Automotive hydrocarbon sensor

• US 6,242,263 B1
• Filed: 12/01/1998
• Issued: 06/05/2001
• Est. Priority Date: 12/20/1996
• Status: Expired due to Fees

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Xie, Yuming, Zhou, Zhigang, Faber, Margaret K.
• Primary Examiner(s): ALEXANDER, LYLE
• Application Number:
  US09/203,085
• Time in Patent Office: 917 Days
• Field of Search: 422/94, 422/95, 422/98, 436/143, 436/147, 436/137, 436/142, 73/233.2, 204/424, 204/426
• US Class Current: 436/143
• CPC Class Codes: F01N 11/00 Monitoring or diagnostic devices for exhaust-gas treatment apparatus , e.g. for catalytic activity safety, indicating or supervising devices for internal combustion engines F02B77/08; testing of machines G01M13/00
• CPC Class Codes: F01N 2550/02 Catalytic activity of catalytic converters
• CPC Class Codes: F02B 77/08 Safety, indicating or supervising devices thermal insulation F02B77/11; rendering engines inoperative or idling F02D17/04; dependent on lubricating conditions F01M1/22; dependent on cooling F01P11/14
• CPC Class Codes: G01N 25/30 using electric temperature-responsive elements
• CPC Class Codes: G01N 27/16 caused by burning or catalytic oxidation of surrounding material to be tested, e.g. of gas
• CPC Class Codes: G01N 33/0047 for organic compounds
• CPC Class Codes: Y02T 10/40 Engine management systems
• CPC Class Codes: Y10T 436/208339 Fuel/air mixture or exhaust gas analysis
• CPC Class Codes: Y10T 436/218 Total hydrocarbon, flammability, combustibility [e.g., air-fuel mixture, etc.]

Abstract

A system for measuring the non-methane HC concentration of gas sample, e.g., automotive exhaust gas, comprises a sensor catalyst capable of selectively oxidizing the combination of CO+H₂+alkene hydrocarbons in a gas sample and a catalytic differential calorimetric sensor downstream of the sensor catalyst, capable of producing an output signal representative of the exothermic effect of oxidation of the remaining aromatic and alkane hydrocarbons in the gas sample. The system also includes a heater for maintaining both the sensor catalyst and the catalytic calorimetric sensor at a temperature sufficient to achieve substantially complete oxidation of the CO+H₂+alkene hydrocarbon combination and the aromatic and alkane hydrocarbons, respectively. Lastly, the system includes a means for analyzing the output signal representative of the concentration of unburned aromatic and alkane hydrocarbons in the exhaust gas to determine concentration of the total non-methane hydrocarbon species. A method carried out by the system comprises the following steps: (1) contacting a portion of a exhaust gas sample with a sensor catalyst which selectively oxidizes a combination of CO+H₂+alkene hydrocarbons; and thereafter, (2) contacting the oxidized portion of the exhaust gas sample with a sensor producing an output signal representative of the concentration of the remaining aromatic and alkane hydrocarbons in the oxidized exhaust gas portion; (3) analyzing the output signal thereby determining the total hydrocarbon concentration in the exhaust gas.

Claims

1. A system for measuring the hydrocarbon concentration of a gas sample, comprising:

a sensor catalyst having an oxidation catalyst capable of selectively oxidizing the combination of CO+H₂+alkene hydrocarbons species in the gas sample, the sensor catalyst comprising an oxidation catalyst having a high surface area catalyst-support material and a precious metal layer comprising an amount of highly dispersed rhodium cluster deposits on the surface of a high surface area catalyst-support material, the rhodium cluster deposits comprising a single rhodium atom or a cluster of at least two rhodium atoms, the deposits having a diameter of less than about 5 nm and covering no greater than about 10% of the surface area of the catalyst-support material;

a catalytic differential calorimetric sensor, capable of producing a output signal representative of the exothermic effect of the remaining aromatic and alkane hydrocarbons species in the gas sample; and

,

a heater for maintaining each of the sensor catalyst and the catalytic calorimetric sensor at a temperature sufficient to effect substantially complete oxidation of the CO+H₂+alkene hydrocarbon and aromatic and alkane hydrocarbon species, respectively;

a means for analyzing the output signal representative of the concentration of unburned aromatic and alkane hydrocarbons in the exhaust gas to determine concentration of the total non-methane hydrocarbon species.

2. The system of claim 1 wherein the catalyst-support material is comprised of a material selected from the group consisting of alumina, zirconia, silica, ceria and mixtures thereof.

3. The system of claim 1 wherein the oxidation catalyst of the sensor catalyst is comprised of a dual layer washcoat layer comprising a mixture of SiO₂ and K—

Al₂O₃ and a precious metal layer comprising Rh.

4. The system of claim 1 wherein the sensor catalyst and the differential catalytic calorimetric sensor are located within a tubular housing which is located in an internal combustion engine exhaust stream downstream of a main catalytic converter.

5. The system of claim 1 wherein the catalytic differential calorimetric sensor comprises a substrate comprising a first catalytic portion having a second oxidation catalyst capable of oxidizing the remaining alkane and aromatic hydrocarbon species in the gas sample and an adjacent second reference portion.

6. The system of claim 5 wherein the sensor includes a means for measuring the temperature the catalyzed portion and the second reference portion.

7. The system of claim 6 wherein the means of measuring the temperature is selected from the group consisting of thermocouples, thermistors and resistance temperature devices.

8. The system of claim 6 wherein both the heater and the means for measuring the temperature comprises a resistance temperature device.

9. The system of claim 5 wherein the adjacent second reference portion comprises a third oxidation catalyst comprising a catalytic-support material and a precious metal material capable of selectively oxidizing the combination of CO+H₂+alkene hydrocarbons.

10. The system of claim 9 wherein the second oxidation catalyst is comprised of a high surface area catalyst-support material and a precious metal material.

11. The system of claim 10 wherein the precious metal of the second oxidation catalyst is selected from the group consisting of rhodium, platinum, palladium, iridium, silver, gold, ruthenium, osmium, and mixtures thereof.

12. The system of claim 10 wherein the second oxidation catalyst is comprised of a ceria/zirconia solid solution catalyst-support material and a precious metal comprised of platinum.