System and Method for Catalyst Preparation

Abstract

Techniques are provided for catalyst preparation. A system for catalyst preparation may include an agitator disposed inside a polymerization catalyst tank and configured to mix a polymerization catalyst and a solvent to generate a polymerization catalyst solution. The system may also include a heating system coupled to the polymerization catalyst tank and configured to maintain a temperature of the polymerization catalyst solution above a threshold. The system may also include a precontactor configured to receive feed streams comprising an activator and the polymerization catalyst solution from the polymerization catalyst tank to generate a catalyst complex. The system may also include a transfer line configured to transfer the catalyst complex from an outlet of the precontactor to a reactor.

1 - 20 . (canceled) 
     
     
         21 . A method for controlling a polymerization reactor system, the method comprising:
 (a) contacting a metallocene catalyst system comprising a metallocene compound with an olefin monomer and an optional olefin comonomer in a polymerization reactor within the reactor system to produce a polyolefin;   (b) determining a concentration of the metallocene compound in a solution comprising the metallocene compound, wherein the concentration is determined by a method comprising the steps of:
 subjecting a sample of the solution to a wavelength of light in an ultraviolet-visible spectrometer; and 
 measuring an absorbance of the sample and correlating the absorbance to determine the concentration of the metallocene compound in the solution; and 
   (c) adjusting a flow rate of the metallocene compound into the polymerization reactor when the concentration of the metallocene compound in the solution has reached a predetermined level.   
     
     
         22 . The method of  claim 21 , wherein the solution comprising the metallocene compound is a catalyst solution feed stream to a precontactor vessel. 
     
     
         23 . The method of  claim 21 , wherein the solution comprising the metallocene compound is a metallocene catalyst system feed stream to the polymerization reactor. 
     
     
         24 . The method of  claim 21 , further comprising a step of filtering prior to subjecting the sample of the solution to the wavelength of light in the ultraviolet-visible spectrometer. 
     
     
         25 . The method of  claim 24 , wherein:
 the metallocene catalyst system is a heterogeneous catalyst system; and   the sample of the solution is prepared from a feed stream of the heterogeneous catalyst system to the polymerization reactor.   
     
     
         26 . The method of  claim 21 , wherein correlating the absorbance to determine the concentration comprises a calibration curve. 
     
     
         27 . The method of  claim 21 , wherein:
 the solution comprises the metallocene compound and a solvent; and   the wavelength of light is selected to minimize absorbance by the solvent.   
     
     
         28 . The method of  claim 21 , wherein:
 the solution comprising the metallocene compound is a catalyst solution feed stream to a precontactor vessel; and   the flow rate of the metallocene compound into the polymerization reactor is adjusted by adjusting a flow rate of the feed stream to the precontactor vessel and/or by adjusting a flow rate of the metallocene catalyst system exiting the precontactor vessel and entering the polymerization reactor.   
     
     
         29 . The method of  claim 21 , wherein the metallocene catalyst system comprises at least one metallocene compound, an activator, and a co-catalyst. 
     
     
         30 . The method of  claim 28 , wherein:
 the activator comprises a chemically-treated solid oxide; and   the co-catalyst comprises an alkyl aluminum compound.   
     
     
         31 . The method of  claim 21 , wherein the metallocene catalyst system is contacted with ethylene and an olefin comonomer comprising butene, 1-hexene, 1-octene, or a mixture thereof. 
     
     
         32 . The method of  claim 21 , wherein the reactor system comprises a fluidized bed reactor, a gas-phase reactor, a loop slurry reactor, or any combination thereof. 
     
     
         33 . A polymerization reactor system comprising:
 (A) a polymerization reactor configured to contact a metallocene catalyst system with an olefin monomer and an optional olefin comonomer to produce a polyolefin;   (B) a precontactor configured to contact a metallocene compound, an activator, and a co-catalyst to form the metallocene catalyst system;   (C) an ultraviolet-visible spectrometer system configured to determine a concentration of the metallocene compound in a solution comprising the metallocene compound present within the reactor system; and   (D) a controller configured to control a flow rate of the metallocene compound into the polymerization reactor based on the concentration determined by the ultraviolet-visible spectrometer system.   
     
     
         34 . The reactor system of  claim 33 , wherein the ultraviolet-visible spectrometer system further comprises a filter for filtering a sample of the solution comprising the metallocene compound prior to analysis. 
     
     
         35 . The reactor system of  claim 33 , wherein the reactor system comprises one or more polymerization reactors selected independently from a fluidized bed reactor, a gas-phase reactor, or a loop slurry reactor. 
     
     
         36 . The reactor system of  claim 33 , wherein the controller is configured to control the flow rate of the metallocene compound into the polymerization reactor continuously based on the concentration determined by the ultraviolet-visible spectrometer system. 
     
     
         37 . The reactor system of  claim 33 , wherein:
 the solution comprising the metallocene compound is a catalyst solution feed stream to the precontactor; and   the controller controls the flow rate of the metallocene compound into the polymerization reactor by adjusting a flow rate of the catalyst solution feed stream to the precontactor and/or by adjusting a flow rate of the metallocene catalyst system exiting the precontactor and entering the polymerization reactor.   
     
     
         38 . The reactor system of  claim 33 , wherein the reactor system comprises a loop slurry reactor. 
     
     
         39 . The reactor system of  claim 33 , wherein the ultraviolet-visible spectrometer system is further configured to determine the concentration of the metallocene compound using a calibration curve.