Mullite-aluminum titanate body and method for making same

• US 20060021308A1
• Filed: 07/29/2004
• Published: 02/02/2006
• Est. Priority Date: 07/29/2004
• Status: Abandoned Application

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Merkel, Gregory A.
• Application Number:
  US10/902,381
• Publication Number:
  US 20060021308A1
• Time in Patent Office: Days
• US Class Current: 55/523
• CPC Class Codes: B01D 2279/30 for treatment of exhaust gases from IC Engines
• CPC Class Codes: B01D 46/2429 of the honeycomb walls or cells
• CPC Class Codes: B01D 46/24491 Porosity
• CPC Class Codes: B01D 46/24492 Pore diameter
• CPC Class Codes: B01D 46/24494 Thermal expansion coefficient, heat capacity or thermal conductivity
• CPC Class Codes: B01D 46/2498 The honeycomb filter being defined by mathematical relationships
• CPC Class Codes: C04B 2111/00129 Extrudable mixtures
• CPC Class Codes: C04B 2111/00793 as filters or diaphragms
• CPC Class Codes: C04B 2235/3205 Alkaline earth oxides or oxide forming salts thereof, e.g. beryllium oxide
• CPC Class Codes: C04B 2235/3208 Calcium oxide or oxide-forming salts thereof, e.g. lime
• CPC Class Codes: C04B 2235/3213 Strontium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3217 Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
• CPC Class Codes: C04B 2235/3218 Aluminium (oxy)hydroxides, e.g. boehmite, gibbsite, alumina sol
• CPC Class Codes: C04B 2235/322 Transition aluminas, e.g. delta or gamma aluminas
• CPC Class Codes: C04B 2235/3222 Aluminates other than alumino-silicates, e.g. spinel (MgAl2O4)
• CPC Class Codes: C04B 2235/3224 Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
• CPC Class Codes: C04B 2235/3225 Yttrium oxide or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3227 Lanthanum oxide or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3229 Cerium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3231 Refractory metal oxides, their mixed metal oxides, or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3232 : Titanium oxides or titanates, e.g. rutile or anatase
• CPC Class Codes: C04B 2235/3236 : Alkaline earth titanates
• CPC Class Codes: C04B 2235/3244 : Zirconium oxides, zirconates, hafnium oxides, hafnates, or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3251 : Niobium oxides, niobates, tantalum oxides, tantalates, or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3256 : Molybdenum oxides, molybdates or oxide forming salts thereof, e.g. cadmium molybdate
• CPC Class Codes: C04B 2235/3258 : Tungsten oxides, tungstates, or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3284 : Zinc oxides, zincates, cadmium oxides, cadmiates, mercury oxides, mercurates or oxide forming salts thereof
• CPC Class Codes: C04B 2235/3286 : Gallium oxides, gallates, indium oxides, indates, thallium oxides, thallates or oxide forming salts thereof, e.g. zinc gallate
• CPC Class Codes: C04B 2235/3293 : Tin oxides, stannates or oxide forming salts thereof, e.g. indium tin oxide [ITO]
• CPC Class Codes: C04B 2235/3298 : Bismuth oxides, bismuthates or oxide forming salts thereof, e.g. zinc bismuthate
• CPC Class Codes: C04B 2235/3409 : Boron oxide, borates, boric acids, or oxide forming salts thereof, e.g. borax
• CPC Class Codes: C04B 2235/3418 : Silicon oxide, silicic acids, or oxide forming salts thereof, e.g. silica sol, fused silica, silica fume, cristobalite, quartz or flint glass constituents C04B2235/36
• CPC Class Codes: C04B 2235/3454 : Calcium silicates, e.g. wollastonite
• CPC Class Codes: C04B 2235/3463 : Alumino-silicates other than clay, e.g. mullite
• CPC Class Codes: C04B 2235/349 : Clays, e.g. bentonites, smectites such as montmorillonite, vermiculites or kaolines, e.g. illite, talc or sepiolite
• CPC Class Codes: C04B 2235/445 : Fluoride containing anions, e.g. fluosilicate
• CPC Class Codes: C04B 2235/5436 : micrometer sized, i.e. from 1 to 100 micron
• CPC Class Codes: C04B 2235/5445 : submicron sized, i.e. from 0,1 to 1 micron
• CPC Class Codes: C04B 2235/656 : characterised by specific heating conditions during heat treatment
• CPC Class Codes: C04B 2235/6567 : Treatment time
• CPC Class Codes: C04B 2235/77 : Density
• CPC Class Codes: C04B 2235/80 : Phases present in the sintered or melt-cast ceramic products other than the main phase
• CPC Class Codes: C04B 2235/96 : Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance
• CPC Class Codes: C04B 2235/9607 : Thermal properties, e.g. thermal expansion coefficient
• CPC Class Codes: C04B 35/185 : Mullite 3Al2O3-2SiO2
• CPC Class Codes: C04B 35/478 : based on aluminium titanates
• CPC Class Codes: C04B 35/6263 : characterised by their solids loadings, i.e. the percentage of solids
• CPC Class Codes: C04B 35/632 : Organic additives
• CPC Class Codes: C04B 38/0006 : Honeycomb structures from one or more corrugated sheets by winding or stacking C04B38/0083
• CPC Class Codes: C04B 38/0009 : characterised by features relating to the cell walls, e.g. wall thickness or distribution of pores in the walls
• CPC Class Codes: C04B 38/0051 : characterised by the pore size, pore shape or kind of porosity
• CPC Class Codes: C04B 38/0054 : the pores being microsized or nanosized
• CPC Class Codes: C04B 38/0074 : expressed as porosity percentage
• CPC Class Codes: F01N 2330/06 : Ceramic, e.g. monoliths
• CPC Class Codes: F01N 2330/14 : Sintered material
• CPC Class Codes: F01N 3/022 : characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous
• CPC Class Codes: Y02T 10/12 : Improving ICE efficiencies
• CPC Class Codes: Y10S 264/48 : Processes of making filters
• CPC Class Codes: Y10S 55/05 : Methods of making filter
• CPC Class Codes: Y10S 55/10 : Residue burned
• CPC Class Codes: Y10S 55/30 : Exhaust treatment

Abstract

This invention relates to a mullite-aluminum titanate body having a low coefficient of thermal expansion of less than 15×10⁻⁷ C⁻¹, a high porosity of at least 38% by volume, a median pore diameter of at least 8 microns, and a narrow pore size distribution as characterized by the relation (d₅₀-d₁₀)/d₅₀ being less than 0.50 corresponding to a high degree of interconnected porosity. The inventive ceramic body also contains at least 0.10% by weight metal oxide, the metal being either yttrium, calcium, bismuth, a lanthanide metal or combinations of thereof. The inventive ceramic body is particularly useful as a wall-flow filter for diesel exhaust. A method of fabrication is provided where the sintering temperature is between 1375°-1550° C.

Claims

1. A ceramic body comprising phase of mullite and aluminum titanate, and at least 0.10% by weight of a metal oxide for a metal selected from the group consisting of bismuth, calcium, yttrium, lanthanides and combinations thereof, while exhibiting a set of properties including a coefficient of thermal expansion (RT-1000°

C.) less than 15×

10<sup>−

7</sup> C<sup>−

1</sup>, a porosity of at least 38% by volume, a median pore diameter of at least 8 microns, and a narrow pore size distribution as characterized by the relation (d₅₀-d₁₀)/d₅₀ being less than 0.50 corresponding to a high degree of interconnected porosity.

2. The ceramic body of claim 1 wherein the metal oxide is in an amount of between 0.10% to 5.0% by weight.

3. The ceramic body of claim 2 wherein the metal is yttrium.

4. The ceramic body of claim 1 wherein the ceramic body exhibits said set of properties when sintered to a temperature of between 1375°

C. to 1550°

C.

5. A diesel exhaust particulate filter comprising the ceramic body of claim 1, wherein the ceramic body is a plugged, wall-flow honeycomb body having a plurality of parallel end-plugged cell channels traversing the body from a frontal inlet end to an outlet end thereof.

6. The diesel exhaust particulate filter of claim 5 further exhibiting a coefficient of thermal expansion (RT-1000°

C.) not greater than 10×

10<sup>−

7</sup> C<sup>−

1</sup>, a porosity of between 45-60% by volume, a median pore diameter of between 10-20 microns, and a narrow pore size distribution as characterized by the relation (d₅₀-d₁₀)/d₅₀ being not greater than 0.35 corresponding to a high degree of interconnected porosity.

7. A method for making a mullite-aluminum titanate ceramic body comprising:

a. providing a mixture of inorganic raw materials comprising an alumina source, a silica source, and a titanium dioxide source, in combination with a source of a metal oxide as a sintering additive in an amount of at least 0.10% by weight super-addition, the source corresponding to an oxide of a metal selected from the group of metals consisting of bismuth, calcium, yttrium, lanthanides and combinations thereof,

b. shaping the mixture into a body; and

,

c. sintering the body to a temperature of between 1375°

C. to 1550°

C. for a period of between 1 hour to 15 hours;

wherein the weighted average of the median particle diameters of the inorganic raw materials, D₅₀, is at least 6 microns to form a pore size in the mullite-aluminum titanate ceramic body after sintering of at least 8 microns.

8. The method of claim 7 wherein the metal oxide is added to the raw material mixture in an amount between 0.10% and 5.0% by weight.

9. The method of claim 8 wherein the metal is yttrium.

10. The method of claim 7 wherein an amount of at least 0.05% by weight of molybdenum oxide or tungsten oxide is further added to the mixture.

11. The method of claim 7 wherein the alumina source is a selected from a group consisting of corundum, gamma-alumina or another transitional alumina, boehmite, alumina hydroxide (gibbsite) and mixtures thereof.

12. The method of claim 11 wherein the alumina source has a median particle diameter greater than 15 microns.

13. The method of claim 7 wherein the mixture of inorganic raw materials further includes an aluminosilicate source.

14. The method of claim 13 wherein the aluminosilicate source is selected from the group consisting of mullite, kyanite, sillimanite, kaolin, calcined kaolin, pyrophyllite, and mixtures thereof.

15. The method of claim 7 wherein the silica source is selected from the group consisting of quartz, cristobalite, zeolite, diatomaceous earth, fused silica, colloidal silica, amorphous silica, and combinations thereof.

16. The method of claim 7 wherein the titanium dioxide source is selected from the group consisting of rutile, anatase, amorphous titania, and mixtures thereof.

17. The method of claim 7 wherein the alumina source and titanium dioxide source have median particle or agglomerate diameters of at least 10 microns.

18. The method of claim 7 wherein the metal oxide source is selected from the group consisting of bismuth oxide, calcium carbonate, calcium hydroxide, calcium aluminate, calcium titanate, calcium silicate, yttrium or rare earth oxide, hydroxide, carbonate, fluoride-carbonate, aluminate, silicate, titanate, chloride, nitrate, acetate, or other soluble or insoluble salt, a mixed rare earth concentrate such as bastnasite, calcined bastnasite, or monazite, and combinations thereof.

19. The method of claim 18 wherein the metal oxide source has a median particle diameter of less than 5 microns.

20. The method of claim 7 wherein the mixture is shaped by extrusion through a die to form a honeycomb structure.