Porous metal-alumina composite
AssigneeUnion Carbide Corporation
InventorHarry Cheung
Life of this patent
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Abstract
A porous composite structure comprising a sintered mixture of metal particles and alumina particles, and a method for producing this composite. The composite is useful as a catalyst support, particularly in apparatus designed to reduce pollutant emissions from automobile engines.
Claims7
The combination of a support structure for catalytic materials and a catalytic metal or metal compound deposited on the transition alumina in said structure, said support structure comprising the combination of a metal screen material having deposited thereon a sintered mixture of metal particles and alumina particles, characterized by the following parameters:
- at least 50 weight percent of the particles in the sintered mixture are metal particles;
- at least 5 weight percent of the particles in the sintered mixture are alumina particles having a surface area of at least 25 square meters per gram;
- and
- the inter-particle porosity in the sintered mixture is between 15 volume percent and 60 volume percent.
A method for producing a porous sintered mixture of metal particles and alumina particles comprising the steps of:
- a. depositing a catalytic metal or metal compound on transition alumina particles having a surface area sufficiently high so that they will retain a surface area of at least 25 square meters per gram after sintering of said metal particles of step (b) pursuant to step (d) below;
- b. forming a mixture of (i) particles of a metal having a sintering temperature below the phase transition temperature for the formation of alpha-alumina and (ii) said transition alumina particles, said mixture containing at least 50 weight percent metal particles and at least 5 weight percent transition alumina particles;
- c. compacting said mixture into a desired shape under a pressure high enough so that said compacted mixture will retain said shape, but low enough so that said mixture after sintering will have an inter-particle porosity of at least 5 volume percent;
- and
- d. heating said compacted mixture to a temperature below the phase transition temperature of transition alumina to alpha-alumina for a sufficient length of time to cause sintering of said metal particles.
A method for producing a porous sintered mixture of metal particles and alumina particles comprising the steps of:
- a. forming a mixture of (i) particles of a metal having a sintering temperature below the phase transition temperature for the formation of alpha-alumina and (ii) transition alumina particles having a surface area sufficiently high so that they will retain a surface area of at least 25 square meters per gram after sintering of said metal mixture containing at least 50 weight percent metal particles and at least 5 weight percent transition alumina particles;
- b. compacting said mixture into a desired shape under a pressure high enough so that said compacted mixture will retain said shape, but low enough so that said mixture after sintering will have an inter-particle porosity of at least 5 volume percent;
- c. heating said compacted mixture to a temperature below the phase transition temperature of transition alumina to alpha-alumina for a sufficient length of time to cause sintering of said metal particles;
- and
- d. depositing a catalytic metal or metal compound on said transition alumina after sintering.
A method for producing a porous mixture of metal particles and alumina particles comprising the steps of:
- a. contacting transition alumina particles with water vapor at temperatures between 600.degree. C and 1000.degree. C for at least 3 hours, said alumina particles having a surface area sufficiently high so that they will retain a surface area of at least 25 square meters per gram after sintering of said metal particles pursuant to step (d) below;
- b. forming a mixture of (i) particles of a metal having a sintering temperature below the phase transition temperature for the formation of alpha-alumina and (ii) transition alumina particles from step (a) above, said mixture containing at least 50 weight percent metal particles and at least 5 weight percent transition alumina particles;
- c. compacting said mixture into a desired shape under a pressure high enough so that said compacted mixture will retain said shape, but low enough so that said mixture after sintering will have an inter-particle porosity of at least 5 volume percent;
- d. heating said compacted mixture in vacuum or in an atmosphere which does not react unfavorably with the components of said mixture to a temperature below the phase transition temperature of transition alumina to alpha-alumina for a sufficient length of time to cause sintering of said metal particles;
- and
- e. depositing a catalytic metal or metal compound on said transition alumina.
Dependencies are inferred from the claim text.