Gasoline engine with an exhaust system for combusting particulate matter

Abstract

A gasoline engine having an exhaust system comprises means for trapping particulate matter (PM) from the exhaust gas and a catalyst for catalysing the oxidation of the PM by carbon dioxide and / or water in the exhaust gas, which catalyst comprising a supported alkali metal. The invention further includes a method of combusting PM from a gasoline engine in CO2 and / or H2O from the exhaust gas at temperatures in excess of 500° C., which method comprising trapping the PM and contacting it with a catalyst comprising a supported alkali metal.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation of U.S. patent application Ser. No. 10 / 485,592, filed Sep. 7, 2004, which is the U.S. National Phase of PCT International Application No. PCT / GB02 / 03500, filed Jul. 30, 2002, and claims priority of British Patent Application No. 0118748.3, filed Aug. 1, 2001, and British Patent Application No. 0119107.1, filed Aug. 6, 2001, the disclosures of all of which are incorporated herein by reference in their entirety for all purposes.FIELD OF THE INVENTION[0002]The present invention relates to an exhaust system for treating exhaust gases from a gasoline engine, and in particular it relates to an exhaust system for trapping and combusting fine particulate matter in the exhaust gas.BACKGROUND OF THE INVENTION[0003]It is very well known that gas-borne particulates can cause health problems if inhaled. It is also well known that diesel engines emit particulates, especially upon start-up and under heavy load, and thi...

AI Technical Summary

Benefits of technology

[0039]An advantage of the present invention incorporating an electrostatic trap, such as the cylinder-wire embodiments, is that they have a relatively low power consumption e.g. about 10 W, therefore there is minimal impact on the overall efficiency of the vehicle.

[0040]According to a further aspect, the invention provides a method of combusting PM from a gasoline engine in CO2 and / or H2O from the exhaust gas at temperatures in excess of 500° C., which method comprising trapping the PM and contacting the trapped PM with a catalyst comprising a supported alkali metal. The temperatures in excess of 500° C. can be e.g. 550° C., 600° C., 650° C. or 700° C.EXAMPLES

[0041]In order that the invention may be more fully understood, the following Examples are provided by way of illustration only:

Problems solved by technology

It is very well known that gas-borne particulates can cause health problems if inhaled.

However, it is not generally appreciated that many modern gasoline engines emit large numbers of very small (<0.1 μm generally 10-100 nm) particulate matter (PM), which because of its small size is not observed by the naked eye.

Nonetheless, the size of this PM is such that it can be inhaled into the deepest recesses of the lungs and may even be more hazardous than the PM from diesel engines.

Indeed, as reported in the Proceedings from the 2″ International Conference on Health Effects of Vehicle Emissions, Ed. K. Donaldson, (2000), PM poses a significant threat to health in the UK.

In seeking to combust gasoline PM, one problem is that the amount of oxidant available in the exhaust gas for combusting the PM downstream of a three-way catalyst (TWC) is generally very low at approximately 0.03% v / v (300 ppm).

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