NOx

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

Release of NOx from sunlight‐irradiated midlatitude snow

Abstract: Photochemical production and release of gas-phase NOx (NO + NO2) from the natural snowpack at a remote site in northern Michigan were investigated during the Snow Nitrogen and Oxidants in Winter study in January 1999. Snow was collected in an open 34 L chamber, which was then sealed with a transparent Teflon cover and used as an outdoor flow and reaction chamber. Significant increases in NOx mixing ratio were observed in synthetic and ambient air pulled through the sunlit chamber. [NOx] enhancements were correlated to ultraviolet sunlight intensity, reaching ∼300 pptv under partially overcast midday, midwinter conditions. These findings are consistent with NOx production from photolysis of snowpack NO3−; the observed NOx release implies production of significant amounts of OH within the snow. Snowpack NO3− photolysis may therefore significantly alter boundary layer levels of both NOx and oxidized compounds over wide regions of the atmosphere.

SO2-Tolerant Selective Catalytic Reduction of NOx over Meso-TiO2@Fe2O3@Al2O3 Metal-Based Monolith Catalysts

Abstract: It is an intractable issue to improve the low-temperature SO2-tolerant selective catalytic reduction (SCR) of NOx with NH3 because deposited sulfates are difficult to decompose below 300 °C. Herein, we established a low-temperature self-prevention mechanism of mesoporous-TiO2@Fe2O3 core–shell composites against sulfate deposition using experiments and density functional theory. The mesoporous TiO2-shell effectively restrained the deposition of FeSO4 and NH4HSO4 because of weak SO2 adsorption and promoted NH4HSO4 decomposition on the mesoporous-TiO2. The electron transfer at the Fe2O3 (core)-TiO2 (shell) interface accelerated the redox cycle, launching the “Fast SCR” reaction, which broadened the low-temperature window. Engineered from the nano- to macro-scale, we achieved one-pot self-installation of mesoporous-TiO2@Fe2O3 composites on the self-tailored AlOOH@Al-mesh monoliths. After the thermal treatment, the mesoporous-TiO2@Fe2O3@Al2O3 monolith catalyst delivered a broad window of 220–420 °C with NO con...

Effect of nanofluid additives on performances and emissions of emulsified diesel and biodiesel fueled stationary CI engine: A comprehensive review

Abstract: This research paper reports the results of various researches carried out up to 2015 on the performance and emission characteristics of compression ignition (CI) engine using nano particles additives in diesel, biodiesel and water emulsified fuels. There are two methods of reducing the exhaust gas emission of the CI engine. First method is to reduce the emissions by using exhaust gas treatment devices like catalytic converter, diesel particulate filter. However, use of these devices affects the performance of CI engine. Second method to reduce emissions and improve performance of CI engine is the use of fuel additive. Main pollutants of CI engine are oxide of nitrogen (NOx) and particulate matter (PM). However, it is difficult to control NOx and PM simultaneously. Many researchers report that the best method to control the emissions and improve the performance is the use of nano particles additives and water emulsified fuels. This research paper also reports the biodiesel fuel as an alternative to diesel fuel by using various nano particle additives. Comparative studies of effects on various properties of diesel and biodiesel fuels without/with water contents and nano particles additives by previous researchers are done. Most of the researchers reported improved performance and reduction in emission characteristics with dosing of nano particles additives in diesel and biodiesel.

The effect of hydrogen on the selective catalytic reduction of NO in excess oxygen over Ag/Al2O3

Abstract: The selective catalytic reduction (SCR) of nitrogen oxides (NOx) by propane in the presence of H2 on sol–gel prepared Ag/Al2O3 catalysts (0.5–5 wt.% Ag) was investigated. It was confirmed that hydrocarbon-assisted SCR of NOx is remarkably enhanced by co-feeding hydrogen to a lean exhaust gas mixture (λ>1), attaining considerable activity within a wide temperature window (470–825 K). The samples had marginal activity at 575 K without co-fed H2, but achieved up to 60% NOx conversion in the presence of H2 at a space velocity of 30,000 h−1. NO2 as NOx feed component is not converted to N2 by C3H8 to a substantial extent under lean conditions. This points to an activation route of NO through direct conversion to adsorbed nitrite/nitrate or to a dissociation of NO over Ag0, formed through short-term reduction by H2. The nature of Ag species was characterized by X-ray diffraction, temperature-programmed reduction, pulse thermoanalytical measurements, electron microscopy and FTIR spectroscopy. It could be shown that Ag2O nano-sized clusters are predominantly present on all samples, whereas formation of silver aluminate could not be confirmed. Nano-sized Ag2O clusters can reversibly be reduced/reoxidized by H2. A silver loading higher than 2 wt.% leads to a part of Ag2O particles, which are thermally decomposed during calcination at 800 K or higher. The catalytic role of this metallic silver is still unclear. Formal kinetic analysis of catalytic data revealed that the activation energy of the overall reaction is significantly lowered in the presence of H2. The presence of water does not change the activation energy. It is concluded that hydrogen reduces the nano-sized Ag2O clusters to Ag0 on a short-term scale. Zero-valent silver promotes a dissociation pathway of NOx conversion. The fact that more oxidized ad-species (nitrite/nitrate) are observed in the presence of H2 is attributed to a dissociative activation of gas-phase oxygen on Ag0.

Manganese Oxide/Titania Materials for Removal of NOx and Elemental Mercury from Flue Gas

Abstract: A novel catalyst for low temperature selective catalytic reduction (SCR) using CO as reductant, MnO x supported on titania, has been shown to be effective for both elemental mercury capture and low temperature SCR. In low temperature (200 °C) SCR trials using an industrially relevant space velocity (50 000 h −1) and oxygen concentration (2 vol %), nearly quantitative reduction of NO x was obtained using CO as the reductant. Fresh catalyst used as an adsorbent for elemental mercury from an inert atmosphere showed remarkable mercury capture capacity, as high as 17.4 mg/g at 200 °C. The catalyst effectively captured elemental mercury after use in NO x reduction. Mercury capture efficiency was not affected by the presence of water vapor. Mercury capacity was reduced in the presence of SO 2. Manganese loading and bed temperature, which influence surface oxide composition, were found to be important factors for mercury capture. X-ray photoelectron spectroscopy (XPS) results reveal that the mercury is present in...