# US 5,330,956 A · Poisoning-resistant catalyst, process for production thereof, and process for using said catalyst

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- Number: US 5,330,956 A
- Document ID: US5330956A
- Status: Granted
- Kind: A
- Application number: 07/947,918
- Filed: 1992-09-21
- Granted: 1994-07-19
- Earliest claimed: 1991-09-20
- Assignees: Hitachi, Ltd.
- Inventors: Tetsuro Haga; Hiroshi Kawagoshi; Hisao Yamashita
- Web page: https://patentgrep.com/patent/US5330956A

## CPC

- B01D 53/864: {Removing carbon monoxide or hydrocarbons}
- B01J 23/40: of the platinum group metals
- B01J 37/0209: {involving a reaction between the support and a fluid}
- B01J 37/0211: {using a colloidal suspension}
- B01J 37/0221: {of particles}
- B01J 2235/30: Scanning electron microscopy; Transmission electron microscopy
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS

## Abstract

The present invention provides a poisoning-resistant catalyst for combustion of CO and inflammable gases which comprises an inorganic carrier, a noble metal active ingredient supported on said inorganic carrier, and silica supported on said noble metal active ingredient, said noble metal active ingredient comprising at least one member selected from the group consisting of Pt, Rh and Pd, the surface of said catalyst being richer in silica and the inner part of said catalyst becoming richer in said noble metal active ingredient the deeper from the surface said inner part becomes; and a catalytic combustion apparatus for burning inflammable gases in a starting gas by the use of said catalyst. Said catalyst has a high resistance to poisoning and has a high level of activity at a low temperature of 200.degree. C. or lower.

## Claims

### Claim 1

A poisoning-resistant catalyst for combustion of CO and inflammable gases in air containing a poisonous component for the catalyst which comprises an inorganic carrier, a noble metal active ingredient supported on said inorganic carrier, and silica supported on said noble metal active ingredient, said noble metal active ingredient comprising at least one member selected from the group consisting of Pt, Rh and Pd, an outer part of the surface of said catalyst being richer in silica and an inner part of said catalyst becoming richer in said noble metal active ingredient the deeper from the outer part of the surface said inner part becomes; the amount of silica relative to said at least one member selected from the group consisting of Pt, Rh and Pd being 4 to 20 in terms of the atomic ratio of Si to said at least one member selected from the group consisting of Pt, Rh and Pd.

### Claim 2 (depends on 1)

A poisoning-resistant catalyst according to claim 1, wherein alumina having a honeycomb structure is used as said inorganic carrier.

### Claim 3

A poisoning-resistant catalyst for combustion of CO and inflammable gases in air containing a poisonous component for the catalyst which is produced by supporting at least one of metal salts of Pt, Rh and Pd on at least the surface layer of an inorganic carrier, carrying out primary firing at 700.degree.-800.degree. C., supporting colloidal silica on a part of the surface of the fired product, and then carrying out secondary firing at 400.degree.-600.degree. C.

### Claim 4 (depends on 3)

A poisoning-resistant catalyst according to claim 3, wherein the concentration of said colloidal silica on a part of the surface is such that the amount of silica relative to at least one of Pt, Rh and Pd is 4 to 20 in terms of the atomic ratio of Si to at least one of Pt, Rh and Pd; the concentration of said colloidal silica being greater at an outer part of the surface than at an inner part of the catalyst.

### Claim 5 (depends on 3, 4)

A poisoning-resistant catalyst according to claim 3 or 4, wherein alumina having a honeycomb structure is used as said inorganic carrier.