초록

A catalyst carrier which comprises particles of a silicon-containing ceramic material. Each of these particles is covered by a film of alumina on which a noble metal is carried.

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What is claimed is: 1. A catalyst which comprises particles of a silicon-containing ceramic material as a carrier, wherein each of these particles has a layer of silicon oxide (SiO2) on a surface thereof, said silicon oxide layer being covered by a film of alumina, on which film a noble metal is ca

What is claimed is: 1. A catalyst which comprises particles of a silicon-containing ceramic material as a carrier, wherein each of these particles has a layer of silicon oxide (SiO2) on a surface thereof, said silicon oxide layer being covered by a film of alumina, on which film a noble metal is carried as an active catalyst. 2. The catalyst of claim 1, wherein said noble metal comprises at least one of Pt, Pd and Rh. 3. The catalyst of claim 1, wherein the silicon-containing ceramic material comprises a non-oxide silicon ceramic material. 4. The catalyst of claim 3, wherein the non-oxide silicon ceramic material comprises at least one of silicon carbide and silicon nitride. 5. The catalyst of claim 1, wherein the silicon-containing ceramic material comprises an oxide silicon ceramic material. 6. The catalyst of claim 5, wherein the oxide silicon ceramic material comprises at least one of sialon, mullite and cordierite. 7. The catalyst of claim 1, wherein the carrier comprises at least one of a porous body, a fiber-shaped body and a pellet-shaped body. 8. The catalyst of claim 1, wherein the carrier comprises a honeycomb-shaped porous sintered body of silicon carbide. 9. The catalyst of claim 1, wherein an amount of SiO2 in the carrier is from 0.001% to 20% by weight. 10. The catalyst of claim 1, wherein the film of alumina has a specific surface area of 50-300 m2/g and a microscopic view thereof indicates a bristled transplant structure comprising fibers having a diameter of from 2 nm to 50 nm, a length of from 20 nm to 300 nm and a ratio of length/diameter of from 5 to 100. 11. The catalyst of claim 1, wherein the alumina film is present in the carrier in an amount of from 0.1% to 15% by weight, based on the carrier and expressed as alumina. 12. A catalyst which comprises particles of a silicon-containing ceramic material as a carrier, wherein each of these particles has a layer of silicon oxide (SiO2) on a surface thereof, said silicon oxide layer being covered by a film of alumina, on which film an active catalyst is carried, said active catalyst being capable of oxidizing carbon monoxide and hydrocarbons contained in exhaust gas and reducing nitrogen oxides. 13. The catalyst of claim 12, wherein said active catalyst comprises at least one of Pt, Pd and Rh. 14. The catalyst of claim 12, wherein the silicon-containing ceramic material comprises a non-oxide silicon ceramic material. 15. The catalyst of claim 14, wherein the non-oxide silicon ceramic material comprises at least one of silicon carbide and silicon nitride. 16. The catalyst of claim 12, wherein the silicon-containing ceramic material comprises an oxide silicon ceramic material. 17. The catalyst of claim 16, wherein the oxide silicon ceramic material comprises at least one of sialon, mullite and cordierite. 18. The catalyst of claim 12, wherein the carrier comprises at least one of a porous body, a fiber-shaped body and a pellet-shaped body. 19. The catalyst of claim 12, wherein the carrier comprises a honeycomb-shaped porous sintered body of silicon carbide. 20. The catalyst of claim 12, wherein an amount of SiO2 in the carrier is from 0.001% to 20% by weight. 21. The catalyst of claim 12, wherein the film of alumina has a specific surface area of 50-300 m2/g and a microscopic view thereof indicates a bristled transplant structure comprising fibers having a diameter of from 2 nm to 50 nm, a length of from 20 nm to 300 nm and a ratio of length/diameter of from 5 to 100. 22. The catalyst of claim 12, wherein the alumina film is present in the carrier in an amount of from 0.1% to 15% by weight, based on the carrier and expressed as alumina. 23. A catalyst carrier comprising a silicon-containing ceramic support for carrying an active catalyst that comprises at least one of a noble metal and a catalyst that is capable of oxidizing carbon monoxide and hydrocarbons contained in exhaust gas and reducing nitrogen oxides, wherein the support comprises particles and each of these particles has a layer of silicon oxide (SiO2) on a surface thereof, said silicon oxide layer being covered by a film of alumina. 24. The catalyst carrier of claim 23, wherein the silicon-containing ceramic material comprises a non-oxide silicon ceramic material. 25. The catalyst carrier of claim 24, wherein the non-oxide silicon ceramic material comprises at least one of silicon carbide and silicon nitride. 26. The catalyst carrier of claim 23, wherein the silicon-containing ceramic material comprises an oxide silicon ceramic material. 27. The catalyst carrier of claim 26, wherein the oxide silicon ceramic material comprises at least one of sialon, mullite and cordierite. 28. The catalyst carrier of claim 23, wherein the carrier comprises at least one of a porous body, a fiber-shaped body and a pellet-shaped body. 29. The catalyst carrier of claim 23, wherein the carrier comprises a honeycomb-shaped porous sintered body of silicon carbide. 30. The catalyst carrier of claim 23, wherein an amount of SiO2 in the carrier is from 0.001% to 20% by weight. 31. The catalyst carrier of claim 23, wherein the film of alumina has a specific surface area of 50-300 m2/g and a microscopic view thereof indicates a bristled transplant structure comprising fibers having a diameter of from 2 nm to 50 nm, a length of from 20 nm to 300 nm and a ratio of length/diameter of from 5 to 100. 32. The catalyst carrier of claim 23, wherein the alumina film is present in the carrier in an amount of from 0.1% to 15% by weight, based on the carrier and expressed as alumina.