Fuel-lean vehicular engine exhaust gas catalyzing and purifying method

Abstract

The invention is catalyst purifying method for tails discharged by fuel-lean car engine. The invention provides a method which applies to fuel-lean car engine, reduces NOx in tails efficiently in wide temperature range, and oxidizes HC and CO. The method includes following steps: sprays carbinol or alcohol into discharging pipe, and makes it blend with the engine tails; the mixed gas is transmitted to front grade catalyzing reaction bed which is loaded with transition metal oxide catalyst and the back grade catalyzing reaction bed which is loaded with laden noble metal catalyst, realizes the purification of NOx, HC and CO with high efficiency, and finally discharges normal gas. The invention can spread the range of NOx reduction active temperature.

Description

technical field [0001] Lean-burn refers to combustion under the condition of excess air. The invention relates to a catalytic purification method for exhaust gas of a lean-burn vehicle engine in which two catalysts are combined in stages as a catalyst system, and belongs to the technical field of catalytic purification of vehicle exhaust. Background technique [0002] At present, the mainstream technology for automobile exhaust purification is three-way catalytic conversion. This purification technology requires the engine to work under the condition of stoichiometric ratio. It is only applicable to gasoline engines, and to a certain extent, it is at the expense of fuel economy. . With the energy saving and reduction of greenhouse gas CO 2 With the increasing emphasis on emissions, the market prospect of lean-burn vehicle engines, including diesel engines and lean-burn gasoline engines, is getting wider and wider. The lean-burn method of gasoline or diesel-fueled vehicle e...

AI Technical Summary

Problems solved by technology

These catalysts all have a certain NO reduction activity. However, when only relying on a single main active component catalyst and no additional reducing agent is added, the NO reduction activity temperature range is narrow, which is not compatible with the wide temperature range of the exhaust gas of the vehicle engine.

In addition, for supported noble metal catalysts, there are also poor selectivity, significant amount of NO being reduced to the greenhouse gas N 2 O; for metal ion-exchanged zeolite catalysts, there are still poor hydrothermal stability; for metal oxide catalysts, there are also problems such as the activation temperature is higher than the main exhaust temperature range of lean-burn vehicle engines

[0004] In order to overcome the deficiency of single main active component catalyst, a lot of research has been done on the combined use of catalyst in recent years. The results show that, with C 3 h 6 or C 3 h 8 As a reducing agent, combine Rh / Al in stages 2 o 3 and Pt / Al 2 o 3 (H.Hamada.Catalysis Surveys from Japan, 1, 53(1997)), in Ga 2 o 3 -Al 2 o 3 Catalyst doped with In 2 o 3 (M.Haneda, Y.Kintaichiand H.Hamada.Catalysis Letters, 55, 47(1998)) etc. all have a certain synergistic NO effect, or broaden the active temperature range, or improve the NO conversion rate, but the effect is not significant , still far from practical requirements

In addition, the greenhouse gas N 2 O generation problem

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