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Showing papers on "NOx published in 2009"


Journal ArticleDOI
TL;DR: In this paper, the main portion of the review discusses the progress and development of various catalysts for NOx removal from exhaust by NO decomposition, NO reduction by CO or H-2 or NH3 or hydrocarbons.

616 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated different parameters for the optimization of biodiesel production and suggested the optimum conditions for the production of the mono-alkyl-esters of long chain fatty acids derived from renewable feedstocks, such as vegetable oils or animal fats, for use in compression ignition engines.

507 citations


Journal ArticleDOI
Sounak Roy1, Alfons Baiker1
TL;DR: Theoretical and Surface Science Studies Studies 4079 6.1.
Abstract: 4.1. Noble Metals 4058 4.1.1. Platinum 4059 4.1.2. Palladium 4060 4.1.3. Bimetallic Systems 4060 4.2. Storage Components 4061 4.2.1. Earth Alkaline Metals 4061 4.2.2. Alkali Metals 4065 4.3. Supports 4065 4.3.1. Single Oxides 4065 4.3.2. Mixed Oxides 4067 4.4. Promoters 4069 4.5. Preparation Methods 4071 4.6. Influence of Remote Control 4073 5. Influence of Exhaust Gas Composition 4074 5.1. Reducing Gas 4074 5.2. Water 4077 5.3. Carbon Dioxide 4077 5.4. Impact of Soot 4079 6. Theoretical and Surface Science Studies 4079 6.1. Theoretical Studies 4079 6.2. Studies on Well-Defined Model Catalysts 4082 7. Reactor Configuration 4082 8. Conclusions and Outlook 4086 9. Acknowledgments 4087 10. References 4087

487 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of the additive Ce on V2O5-WO3/TiO2 with low vanadium loadings for the selective catalytic reduction (SCR) of NOx with NH3 was investigated.
Abstract: The effect of the additive Ce on V2O5-WO3/TiO2 with low vanadium loadings for the selective catalytic reduction (SCR) of NOx with NH3 was investigated. The catalytic activity of 0.1% V2O5-6% WO3/TiO2 (V0.1W6Ti) was greatly enhanced by the addition of 10 wt % of Ce in the broad temperature range of 200−500 °C. The catalysts were characterized by BET, XRD, XPS, TPD, H2-TPR, and DRIFTS. The results indicated that the active components of V and W were well-dispersed, while a small cluster of cubic CeO2 appeared over the V0.1W6Ce10Ti catalyst. The Ce additive could enhance the NOx adsorption and then accelerate the SCR reaction due to the synergetic interaction among the Ce and V,W species. Ce mainly existed in the form of Ce3+ oxide in V0.1W6Ce10Ti catalysts, which was beneficial for the oxidation of NO to NO2. Moreover, the DRIFTS results showed that the Ce additive on V0.1W6Ti could provide stronger and more active Bronsted acid sites, which were beneficial for the SCR reaction. The Ce additive also enhance...

436 citations


Journal ArticleDOI
TL;DR: In this article, a single-cylinder version of a heavy-duty diesel engine with extensive optical access to the combustion chamber was used to investigate the cause of diesel NOx emissions.
Abstract: It is generally accepted that emissions of nitrogen oxides (NOx) increase as the volume fraction of biodiesel increases in blends with conventional diesel fuel. While many mechanisms based on biodiesel effects on in- cylinder processes have been proposed to explain this observation, a clear understanding of the relative importance of each has remained elusive. To gain further insight into the cause(s) of the biodiesel NOx increase, experiments were conducted in a single- cylinder version of a heavy-duty diesel engine with extensive optical access to the combustion chamber. The engine was operated using two biodiesel fuels and two hydrocarbon reference fuels, over a wide range of loads, and using undiluted air as well as air diluted with simulated exhaust gas recirculation. Measurements were made of cylinder pressure, spatially integrated natural luminosity (a measure of radiative heat transfer), engine-out emissions of NOx and smoke, flame lift-off length, actual start of injection, ignition delay, and efficiency. Adiabatic flame temperatures for the test fuels and a surrogate #2 diesel fuel also were computed at representative diesel-engine conditions. Results suggest that the biodiesel NOx increase is not quantitatively determined by a change in a single fuel property, but rather is the result of a number of coupled mechanisms whose effects may tend to reinforce or cancel one another under different conditions, depending on specific combustion and fuel characteristics. Nevertheless, charge-gas mixtures that are closer to stoichiometric at ignition and in the standing premixed autoignition zone near the flame lift- off length appear to be key factors in helping to explain the biodiesel NOx increase under all conditions. These differences are expected to lead to higher local and average in-cylinder temperatures, lower radiative heat losses, and a shorter, more-advanced combustion event, all of which would be expected to increase thermal NOx emissions. Differences in prompt NO formation and species concentrations resulting from fuel and jet-structure changes also may play important roles.

392 citations


Journal ArticleDOI
Timothy V. Johnson1
TL;DR: A summary of diesel emissions regulations, engine developments, and nitrogen oxide (NOx), particulate matter (PM), and hydrocarbon (HC) remedia... is provided in this paper.
Abstract: This summary covers key and representative developments in diesel emissions regulations, engine developments, and nitrogen oxide (NOx), particulate matter (PM), and hydrocarbon (HC) remedia...

291 citations


Journal ArticleDOI
TL;DR: In this article, the authors performed a statistical analysis of 21 years of ozone and temperature observations across the rural eastern U.S. for two precursor emission regimes, before and after 2002, the climate penalty factor was consistent across the distribution of ozone observations.
Abstract: [1] Higher temperatures caused by increasing greenhouse gas concentrations are predicted to exacerbate photochemical smog if precursor emissions remain constant. We perform a statistical analysis of 21 years of ozone and temperature observations across the rural eastern U.S. The climate penalty factor is defined as the slope of the ozone/temperature relationship. For two precursor emission regimes, before and after 2002, the climate penalty factor was consistent across the distribution of ozone observations. Prior to 2002, ozone increased by an average of ∼3.2 ppbv/°C. After 2002, power plant NOx emissions were reduced by 43%, ozone levels fell ∼10%, and the climate penalty factor dropped to ∼2.2 ppbv/°C. NOx controls are effective for reducing photochemical smog and might lessen the severity of projected climate change penalties. Air quality models should be evaluated against these observations, and the climate penalty factor metric may be useful for evaluating the response of ozone to climate change.

286 citations


Journal ArticleDOI
TL;DR: In this paper, the authors reported on the successfully production of biodiesel by transesterification of crude rice bran oil (RBO) by three-step process, which included two-steps pretreatment process in the presence of sulfuric acid catalyst.

283 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present a review of available techniques for controlling both the emission of nitrogen oxides (NOx) to the atmosphere and the content of NOx in the captured carbon dioxide.

268 citations


Journal ArticleDOI
01 Sep 2009-Fuel
TL;DR: In this paper, a Euro 2 diesel passenger car with a soybean-oil derived biodiesel (B100) and its 50 vol.% blend with petroleum diesel (B50) was used on a chassis dynamometer.

265 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of injection timing on the exhaust emissions of a single cylinder, naturally aspirated, four-stroke, direct injection diesel engine has been experimentally investigated by using methanol-blended diesel fuel from 0% to 15% with an increment of 5%.

Journal ArticleDOI
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.

Journal ArticleDOI
TL;DR: In this article, a series of experiments were conducted on a single-cylinder research engine investigating the influence of molecular structure on the combustion behavior of fatty acid alcohol ester (biodiesel) molecules under diesel engine conditions.

Journal ArticleDOI
TL;DR: In this paper, the authors present the first global model of atmospheric nitrate Δ17O and compare with available observations, showing that the model shows the best agreement with a global compilation of observations when assuming a Δ 17O value of tropospheric ozone equal to 35 and preferential oxidation of NOx by the terminal oxygen atoms of ozone.
Abstract: . The oxygen isotopic composition (Δ17O) of atmospheric nitrate is a function of the relative abundance of atmospheric oxidants (O3, ROx=OH+HO2+RO2) and the formation pathway of nitrate from its precursor NOx (=NO+NO2). Coupled observations and modeling of nitrate Δ17O can be used to quantify the relative importance of chemical formation pathways leading to nitrate formation and reduce uncertainties in the budget of reactive nitrogen chemistry in the atmosphere. We present the first global model of atmospheric nitrate Δ17O and compare with available observations. The largest uncertainty for calculations of nitrate Δ17O is the unconstrained variability in the Δ17O value of tropospheric ozone. The model shows the best agreement with a global compilation of observations when assuming a Δ17O value of tropospheric ozone equal to 35‰ and preferential oxidation of NOx by the terminal oxygen atoms of ozone. Calculated values of annual-mean nitrate Δ17O in the lowest model layer (0–200 m above the surface) vary from 7‰ in the tropics to 41‰ in the polar-regions. The global, annual-mean tropospheric inorganic nitrate burden is dominated by nitrate formation via NO2+OH (76%), followed by N2O5 hydrolysis (18%) and NO3+DMS/HC (4%). Calculated nitrate Δ17O is sensitive to the relative importance of each nitrate formation pathway, suggesting that observations of nitrate Δ17O can be used to quantify the importance of individual reactions (e.g. N2O5 hydrolysis) leading to nitrate formation if the Δ17O value of ozone is known.

01 Jan 2009
TL;DR: In this article, the performance and emission characteristics of a compression ignition engine while using cerium oxide nanoparticles as additive in neat diesel and diesel-biodiesel-ethanol blends are analyzed.
Abstract: An experimental investigation is carried out to establish the performance and emission characteristics of a compression ignition engine while using cerium oxide nanoparticles as additive in neat diesel and diesel-biodiesel-ethanol blends. In the first phase of the experiments, stability of neat diesel and diesel-biodiesel-ethanol fuel blends with the addition of cerium oxide nanoparticles are analyzed. After series of experiments, it is found that the blends subjected to high speed blending followed by ultrasonic bath stabilization improves the stability. The phase separation between diesel and ethanol is prevented using vegetable methyl ester (Biodiesel) prepared from the castor oil through transesterification process. In the second phase, performance characteristics are studied using the stable fuel blends in a single cylinder four stroke computerised variable compression ratio engine coupled with an eddy current dynamometer and a data acquisition system. The cerium oxide acts as an oxygen donating catalyst and provides oxygen for the oxidation of CO or absorbs oxygen for the reduction of NOx. The activation energy of cerium oxide acts to burn off carbon deposits within the engine cylinder at the wall temperature and prevents the deposition of non-polar compounds on the cylinder wall results reduction in HC emissions. The tests revealed that cerium oxide nanoparticles can be used as additive in diesel and diesel-biodieselethanol blend to improve complete combustion of the fuel and reduce the exhaust emissions significantly.

Journal ArticleDOI
TL;DR: In this paper, the effect of injection pressure on performance, emissions and combustion characteristics of the engine was investigated in a constant speed, DI diesel engine with varied fuel injection pressures (200, 220 and 240 bar).

Journal ArticleDOI
TL;DR: In this article, a Cummins 6BTA 5.9 G2-1, 158 HP rated power, turbocharged, DI, water cooled diesel engine was run on diesel, methyl ester of mahua oil and its blends at constant speed of 1500 rpm under variable load conditions.

Journal ArticleDOI
TL;DR: In this paper, the performance of five methyl esters with different sources was studied: cottonseed methyl ester (CME), soybean methyl enters (SME), rapeseed methyl enester (RME), palm oil methyl enter (PME), and waste cooking oil methyl eter (WME).

Journal ArticleDOI
05 Jun 2009-Science
TL;DR: This record indicates that ice-core nitrate reflects changes in nitrogen oxide (NOx) source emissions and that anthropogenic emissions of NOx have resulted in a 12 per mil decline in δ15N of atmospheric nitrate from preindustrial values to present.
Abstract: A strong, unambiguous negative trend is found in the nitrogen isotopic composition (delta15N) of nitrate over the industrial period, on the basis of a 100-meter ice core from Summit, Greenland. This record indicates that ice-core nitrate reflects changes in nitrogen oxide (NOx) source emissions and that anthropogenic emissions of NOx have resulted in a 12 per mil decline in delta15N of atmospheric nitrate from preindustrial values to present. Variations in the isotopic composition of nitrate may affect the interpretation of other records of environmental change that are affected by atmospheric nitrate.

Journal ArticleDOI
TL;DR: In this article, the discarded parts of mixed marine fish species were used as the raw material to produce biodiesel, and the refined marine fish oil was then transesterified with methyl alcohol to generate biodiesel which was used thereafter as engine fuel to investigate its engine performance and emission characteristics.

Journal ArticleDOI
01 Sep 2009-Fuel
TL;DR: In this article, the characteristics of the flow, combustion, temperature and NO x emissions in a tangentially fired pulverized-coal boiler are numerically studied using comprehensive models, with emphasis on fuel and thermal NO x formations.

Journal ArticleDOI
TL;DR: In this paper, the Sodankyla ion and Neurtal Chemistry (SIC) model was used to simulate the production of NOx from examples of the most representative particle flux and energy spectra available today of solar proton events, auroral energy electrons, and relativistic electron precipitation (REP).

Journal ArticleDOI
TL;DR: In this paper, the catalytic activity for soot combustion of cerium-containing catalysts depends on the NO 2 production capacity, and a linear relationship between the temperature of maximum NO2 production and the temperature for half soot conversion has been obtained.
Abstract: CeO2, ZrO2 and CexZr1−xO2 mixed oxides with different Ce/Zr ratios were prepared by (co-)precipitation and 500 °C-calcination, and were characterized by Raman spectroscopy, XRD and N2 adsorption at −196 °C. The catalytic activity of these materials for soot oxidation by NOx/O2 has been correlated with the catalytic activity for NO2 production, and the surface processes occurring upon NO + O2 interaction with the different catalysts have been studied by in situ DRIFTS and NOx adsorption and further He-TPD. The catalytic activity for soot combustion of cerium-containing catalysts depends on the NO2 production capacity, and a linear relationship between the temperature of maximum NO2 production and the temperature of half soot conversion has been obtained. In a first step, surface nitrites are formed upon catalysts interaction with NO + O2, for all the catalysts. These nitrites are progressively converted to nitrates, and NO2 is yielded after these adsorption/oxidation/desorption processes. For CexZr1−xO2 mixed oxides, the catalytic activity for NO2 production depends on the cerium content, the higher the better, rather than on the BET area of the catalyst. The whole results demonstrate that the production of NO2 in the range of temperatures relevant to soot oxidation not only depends on the NO/nitrites oxidation capacity of the catalyst used but also probably on the adsorption strength of the nitrates under NO oxidation conditions. The thermostability of the nitrates adsorbed on zirconium sites is higher than that of nitrates adsorbed on cerium sites.

Journal ArticleDOI
TL;DR: In this paper, the authors report dual nitrate isotopic composition (δ15N and δ18O) in actively collected dry and wet deposition across the high-deposition region of Ohio, New York, and Pennsylvania.
Abstract: [1] Dry deposition is a major component of total atmospheric nitrogen deposition and thus an important source of bioavailable nitrogen to ecosystems. However, relative to wet deposition, less is known regarding the sources and spatial variability of dry deposition. This is in part due to difficulty in measuring dry deposition and associated deposition velocities. Passive sampling techniques offer potential for improving our understanding of the spatial distribution and sources of gaseous and aerosol N species, referred to here as dry deposition. We report dual nitrate isotopic composition (δ15N and δ18O) in actively collected dry and wet deposition across the high-deposition region of Ohio, New York, and Pennsylvania. We also present results from initial tests to examine the efficacy of using passive nitric acid collectors as a collection medium for isotopic analysis at a site in New York. Isotopic values in actively collected dry deposition, including particulate nitrate and gaseous nitric acid, are compared with those in wet nitrate deposition and surrounding NOx emission sources. δ15N values in dry and wet fractions are highest at the westernmost sites and lowest at the easternmost sites, and stationary source NOx emissions (e.g., power plants and incinerators) appear to be the primary control on δ15N spatial variability. In contrast, δ18O values show a less consistent spatial pattern in dry deposition. Both δ15N and δ18O show strong seasonality, with higher values in winter than summer. Seasonal variations in stationary source NOx emissions appear to be the most likely explanation for seasonal variations in δ15N, whereas seasonal variations in air temperature and solar radiation indicate variable chemical oxidation pathways control δ18O patterns. Additionally, we demonstrate the utility of passive samplers for collecting the nitric acid (HNO3) component of dry deposition suitable for isotopic analysis. We observe slight differences in δ15N-HNO3 values between simultaneous samples collected actively and passively (0.6‰). However, we observe a larger offset in δ18O values between actively and passively collected samples; the causes for this offset warrant further investigation. Nonetheless, passive sample collection represents a significant cost savings over active sampling techniques and could allow a more extensive understanding of patterns of dry deposition and associated insights to nitrogen sources across landscapes.

Journal ArticleDOI
TL;DR: The mechanism of selective catalytic oxidation (SCO) of NH3 over Ag/Al2O3 was studied by NH3 temperature-programed oxidation, O-2-pulse adsorption, and in situ DRIFTS of NH-3 adaption and oxidation.

Journal ArticleDOI
TL;DR: In this paper, an experimental work performed at General Electric Global Research Center in order to better understand the risks of utilizing exhaust gas recirculation in combination with dry low NOx (DLN) combustors is presented.

Journal ArticleDOI
TL;DR: In this paper, thermogravimetry coupled with Fourier Transform Infrared (TG-FTIR) analysis was employed to measure the volatile yield and gas evolution features during coal pyrolysis process in CO2 atmosphere.
Abstract: Considerable studies have been reported on the coal pyrolysis process and the formation of SO2 and NOx processors such as H2S, COS, SO2, HCN, and NH3 in inert atmospheres. Similar studies in CO2 atmosphere also need to be accomplished for better understanding of the combustion characteristics and the SO2/NOx formation mechanism of oxy-fuel combustion, which is one of the most important technologies for CO2 capture. In this study, thermogravimetry coupled with Fourier Transform Infrared (TG-FTIR) analysis was employed to measure the volatile yield and gas evolution features during coal pyrolysis process in CO2 atmosphere. Results show that replacing N2 with CO2 does not influence the starting temperature of volatile release but seems to enhance the volatile releasing rate even at 480 °C. At about 760 °C, CO2 prevents the calcite from decomposing. In CO2 atmosphere, the volatile yield increases as the temperature increases and decreases as the heating rate increases. COS is monitored during coal pyrolysis i...


Journal ArticleDOI
H.E. Saleh1
TL;DR: In this article, the authors quantify the efficiency of exhaust gas recirculation (EGR) when using JME fuel in a fully instrumented, two-cylinder, naturally aspirated, four-stroke direct injection diesel engine.

Journal ArticleDOI
TL;DR: In this paper, 45 fuel blends were prepared and their stability was evaluated and the following mixtures were stable for the 90-day period and were used in the emission study: diesel/ethanol, ethanol, biodiesel, and castor oil.