Topic
NOx
About: NOx is a research topic. Over the lifetime, 26367 publications have been published within this topic receiving 496555 citations.
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TL;DR: In this article, the properties, engine performance, and emission characteristics of biodiesel-diesel blends employed in CI engines under different conditions worldwide as well as the environmental and economic impacts of the biodiesel production, and the effects of this blend on engine durability are also discussed.
Abstract: The objective of this review is to illustrate the properties, engine performance, and emission characteristics of biodiesel–diesel blends employed in CI engines under different conditions worldwide as well as the environmental and economic impacts of biodiesel production, and the effects of this blend on engine durability are also discussed. Biodiesels are gaining more importance as a promising alternative energy resource due to the global fossil fuel crisis and emission problems. However, it was realized that extensive utilization of biodiesel would tax the food chain and could lead to food shortages. Thus, the use of a blend of biodiesel with conventional fuel was suggested to balance its usage, which could still provide a beneficial greenhouse effect. From the results of the investigation, it is reported that blends containing up to 30% biodiesel have almost the same properties as diesel. Most investigation results have shown that, compared to diesel, biodiesel–diesel blend provides shorter ignition delay and a reduced heat release rate as well as a slightly higher efficiency by sacrificing a small amount of fuel. The HC, CO, and PM emissions are reduced to a great extent but the NOx emission becomes slightly higher. Biodiesels are expected to reduce the dependence on imported petroleum with the associated economic vulnerability, reduce greenhouse gas emissions and other pollutants, and revitalize the economy by increasing demand and prices for agricultural products. From the review, it can be said that blends of biodiesel with a small content by volume can be used in existing CI engines without any major modifications.
247 citations
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TL;DR: An improved representation of NMVOCs in a global 3-D chemical transport model (GEOS-Chem) is used and it is shown that it can simulate PAN observations from aircraft campaigns worldwide and is very sensitive to plume chemistry and plume rise.
Abstract: . Peroxyacetyl nitrate (PAN) formed in the atmospheric oxidation of non-methane volatile organic compounds (NMVOCs) is the principal tropospheric reservoir for nitrogen oxide radicals (NOx = NO + NO2). PAN enables the transport and release of NOx to the remote troposphere with major implications for the global distributions of ozone and OH, the main tropospheric oxidants. Simulation of PAN is a challenge for global models because of the dependence of PAN on vertical transport as well as complex and uncertain NMVOC sources and chemistry. Here we use an improved representation of NMVOCs in a global 3-D chemical transport model (GEOS-Chem) and show that it can simulate PAN observations from aircraft campaigns worldwide. The immediate carbonyl precursors for PAN formation include acetaldehyde (44% of the global source), methylglyoxal (30%), acetone (7%), and a suite of other isoprene and terpene oxidation products (19%). A diversity of NMVOC emissions is responsible for PAN formation globally including isoprene (37%) and alkanes (14%). Anthropogenic sources are dominant in the extratropical Northern Hemisphere outside the growing season. Open fires appear to play little role except at high northern latitudes in spring, although results are very sensitive to plume chemistry and plume rise. Lightning NOx is the dominant contributor to the observed PAN maximum in the free troposphere over the South Atlantic.
247 citations
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TL;DR: CeO 2 and CeZr mixed oxides with different Ce:Zr ratios were prepared; characterised by Raman spectroscopy, XRD, TEM, N 2 adsorption at −196 °C, and H 2 -TPR; and tested for soot oxidation under NO x /O 2 as discussed by the authors.
246 citations
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TL;DR: In this paper, the effect of different dopants including niobium, iron, tungsten and zirconium oxide on the low-temperature activity of MnOx-CeO2 catalysts for the selective catalytic reduction (SCR) of NOx with ammonia has been studied with coated cordierite monoliths in model gas experiments.
Abstract: The effect of different dopants including niobium, iron, tungsten and zirconium oxide on the low-temperature activity of MnOx–CeO2 catalysts for the selective catalytic reduction (SCR) of NOx with ammonia has been studied with coated cordierite monoliths in model gas experiments. A clearly higher activity and particularly superior nitrogen selectivity was obtained with the niobium-doped catalyst in comparison with the MnOx–CeO2 reference system. At 200 °C, the DeNOx was 80% while the N2 selectivity reached more than 96%. In contrast, a decrease of the SCR activity was observed when iron, zirconium or tungsten oxides were added to MnOx–CeO2. However, the addition of niobium oxide did not improve the resistance of the catalyst against SO2 poisoning. A strong and irreversible deactivation occurred after exposure to SO2.
245 citations
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244 citations