Hollow ceramic balls as automotive catalysts supports

Claim 1

A method of producing hollow ceramic balls of spherical shape having a smooth and dust-free surface and a crush strength of at least 10 pounds, comprising: A. producing dried spherical pellets of largely combustible material, comprising the following steps: 1. forming a slurry comprising a clay, a combustible binder, and water, 2. admixing a particulate combustible filler material with said slurry to form an extrusion mass, the weight of said filler material being at least five times the weight of said clay, 3. extruding said mass, 4. pelletizing the product from step 3 with input of high packing energy to form wet, compacted spherical pellets, and 5. drying said pellets to obtain said dried spherical pellets of largely combustible material; B. boiling said dried spherical pellets in a liquid selected from the group consisting of water, a solution of triethanolamine, and an alum solution; C. draining and cooling said pellets: D. coating said pellets, as cores, with a ceramic-forming powder to obtain a homogeneous deposit of substantially uniform thickness, said coating operation being conducted with gentle tumbling action, and continuing said tumbling of the coated pellets to form wet-appearing but non-sticking balls; E. slowly drying said wet-appearing but non-sticking balls to prevent surface cracking; F. preheating said balls to volatilize said cores, then firing the balls to form hollow ceramic balls at sintering temperatures sufficient to form a smooth and dust-free surface and sufficient for substantially eliminating pores of a diameter up to three-tenths micron in their fired ceramic walls; and G. cooling and recovering said hollow ceramic balls.

Claim 2

A method of producing hollow ceramic balls of spherical shape having a smooth and dust-free surface and a crush strength of at least 10 pounds, comprising: A. producing dried spherical pellets of largely combustible material, comprising the following steps: 1. forming a slurry comprising a clay, a combustible binder, and water, 2. admixing a particulate combustible filler material with said slurry to form an extrusion mass, the weight of said filler material being at least five times the weight of said clay, 3. extruding said mass, 4. pelletizing the product from step 3 with input of high packing energy to form wet, compacted spherical pellets, and 5. drying said pellets to obtain said dried spherical pellets of largely combustible material; B. boiling said dried spherical pellets in a liquid selected from the group consisting of water, a solution of triethanolamine, and an alum solution; C. draining and cooling said pellets: D. coating said pellets, as cores, with a ceramic-forming powder to obtain a homogeneous deposit of substantially uniform thickness, said coating operation being conducted with gentle tumbling action, and continuing said tumbling of the coated pellets to form wet-appearing but non-sticking balls; E. slowly drying said wet-appearing but non-sticking balls to prevent surface cracking; F. preheating said balls to volatilize said cores, then firing the balls to form hollow ceramic balls at sintering temperatures sufficient to form a smooth and dust-free surface and sufficient for substantially eliminating pores of a diameter up to three-tenths micron in their fired ceramic walls; and G. cooling and recovering said hollow ceramic balls.

Claim 18

A method for preparing a fresh oxidation catalyst, for use in a catalytic muffler of an automobile catalyst system, having the following physical properties: 1. uniform, smooth, dustless surfaces with a surface area less than 10 m 2 /g; 2. approximately 5 × 7 mesh size; 3. bulk density below 50 pounds per cubic foot; 4. minumum crush strength of 10 pounds;

Claim 19

A method for preparing a fresh oxidation catalyst, for use in a catalytic muffler of an automobile catalyst system, having the following physical properties: 1. uniform, smooth, dustless surfaces with a surface area less than 10 m 2 /g; 2. approximately 5 × 7 mesh size; 3. bulk density below 50 pounds per cubic foot; 4. minumum crush strength of 10 pounds;

Claim 26

A method for reconditioning hollow ceramic balls having sintered walls and containing a spent elemental catalyst deposited on the surfaces thereof without adversely affecting the physical properties of said balls to produce a fresh oxidation catalyst, for use in a catalytic muffler of an automobile catalyst system, having the following physical properties: 1. uniform, smooth, dustless surfaces with a surface area less than 10 m 2 /g; 2. approximately 5×7 mesh size; 3. bulk density below 50 pounds per cubic foot; 4. minimum crush strength of 10 pounds; 5. air attrition loss of less than 5%; and 6. less than 5% shrinkage at 1,800° F for 24 hours with no loss in crush strength or increase in compaction, said method comprising: A. leaching said spent elemental catalyst with aqua regia to form leached balls, B. coating said leached balls with a noble salt selected from the group consisting of platinum and palladium salts, C. drying said balls so that said noble salt migrates to said surfaces to form salt crystals therein, and D. heating said hollow ceramic balls in an oxidizing atmosphere to decompose said salt crystals to a fresh elemental catalyst.

Claim 27

A method for reconditioning hollow ceramic balls having sintered walls and containing a spent elemental catalyst deposited on the surfaces thereof without adversely affecting the physical properties of said balls to produce a fresh oxidation catalyst, for use in a catalytic muffler of an automobile catalyst system, having the following physical properties: 1. uniform, smooth, dustless surfaces with a surface area less than 10 m 2 /g; 2. approximately 5×7 mesh size; 3. bulk density below 50 pounds per cubic foot; 4. minimum crush strength of 10 pounds; 5. air attrition loss of less than 5%; and 6. less than 5% shrinkage at 1,800° F for 24 hours with no loss in crush strength or increase in compaction, said method comprising: A. leaching said spent elemental catalyst with aqua regia to form leached balls, B. coating said leached balls with a noble salt selected from the group consisting of platinum and palladium salts, C. drying said balls so that said noble salt migrates to said surfaces to form salt crystals therein, and D. heating said hollow ceramic balls in an oxidizing atmosphere to decompose said salt crystals to a fresh elemental catalyst.