Polyolefin production with chromium-based catalysts

Abstract

A method including contacting a chromium-based catalyst with a reducing agent in a solvent to lower an oxidation state of at least some chromium in the chromium-based catalyst to give a reduced chromium-based catalyst, drying the reduced chromium-based catalyst at a temperature, and adjusting the temperature to affect the flow index response of the reduced chromium-based catalyst.

1 .- 16 . (canceled) 
     
     
         17 . A method of preparing a chromium-based catalyst for the production of polyolefin, the method comprising:
 contacting a chromium-based catalyst with a reducing agent in presence of a solvent in a mix vessel to produce a reduced chromium-based catalyst;   evaporating the solvent at a drying temperature to dry the reduced chromium-based catalyst; and   specifying the drying temperature to give a desired flow index response of the reduced chromium-based catalyst.   
     
     
         18 . The method of  claim 17 , wherein the drying temperature is less than 68° C. 
     
     
         19 . The method of  claim 17 , wherein the drying temperature is less than 76° C. 
     
     
         20 . The method of  claim 17 , wherein evaporating comprises increasing an operating temperature of the mix vessel from a reaction temperature to the drying temperature. 
     
     
         21 . The method of  claim 17 , wherein evaporating comprises increasing a jacket temperature of the mix vessel from a reaction temperature to the drying temperature. 
     
     
         22 . The method of  claim 17 , wherein evaporating comprises reducing an operating pressure of the mix vessel. 
     
     
         23 . The method of  claim 17 , comprising polymerizing an olefin into a polyolefin in presence of the reduced chromium-based catalyst in a polymerization reactor. 
     
     
         24 . The method of  claim 17 , wherein the chromium-based catalyst comprises an inorganic oxide support having a pore volume of about 0.5 to about 6.0 cubic centimeters (cm3)/gram (g) and a surface area of about 200 to about 600 square meters (m2)/g. 
     
     
         25 . A method comprising:
 preparing a chromium oxide catalyst for the polymerization of an olefin into a polyolefin, the preparing comprising:
 mixing the chromium oxide catalyst with a reducing agent in a solvent to give a reduced chromium oxide catalyst; 
 removing solvent from the reduced chromium oxide catalyst at a specified temperature set point; and 
 adjusting the specified temperature set point to give a desired flow index response of the reduced chromium oxide catalyst; and 
   collecting the reduced chromium oxide catalyst for delivery to a polyolefin polymerization reactor.   
     
     
         26 . The method of  claim 25 , wherein the reducing agent comprises an alkyl aluminum alkoxide.