Methods for determining transition metal compound concentrations in multicomponent liquid systems

Patent metadata

Field	Value
Publication number	US-10501567-B2
Application number	US-201815997744-A
Country	US
Kind code	B2
Filing date	Jun 5, 2018
Priority date	Jul 21, 2017
Publication date	Dec 10, 2019
Grant date	Dec 10, 2019

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;
wherein the polymerization reactor system comprises a solution reactor, a gas-phase reactor, a slurry reactor, or a combination thereof;
(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 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;
the reference solution comprises the second transition metal compound and a hydrocarbon solvent; and
the step of correlating is performed at a single wavelength.

3. The process of claim 1 , wherein a weight ratio of the first transition metal compound to the second transition metal compound in the solution is in a range from about 1:20 to about 1:1.

4. The process of claim 3 , wherein:
the catalyst system comprises a first metallocene compound, a second metallocene compound, an activator, and a co-catalyst;
the catalyst system is contacted with ethylene and an olefin comonomer comprising 1-butene, 1-hexene, 1-octene, or a mixture thereof;
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.

5. The process of claim 1 , wherein:
the olefin polymer comprises an ethylene homopolymer and/or an ethylene ethylene/α-olefin copolymer; and
at least one of the first transition metal compound and the second transition metal compound is a metallocene compound.

6. The process of claim 5 , 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 of the feed stream to the catalyst preparation vessel, and/or by adjusting a flow rate ratio of the first:second transition metal compound to the catalyst preparation vessel, and/or by adjusting a flow rate of the catalyst system exiting the catalyst preparation vessel and entering the reactor.

7. The process of claim 5 , wherein:
the solution comprising the first transition metal compound and the second transition metal compound is a liquid or homogeneous catalyst system; 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 reactor, and/or by adjusting a flow rate of the liquid or homogeneous catalyst system entering the reactor.

8. The process of claim 5 , wherein:
the solution comprising the first transition metal compound and the second transition metal compound is a solution prepared from a heterogeneous or supported catalyst system; 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 reactor, and/or by adjusting a flow rate of the heterogeneous or supported catalyst system entering the reactor.

9. The process of claim 5 , wherein:
the solution comprising the first transition metal compound and the second transition metal compound is a solution prepared from a sample mixture from the reactor; 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 reactor, and/or by adjusting a flow rate of the catalyst system entering the reactor.

10. 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.

11. The process of claim 1 , wherein the olefin polymer comprises an oligomerization product of a C 6 -C 24 olefin.

12. A method for determining a concentration of a first transition metal compound in a solution comprising the first transition metal compound and a second transition metal compound, the method comprising:
submitting a sample of the solution to a sample chamber comprising a flow cell;
(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;
wherein the solution comprises the first transition metal compound, the second transition metal compound, and a hydrocarbon solvent.

13. The method of claim 12 , wherein the wavelength in step (ii) comprises wavelengths in the 300 nm to 600 nm range.

14. The method of claim 12 , 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 reference solution comprises the second transition metal compound and the hydrocarbon solvent.

15. A polymerization reactor system comprising:
(A) a reactor configured to contact a catalyst system with ethylene and an optional olefin comonomer under polymerization reaction conditions to produce an ethylene 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;
(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; and
(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 react

Assignees

• Chevron Phillips Chemical Co Lp
• Chevron Philips Chemical Company Lp

Inventors

• Yang Qing
• Buck Richard M

Classifications

• 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

• G01N21/33

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

• B01J2219/00164

  controlling the flow · CPC title

• B01J19/0006 Primary

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

• C08F210/16 Primary

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