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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: Some of the approaches that have been developed in the Aeronomy Laboratory and used to determine the rate and amount of ozone that is photochemically produced in the atmosphere from human-made and natural ozone precursors are reviewed below as mentioned in this paper.
139 citations
TL;DR: In this article, a four-stroke diesel engine, in combination with an eddy-current dynamometer, was used to investigate the engine performance and emission characteristics of the biodiesel, which was then emulsified with distilled water and emulsifying surfactant by a high-speed mechanical homogenizer.
138 citations
TL;DR: In this article, a 6-m3 photochemical reaction chamber equipped with a long path length Fourier transform infrared spectrometer was used for photooxidation of isoprene.
Abstract: The OH radical- initiated photooxidation of isoprene has been investigated experimentally by a 6-m3 photochemical reaction chamber equipped with a long path length Fourier transform infrared spectrometer. In the presence of NOx, the major primary reaction products were methyl vinyl ketone, methacrolein, and formaldehyde. Their yields were in quantitative agreement with previous measurements. In the absence of NOx, the reaction mechanism was found to be quite different from that in the presence of NOx, and major reaction products observed in the infrared spectra were attributed to organic hydroperoxides. Based on the model experiments, the ultimate yield of CO was evaluated to be 60% on the carbon number basis in the presence of NOx and 23% in the absence of NOx. The CO yield in the real atmosphere was evaluated as 30% on the carbon number basis, and global annual CO production from isoprene was estimated to be 105 Tg C yr−1. Together with a previous estimate of the CO production from terpenes, global CO production from natural hydrocarbons was evaluated to be 200±60 Tg C yr−1.
138 citations
TL;DR: A multi-component NOx-trap catalyst consisting of Pt and K supported on γ-Al2O3 was studied at 250°C to determine the roles of the individual catalyst components, to identify the adsorbing species during the lean capture cycle, and to assess the effects of H2O and CO2 on NOx storage as discussed by the authors.
Abstract: A multi-component NOx-trap catalyst consisting of Pt and K supported on γ-Al2O3 was studied at 250 °C to determine the roles of the individual catalyst components, to identify the adsorbing species during the lean capture cycle, and to assess the effects of H2O and CO2 on NOx storage. The Al2O3 support was shown to have NOx trapping capability with and without Pt present (at 250 °C Pt/Al2O3 adsorbs 2.3 μmols NOx/m2). NOx is primarily trapped on Al2O3 in the form of nitrates with monodentate, chelating and bridged forms apparent in Diffuse Reflectance mid-Infrared Fourier Transform Spectroscopy (DRIFTS) analysis. The addition of K to the catalyst increases the adsorption capacity to 6.2 μmols NOx/m2, and the primary storage form on K is a free nitrate ion. Quantitative DRIFTS analysis shows that 12% of the nitrates on a Pt/K/Al2O3 catalyst are coordinated on the Al2O3 support at saturation. When 5% CO2 was included in a feed stream with 300 ppm NO and 12% O2, the amount of K-based nitrate storage decreased by 45% after 1 h on stream due to the competition of adsorbed free nitrates with carboxylates for adsorption sites. When 5% H2O was included in a feed stream with 300 ppm NO and 12% O2, the amount of K-based nitrate storage decreased by only 16% after 1 h, but the Al2O3-based nitrates decreased by 92%. Interestingly, with both 5% CO2 and 5% H2O in the feed, the total storage only decreased by 11%, as the hydroxyl groups generated on Al2O3 destabilized the K–CO2 bond; specifically, H2O mitigates the NOx storage capacity losses associated with carboxylate competition.
138 citations
TL;DR: The selective catalytic reduction (SCR) technique that converts NOx from the outlet of industrial boilers at low temperature (<200 °C) requires catalysts that possess both the oxidization property and the catalytic property as mentioned in this paper.
Abstract: The selective catalytic reduction (SCR) technique that converts NOx from the outlet of industrial boilers at low temperature (<200 °C) requires catalysts that possess both the oxidization property ...
138 citations