Method and device for optimizing catalyst supply to a polymerization reactor

Abstract

The present invention relates to a method for optimizing catalyst supply to a polymerization reactor ( 1 ), comprising the steps of a) preparing catalyst slurry in a vessel ( 3 ), said slurry comprising solid catalyst in a hydrocarbon diluent having a suitable concentration for use in a polymerization reaction, b) providing said catalyst slurry from said vessel ( 3 ) to a buffer vessel ( 4 ) wherein said slurry is stored, and c) supplying said catalyst slurry from said buffer vessel ( 4 ) to said reactor ( 1 ) through conduits ( 8 ) at a suitable flow rate, and d) bringing a suitable amount of co-catalyst into contact with the catalyst slurry before supplying said catalyst slurry to said reactor.

1 - 22 . (canceled)  
     
     
         23 . A method for supplying a catalyst to an ethylene slurry loop polymerization reactor comprising: 
 a) preparing a catalyst slurry in a preparation vessel wherein said slurry comprises a hydrocarbon diluent liquid which contains a Ziegler-Natta catalyst;    b) supplying said catalyst slurry from said preparation vessel to a buffer vessel;    c) withdrawing said catalyst slurry from said buffer vessel and supplying said catalyst slurry to a slurry loop polymerization reactor in which ethylene is polymerized;    d) mixing a co-catalyst with the Ziegler Natta catalyst in said slurry prior to the supplying of said catalyst slurry to said slurry loop polymerization reactor; and    e) controlling the transfer of catalyst slurry from said preparation vessel to said buffer vessel and the withdrawal of catalyst slurry from said buffer vessel to maintain the level of catalyst slurry in said buffer vessel substantially constant relative to the level of catalyst slurry in said preparation vessel.    
     
     
         24 . The method of  claim 23  comprising mixing said co-catalyst with said catalyst slurry while transferring said catalyst slurry through a conduit to said polymerization reactor.  
     
     
         25 . The method of  claim 24  wherein the contact time of the co-catalyst with said catalyst slurry is increased by providing a chamber of increased volume in said conduit at a location between the mixing of said co-catalyst into said slurry and the introduction of said slurry into said polymerization reactor.  
     
     
         26 . The method of  claim 24  wherein said co-catalyst is mixed with said catalyst slurry by supplying said co-catalyst to said preparation vessel.  
     
     
         27 . The method of  claim 23  wherein the Ziegler-Natta catalyst is characterized by the formula: 
         MX n   
       wherein: M is a transition metal compound selected from group IV to VIII of the Periodic Table of Elements, X is a halogen, and n is the valence of the metal M.  
     
     
         28 . The method of  claim 27  wherein said co-catalyst is an organo aluminum compound having the formula: 
         AlR 3  or AlR 2 Y 
       wherein R is an alkyl group having 1-16 carbon atoms which may be the same or different and Y is hydrogen or a halogen.  
     
     
         29 . The volume of catalyst slurry in said buffer vessel is maintained within the range of 80% to 90% of the volume of said buffer vessel.  
     
     
         30 . The method of  claim 23  further comprising storing said Ziegler-Natta catalyst in a container vessel at a designated pressure and transferring said solid catalyst from said container vessel to said preparation vessel which is maintained at a higher pressure than the pressure in said container vessel.  
     
     
         31 . The method of  claim 23  wherein the buffer vessel is maintained at a lower pressure than the pressure within said slurry loop polymerization reactor.  
     
     
         32 . The method of  claim 31  wherein the pressure in said buffer vessel is within the range of 6-16 bar.  
     
     
         33 . The method of  claim 23  wherein said catalyst slurry is withdrawn from said buffer vessel and supplied to said slurry loop reactor through a plurality of conduits extending from said buffer vessel to said slurry loop reactor.  
     
     
         34 . The method of  claim 33  wherein said conduits are provided with pumps at a locations intermediate said buffer vessel and said reactor and wherein said conduits extending from said buffer vessel to the locations of said pumps extend upwardly from said buffer vessel to said pumps by an angle of at least 10 degrees.  
     
     
         35 . A system for supplying a polymerization catalyst to a polymerization reactor comprising: 
 a) a preparation vessel adapted to contain a catalyst slurry;    b) a buffer vessel connected to said preparation vessel by at least one conduit extending from said preparation vessel to said buffer vessel;    c) a transfer conduit extending from said buffer vessel to said polymerization reactor to provide for the transfer of catalyst slurry from said buffer vessel to said reactor;    d) a co-catalyst storage vessel adapted to contain a co-catalyst;    e) a co-catalyst supply conduit extending from said co-catalyst storage vessel to a least one of said preparation vessel and said transfer conduct extending from said buffer vessel to said reactor.    
     
     
         36 . The system of  claim 35  further comprising a first co-catalyst conduit extending from said co-catalyst storage vessel to said preparation vessel, and a second cocatlyst supply conduit extending from said co-catalyst storage vessel to said transfer conduit at a location between said buffer vessel and said reactor.  
     
     
         37 . The system of  claim 36  further comprising an enlarged contact vessel interfaced in said transfer conduit between and said second co-catalyst supply conduit and said reactor.  
     
     
         38 . The system of  claim 37  wherein said enlarged contact vessel is positioned vertically in said transfer conduit to provide for the downward flow of said co-catalyst and catalyst in said contact vessel.  
     
     
         39 . The system of  claim 38  wherein said enlarged contact vessel is provided with an agitator.  
     
     
         40 . The system of  claim 38  wherein said enlarged contact vessel has a diameter which is at least one and one-half the diameter of said transfer conduit.  
     
     
         41 . The system of  claim 40  wherein said transfer conduit has a diameter within the range of 0.3-2 cm and said enlarged contact vessel has a diameter within the range of 6-9 cm.  
     
     
         42 . The system of  claim 35  wherein said transfer conduit is provided with a pump at a location intermediate said buffer vessel and said reactor and wherein said transfer conduit extends from said buffer vessel to the location of said pump upwardly from said buffer vessel to said pump by an angle of at least 10 degrees.  
     
     
         43 . The system of  claim 42  wherein a section of said transfer conduit between said pump and said reactor extends downwardly from said pump by an angle of at least 10 degrees.