0.01:1 to about 50:1, based on the weight of the halogenated hydrocarbon compound to the weight of the transition metal-based catalyst system.

7. The method of claim 1 , further comprising a step of adding hydrogen to the polymerization reactor system to increase the melt index (MI) of the olefin polymer, reduce the weight-average molecular weight (Mw) of the olefin polymer, or both.

8. The method of claim 1 , wherein the introduction of the halogenated hydrocarbon compound into the polymerization reactor system increases the productivity of the olefin polymer by from about 5% to about 350%.

9. The method of claim 1 , wherein the introduction of the halogenated hydrocarbon compound into the polymerization reactor system decreases the weight-average molecular weight (Mw) of the olefin polymer, decreases the zero-shear viscosity of the olefin polymer, or both.

10. A process for producing an olefin polymer at a target productivity, the process comprising:

(a) contacting a transition metal-based catalyst system with an olefin monomer and an optional olefin comonomer in a polymerization reactor system under polymerization conditions; and

(b) controlling an amount of a halogenated hydrocarbon compound introduced into the polymerization reactor system to produce the olefin polymer at the target productivity; wherein:

the transition metal-based catalyst system comprises one or two metallocene compounds; and

the polymerization reactor system comprises a loop slurry reactor.

11. The process of claim 10 , wherein the productivity of the olefin polymer increases as the amount of the halogenated hydrocarbon compound added to the polymerization reactor system increases.

12. The process of claim 10 , wherein the Mw and zero-shear viscosity of the olefin polymer decrease as the amount of the halogenated hydrocarbon compound added to the polymerization reactor system increases.

13. The process of claim 10 , wherein:

the halogenated hydrocarbon compound comprises a halogenated aromatic compound, a halogenated alkane compound, or a combination thereof; and

the olefin polymer comprises an ethylene homopolymer, an ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, or an ethylene/1-octene copolymer.

14. The process of claim 10 , wherein:

the amount of the halogenated hydrocarbon compound introduced into the polymerization reactor system is in a range from about 5 ppm to about 2000 ppm, based on the weight of the halogenated hydrocarbon compound to the weight of contents of the polymerization reactor system; or

the amount of the halogenated hydrocarbon compound introduced into the polymerization reactor system is in a range from about 0.2:1 to about 8:1, based on the weight of the halogenated hydrocarbon compound to the weight of the transition metal-based catalyst system; or

both.

15. The process of claim 10 , wherein:

a productivity of the olefin polymer increases as the amount of the halogenated hydrocarbon compound added to the polymerization reactor system increases;

the halogenated hydrocarbon compound comprises a halogenated aromatic compound;

the olefin polymer comprises an ethylene polymer; and

the amount of the halogenated hydrocarbon compound introduced into the polymerization reactor system is in a range from about 5 ppm to about 2000 ppm, based on the weight of the halogenated hydrocarbon compound to the weight of contents of the polymerization reactor system.

16. The process of claim 10 , wherein:

a productivity of the olefin polymer increases as the amount of the halogenated hydrocarbon compound added to the polymerization reactor system increases;

the halogenated hydrocarbon compound comprises a halogenated alkane compound;

the olefin polymer comprises an ethylene polymer; and

the amount of the halogenated hydrocarbon compound introduced into the polymerization reactor system is in a range from about 0.2:1 to about 8:1, based on the weight of the halogenated hydrocarbon compound to the weight of the transition metal-based catalyst system.

17. An olefin polymerization process, the process comprising:

contacting a transition metal-based catalyst system with an olefin monomer and an optional olefin comonomer in a polymerization reactor system under polymerization conditions, and in the presence of a halogenated hydrocarbon compound, to produce an olefin polymer; wherein:

a productivity of the olefin polymer is greater than that obtained under the same polymerization conditions without the halogenated hydrocarbon compound;

the halogenated hydrocarbon compound comprises perfluorohexane, hexafluorobenzene, or both; and

the transition metal-based catalyst system is a chromium-based catalyst system, a metallocene-based catalyst system, or a combination thereof.

18. The process of claim 17 , wherein the productivity of the olefin polymer is greater by from about 20% to about 250%.

19. The process of claim 17 , wherein:

the olefin polymer comprises an ethylene polymer.

20. The process of claim 19 , wherein the polymerization reactor system comprises a slurry reactor, a gas-phase reactor, a solution reactor, or a combination thereof.

21. The process of claim 18 , wherein:

the olefin polymer comprises an ethylene polymer; and

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

22. The process of claim 21 , wherein the polymerization reactor system comprises a loop slurry reactor.