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Showing papers on "NOx published in 2008"


Journal ArticleDOI
TL;DR: Biodiesel is a domestic and renewable alternative with the potential to replace some of the petrodiesel market as mentioned in this paper, which is obtained from vegetable oils, animal fats, or other sources with a significant content of triacylglycerols by means of a transesterification reaction.
Abstract: Biodiesel is a domestic and renewable alternative with the potential to replace some of the petrodiesel market. It is obtained from vegetable oils, animal fats, or other sources with a significant content of triacylglycerols by means of a transesterification reaction. The fatty acid profile of biodiesel thus corresponds to that of the parent oil or fat and is a major factor influencing fuel properties. Besides being renewable and of domestic origin, advantages of biodiesel compared to petrodiesel include biodegradability, higher flash point, reduction of most regulated exhaust emissions, miscibility in all ratios with petrodiesel, compatibility with the existing fuel distribution infrastructure, and inherent lubricity. Technical problems with biodiesel include oxidative stability, cold flow, and increased NOx exhaust emissions. Solutions to one of these problems often entail increasing the problematic behavior of another property and have included the use of additives or modifying the fatty acid compositi...

1,258 citations


Journal ArticleDOI
TL;DR: An overview of the selective catalytic reduction of NOx by ammonia (NH3•SCR) over metal-exchanged zeolites is given in this paper, where a comparison of Fe•ZSM•5 catalysts prepared by different methods and research groups shows that the preparation method is not a decisive factor in determining catalytic activity.
Abstract: An overview is given of the selective catalytic reduction of NOx by ammonia (NH3‐SCR) over metal‐exchanged zeolites. The review gives a comprehensive overview of NH3‐SCR chemistry, including undesired side‐reactions and aspects of the reaction mechanism over zeolites and the active sites involved. The review attempts to correlate catalyst activity and stability with the preparation method, the exchange metal, the exchange degree, and the zeolite topology. A comparison of Fe‐ZSM‐5 catalysts prepared by different methods and research groups shows that the preparation method is not a decisive factor in determining catalytic activity. It seems that decreased turnover frequency (TOF) is an oft‐neglected effect of increasing Fe content, and this oversight may have led to the mistaken conclusion that certain production methods produce highly active catalysts. The available data indicate that both isolated and bridged iron species participate in the NH3‐SCR reaction over Fe‐ZSM‐5, with isolated species being the ...

785 citations


Journal ArticleDOI
01 Jan 2008-Energy
TL;DR: In this paper, an experimental study has been conducted on a 2.0l HSDI automotive diesel engine under low-load and part load conditions in order to distinguish and quantify some effects of EGR on combustion and NOx/PM emissions.

384 citations


Patent
Kenichi Tsujimoto1, Shinya Hirota1
25 Feb 2008
TL;DR: In this article, an internal combustion engine with an HC treatment catalyst having the function of adsorbing the HC in the exhaust gas is arranged upstream of the NOx selective reducing catalyst.
Abstract: An internal combustion engine wherein an HC treatment catalyst (12) having the function of adsorbing the HC in the exhaust gas is arranged upstream of the NOx selective reducing catalyst (14), an urea aqueous solution fed from the reducing agent feed valve (15) is arranged upstream of the HC treatment catalyst (12), urea, and NOx contained in the exhaust gas, and HC adsorbed on the HC treatment catalyst 12 are reacted with each other to form intermediate products having cyano groups, oximes, and amino groups, and these intermediate products are sent to the NOx selective reducing catalyst (14).

361 citations


Journal ArticleDOI
Jingchun Duan1, Jihua Tan1, Liu Yang1, Shan Wu1, Jimin Hao1 
TL;DR: In this article, principal component analysis/absolute principal component scores (PCA/APCS) was used to identify the dominant emission sources and evaluate their contribution to NMHCs and carbonyls.

338 citations


Journal ArticleDOI
01 Sep 2008-Fuel
TL;DR: In this paper, the authors investigated the combustion behavior of a DI diesel engine with diesel-oxygenate blends and found that the reduction of smoke is strongly related to the oxygen content of blends.

318 citations


Journal ArticleDOI
01 May 2008-Fuel
TL;DR: In this article, a comparison between the use of soy, Canola and yellow grease derived B100 biodiesel fuels and an ultra-low sulphur diesel fuel in the high load engine operating conditions was made.

288 citations


Journal ArticleDOI
01 Nov 2008-Fuel
TL;DR: In this article, two different alcohol-derived biodiesel fuels: methyl ester and ethyl ester, both obtained from waste cooking oil, were tested pure and blended with a diesel reference fuel, which was tested too, in a 2.2l, common-rail injection diesel engine.

265 citations


Journal ArticleDOI
TL;DR: A literature review of use of biodiesel fuel for compression ignition engines is presented in this article, based on the reports of about 50 scientists including (some manufacturers and agencies) who published their results between 1900 and 2005.
Abstract: This article is a literature review of use of biodiesel fuel for compression ignition engines. This study is based on the reports of about 50 scientists including (some manufacturers and agencies) who published their results between 1900 and 2005. The scientists and researchers conducted the test, using different types of raw and refined oils. These experiments with raw biodiesel as fuel did not show the satisfactory results, when they used the raw biodiesel. The fuel showed injector coking and piston ring sticking. Some of the scientists mixed with methanol or ethanol in presence of KOH or NaOH and then filtered and washed. The process is called transeterfication and is used to degum, dewax and to remove triglycerides from the vegetable oils. Transeterfication decreases the viscosity, density and flash point of the fuel. The results obtained, by using such oils in compression ignition engines as fuel, were satisfactory only for short term. A vast majority of scientists mixed the transesterified biodiesel oil with diesel with different ratios. When tested in long run, blends of the oil above 20% (B20) caused maintenance problems and even sometimes damaged the engine. Some authors reported success in using vegetable oils as diesel fuel extenders in blends of more than 20% even in long-term studies. The main conclusion derived by the researchers is that coking is a potentially serious problem with the use of unmodified vegetable biodiesel. However, the refined, chemically processed and degumed vegetable oil mixed with diesel can be used to run compression ignition engine for longer duration. It was reported that there was a slight decrease in brake power and a slight increase in fuel consumption. However, the lubricant properties of the biodiesel are better than diesel, which can help to increase the engine life. Moreover, the biodiesel fuel is environment friendly, produces much less NOx and HC and absolutely no Sox and no increase in CO2 at global level.

265 citations


Journal ArticleDOI
TL;DR: In this article, the authors measured gas and particle-phase pollutants separately for light-duty (LD) vehicles and (b) medium-duty and heavy-duty diesel trucks, respectively, at the Caldecott Tunnel in the San Francisco Bay area.

252 citations


Journal ArticleDOI
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.

Journal ArticleDOI
01 Feb 2008-Energy
TL;DR: In this article, the effect of cooled EGR gas temperature level for various EGR percentages on performance and emissions of a turbocharged DI heavy duty diesel engine operating at full load was examined, using a multi-zone combustion model.

Journal ArticleDOI
21 Mar 2008-Science
TL;DR: It is demonstrated that the reaction of electronically excited nitrogen dioxide with water can be an important source of tropospheric hydroxyl radicals, and inclusion of this chemistry is expected to affect modeling of urban air quality.
Abstract: Hydroxyl radicals are often called the “detergent” of the atmosphere because they control the atmosphere9s capacity to cleanse itself of pollutants. Here, we show that the reaction of electronically excited nitrogen dioxide with water can be an important source of tropospheric hydroxyl radicals. Using measured rate data, along with available solar flux and atmospheric mixing ratios, we demonstrate that the tropospheric hydroxyl contribution from this source can be a substantial fraction (50%) of that from the traditional O(1D) + H2O reaction in the boundary-layer region for high solar zenith angles. Inclusion of this chemistry is expected to affect modeling of urban air quality, where the interactions of sunlight with emitted NOx species, volatile organic compounds, and hydroxyl radicals are central in determining the rate of ozone formation.

Patent
17 Oct 2008
TL;DR: In this article, the authors used (Ce, Pr) compound oxide and cerium oxide as a promoter to improve the performance of the exhaust gas purifying catalytic component.
Abstract: In the exhaust gas purifying catalyst (3), palladium is contained as a catalytic component and cerium oxide and (Ce, Pr) compound oxide is contained as a promoter. Now, the weight ratio of cerium oxide to (Ce, Pr) compound oxide is set between 9/1 and 7/3, and the ratio of praseodymium to cerium in the (Ce, Pr) compound oxide is set between 3 mol % and 50 mol %. In this way, because in this exhaust gas purifying catalyst (3), palladium with high low-temperature activity is used for a catalytic component, the exhaust gas purifying performance at low temperature is improved. And because cerium oxide and (Ce, Pr) compound oxide improves catalytic activity of palladium at high temperature, the exhaust gas purifying performance at high temperature, in particular, NOx purifying performance, is improved.

Journal ArticleDOI
TL;DR: In this paper, a chemical mechanism model was applied to assess the sensitivity of the O3 formation to NOx and VOC concentrations in Shanghai, and the results showed that O3 concentrations are higher in rural area than in center of the city, suggesting that there are O3 depression processes in the center of city and air pollutant emissions are not favorable for the chemical formation.

Journal ArticleDOI
TL;DR: In this article, a bench-scale study was conducted on the simultaneous removal of SO2, NOX, and mercury (both Hg0 and Hg2+) from a simulated coal flue gas using a wet calcium carbonate scrubber.
Abstract: A bench-scale study was conducted on the simultaneous removal of SO2, NOX, and mercury (both Hg0 and Hg2+) from a simulated coal flue gas using a wet calcium carbonate scrubber. The multipollutant capacity of the scrubber was enhanced with the addition of the oxidizing salt, sodium chlorite. The results showed a maximum scrubbing of 100% for SO2 and Hg species and near complete NO oxidation with about 60% scrubbing of the resulting NOX species. The chlorite additive was less effective as an oxidant in the absence of SO2 and NO in the flue gas. Oxidation of NO and mercury were only about 50% and 80%, respectively, in the case of no SO2 in the simulated flue gas. The mercury oxidation was similarly affected by the absence of NO in the flue gas.

Journal ArticleDOI
TL;DR: In this paper, experimental measurements and kinetic modeling of CO/H₂/O/O₆/NO conversion at high pressure were used to investigate the effect of high pressure on CO 2.
Abstract: Article on experimental measurements and kinetic modeling of CO/H₂/O₂/NOₓ conversion at high pressure.

Journal ArticleDOI
31 Oct 2008-Science
TL;DR: The comprehensive isotopic composition of nitrate provides strong constraints on the relative importance of the key atmospheric oxidants in the present atmosphere, with the potential for extension into the past using ice cores.
Abstract: Atmospheric nitrogen oxides (NOx =NO+ NO2) play a pivotal role in the cycling of reactive nitrogen (ultimately deposited as nitrate) and the oxidative capacity of the atmosphere. Combined measurements of nitrogen and oxygen stable isotope ratios of nitrate collected in the Arctic atmosphere were used to infer the origin and fate of NOx and nitrate on a seasonal basis. In spring, photochemically driven emissions of reactive nitrogen from the snowpack into the atmosphere make local oxidation of NOx by bromine oxide the major contributor to the nitrate budget. The comprehensive isotopic composition of nitrate provides strong constraints on the relative importance of the key atmospheric oxidants in the present atmosphere, with the potential for extension into the past using ice cores.

Journal ArticleDOI
Breda Kegl1
TL;DR: The results indicate that, by using biodiesel, harmful emissions can be reduced to some extent by adjusting the injection pump timing properly.

Journal ArticleDOI
TL;DR: In this paper, the performance parameters and exhaust emissions of a diesel engine fuelled with diesel fuel and a biodiesel, namely cottonseed oil methyl ester (COME), subjected to preheating at different temperatures in order to lower its viscosity have been investigated.

Journal ArticleDOI
TL;DR: In this paper, 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.
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...

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

Journal ArticleDOI
01 Feb 2008-Fuel
TL;DR: In this paper, the authors found that two types of active sites were present; one forming weak bonds (physisorption), and the other undergoing chemisorption to form groupings such as -C-ONO, -C -ONO2 or -C −NO2.

Journal ArticleDOI
TL;DR: In this article, an in-series two-step process involving at first the formation of ammonia on reaction of nitrates with H2, followed by the reaction of ammonia with residual stored nitrates to give N2 (step 2) is proposed.

Journal ArticleDOI
TL;DR: The weekend effect is empirical evidence that photochemical O3 production is NOx-inhibited, and to the extent that emissions of CO are proportional to those of reactive volatile organic compounds (VOCs), it is VOC-limited, at least in the urban areas for which the monitoring stations are represen- tative as mentioned in this paper.
Abstract: Surface pollutant concentrations in M´ exico City show a distinct pattern of weekly variations similar to that observed in many other cities of the world. Measurements of the concentrations of carbon monoxide (CO), nitrogen ox- ides (NOx=NO+NO2), particulate matter smaller than 10 µm (PM10), and ozone (O3) collected hourly over 22 years (1986-2007) at 39 urban monitoring locations were ana- lyzed. Morning concentrations of CO, NOx, and PM10 are lower on Saturdays and even more so on Sundays, compared to workdays (Monday-Friday), while afternoon O3 concen- trations change minimally and are occasionally even higher. This weekend effect is empirical evidence that photochem- ical O3 production is NOx-inhibited, and to the extent that emissions of CO are proportional to those of reactive volatile organic compounds (VOCs), it is VOC-limited, at least in the urban areas for which the monitoring stations are represen- tative. The VOC-limitation has increased in the past decade, due to decreases in the concentrations of CO (and presum- ably VOCs) and consequent decreases in the CO/NOx and VOC/NOx ratios. Enhancements of photolysis frequencies resulting from smaller weekend aerosol burdens are not neg- ligible, but fall short of being an alternate explanation for the observed weekend effect. The strength of the weekend effect indicates that local radical termination occurs primar- ily via formation of nitric acid and other NOx-related com- pounds, some of which (e.g. peroxy acyl nitrates) can con- tribute to the regional NOx budget. While VOC emission reductions would be most effective in reducing local O3 pro- duction, NOx emission reduction may be more important for controlling regional oxidants.

Journal ArticleDOI
TL;DR: In this paper, the exhaust gas from a common-rail direct injection diesel engine was investigated both upstream and downstream warm-up catalytic converters (WCC) and three different types of ultra-low sulfur fuels (ethanol-diesel blend, ethanol-diesels blend with cetane improver and pure diesel) were tested in this study.

Journal ArticleDOI
TL;DR: A WO3/CeO2-ZrO2 catalyst system was discovered for selective catalytic reduction of NOx with NH3 and showed nearly 100% NOx conversion in a temperature range of 200-500 degrees C.

Journal ArticleDOI
TL;DR: The secondary organic aerosol (SOA) module in PMCAMx, a three-dimensional chemical transport model, has been updated to incorporate NOx-dependent SOA yields, which results in changes in NOx levels result in changes of both the oxidants and theSOA yields during the oxidation of the corresponding organic vapors.
Abstract: The secondary organic aerosol (SOA) module in PMCAMx, a three-dimensional chemical transport model, has been updated to incorporate NOx-dependent SOA yields. Under low-NOx conditions, the RO2 radicals react with other peroxy radicals to form a distribution of products with lower volatilities, resulting in higher SOA yields. At high-NOx conditions, the SOA yields are lower because aldehydes, ketones, and nitrates dominate the product distribution. Based on recent laboratory smog chamber experiments, high-NOx SOA parametrizations were created using the volatility basis-set approach. The organic aerosol (OA) concentrations in the Eastern US are simulated for a summer episode, and are compared to the available ambient measurements. Changes in NOx levels result in changes of both the oxidants (ozone, OH radical, etc.) and the SOA yields during the oxidation of the corresponding organic vapors. The NOx dependent SOA parametrization predicts a maximum average SOA concentration of 5.2 μg m−3 and a domain average ...

Journal ArticleDOI
TL;DR: In this paper, experimental results and modeling of the combustion chemistry of the oxy-fuel (O2/CO2 recycle) combustion process with a focus on the difference in NO formation between oxy-fired and air-fired conditions are presented.
Abstract: This work presents experimental results and modeling of the combustion chemistry of the oxy-fuel (O2/CO2 recycle) combustion process with a focus on the difference in NO formation between oxy-fired and air-fired conditions. Measurements were carried out in a 100 kW test unit, designed for oxy-fuel combustion with flue gas recycling. Gas concentration and temperature profiles in the furnace were measured during combustion of lignite. The tests comprise a reference test in air and three oxy-fuel cases with different oxygen fractions in the recycled feed gas. With the burner settings used, lignite oxy-combustion with a global oxygen fraction of 25 vol % in the feed gas results in flame temperatures close to those of air-firing. Similar to previous work, the NO emission [mg/MJ] during oxy-fuel operation is reduced to less than 30% of that of air-firing. Modeling shows that this reduction is caused by increased destruction of formed and recycled NO. The reverse Zeldovich mechanism was investigated by detailed ...

Journal ArticleDOI
TL;DR: In this article, the nanometric Ln-Na-Cu-O (Ln = La, Pr, Nd, Sm, Gd) perovskite-like complex oxide catalysts were prepared by using citric acid as a ligand and an adjusting agent of particle-size and morphology.
Abstract: The nanometric Ln-Na-Cu-O (Ln = La, Pr, Nd, Sm, Gd) perovskite-like complex oxide catalysts were prepared by sol–gel auto-combustion method using citric acid as a ligand and an adjusting agent of particle-size and morphology. Their structures and physico-chemical properties were examined by chemical analysis, XRD, SEM, FT-IR, H2-TPR and MS-NO-TPD. The catalytic performances of these perovskite-like oxides for the simultaneous removal of soot and NOx were investigated by a technique of the temperature-programmed reaction (TPR). In the Ln-Na-Cu-O catalysts, the partial substitution of Na for La at A-site led to the formation of Cu3+ and/or oxygen vacancy, thus the catalytic activity was remarkably enhanced. The optimal substitution amount of Na (x) is equal to 0.3 for the reduction of NOx, and x is equal to 0.7 for soot combustion. Moreover, attributing to the effects of very small surface particle sizes of the catalysts and the strong oxidizing ability of NO2 which was produced from NO and O2 in the reactant gases on these catalysts, the nanometric Ln-Na-Cu-O perovskite-like oxides exhibit very high catalytic activities for soot combustion even under loose contact conditions between soot and the catalyst.