Ceria composition and process for preparing same

Abstract

The present invention provides a cerium oxide particulate composition and a process for preparing a cerium oxide particulate composition comprising aggregates of approximately spherical primary particles of cerium oxide. The method involves preparing a solution of a cerium oxide precursor, aerosolizing the cerium oxide precursor solution, and heating the aerosol to provide the cerium oxide particle composition.

1 . A method of preparing a cerium oxide particle composition comprising preparing a solution consisting essentially of a cerium oxide precursor, converting the cerium oxide precursor solution into an aerosol having droplets with a diameter of about 100 μm or less, passing the aerosol through a high temperature reaction zone so that the cerium oxide precursor is converted to aggregates consisting essentially of approximately spherical primary particles of cerium oxide, and recovering the resulting aggregates as a cerium oxide particle composition.  
     
     
         2 . The method of  claim 1 , wherein the high temperature reaction zone is a flame.  
     
     
         3 . The method of  claim 2 , wherein the aggregates are a mixture of aciniform aggregates and cenospherical aggregates.  
     
     
         4 . The method of  claim 3 , wherein about 90% or more (by weight) of the aggregates are cenospherical aggregates.  
     
     
         5 . The method of  claim 4 , wherein about 95% or more (by weight) of the aggregates are cenospherical aggregates.  
     
     
         6 . The method of  claim 5 , wherein about 98% or more (by weight) of the aggregates are cenospherical aggregates.  
     
     
         7 . The method of  claim 1 , wherein the solution of a cerium oxide precursor is an aqueous solution.  
     
     
         8 . The method of  claim 7 , wherein the aqueous solution comprises alcohol.  
     
     
         9 . The method of  claim 8 , wherein the alcohol is methanol or ethanol.  
     
     
         10 . The method of  claim 7 , wherein the solution of a cerium oxide precursor is acidic.  
     
     
         11 . The method of  claim 1 , wherein the solution of a cerium oxide precursor is about 5 wt. % or more of the cerium oxide precursor.  
     
     
         12 . The method of  claim 11 , wherein the solution of a cerium oxide precursor is about 10 wt % or more of the cerium oxide precursor.  
     
     
         13 . The method of  claim 1 , wherein the droplets have a diameter of about 10-100 μm.  
     
     
         14 . The method of  claim 1 , wherein the high temperature reaction zone has a temperature of about 700-2000 K.  
     
     
         15 . The method of  claim 14 , wherein the high temperature reaction zone has a temperature of about 700-1100 K.  
     
     
         16 . The method of  claim 1 , wherein the cerium oxide precursor is selected from the group consisting of cerium acetate, cerium acetylacetonate, cerium chloride, cerium nitrate, cerium oxalate, and cerium perchlorate.  
     
     
         17 . The method of  claim 16 , wherein the cerium oxide precursor is cerium acetate.  
     
     
         18 . The method of  claim 16 , wherein the cerium oxide precursor is cerium acetylacetonate.  
     
     
         19 . The method of  claim 1 , wherein the primary particles are of crystalline cerium oxide.  
     
     
         20 . The method of  claim 19 , wherein the crystalline cerium oxide comprises cubic phase crystalline cerium oxide.  
     
     
         21 . The method of claims  1 , wherein the primary particles have an average diameter (by number) of about 30 nm or less.  
     
     
         22 . The method of  claim 21 , wherein the primary particles have an average diameter (by number) of about 20 nm or less.  
     
     
         23 . The method of  claim 22 , wherein the primary particles have an average diameter (by number) of about 10 nm or less.  
     
     
         24 . The method of  claim 1 , wherein the aggregates have a density of about 6 g/cm 3  or more.  
     
     
         25 . The method of  claim 24 , wherein the aggregates have a density of about 6-7 g/cm 3 .  
     
     
         26 . The method of  claim 3 , wherein the cenospherical aggregates have an average particle diameter (by weight) of about 1-20 μm.  
     
     
         27 . The method of  claim 26 , wherein the cenospherical aggregates have an average particle diameter (by weight) of about 5-10 μm.  
     
     
         28 . The method of claims  3 , wherein the aciniform aggregates have an average particle diameter (by number) of about 500 nm or less.  
     
     
         29 . The method of  claim 28 , wherein the aciniform aggregates have an average diameter (by number) of about 200 nm or less.  
     
     
         30 . The method of  claim 29 , wherein the aciniform aggregates have an average diameter (by number) of about 100 nm or less.  
     
     
         31 . The method of  claim 1 , wherein the aggregates have a surface area of about 50 m 2 /g or more.  
     
     
         32 . The method of  claim 31 , wherein the aggregates have has a surface area of about 70 m 2 /g or more.  
     
     
         33 . The method of  claim 1 , wherein the aggregates are not calcined.  
     
     
         34 . A cerium oxide particulate composition comprising aggregates consisting essentially of approximately spherical primary particles of cerium oxide, wherein at least some of the aggregates are cenospherical aggregates.  
     
     
         35 . The composition of  claim 34 , wherein the remainder of the aggregates are aciniform aggregates.  
     
     
         36 . The composition of  claim 35 , wherein about 90% or more (by weight) of the aggregates are cenospherical aggregates.  
     
     
         37 . The composition of  claim 36 , wherein about 95% or more (by weight) of the aggregates are cenospherical aggregates.  
     
     
         38 . The composition of  claim 37 , wherein about 98% or more (by weight) of the aggregates are cenospherical aggregates.  
     
     
         39 . The composition of  claim 34 , wherein the primary particles have an average diameter (by number) of about 30 nm or less.  
     
     
         40 . The composition of  claim 39 , wherein the primary particles have an average diameter (by number) of about 20 nm or less.  
     
     
         41 . The composition of  claim 40 , wherein the primary particles have an average diameter (by number) of about 10 nm or less.  
     
     
         42 . The composition of  claim 34 , wherein the aggregates have a density of about 6 g/cm 3  or more.  
     
     
         43 . The composition of  claim 42 , wherein the aggregates have a density of about 6-7 g/cm 3 .  
     
     
         44 . The composition of  claim 34 , wherein the cenospherical aggregates have an average diameter (by weight) of about 1-20 μm.  
     
     
         45 . The composition of  claim 44 , wherein the cenospherical aggregates have an average diameter (by weight) of about 5-10 μm.  
     
     
         46 . The composition of  claim 35 , wherein the aciniform aggregates have an average diameter (by number) of about 500 nm or less.  
     
     
         47 . The composition of  claim 46 , wherein the aciniform aggregates have an average diameter (by number) of about 200 nm or less.  
     
     
         48 . The composition of  claim 47 , wherein the aciniform aggregates have an average diameter (by number) of about 100 nm or less.  
     
     
         49 . The composition of  claim 34 , wherein the aggregates have a surface area of about 50 m 2 /g or more.  
     
     
         50 . The composition of  claim 49 , wherein the aggregates have a surface area of about 70 m 2 /g or more.  
     
     
         51 . The composition of  claim 1 , wherein the primary particles have a crystallite size of about 1-30 nm.  
     
     
         52 . The composition of  claim 51 , wherein the primary particles have a crystallite size of about 5-15 nm.  
     
     
         53 . The method of  claim 9 , wherein the solution of a cerium oxide precursor is acidic.  
     
     
         54 . The method of  claim 10 , wherein the solution of a cerium oxide precursor contains nitric acid.  
     
     
         55 . The method of  claim 53 , wherein the solution of a cerium oxide precursor contains nitric acid.