Showing papers on "NOx published in 2001"

The effect of biodiesel oxidation on engine performance and emissions

Abstract: Biodiesel is an alternative fuel consisting of the alkyl monoesters of fatty acids from vegetable oils or animal fats. Previous research has shown that biodiesel-fueled engines produce less carbon monoxide, unburned hydrocarbons, and particulate emissions compared to diesel fuel. One drawback of biodiesel is that it is more prone to oxidation than petroleum-based diesel fuel. In its advanced stages, this oxidation can cause the fuel to become acidic and to form insoluble gums and sediments that can plug fuel filters. The objective of this study was to evaluate the impact of oxidized biodiesel on engine performance and emissions. A John Deere 4276T turbocharged DI diesel engine was fueled with oxidized and unoxidized biodiesel and the performance and emissions were compared with No. 2 diesel fuel. The neat biodiesels, 20% blends, and the base fuel (No. 2 diesel) were tested at two different loads (100 and 20%) and three injection timings (3° advanced, standard; 3° retarded). The tests were performed at steady-state conditions at a single engine speed of 1400 rpm. The engine performance of the neat biodiesels and their blends was similar to that of No. 2 diesel fuel with the same thermal efficiency, but higher fuel consumption. Compared with unoxidized biodiesel, oxidized neat biodiesel produced 15 and 16% lower exhaust carbon monoxide and hydrocarbons, respectively. No statistically significant difference was found between the oxides of nitrogen and smoke emissions from oxidized and unoxidized biodiesel.

Impact of biodiesel source material and chemical structure on emissions of criteria pollutants from a heavy-duty engine.

Abstract: Biodiesel is an oxygenated diesel fuel made from vegetable oils and animal fats by conversion of the triglyceride fats to esters via transesterification. In this study we examined biodiesels produced from a variety of real-world feedstocks as well as pure (technical grade) fatty acid methyl and ethyl esters for emissions performance in a heavy-duty truck engine. The objective was to understand the impact of biodiesel chemical structure, specifically fatty acid chain length and number of double bonds, on emissions of NOx and particulate matter (PM). A group of seven biodiesels produced from real-world feedstocks and 14 produced from pure fatty acids were tested in a heavy-duty truck engine using the U.S. heavy-duty federal test procedure (transient test). It was found that the molecular structure of biodiesel can have a substantial impact on emissions. The properties of density, cetane number, and iodine number were found to be highly correlated with one another. For neat biodiesels, PM emissions were essentially constant at about 0.07 g/bhp-h for all biodiesels as long as density was less than 0.89 g/cm3 or cetane number was greater than about 45. NOx emissions increased with increasing fuel density or decreasing fuel cetane number. Increasing the number of double bonds, quantified as iodine number, correlated with increasing emissions of NOx. Thus the increased NOx observed for some fuels cannot be explained by the NOx/PM tradeoff and is therefore not driven by thermal NO formation. For fully saturated fatty acid chains the NOx emission increased with decreasing chain length for tests using 18, 16, and 12 carbon chain molecules. Additionally, there was no significant difference in NOx or PM emissions for the methyl and ethyl esters of identical fatty acids.

Generalized model for NOx and N2O emissions from soils

Abstract: We describe a submodel to simulate NOx and N2O emissions from soils and present comparisons of simulated NOx and N2O fluxes from the DAYCENT ecosystem model with observations from different soils. The N gas flux submodel assumes that nitrification and denitrification both contribute to N2O and NOx emissions but that NOx emissions are due mainly to nitrification. N2O emissions from nitrification are calculated as a function of modeled soil NH4+ concentration, water-filled pore space (WFPS), temperature, pH, and texture. N2O emissions from denitrification are a function of soil NO3− concentration, WFPS, heterotrophic respiration, and texture. NOx emissions are calculated by multiplying total N2O emissions by a NOx:N2O equation which is calculated as a function of soil parameters (bulk density, field capacity, and WFPS) that influence gas diffusivity. The NOx submodel also simulates NOx emission pulses initiated by rain events onto dry soils. The DAYCENT model was tested by comparing observed and simulated parameters in grassland soils across a range of soil textures and fertility levels. Simulated values of soil temperature, WFPS (during the non-winter months), and NOx gas flux agreed reasonably well with measured values (r2 = 0.79, 0.64, and 0.43, respectively). Winter season WFPS was poorly simulated (r2 = 0.27). Although the correlation between simulated and observed N2O flux was poor on a daily basis (r2 = 0.02), DAYCENT was able to reproduce soil textural and treatment differences and the observed seasonal patterns of gas flux emissions with r2 values of 0.26 and 0.27, for monthly and NOr flux rates, respectively.

Reaction Pathways in the Selective Catalytic Reduction Process with NO and NO2 at Low Temperatures

Abstract: The low-temperature behavior of the selective catalytic reduction (SCR) process with feed gases containing both NO and NO2 was investigated. The two main reactions are 4NH3 + 2NO + 2NO2 → 4N2 + 6H2O and 2NH3 + 2NO2 → NH4NO3 + N2 + H2O. The “fast SCR reaction” exhibits a reaction rate at least 10 times higher than that of the well-known standard SCR reaction with pure NO and dominates at temperatures above 200 °C. At lower temperatures, the “ammonium nitrate route” becomes increasingly important. Under extreme conditions, e.g., a powder catalyst at T ≈ 140 °C, the ammonium nitrate route may be responsible for the whole NOx conversion observed. This reaction leads to the formation of ammonium nitrate within the pores of the catalyst and a temporary deactivation. For a typical monolithic sample, the lower threshold temperature at which no degradation of catalyst activity with time is observed is around 180 °C. The ammonium nitrate route is interesting from a standpoint of general DeNOx mechanisms: This reac...

The effect of timing and oxidation on emissions from biodiesel-fueled engines.

Abstract: The alkyl monoesters of fatty acids derived from vegetable oils or animal fats, known as biodiesel, are attracting considerable interest as an alternative fuel for diesel engines. Biodiesel-fueled engines produce less carbon monoxide, unburned hydrocarbons, and particulate emissions than diesel-fueled engines. However, biodiesel has different chemical and physical properties than diesel fuel, including a larger bulk modulus and a higher cetane number. Some of these properties can be affected by oxidation of the fuel during storage. These changes can affect the timing of the combustion process and potentially cause increases in emissions of oxides of nitrogen. The objective of this study was to evaluate the effect of injection and combustion timing on biodiesel combustion and exhaust emissions. A John Deere diesel engine was fueled with two different biodiesel fuels, one of which had been deliberately oxidized, and with their 20% blends with No. 2 diesel fuel. The engine was operated at three different timings and two loads at a single engine speed of 1400 rpm. The engine performance of the biodiesel was similar to that of No. 2 diesel fuel with nearly the same thermal efficiency. The range of injection timings studied produced changes of 50% and 34% in the CO and HC emissions, respectively. A reduction in NO x emissions of 35% to 43% was observed for a 3° retarded injection timing compared with a 3° advanced injection timing. A common linear relationship was found between the start of injection and the NO x emissions for all the fuels studied. When compared at the same start of combustion, the neat biodiesel produced lower NO x emissions than the No. 2 diesel fuel.

Ultrafine particles and nitrogen oxides generated by gas and electric cooking

Abstract: Objectives—To measure the concentrations of particles less than 100 nm diameter and of oxides of nitrogen generated by cooking with gas and electricity, to comment on possible hazards to health in poorly ventilated kitchens. Methods—Experiments with gas and electric rings, grills, and ovens were used to compare diVerent cooking procedures. Nitrogen oxides (NOx) were measured by a chemiluminescent ML9841A NOx analyser. A TSI 3934 scanning mobility particle sizer was used to measure average number concentration and size distribution of aerosols in the size range 10‐500 nm. Results—High concentrations of particles are generated by gas combustion, by frying, and by cooking of fatty foods. Electric rings and grills may also generate particles from their surfaces. In experiments where gas burning was the most important source of particles, most particles were in the size range 15‐40 nm.When bacon was fried on the gas or electric rings the particles were of larger diameter, in the size range 50‐100 nm. The smaller particles generated during experiments grew in size with time because of coagulation. Substantial concentrations of NOX were generated during cooking on gas; four rings for 15 minutes produced 5 minute peaks of about 1000 ppb nitrogen dioxide and about 2000 ppb nitric oxide. Conclusions—Cooking in a poorly ventilated kitchen may give rise to potentially toxic concentrations of numbers of particles. Very high concentrations of oxides of nitrogen may also be generated by gas cooking, and with no extraction and poor ventilation, may reach concentrations at which adverse health eVects may be expected. Although respiratory eVects of exposure to NOx might be anticipated, recent epidemiology suggests that cardiac eVects cannot be excluded, and further investigation of this is desirable. (Occup Environ Med 2001;58:511‐516)

exhaust gas purification device

Abstract: An exhaust gas purification device having a NOx absorbent includes a by-pass passage for by-passing the NOx absorbent, an exhaust gas flow rate control portion for regulating both a flow rate of exhaust gas flowing to the NOx absorbent and the flow rate of the exhaust gas bypassing the NOx absorbent, and a reductant addition portion for adding reductant into an exhaust passage upstream of the NOx absorbent In this device, when it is necessary to discharge sulfur components from the NOx absorbent, a temperature rise control is executed such that a temperature of the NOx absorbent becomes higher than a predetermined temperature Next, a rich condition control is executed such that an air-fuel ratio of the exhaust gas flowing to the NOx absorbent becomes one of a substantially stoichiometric condition and a rich condition The flow rate of the exhaust gas to the NOx absorbent during the temperature rise control is controlled so as to be higher than that during the rich condition control

A semiconducting metal oxide sensor array for the detection of NOx and NH3

Abstract: In many fossil fuel burning systems, NOx emissions are minimized by a selective catalytic reduction (SCR) technique where NH3 is injected into the flue gas stream to react with NOx to form environmentally safe gases, such as nitrogen and water vapor. Unfortunately, this process is usually incomplete, resulting in either NOx emissions or excess NH3 (NH3 slip). Therefore, a critical need exits for an in situ sensor array near the stack to provide real-time control of the NH3 injection, and hence, minimize the NOx emissions released into the environment. In the present work, semiconducting metal oxide (SMO) film technology is used to engineer a small, robust, sensitive, and selective sensor array to detect NOx and NH3 emissions. Many thin film tungsten trioxide (WO3) based sensing elements were tested in order to identify two film recipes capable of sensitively and selectively detecting NOx and NH3. The critical parameters inherent in each film recipe are type of substrate material, film thickness, doping, deposition temperature, and operating temperature. The two element sensor array’s response characteristics analyzed include the response and recovery times, rates of reaction, dynamic range, sensitivity, repeatability and selectivity.

Synthesis of LaKMnO perovskite-type oxides and their catalytic property for simultaneous removal of NOx and diesel soot particulates

Abstract: Mixed metal oxides in the LaKMnO system were synthesized and their catalytic properties toward the simultaneous NO x –soot removal reaction were investigated. The solubility limit of K in La 1− x K x MnO 3 was determined between 0.2 and 0.25 from X-ray diffraction (XRD) measurement and crystal structure investigation, and K 2 Mn 4 O 8 was by-produced beyond the solubility limit. The activity and the NO x reduction selectivity depended significantly on the K content, and the oxides with intermediate K contents ( x =0.2 and x =0.25) or with the composition close to the solubility limit were good catalysts with higher activity and selectivity. The present study revealed that the LaKMnO oxides are good candidates of catalysts for the simultaneous NO x –soot removal reaction.

Heterogeneous reactions of NO2 and HNO3 on oxides and mineral dust: A combined laboratory and modeling study

Abstract: This study combines laboratory measurements and modeling analysis to quantify the role of heterogeneous reactions of gaseous nitrogen dioxide and nitric acid on mineral oxide and mineral dust particles in tropospheric ozone formation. At least two types of heterogeneous reactions occur on the surface of these particles. Upon initial exposure of the oxide to NO2 there is a loss of NO2 from the gas phase by adsorption on the particle surface, i.e., NO2(g) → NO2(a). As the reaction proceeds, a reduction of gaseous NO2 to NO, NO2 (g) → NO (g) is found to occur. Initial uptake coefficients γ0 for NO2 on the surface of these particles have been measured at 298 K using a Knudsen cell reactor coupled to a mass spectrometer. For the oxides studied, α,γ-Al2O3, α,γ-Fe2O3, TiO2, SiO2, CaO, and MgO, γ0 ranges from <4×10−10 for SiO2 to 2×10−5 for CaO with most values in the 10−6 range. For authentic samples of China loess and Saharan sand, similar reactivity to the oxides is observed with γ0 values of 2×10−6 and 1×10−6, respectively. For HNO3 the reactivity is 1–2 orders of magnitude higher. Using these laboratory measurements, the impact of heterogeneous reactions of NO2 and HNO3 on mineral dust in tropospheric ozone formation and on O3-precursor relationships is assessed using a time-dependent, multiphase chemistry box model. Simulations with and without heterogeneous reactions were conducted to evaluate the possible influence of these heterogeneous reactions on ambient levels. Results show that values of the initial uptake for NO2 and HNO3, adjusted for roughness effects, must be greater than 10−4 to have an appreciable impact on NOx, HNO3, and O3 concentrations for the conditions modeled here. Thus the measured uptake coefficients for NO2 on dry surfaces are just below the lower limit to have an impact on the photochemical oxidant cycle, while the heterogeneous reactivity of HNO3 is sufficiently large to have an effect. Under conditions of high mineral dust mass loadings and/or smaller size distributions the importance of these reactions (both NO2 and HNO3) is expected to increase.

Chemistry and oxidation capacity of the nitrate radical in the continental boundary layer near Berlin

Abstract: The nitrate radical is in many situations the most important nighttime oxidizing species, removing, for example, hydrocarbons, which would otherwise be available to daytime ozone formation. In spite of its importance in the night and probably also under certain conditions during the day, our understanding of the NO3 chemistry and its impact on the oxidation capacity of the atmosphere is still incomplete. Here we present measurements of NO3 by differential optical absorption spectroscopy (DOAS) and a number of other atmospheric trace gases performed during the Berliner Ozonexperiment (BERLIOZ) campaign at Pabstthum near Berlin, Germany, to quantify the contribution of NO3 to the atmospheric oxidation rate of volatile organic compounds (VOCs) and NOx removal. The measurements show that only two NO3 sinks were of importance: (1) About 50–30% (depending on the distance (0.1–3 km) to a near forest) of the NO3 was lost due to reaction with biogenic hydrocarbons. (2) The major part of the remaining loss probably can be attributed to the indirect loss via the reaction of N2O5 on aerosol surfaces. Assuming that heterogeneous hydrolysis of N2O5 is occurring, the nonphotolytical conversion of NOx to HNO3 via N2O5 was found to be comparable with daytime conversion by the reaction of OH with NO2. In combination with measurements of the OH concentration, it was possible for the first time to derive a relative contribution of 28% (24-hour average) for the NO3-initiated oxidation to the total VOC degradation.

Exchange of gaseous nitrogen compounds between agricultural systems and the atmosphere

Abstract: Crop and livestock agricultural production systems are important contributors to local, regional and global budgets of NH3, NOx (NO + NO2) and N2O. Emissions of NH3 and NOx (which are biologically and chemically active) into the atmosphere serve to redistribute fixed N to local and regional aquatic and terrestrial ecosystems that may otherwise be disconnected from the sources of the N gases. The emissions of NOx also contribute to local elevated ozone concentrations while N2O emissions contribute to global greenhouse gas accumulation and to stratospheric ozone depletion.

Transfer of mass-independent fractionation in ozone to other oxygen-containing radicals in the atmosphere

Abstract: Mass-independent fractionation (MIF) of ozone has been observed in both the troposphere and stratosphere. Because ozone is a photochemically active species, its MIF signature can be imparted to other atmospheric molecules. Using a photochemical equilibrium model for short-lived radical species, I have computed the expected MIF for typical mid-latitude conditions. The model accounts for about ∼70% of recent measurements of Δ177O for H2O2 in rainwater, and predicts large MIF for NOx and ClO species (∼40–70‰), and their products (ClONO2 and HNO3). Furthermore, in the stratosphere oxygen exchange reactions between OH and NOx yield OH with Δ17O from 2 to 45‰. Stratospheric water produced during H abstraction by OH would be similarly mass-independently fractionated. In the troposphere rapid exchange between OH and H2O erases any MIF signature in OH. These model results depend on several O exchange reactions with unknown activation energies or with rate coefficients known only as upper limits.

Exhaust system for enhanced reduction of nitrogen oxides and particulates from diesel engines

Abstract: A diesel engine aftertreatment exhaust system uses catalyzed soot filters for particulate matter reduction and urea SCR catalysts for NOx reduction on diesel engines in a combined system to lower particulate matter and NOx at the same time. With this integral emission control system, diesel engines are able to meet ultra low emission standards.

Modeling Aerosol Formation from α-Pinene + NOx in the Presence of Natural Sunlight Using Gas-Phase Kinetics and Gas-Particle Partitioning Theory

Abstract: A kinetic mechanism was used to link and model the gas-phase reactions and aerosol accumulation resulting from α-pinene reactions in the presence of sunlight, ozone (O3), and oxides of nitrogen (NOx). Reaction products and aerosol formation from the kinetic model were compared to outdoor smog chamber experiments conducted under natural sunlight in the presence of NOx and in the dark in the presence of O3. The gas−particle partitioning of semivolatile organics generated in the gas phase was treated as an equilibrium process between particle absorption and desorption. Models vs experimental aerosol yields illustrate that reasonable predictions of secondary aerosol formation are possible from both dark ozone and light NOx/α-pinene systems over a variety of different outdoor conditions. On average, measured gas- and particle-phase products accounted for ∼54−72% of the reacted α-pinene carbon. Model predictions suggest that organic nitrates account for another ∼25% of the reacted carbon, and most of this is in...

Exhaust emission control device for internal combustion engine

Abstract: PROBLEM TO BE SOLVED: To suppress exhaust of NOx into the atmosphere. SOLUTION: In this device, a NOx absorbing agent 18 is disposed inside an engine exhaust passage, while SOx is discharged from the NOx absorbing agent 18 when it is decided that SOx is to be discharged from the NOx absorbing agent 18 in an operation state of an engine suitable for the discharge of SOx from the NOx absorbing agent 18. When it is decided that SOx is to be discharged from the NOx absorbing agent 18 in an operation state of the engine unsuitable for the discharge of SOx from the NOx absorbing agent 18, a NOx amount exhausted from the engine is reduced.

Low-temperature NOx reduction processes using combined systems of pulsed corona discharge and catalysts

Abstract: In this paper, we will report NOx removal via reduction processes using two types of combined system of pulse corona discharge and catalysts: the single-stage plasma-driven catalyst (PDC) system, and the two-stage plasma-enhanced selective catalytic reduction (PE-SCR) system. Several catalysts, such as γ-alumina catalysts, mechanically mixed catalysts of γ-alumina with BaTiO3 or TiO2, and Co-ZSM-5 were tested. In the PDC system, which is directly activated by the discharge plasma, it was found that the use of additives was necessary to achieve NOx removal by reduction. Removal rates of NO and NOx were linearly increased as the molar ratio of additive to NOx increased. The dependence of NO and NOx removal on the gas hourly space velocity (GHSV) at a fixed specific input energy (SIE) indicates that plasma-induced surface reaction on the catalyst plays an important role in the PDC system. It was found that the optimal GHSV of the PDC system with the γ-alumina catalyst was smaller than 6000 h-1. Mechanical mixing of γ-alumina with BaTiO3 or TiO2 did not enhance NO and NOx removal and γ-alumina alone was found to be the most suitable catalyst. The dielectric constant of the catalyst only influenced the plasma intensity, not the NOx removal. In the PE-SCR system, plasma-treated NOx (mostly NO2) was reduced effectively with NH3 over the Co-ZSM-5 catalyst at a relatively low temperature of 150 °C. Under optimal conditions the energy cost and energy yield were 25 eV/molecule and 21 g-N (kWh)-1, respectively.

Organic aerosol formation during the atmospheric degradation of toluene

Abstract: Organic aerosol formation during the atmospheric oxidation of toluene was investigated using smog chamber systems. Toluene oxidation was initiated by the UV irradiation of either toluene/air/NOx or toluene/air/CH3ONO/NO mixtures. Aerosol formation was monitored using scanning mobility particle sizers and toluene loss was monitored by in-situ FTIR spectroscopy or GC-FID techniques. The experimental results show that the reaction of OH radicals, NO3 radicals and/or ozone with the first generation products of toluene oxidation are sources of organic aerosol during the atmospheric oxidation of toluene. The aerosol results fall into two groups, aerosol formed in the absence and presence of ozone. An analytical expression for aerosol formation is developed and values are obtained for the yield of the aerosol species. In the absence of ozone the aerosol yield, defined as aerosol formed per unit toluene consumed once a threshold for aerosol formation has been exceeded, is 0.075 ± 0.004. In the presence of ozone t...

Low temperature catalytic NOx–H2 reactions over Pt/TiO2-ZrO2 in an excess oxygen

Abstract: Platinum catalysts supported on noncrystalline TiO2-ZrO2 binary oxides were found to be highly active for the selective NO reduction in a stream of NO (008 vol%)–H2 (008–056 vol%)–O2 (10 vol%) at low temperatures ( 008 vol% H2 and the selectivity to N2 increased with increasing H2 concentration In situ DRIFTS measurement suggested that the high selectivity in this temperature range is closely related to a stoichiometric reaction between H2 and NO oxidatively adsorbed as nitrate (NO3−) By comparison with the results from a parallel study of H2–O2 combustion, we propose that almost all of H2 reacted is consumed by the reduction of nitrate species, which covered the Pt surface to inhibit H2–O2 combustion The NO reduction activity was sensitive to the catalyst pretreatment; the catalyst reduced in H2 allowed 89% NO conversion at 90°C, whereas the catalyst treated in O2 required 175°C to attain the lower conversion of 50% The effect of the pretreatment is closely related to the reactivity of nitrate adsorbates produced via different routes

Transient behaviour of tropospheric ozone precursors in a global 3-d ctm and their indirect greenhouse effects

Abstract: The global three-dimensional Lagrangian chemistry-transport model STOCHEM has been used to follow the changes in the tropospheric distributions of the two major radiatively-active trace gases, methane and tropospheric ozone, following the emission of pulses of the short-lived tropospheric ozone precursor species, methane, carbon monoxide, NOx and hydrogen. The radiative impacts of NOx emissionswere dependent on the location chosen for the emission pulse, whether at the surface or in the upper troposphere or whether in the northern or southern hemispheres. Global warming potentials were derived for each of the short-lived tropospheric ozone precursor species by integrating the methane and tropospheric ozone responses over a 100 year time horizon. Indirect radiative forcing due to methane and tropospheric ozone changes appear to be significant for all of the tropospheric ozone precursor species studied. Whereas the radiative forcing from methane changes is likely to be dominated by methane emissions, that from tropospheric ozone changes is controlled by all the tropospheric ozone precursor gases, particularly NOxemissions. The indirect radiative forcing impacts of tropospheric ozone changes may be large enough such that ozone precursors should be considered in the basket of trace gases through which policy-makers aim to combat global climate change.

Detailed Chemical Kinetic Modeling of Diesel Combustion with Oxygenated Fuels

Abstract: The influence of oxygenated hydrocarbons as additives to diesel fuels on ignition, NOx emissions and soot production has been examined using a detailed chemical kinetic reaction mechanism. N-heptane was used as a representative diesel fuel, and methanol, ethanol, dimethyl ether and dimethoxymethane were used as oxygenated fuel additives. It was found that addition of oxygenated hydrocarbons reduced NOx levels and reduced the production of soot precursors. When the overall oxygen content in the fuel reached approximately 25% by mass, production of soot precursors fell effectively to zero, in agreement with experimental studies. The kinetic factors responsible for these observations are discussed.

Study of thermal deactivation of a de-NOx commercial catalyst

Abstract: In the present paper, the thermal deactivation of a commercial de-NO x V 2 O 5 –WO 3 /TiO 2 catalyst is investigated. In order to simulate long-term operation in gas firing samples of the catalyst are calcined at different temperatures from 773 to 1173 K. The structural, morphological and chemico-physical changes caused by calcination at high temperatures are investigated by XRD, BET and Hg porosimetry measurements, FT-IR, FT-Raman and EPR spectroscopies, and the activity in the reduction of NO with ammonia, the direct oxidation of ammonia and the oxidation of SO 2 is measured over the different catalyst samples. It is shown that sintering of the TiO 2 support leads to aggregation of isolated vanadium ions; this favours the selective catalytic reduction (SCR) reaction at low temperatures, the oxidation of ammonia at high temperatures and the undesired oxidation of SO 2 as well. Thus, it is expected that catalysts operated for long-term in gas firing at high temperatures are no longer appropriate for commercial use in the SCR process, because in spite of the greater activity in the de-NO x reaction, the temperature window is too narrow and the activity in the oxidation of SO 2 is too high.

SYSTEM FOR REDUCING NOx TRANSIENT EMISSION

Abstract: A catalyst reduction system using diesel fuel as a reductant for vehicles equipped with diesel engines reduces NOx transient emissions produced during acceleration. Impending engine accelerations are sensed to produce metered pulse(s) of fuel oil simultaneously with and preferably in advance of, the NOx transient emission. The fuel pulse is sufficient in quantity to reduce the NOx transient emission when the NOx and HC resulting from the cracked fuel oil are present at spatially equal distances within the reducing catalytic converter. Optionally, the washcoat of the reducing catalyst is formulated to delay the adsorption/desorbtion of one of the gases on the washcoat to assure proper timing of the NOx transient and fuel pulse(s).