Catalyst compositions comprising small silica support materials and methods of use in polymerization reactions

Abstract

Improved catalyst compositions, and polymerization processes using such improved catalyst compositions, are provided. An example of an improved catalyst composition is a supported catalyst system that includes at least one titanium compound, at least one magnesium compound, at least one electron donor compound, at least one activator compound, and at least one silica support material, the at least one silica support material having a median particle size in the range of from 20 to 50 microns with no more than 10% of the particles having a size less than 10 microns and no more than 10% of the particles having a size greater than 50 microns.

1 . A process for making polyolefins, comprising contacting, in a reactor, ethylene and at least one comonomer selected from the group consisting of C3 to C8 alpha olefin in the presence of a supported catalyst system comprising at least one titanium compound, at least one magnesium compound, at least one electron donor compound, at least one activator compound, and at least one silica support material, the at least one silica support material having a median particle size in the range of from 20 to 50 microns with no more than 10% of the particles having a size less than 10 microns and no more than 10% of the particles having a size greater than 50 microns.  
     
     
         2 . The process of  claim 1 , wherein the at least one magnesium compound has the formula MgX 2 , wherein X is selected from the group consisting of Cl, Br, I or mixtures thereof  
     
     
         3 . The process of  claim 2 , wherein the at least one magnesium compound is selected from the group consisting of: MgCl 2 , MgBr 2  and MgI 2 .  
     
     
         4 . The process of  claim 1 , wherein the at least one titanium compound has the formula Ti(OR) a X b , wherein R is selected from the group consisting of: a C 1  to C 14  aliphatic hydrocarbon radical, a C 1  to C 14  aromatic hydrocarbon radical, and COR′ where R′ is a C 1  to C 14  aliphatic or aromatic hydrocarbon radical; X is selected from the group consisting of Cl, Br, I and mixtures thereof; a is selected from the group consisting of 0, 1 and 2; b is 1 to 4 inclusive; and a+b=3 or 4.  
     
     
         5 . The process of  claim 1 , wherein the at least one titanium compound is selected from the group consisting of: TiCl 3 , TiCl 4 , Ti(OCH 3 )Cl 3 , Ti(OC 6 H 5 )Cl 3 , Ti(OCOCH 3 )Cl 3  and Ti(OCOC 6 H 5 )Cl 3 .  
     
     
         6 . The process of  claim 1 , wherein the at least one silica support material has a median particle size in the range of from 20 to 35 microns.  
     
     
         7 . The process of  claim 1 , wherein the at least one silica support material has a median particle size in the range of from 20 to 30 microns.  
     
     
         8 . The process of  claim 1 , wherein the at least one silica support material has a particle size distribution in which no more than 10% of the particles have a size below 12 microns, and no more than 8% of the particles have a size above 50 microns.  
     
     
         9 . The process of  claim 1 , wherein the at least one silica support material has a surface area of at least 200 square meters per gram.  
     
     
         10 . The process of  claim 1 , wherein the at least one silica support material has an average pore volume of at least 1.4 ml/gram.  
     
     
         11 . A supported catalyst system comprising at least one titanium compound, at least one magnesium compound, at least one electron donor compound, at least one activator compound, and at least one silica support material, the at least one silica support material having a median particle size in the range of from 20 to 50 microns with no more than 10% of the particles having a size less than 10 microns and no more than 10% of the particles having a size greater than 50 microns.  
     
     
         12 . The supported catalyst system of  claim 11 , wherein the at least one magnesium compound has the formula MgX 2 , wherein X is selected from the group consisting of Cl, Br, I or mixtures thereof  
     
     
         13 . The supported catalyst system of  claim 11 , wherein the at least one magnesium compound is present in the catalyst system in an amount in the range of from 1.5 to 7 moles of magnesium compound per mole of titanium compound.  
     
     
         14 . The supported catalyst system of  claim 11 , wherein the at least one titanium compound has the formula Ti(OR) a X b , wherein R is selected from the group consisting of: a C 1  to C 14  aliphatic hydrocarbon radical, a C 1  to C 14  aromatic hydrocarbon radical, and COR′ where R′ is a C 1  to C 14  aliphatic or aromatic hydrocarbon radical; X is selected from the group consisting of Cl, Br, I and mixtures thereof; a is selected from the group consisting of 0, 1 and 2; b is 1 to 4 inclusive; and a+b=3 or 4.  
     
     
         15 . The supported catalyst system of  claim 14 , wherein the at least one titanium compound is selected from the group consisting of: TiCl 3 , TiCl 4 , Ti(OCH 3 )Cl 3 , Ti(OC 6 H 5 )Cl 3 , Ti(OCOCH 3 )Cl 3  and Ti(OCOC 6 H 5 )Cl 3 .  
     
     
         16 . The supported catalyst system of  claim 11 , wherein the at least one silica support material has a median particle size in the range of from 20 to 35 microns.  
     
     
         17 . The supported catalyst system of  claim 11 , wherein the at least one silica support material has a median particle size in the range of from 20 to 30 microns.  
     
     
         18 . The supported catalyst system of  claim 11 , wherein the at least one silica support material has a particle size distribution in which no more than 10% of the particles have a size below 12 microns, and no more than 8% of the particles have a size above 50 microns.