Methods for determining transition metal compound concentrations in multicomponent liquid systems

Patent metadata

Field	Value
Publication number	US-10507445-B2
Application number	US-201815939446-A
Country	US
Kind code	B2
Filing date	Mar 29, 2018
Priority date	Mar 29, 2018
Publication date	Dec 17, 2019
Grant date	Dec 17, 2019

Abstract

Methods for simultaneously determining the concentrations of transition metal compounds in solutions containing two or more transition metal compounds 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 first concentration of the first transition metal compound and a second concentration of the second transition metal compound in a solution comprising the first transition metal compound and the second transition metal compound, the first concentration and the second concentration determined via the steps of
(i) providing a first reference absorbance profile (F 1 ) of the first transition metal compound in a first reference solution at a first known concentration, and a second reference absorbance profile (F 2 ) of the second transition metal compound in a second reference solution at a second known concentration;
(ii) submitting a sample of the solution to a sample chamber;
(iii) irradiating the sample in the chamber with a light beam at a wavelength in the UV-visible spectrum;
(iv) generating a sample absorbance profile of the sample, and calculating a curve having the formula β 1 F 1 +β 2 F 2 to fit the sample absorbance profile to a least-squares regression fit value (R 2 ) of at least 0.9; wherein:
β 1 is a first weighting coefficient;
F 1 is the first reference absorbance profile of the first transition metal compound in the first reference solution at the first known concentration;
β 2 is a second weighting coefficient; and
F 2 is the second reference absorbance profile of the second transition metal compound in the second reference solution at the second known concentration; and
(v) multiplying the first known concentration with β 1 to determine the first concentration of the first transition metal compound in the solution, and multiplying the second known concentration with β 2 to determine the second concentration of the second transition metal compound in the solution; and

(III) adjusting a first flow rate of the first transition metal compound and/or a second flow rate of the second transition metal compound into the reactor when the first concentration and/or the second concentration 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 first reference absorbance profile (F 1 ), the second reference absorbance profile (F 2 ), and the sample absorbance profile independently comprise an absorbance curve over a range of wavelengths in the 300 nm to 600 nm range, or a subset thereof; and
the curve having the formula β 1 F 1 +β 2 F 2 is determined over a range of wavelengths in the 300 nm to 600 nm range, or a subset thereof, to fit the sample absorbance profile.

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 least-squares regression fit value (R 2 ) is at least 0.999.

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 solution, the first reference solution, and the second reference solution comprise the same 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 1:20 to about 1:1.

10. The process of claim 1 , wherein:
the first reference absorbance profile (F 1 ), the second reference absorbance profile (F 2 ), and the sample absorbance profile independently comprise an absorbance curve over a subset of wavelengths spanning less than 350 nm within the 200 nm to 750 nm range; and
the curve having the formula β 1 F 1 +β 2 F 2 is determined over a subset of wavelengths spanning less than 350 nm within the 200 nm to 750 nm range, to fit the sample absorbance profile.

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 first flow rate and the second flow rate are controlled 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.

12. A method for determining a first concentration of a first transition metal compound, a second concentration of a second transition metal compound, and a third concentration of a third transition metal compound in a solution comprising the first transition metal compound, the second transition metal compound, and the third transition metal compound, the method comprising:
providing a first reference absorbance profile (F 1 ) of the first transition metal compound in a first reference solution at a first known concentration, a second reference absorbance profile (F 2 ) of the second transition metal compound in a second reference solution at a second known concentration, and a third reference absorbance profile (F 3 ) of the third transition metal compound in a third reference solution at a third known concentration;
(ii) submitting a sample of the solution to a sample chamber;
(iii) irradiating the sample in the chamber with a light beam at a wavelength in the UV-visible spectrum;
(iv) generating a sample absorbance profile of the sample, and calculating a curve having the formula β 1 F 1 +β 2 F 2 +β 3 F 3 to fit the sample absorbance profile to a least-squares regression fit value (R 2 ) of at least 0.9; wherein:
β 1 is a first weighting coefficient;
F 1 is the first reference absorbance profile of the first transition metal compound in the first reference solution at the first known concentration;
β 2 is a second weighting coefficient;
F 2 is the second reference absorbance profile of the second transition metal compound in the second reference solution at the second known concentration;
β 3 is a third weighting coefficient; and
F 3 is the third reference absorbance profile of the third transition metal compound in the third reference solution at the third known concentration; and
(v) multiplying the first known concentration with β 1 to determine the first concentration of the first transition metal compound in the solution, multiplying the sec

Assignees

• Chevron Phillips Chemical Co Lp

Inventors

• Buck Richard M
• Yang Qing

Classifications

• C08F210/16

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

• C08F4/65927

  two cyclopentadienyl rings being mutually bridged · CPC title

• C08F4/65925

  two cyclopentadienyl rings being mutually non-bridged · CPC title

• C08F10/14

  Monomers containing five or more carbon atoms · CPC title

• C08F2500/08

  Low density, i.e. < 0.91 g/cm3 · CPC title