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US 6,153,159 AGranted
Method for purifying exhaust gases
AssigneeVolkswagen Aktiengesellschaft
InventorsWerner Engeler, Dieter Neyer, Martina Kosters, Diethard Hesse
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AssigneeVolkswagen Aktiengesellschaft
InventorsWerner Engeler, Dieter Neyer, Martina Kosters, Diethard Hesse
Estimating the term…
Thermal catalysts, particularly catalysts coated with precious metals, are used to reduce the concentration of CO, HC and NOx in exhaust gases from internal-combustion engines. While catalysts coated with precious metals exhibit catalytic activity from about 140.degree. C., to ensure very low emission levels thermal catalysts need to be heated during cold starting so that the pollutants produced during the cold start react. The specification discloses a catalyst with a photocatalytic semiconductor illuminated with UV light for this purpose. Suitable for use as the photocatalytic material is e.g. titanium dioxide. This enables pollutant levels to be reduced immediately after the engine has been started and even at relatively low ambient temperatures. The invention is suitable for use with diesel engines and lean-mixture spark-ignition engines.
A method of catalytic conversion of NO.sub.x, HC and/or CO in an exhaust gas system of an internal combustion engine comprising supplying exhaust gas components from an internal combustion engine together with O.sub.2 to a passage extending between spaced surfaces supporting a photocatalyst containing TiO.sub.2 for reaction with the TiO.sub.2 photocatalyst and directing catalyst-activating illumination from a location outside the passage into the passage in a direction extending between the spaced surfaces to activate the photocatalyst during the reaction.
A method of catalytic conversion of HC and/or CO contained in an exhaust gas in an exhaust gas system of an internal combustion engine comprising supplying exhaust gas components from an internal combustion engine together with O.sub.2 to a passage extending between spaced surfaces supporting a photocatalyst for reaction with the photocatalyst and directing catalyst-activating illumination from a location outside the passage into the passage in a direction extending between the spaced surfaces to activate the photocatalyst during the reaction.
A method of catalytic conversion of NOx, HC and/or CO in an exhaust gas system of an internal combustion engine comprising supplying exhaust gas components from an internal combustion engine together with O.sub.2 to a passage extending between spaced surfaces supporting a semiconductor photocatalyst which contains a transition metal for reaction with the photocatalyst and directing catalyst-activating illumination from a location outside the passage into the passage in a direction extending between the spaced surfaces to activate the photocatalyst during the reaction.
Dependencies are inferred from the claim text.