NOx

About: NOx is a research topic. Over the lifetime, 26367 publications have been published within this topic receiving 496555 citations.

Exhaust gas purification system for internal combustion engine

Abstract: A system for purifying exhaust gas of an internal combustion engine (10) having a NOx reduction catalyst (24) (NOx absorber) installed in the exhaust system (22) of the engine which absorbs NOx in the exhaust gas generated by the engine in a lean environment where a lean fuel mixture is supplied and desorbs to reduce the absorbed NOx in a rich environment where a rich mixture is supplied. In the system, the rich fuel mixture is supplied for a period immediately before fuel cutoff. With the arrangement, the NOx reduction catalyst desorbs the absorbed NOx and is regenerated to absorb NOx sufficiently. At the same time, the NOx reduction catalyst is regenerated from sulfur poisoning, thereby preventing the NOx purification efficiency from being degraded.

Exhaust emission control device of internal combustion engine

Abstract: PROBLEM TO BE SOLVED: To realize a more accurate grasping of a deterioration degree of a NOx catalyst. SOLUTION: In the device, it is presumed that a NOx occlusion amount of a NOx occlusion catalyst 18 becomes the maximum occlusion amount when a first NOx presumption amount presumed to be adsorbed to the NOx occlusion catalyst 18 exceeds a judgment level and a second NOx presumption amount is presumed from a time required for a variation of an output level of an air- fuel ratio sensor 22 when the air-fuel ratio of a flowing-in exhaust gas to the NOx occlusion catalyst 18 is changed from a lean to a rich. A deterioration of the NOx occlusion catalyst 18 is judged by comparing the first NOx presumption amount and the second NOx presumption amount. When the time required for the variation of the output level of the airfuel ratio sensor 22, a rich degree is made small at the time of a rich operation and the time required for the variation of the output level of the air-fuel ratio sensor 22 is lengthened.

Dynamic behaviour of activated carbon catalysts during ozone decomposition at room temperature

Abstract: The catalytic decomposition of ozone (200–1600 ppm) to molecular oxygen was investigated over activated carbons in the form of woven fibre fabrics (ACF) or granules (ACG) at room temperature. The dynamics of carbon activity was characterised by two distinct regions. First the ‘‘high activity’’ towards ozone decomposition was observed, which was mainly due to chemical interaction of ozone with carbon. This interaction resulted in the formation of oxygen containing surface groups on carbon until saturation. Then the conversion was sharply decreased and carbons went to ‘‘low activity’’ region. The ozone decomposition to molecular oxygen takes place in this region following a catalytic route. The carbon activity in dry atmosphere was compared with the activity in the presence of water vapour and NOx. Water vapour diminished the catalytic activity, but in the presence of NOx carbons were observed to be more active due to the change in the C-surface functionality. The surface functional groups were modified in two ways: by boiling in diluted HNO3 or by thermal treatment in He at temperatures up to 1273 K. The acid pre-treatment was found to increase the activity of carbons under the quasi steady-state, while the thermal treatment at 1273 K renders catalysts with lower activity. The ozone decomposition toward gasification of carbon producing COx took place with the selectivity less then 25%. The catalysts were characterised by temperature-programmed decomposition of surface functional groups, X-ray photo-electron and IR-spectroscopy. Mechanistic aspects of the reaction are discussed. # 2005 Elsevier B.V. All rights reserved.