Method for treating a gas containing nitrogen oxides (NOx), using as nox trap a composition based on zirconium oxide and praseodymium oxide

Abstract

The invention concerns a method for treating a gas containing nitrogen oxides (NOx) characterized in that it consists in using as NOx trap a composition based on a catalyst for oxidizing NOx into NO2 and a compound based on zirconium oxide and praseodymium oxide in a proportion of praseodymium oxide ranging between 5 wt. % and 50 wt. % of oxide. Said compound may further comprise cerium oxide. The inventive method can be used for treating exhaust gas of a Diesel or lean mixture gasoline internal combustion engine.

Description

technical field

[0001] The present invention relates to a method for treating NOx-containing gases by using a composition based on zirconium oxide and praseodymium oxide as nitrogen oxide (NOx) trap. Background technique

[0002] It is known that environmental standards are increasingly demanding the reduction of nitrogen oxide (NOx) emissions from the exhaust of motor vehicle engines, especially diesel engines or gasoline engines operating under lean burn conditions, "ternary" Catalysts are not suitable for these engines.

[0003] Systems known as NOx traps have been proposed as catalyst types that can meet this requirement. They are systems that are able to partially oxidize and then store the nitrogen oxides present in the lean gas and to release and reduce them to nitrogen when the surrounding mixture is rich.

[0004] However, known NOx traps still have certain drawbacks. Their ability to capture or store NOx is optimal at high temperatures (that is, typically around...

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