# US 7,743,772 B2 · Silver and silver oxide catalysts for the oxidation of carbon monoxide in cigarette smoke

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- Number: US 7,743,772 B2
- Document ID: US7743772B2
- Status: Granted
- Kind: B2
- Application number: 10/868,015
- Filed: 2004-06-16
- Published: 2005-12-22
- Granted: 2010-06-29
- Earliest claimed: 2004-06-16
- Assignees: Philip Morris USA Inc.
- Inventors: Rangaraj S. Sundar; Sarojini Deevi
- Web page: https://patentgrep.com/patent/US7743772B2

## CPC

- A24B 15/288: {Catalysts or catalytic material, e.g. included in the wrapping material}
- A24B 15/28: by chemical substances
- A24B 15/286: {Nanoparticles}
- A24B 15/287: {by inorganic substances only}
- A24D 1/002: {with additives, e.g. for flavouring}
- A24D 1/02: with special covers
- A24D 3/16: of inorganic materials
- B01D 53/865: {characterised by a specific catalyst}
- B01J 23/50: Silver
- B01J 23/66: Silver or gold
- B01J 35/45: Nanoparticles
- B01D 2255/104: Silver
- Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product
- A24B: MANUFACTURE OR PREPARATION OF TOBACCO FOR SMOKING OR CHEWING; TOBACCO; SNUFF
- A24D: CIGARS; CIGARETTES; TOBACCO SMOKE FILTERS; MOUTHPIECES OF CIGARS OR CIGARETTES; MANUFACTURE OF TOBACCO SMOKE FILTERS OR MOUTHPIECES
- 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
- Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS

## Abstract

A component of a cigarette comprises a silver-based catalyst for the conversion of carbon monoxide to carbon dioxide. The silver-based catalyst comprises particles (e.g., nanoscale or larger sized particles) of metallic silver and/or silver oxide supported in and/or on metal oxide support particles. The silver-based catalyst can be incorporated into a cigarette component such as tobacco cut filler, cigarette paper and cigarette filter material to reduce the concentration of carbon monoxide in the mainstream smoke of a cigarette during smoking. The catalyst can also be used in non-cigarette applications.

## Claims

### Claim 1

A component of a cigarette comprising a particulate catalyst for the conversion of carbon monoxide to carbon dioxide, wherein the catalyst comprises agglomerates of nanoscale particles comprising silver and/or silver oxide supported in and/or on support particles of cerium oxide, wherein the component is selected from the group consisting of tobacco cut filler, cigarette paper and cigarette filter material, and wherein the catalyst has been heat treated under conditions which provide a light off temperature of not more than 100° C. in a gas flow consisting of 3% CO, 21% O2 and balance argon, wherein the light off temperature is a temperature for 5% CO conversion.

### Claim 2 (depends on 1)

The component of claim 1, wherein the catalyst has been heat treated at 300 to 400° C. and consists essentially of the agglomerates of nanoscale particles comprising silver and/or silver oxide supported in and/or on cerium oxide particles.

### Claim 3 (depends on 1)

The component of claim 1, wherein the particles comprising silver and/or silver oxide have an average particle size of less than about 100 nm.

### Claim 4 (depends on 1)

The component of claim 1, wherein the agglomerates of nanoscale particles have an average size of from about 1 to 50 microns.

### Claim 5 (depends on 4)

The component of claim 4, wherein the agglomerates of nanoscale particles consist essentially of silver and/or silver oxide supported in and/or on the support particles of cerium oxide.

### Claim 6 (depends on 2)

The component of claim 2, wherein the particles of silver and/or silver oxide have an average particle size of less than about 100 nm.

### Claim 7 (depends on 1)

The component of claim 1, wherein the support particles have an average particle size of less than about 500 nm.

### Claim 8 (depends on 1)

The component of claim 1, wherein the cerium oxide is at least partially a non-stoichiometric oxide.

### Claim 9 (depends on 1)

The component of claim 1, wherein the catalyst comprises from about 1 to 70% by weight silver and/or silver oxide supported in and/or on particles of cerium oxide.

### Claim 10 (depends on 1)

The component of claim 1, wherein the catalyst is capable of acting as both an oxidant for the conversion of carbon monoxide to carbon dioxide and as a catalyst for the conversion of carbon monoxide to carbon dioxide.

### Claim 11 (depends on 1)

A cigarette comprising the component of claim 1.

### Claim 12 (depends on 11)

The cigarette of claim 11, wherein the catalyst consists essentially of silver and/or silver oxide and the cerium oxide.

### Claim 13 (depends on 11)

The cigarette of claim 11, wherein the particles comprising silver have an average particle size of less than about 100 nm or less than about 50 nm.

### Claim 14 (depends on 11)

The cigarette of claim 11, wherein the particles comprising silver comprise agglomerates of nanoscale particles, wherein the agglomerates have an average size of from about 1 to 50 microns.

### Claim 15 (depends on 14)

The cigarette of claim 14, wherein the agglomerates consist essentially of silver and/or silver oxide.

### Claim 16 (depends on 12)

The cigarette of claim 12, wherein the particles of silver and/or silver oxide have an average particle size of less than about 100 nm or less than about 50 nm.

### Claim 17 (depends on 11)

The cigarette of claim 11, wherein the support particles have an average particle size of less than about 500 nm.

### Claim 18 (depends on 11)

The cigarette of claim 11, wherein the cerium oxide is at least partially a non-stoichiometric oxide.

### Claim 19 (depends on 11)

The cigarette of claim 11, wherein the catalyst comprises from about 1 to 70% by weight or from about 5 to 20% by weight silver and/or silver oxide.

### Claim 20 (depends on 11)

The cigarette of claim 11, wherein the catalyst is capable of acting as both an oxidant for the conversion of carbon monoxide to carbon dioxide and as a catalyst for the conversion of carbon monoxide to carbon dioxide.

### Claim 21 (depends on 1)

A method of making a cigarette comprising the component of claim 1, the method comprising the steps of:
a. incorporating the catalyst in at least one of tobacco cut filler, cigarette paper and cigarette filter material;
b. providing the tobacco cut filler to a cigarette making machine to form a tobacco column;
c. placing the cigarette paper around the tobacco column to form a tobacco rod of a cigarette; and
d. optionally attaching a cigarette filter comprising the cigarette filter material to the tobacco rod using tipping paper.

### Claim 22 (depends on 21)

The method of claim 21, wherein the incorporating comprises spraying, dusting or immersion.

### Claim 23 (depends on 21)

The method of claim 21, wherein the catalyst consists essentially of particles of silver and/or silver oxide and the cerium oxide.

### Claim 24 (depends on 21)

The method of claim 21, further comprising forming the catalyst via the precipitation or thermal decomposition of a silver salt.

### Claim 25 (depends on 24)

The method of claim 24, wherein the salt is silver nitrate.

### Claim 26 (depends on 24)

The method of claim 24, wherein the precipitation or thermal decomposition of the silver salt forms nanoscale particles of silver and/or silver oxide.

### Claim 27 (depends on 24)

The method of claim 24, wherein the catalyst consists essentially of particles of silver and/or silver oxide and the cerium oxide.

### Claim 28 (depends on 21)

The method of claim 21, wherein the particles of silver and/or silver oxide have an average particle size of less than about 100 nm or less than about 50 nm.

### Claim 29 (depends on 24)

The method of claim 24, further comprising;
a. combining the salt with a solvent to form a silver precursor solution;
b. combining the silver precursor solution with a colloidal solution of an oxide of cerium to form a mixture, wherein the second metal is different than silver;
c. heating the mixture to a temperature sufficient to thermally decompose the silver salt to form nanoscale particles of silver and/or silver oxide, wherein the nanoscale particles are incorporated in and/or on the cerium oxide; and
d. drying the mixture to form the catalyst.

### Claim 30 (depends on 29)

The method of claim 29, wherein the cerium oxide is at least partially a non-stoichiometric oxide.

### Claim 31 (depends on 29)

The method of claim 29, wherein the catalyst comprises from about 1 to 70% by weight or from about 5 to 20% by weight silver and/or silver oxide.

### Claim 32 (depends on 29)

The method of claim 29, further comprising heating the catalyst at a temperature of at least 200° C. prior to incorporating the catalyst in and/or on the at least one of tobacco cut filler, cigarette paper and cigarette filter material.

### Claim 33 (depends on 32)

The method of claim 32, wherein the catalyst is heated in an atmosphere that oxidizes the silver to form a catalyst consisting essentially of silver oxide supported in and/or on the cerium oxide.

### Claim 34 (depends on 21)

The method of claim 21, further comprising forming the catalyst via laser vaporization and controlled condensation of a target material.

### Claim 35 (depends on 34)

The method of claim 34, wherein the target material comprises silver and cerium.

### Claim 36 (depends on 34)

The method of claim 34, wherein the cerium oxide is at least partially a non-stoichiometric oxide.

### Claim 37 (depends on 34)

The method of claim 34, wherein the catalyst comprises from about 1 to 70% by weight or from about 5 to 20% by weight silver and/or silver oxide.

### Claim 38 (depends on 34)

The method of claim 34, wherein the catalyst consists essentially of nanoscale particles of silver and/or silver oxide supported in and/or on an oxide of cerium.

### Claim 39 (depends on 38)

The method of claim 38, wherein at least some of the silver is incorporated on a surface of the cerium oxide.

### Claim 40 (depends on 34)

The method of claim 34, wherein the nanoscale particles of silver and/or silver oxide and the nanoscale particles of cerium oxide condense in the gas phase to form the catalyst.

### Claim 41 (depends on 34)

The method of claim 34, wherein the catalyst consists essentially of nanoscale particles of silver and/or silver oxide supported in and/or on nanoscale or micron-sized particles of cerium oxide.

### Claim 42 (depends on 34)

The method of claim 34, further comprising heating the catalyst at a temperature of at least 200° C. in an atmosphere that oxidizes the silver prior to incorporating the catalyst in and/or on the at least one of tobacco cut filler, cigarette paper and cigarette filter material.

### Claim 43 (depends on 11)

The cigarette of claim 11, wherein the catalyst is present in an amount effective to convert at least 5% of the carbon monoxide in mainstream smoke drawn through the cigarette to carbon dioxide at a temperature of less than about 210° C.

### Claim 44 (depends on 11)

The cigarette of claim 11, wherein the catalyst is present in an amount effective to reduce the concentration of CO and/or reduce the concentration of total particulate matter drawn through the cigarette during smoking.

### Claim 45 (depends on 1)

The component of claim 1, wherein the particles comprising silver and/or silver oxide have an average particle size of less than about 50 nm.

### Claim 46 (depends on 2)

The component of claim 2, wherein the particles of silver and/or silver oxide have an average particle size of less than about 50 nm.

### Claim 47 (depends on 1)

The component of claim 1, wherein the catalyst comprises from about 5 to 20% by weight silver and/or silver oxide.

### Claim 48 (depends on 1)

The component of claim 1, wherein the catalyst is a calcined catalyst.