Methods for determining transition metal compound concentrations in multicomponent liquid systems

Patent metadata

Field	Value
Publication number	US-10030086-B1
Application number	US-201715655929-A
Country	US
Kind code	B1
Filing date	Jul 21, 2017
Priority date	Jul 21, 2017
Publication date	Jul 24, 2018
Grant date	Jul 24, 2018

Abstract

Methods for determining the concentration of transition metal compounds in a solution containing more than one transition metal compound are described. Polymerization reactor systems providing real-time monitoring and control of the concentrations of the transition metal components of a multicomponent catalyst system are disclosed, as well as methods for operating such polymerization reactor systems.

First claim

We claim:

1. A process for operating a polymerization reactor system, the process comprising:
(I) contacting a catalyst system comprising a first transition metal compound, a second transition metal compound, an activator, and an optional co-catalyst, with an olefin monomer and an optional olefin comonomer in a reactor within the polymerization reactor system under polymerization reaction conditions to produce an olefin polymer;
(II) determining a concentration of the first transition metal compound in a solution comprising the first transition metal compound and the second transition metal compound, the concentration determined via the steps of:
(i) submitting a sample of the solution to a sample chamber;
(ii) irradiating the sample in the chamber with a light beam at a wavelength in the UV-visible spectrum; and
(iii) generating a sample absorbance profile of the sample, subtracting a reference absorbance profile of the second transition metal compound in a reference solution from the sample absorbance profile to result in a first transition metal compound absorbance profile, and correlating the first transition metal compound absorbance profile to a standard to determine the concentration of the first transition metal compound in the solution; and

(III) adjusting a flow rate of the first transition metal compound into the reactor when the concentration of the first transition metal compound in the solution has reached a predetermined level.

2. The process of claim 1 , wherein the solution comprising the first transition metal compound and the second transition metal compound is:
a feed stream to a catalyst preparation vessel;
a liquid or homogeneous catalyst system;
a solution prepared from a heterogeneous or supported catalyst system; or
a solution prepared from a sample mixture from the reactor.

3. The process of claim 1 , wherein:
the wavelength in step (ii) comprises wavelengths in the 300 nm to 600 nm range;
the sample absorbance profile in step (iii) comprises an absorbance curve over a range of wavelengths; and
the step of correlating is performed at a single wavelength.

4. The process of claim 1 , wherein:
the first transition metal compound and the second transition metal compound independently comprise chromium, vanadium, titanium, zirconium, hafnium, or a combination thereof;
the olefin monomer comprises a C 2 -C 24 olefin; and
the polymerization reactor system comprises a solution reactor, a gas-phase reactor, a slurry reactor, or a combination thereof.

5. The process of claim 1 , wherein:
the first transition metal compound is an unbridged metallocene compound; and
the second transition metal compound is a bridged metallocene compound.

6. The process of claim 1 , wherein the second transition metal compound comprises two or more different second transition metal compounds.

7. The process of claim 1 , wherein:
the catalyst system comprises a first metallocene compound, a second metallocene compound, an activator, and a co-catalyst; and
the catalyst system is contacted with ethylene and an olefin comonomer comprising 1-butene, 1-hexene, 1-octene, or a mixture thereof.

8. The process of claim 1 , wherein the reference solution comprises the second transition metal compound and a hydrocarbon solvent.

9. The process of claim 8 , wherein:
the hydrocarbon solvent comprises 1-hexene, isobutane, toluene, cyclohexene, or any combination thereof; and
a weight ratio of the first transition metal compound to the second transition metal compound in the solution is in a range from about 1:50 to about 1:5.

10. The process of claim 1 , wherein:
the sample absorbance profile, the reference absorbance profile, and the first transition metal compound absorbance profile independently comprise an absorbance curve over a range of wavelengths; and
the standard comprises a calibration curve.

11. The process of claim 1 , wherein the solution comprising the first transition metal compound and the second transition metal compound is a feed stream to a catalyst preparation vessel, and the flow rate of the first transition metal compound into the reactor is controlled by adjusting a flow rate ratio of the first:second transition metal compound to the catalyst preparation vessel.

12. A polymerization reactor system comprising:
(A) a reactor configured to contact a catalyst system with an olefin monomer and an optional olefin comonomer under polymerization reaction conditions to produce an olefin polymer;
(B) a catalyst preparation vessel configured to contact a first transition metal compound, a second transition metal compound, an activator, and an optional co-catalyst to form the catalyst system; and
(C) an analytical system configured to determine a concentration of the first transition metal compound in a solution comprising the first transition metal compound and the second transition metal compound present within the polymerization reactor system.

13. The reactor system of claim 12 , wherein the analytical system comprises an ultraviolet-visible spectrometer.

14. The reactor system of claim 13 , wherein the analytical system further comprises a filter assembly configured to filter a sample of the solution comprising the first transition metal compound and the second transition metal compound before analysis by the ultraviolet-visible spectrometer.

15. The reactor system of claim 12 , wherein the reactor system further comprises (D) a controller configured to control a flow rate of the first transition metal compound into the reactor based on the concentration determined by the analytical system.

16. The reactor system of claim 15 , wherein:
the reactor system comprises a slurry reactor, a gas-phase reactor, a solution reactor, or a combination thereof; and
the analytical system comprises an ultraviolet-visible spectrometer with an integrated computer system for measuring a sample absorbance profile of the first transition metal compound in the solution, for subtracting a reference absorbance profile of the second transition metal compound in a reference solution from the sample absorbance profile to result in a first transition metal compound absorbance profile, and for correlating the first transition metal compound absorbance profile to a standard to determine the concentration of the first transition metal compound in the solution.

17. The reactor system of claim 15 , wherein:
the solution comprises the first transition metal compound, the second transition metal compound, and a hydrocarbon solvent; and
the solution is a feed stream to the catalyst preparation vessel, and the controller controls the flow rate of the first transition metal compound into the reactor by adjusting a flow rate ratio of the first:second transition metal compound to the catalyst preparation vessel.

18. The reactor system of claim 15 , wherein the controller is configured to control the flow rate of the transition metal compound into the reactor based on the concentration determined by the analytical system in real-time.

19. The reactor system of claim 15 , wherein:
the reactor system comprises two or more reactors, at least one of which is a loop slurry reactor;
the polymerization reaction conditions comprise a reaction temperature in a range from about 60° C. to about 185° C., and a reaction pressure of less than about 1000 psig;
the olefin polymer comprises an ethylene homopolymer, an ethylene/1-butene copolymer, an ethylene/1-hexene copolymer, or an ethylene/1-octene copolymer; and
the first transition metal com

Assignees

• Chevron Phillips Chemical Co Lp

Inventors

• Yang Qing
• Buck Richard M

Classifications

• G01N21/33

  using ultraviolet light (G01N21/39 takes precedence) · CPC title

• C08F10/00

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

• B01J19/0006 Primary

  Controlling or regulating processes (controlling or regulating in general G05) · CPC title

• G01N21/31

  Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry {(G01N21/72 takes precedence)} · CPC title

• B01J2219/00164

  controlling the flow · CPC title