Vanadium-based Selective Catalytic Reduction Research Articles

Simulation study of De-NO x and ammonia slip with two-stage selective catalytic reduction for diesel engine

ABSTRACT Selective catalytic reduction (SCR) technology has several benefits for reducing NO x . It offers significant NO x removal efficiency, often greater than 90%. Due to increasingly strict pollution rules, SCR catalysts have lately been installed in diesel engines all over the world. The dynamics and economy of the original diesel engine are examined in this work concerning the addition of various SCR catalyst after-treatment methods, including a one-stage vanadium-based SCR catalyst (V-I), a two-stage vanadium-based SCR catalyst (V/V-II), and a two-stage vanadium-based-copper-based SCR catalyst (V/Cu-II). A complete engine model of a marine diesel engine is built on this model. The findings indicate that each of the three layouts decreases diesel engine power and raises fuel consumption rates. The V/Cu-II is the best configuration for this kind of marine machine because the V-I satisfies the most recent Tier III NO x emission limits only at 100% load, the V/V-II satisfies them at 75% to 100% load, and the V/Cu-II satisfies them at 50% to 100% load. For all three arrangements, ammonia slip reduces with increasing load, with the V/Cu-II having the lowest ammonia slip. In the end, it was determined for the V/Cu-II how different ammonia-to-nitrogen ratios affected ammonia slip and NO x conversion. The results revealed that with an ammonia-to-nitrogen ratio of 0.7, both the ammonia slip and NO x emission limits could be reached at 50% to 100% load, saving urea expenditures.

Storage-reduction strategy for NOx reduction from gas turbine exhaust with W–Ti-CeOx catalyst in natural gas power plants

Traditional vanadium-based selective catalytic reduction (SCR) deNOx catalyst can hardly adapt to the gas conditions (much high NO2/NOx ratio at lower temperature) of the start-up and low loading periods for a gas turbine. Therefore, a W–Ti-CeOx catalyst with NOx storage and reduction (NSR) function was developed in this work for gas turbine exhaust NOx elimination. The experimental results reveal that W–Ti-CeOx catalyst exhibits high NO2 adsorption capacity at relatively low temperature while that is quite low for V–W/TiO2. The abundant surface Ce3+ species can be mainly responsible for its high adsorption ability owing to the reaction between NO2 and Ce3+ to form nitrate/nitrite species and NO. Meanwhile, the adsorption capacity of W–Ti-CeOx can easily regenerate at medium–high temperature and NH3-SCR reaction. Furthermore, W–Ti-CeOx also shows good NH3-SCR activity, which can fulfill the deNOx process at high temperature. The addition of W and Ti into ceria can enhance the surface acidity and redox ability, thereby increasing the SCR activity. This work proposes a novel storage-reduction strategy for NOx elimination throughout the operation of gas turbines.

Understanding the NH3 adsorption mechanism on a vanadium-based SCR catalyst: A data-driven modeling approach

Ammonia adsorption is a precondition for the selective catalytic reduction (SCR) of nitrogen oxides (NOx) to take place and it influences catalyst performance under transient conditions. For a vanadium-based SCR catalyst NH3 adsorption takes place on multiple adsorption sites over the catalyst surface with different behaviours depending on temperature, gas concentration and catalyst oxidation state. In this study, a mechanistic NH3 adsorption model within the framework of Langmuir adsorption models was developed for describing the NH3 adsorption isotherms obtained with a gas flow reactor for a vanadium-based SCR. The model was created by a data-driven modeling process, which involves different steps. First, a large set of candidate models was created systematically by combining multiple feasible adsorption mechanisms. Then, a parameter estimation workflow was performed using three different objective functions with increased complexity. Finally, a model reconciliation step was executed and a quality assessment was done for creating a unified robust model with a high degree of validity. As a result of this method, an NH3 adsorption model with five adsorption sites with different mechanisms was obtained that captures the main features from the experimental data. Furthermore, the model parameters have physical significance and relate to the adsorption strength and spatial arrangement for NH3 and water molecules. The proposed model can be used in the development of transient models with increased validity over a wide experimental region.

Study on Emission Characteristics and Emission Reduction Effect for Construction Machinery under Actual Operating Conditions Using a Portable Emission Measurement System (Pems).

With the acceleration of urban construction, the pollutant emission of non-road mobile machinery such as construction machinery is becoming more and more prominent. In this paper, a portable emissions measurement system (PEMS) tested the emissions of eight different types of construction machinery under actual operating conditions and was used for idling, walking, and working under the different emission reduction techniques. The results showed that the pollutant emission of construction machinery is affected by the pollutant contribution of working conditions. According to different emission reduction techniques, the diesel oxidation catalyst (DOC) can reduce carbon monoxide (CO) by 41.6–94.8% and hydrocarbon (HC) by 92.7–95.1%, catalytic diesel particulate filter (CDPF) can reduce particulate matter (PM) by 87.1–99.5%, and selective catalytic reduction (SCR) using urea as a reducing agent can reduce nitrogen oxides (NOx) by 60.3% to 80.5%. Copper-based SCR is better than vanadium-based SCR in NOx reduction. In addition, the study found that when the enhanced 3DOC + CDPF emission reduction technique is used on forklifts, DOC has a “low-temperature saturation effect”, which will reduce the emission reduction effect of CO and THC. The use of Burner + DOC + CDPF emission reduction techniques and fuel injection heating process will increase CO’s emission factors by 3.2–3.5 and 4.4–6.7 times compared with the actual operating conditions.

Experimental Research on Distribution Characteristics of NO x Conversion Efficiency of a Diesel Engine SCR Catalyst.

An experimental investigation of the distribution characteristics of NOx conversion efficiency inside a selective catalytic reduction system is presented in this paper. Wash-coated and extruded vanadium-based selective catalytic reduction catalysts were investigated under an ANR (ammonia nitrogen ratio) of 1.0 and various exhaust gas temperature and flow rate conditions. A moveable sampling probe was located at various measuring points on the exit cross section of the selective catalytic reduction catalyst shell, and the final distribution maps of NOx conversion efficiency were obtained by the interpolation of measured data. The experimental result showed that the distribution of NOx conversion efficiency of the wash-coated selective catalytic reduction catalyst at the exit cross section was extremely nonuniform and the efficiency of the extruded SCR catalyst was uniform with a higher distribution at the center. A comparison experiment with 180° rotation of the selective catalytic reduction catalysts was implemented, and the efficiency distribution map of the wash-coated selective catalytic reduction catalyst also rotated 180° but that of the extruded selective catalytic reduction catalyst remained unchanged. The uniformity coefficient of the extruded selective catalytic reduction catalyst was higher than that of the wash-coated selective catalytic reduction catalyst used in this study.

Review of Hydrocarbon Poisoning and Deactivation Effects on Cu-Zeolite, Fe-Zeolite, and Vanadium-Based Selective Catalytic Reduction Catalysts for NOx Removal from Lean Exhausts

Low-temperature operation of NH3-SCR (selective catalytic reduction) systems for NOx abatement in lean streams raises major challenges caused by the need to fix different problems related to poor c...

Enhanced activity of vanadia supported on microporous titania for the selective catalytic reduction of NO with NH3: Effect of promoters

Vanadium oxide-based catalysts are considered a promising catalyst for selective catalytic reduction (SCR) of NO with NH3, which is an effective NOx removal technology. As environmental issues have garnered more attention, however, improvements to vanadium-based SCR catalysts are strongly required. In a previous study, we found that vanadium oxide on microporous titania as a support (V/MPTiO2) has certain advantages, such as improved thermal stability and more suppressed N2O formation, over the use of conventional nanoparticle titania (DT-51) as a support. In this study, widely used promoters, such as W, Sb, and Mo, were added to V/MPTiO2 to investigate whether they have promoting effects on V/MPTiO2 as well. Among these promoters added catalysts, the W and Mo were found to have significant promoting effects on the enhancement of deNOx activities at low temperatures, while the addition of Sb to V/MPTiO2 tended to have a negative effect on the SCR activity. Based on the characterizations, including laser Raman, H2-temperature programmed reduction (H2-TPR), and in situ diffuse reflectance infrared Fourier transform (in situ DRIFT) analysis, we found that the addition of W and Mo increased the degree of polymerization in V/MPTiO2, which generated more reactive vanadia species. Hence, such changes, resulting from the addition of W and Mo promoters to V/MPTiO2, yielded enhanced catalytic activity at low temperatures.

Study on volatilization characteristic of vanadium and tungsten of vanadium-based selective catalytic reduction

Vanadium-based selective catalyst reduction (V-SCR) has made significant contributions to De-NOx of diesel vehicles. However, the two main catalyst components, V2O5 and WO3, are volatile and toxic. Therefore, there are some restrictions for its application on heavy duty diesel vehicles (HDDV) in the CHINA VI stage. In view of this problem, the volatilization rates of two kinds of volatiles under different inlet temperature and test duration were measured on three V-SCR samples from different catalyst manufacturers. The effects of V-SCR inlet temperature and test duration on the volatilization characteristics of the two volatiles on different samples were systematically studied and compared. The emission concentrations of V2O5 and WO3 at different temperatures were compared with the occupational exposure limits of chemical harmful factors in the workplace which is specified in the GBZ 2.1-2019. The results show that the initial temperature of volatilization of V-SCR is directly related to the technical level of the catalyst itself; whether the volatilization characteristics of V-SCR will change with the prolongation of test duration depends on its inlet temperature; V2O5 emission concentration of V-SCR at 550 C° can reach a quite high exposure level, and the exposure level of WO3 volatiles at 650 C° may be equivalent to that of V2O5 volatiles at 550 C°.

Deactivation of a Vanadium-Based SCR Catalyst Used in a Biogas-Powered Euro VI Heavy-Duty Engine Installation

We have investigated how the exhaust gases from a heavy-duty Euro VI engine, powered with biogas impact a vanadium-based selective catalytic reduction (SCR) catalyst in terms of performance. A full Euro VI emission control system was used and the accumulation of catalyst poisons from the combustion was investigated for the up-stream particulate filter as well as the SCR catalyst. The NOx reduction performance in terms of standard, fast and NO2-rich SCR was evaluated before and after exposure to exhaust from a biogas-powered engine for 900 h. The SCR catalyst retains a significant part of its activity towards NOx reduction after exposure to biogas exhaust, likely due to capture of catalyst poisons on the up-stream components where the deactivation of the oxidation catalyst is especially profound. At lower temperatures some deactivation of the first part of the SCR catalyst was observed which could be explained by a considerably higher surface V4+/V5+ ratio for this sample compared to the other samples. The higher value indicates that the reoxidation of V4+ to V5+ is partially hindered, blocking the redox cycle for parts of the active sites.

Selective Catalytic Reduction of NOx over V2O5-WO3-TiO2 SCR Catalysts—A Study at Elevated Pressure for Maritime Pre-turbine SCR Configuration

The selective catalytic reduction (SCR) of NOx using NH3 was studied at pressures up to 5 bar over a vanadium-based SCR catalyst (~1 wt% V2O5 and 10 wt% WO3/TiO2), relevant for the installation of SCR reactors upstream of the turbocharger at marine engines. Experiments were performed using both granulated catalyst in a lab-scale fixed-bed reactor and a monolith catalyst in a bench-scale setup. The residence time across the catalytic bed was kept constant, by increasing the (normalized (0 °C, 1 atm)) volumetric flow rate proportionally to the pressure. The results show that for the granulated catalyst, the NOx conversion was independent of the pressure, indicating that the SCR kinetics are not affected by the increased pressure up to 5 bar. NH3 temperature-programmed desorption experiments showed that the catalyst NH3 adsorption increased with more than 30% when the pressure was increased from 1 bar to 4.5 bar. On the other hand, when the adsorption temperature was increased from 150 to 300 °C, the adsorption capacity decreased by approximately 60% independent on the pressure. The SCR reaction was unaffected by the increased NH3 uptake caused by the increased pressure, because only a certain fraction of the sites ( $$ {\theta}_{N{H}_3}^{\ast } $$ = 0.14) was found to be active in the SCR reaction, and these are filled up at lower NH3 partial pressure than the total number of sites. Experiments using a monolithic catalyst showed that at temperatures above 250 °C, the NOx conversion was lower at an increased pressure (3.1 bar) when the residence time was held constant. This decrease was ascribed to increased internal and external diffusion limitations at the elevated pressure.

Individual effects of antioxidant additive and SCR system on the NOx reduction of a CI engine powered by cottonseed oil blend

The rapid utilization of fossil fuel has paved the way for the large amount of pollutants such as NOx and other harmful components. Pre-treatment of fuel and after-treatment of exhaust process becomes vital due to India’s commitment towards BS VI emission norms by 2020. This paper is aimed to reduce the NOx emission in a stationary engine powered by cottonseed oil blend with antioxidant additive. The vanadium-based SCR (Selective Catalytic Reduction) system is used in the exhaust system for the after-treatment of oxides of nitrogen. The load varied from 0% to full load for performance and emission analysis. The results show that the NOx emissions of the CI engine running on cotton seed oil blend with the catalytic convertor under urea injection is reduced by 88% at full load. Furthermore HC emission reduction is also noticed significantly with the after-treatment strategy being applied.

Gas-phase and semivolatile organic emissions from a modern nonroad diesel engine equipped with advanced aftertreatment

ABSTRACTU.S. Tier 4 Final and Euro Stage IV and V regulations for nonroad compression-ignition engines have led to the development of exhaust aftertreatment technologies optimized for nonroad engines and duty cycles. In this study, several aftertreatment configurations consisting of state-of-the-art diesel oxidation catalysts (DOCs), diesel particulate filters (DPFs), copper (Cu) zeolite– and vanadium-based selective catalytic reduction (SCR) catalysts, and ammonia oxidation (AMOX) catalysts are evaluated using both nonroad transient (NRTC) and steady (8-mode NRSC) cycles in order to understand both component- and system-level effects of diesel aftertreatment on gas-phase, semivolatile, and particle-phase and particle-bound unregulated organic emissions. Organic emissions reported in this work include total hydrocarbon (THC), n-alkanes, branched alkanes, saturated cycloalkanes, aromatics, aldehydes, ketones, hopanes, steranes, and soluble organic fraction (SOF). Brake-specific emissions are reported for four configurations, including engine-out, DOC+CuZ-SCR+AMOX, V-SCR+AMOX, and DOC+DPF+CuZ-SCR+AMOX, and conversion of engine-out emissions is reported for the three aftertreatment configurations. Mechanisms responsible for the reduction of organic species are discussed in detail. This summary of emissions from a current nonroad diesel engine equipped with advanced aftertreatment can be used to more accurately model the impact of anthropogenic emissions on the atmosphere with tools such as the U.S. Environmental Protection Agency’s Motor Vehicle Emissions Simulator (MOVES2014a) model.Implications: Anthropogenic emissions are a source of significant human health and environmental risk. This study, focused on the treatment of exhaust emissions from a modern nonroad diesel engine with a variety of aftertreatment configurations, examines the impact that human industrial activity can have on air pollution. In particular, we focus on the remediation of gas-phase and semivolatile organic emissions by emission reduction technologies. This detailed summary of emissions from a current nonroad diesel engine equipped with advanced aftertreatment can be used to more accurately model the impact of anthropogenic emissions on the atmosphere with tools such as the U.S. Environmental Protection Agency’s MOVES2014a model.

Experimental mitigation of NO x emission in exhaust gases of CI engine fuelled with methyl ester of cottonseed oil blend

ABSTRACT This paper discusses the development of a B20 cottonseed oil blend for passenger vehicle with vanadium-based Selective Catalytic Reduction (SCR) technology addition on exhaust system. SCR is a progressive emissions governor technology organism that injects a liquid-Urea (also called aqueous urea, Ad Blue or Diesel Exhaust Fluid) through an injector nozzle into the exhaust manifold of diesel engine. The methyl ester of cottonseed oil blend was analysed in a single cylinder, 4-stroke, computerised water-cooled, diesel engine of 5.2 kW rated power for performance and emission characteristics with SCR. The results indicate that the emissions of the CI engine running on B20 blend with the catalytic convertor reduced NO x emission up to 76% with different quantity of dosing. However, it is noted that the brake thermal efficiency is reduced slightly by 2% for SCR due to the back pressure created by the SCR system.

Effect of M-Doped (M = Cr, Fe, Co, and Nb) V2O5/TiO2(001) on Mercury Oxidation: The Insights from DFT Calculation

Modification of vanadium-based selective catalytic reduction (SCR) catalysts by transition metal allows for the design of wide temperature range catalysts for mercury removal. In this paper, by doping V2O5 supported on the TiO2(001) surface with Cr, Fe, Co, and Nb, the effect of doping on Hg0 oxidation is investigated based on DFT calculation. By analyzing electronic properties of doped models, as well as HCl and Hg0 adsorption, it is concluded that the introduction of Cr, Fe, Co, and Nb did not significantly affect the oxidizability of VOx species toward Hg0. However, the introduction of Fe promotes the formation of oxygen ions with strong oxidizability as new active sites for Hg0 oxidation. Additionally, the reaction energies and energy barriers for Hg0 oxidization show that the undoped vanadium-based catalyst and Fe-doped vanadium-based catalyst are favorable at high temperature and low temperature, respectively.

Mitigation of PAH and nitro-PAH emissions from nonroad diesel engines.

More stringent emission requirements for nonroad diesel engines introduced with U.S. Tier 4 Final and Euro Stage IV and V regulations have spurred the development of exhaust aftertreatment technologies. In this study, several aftertreatment configurations consisting of diesel oxidation catalysts (DOC), diesel particulate filters (DPF), Cu zeolite-, and vanadium-based selective catalytic reduction (SCR) catalysts, and ammonia oxidation (AMOX) catalysts are evaluated using both Nonroad Transient (NRTC) and Steady (8-mode NRSC) Cycles in order to understand both component and system-level effects of diesel aftertreatment on emissions of polycyclic aromatic hydrocarbons (PAH) and their nitrated derivatives (nitro-PAH). Emissions are reported for four configurations including engine-out, DOC+CuZ-SCR+AMOX, V-SCR+AMOX, and DOC+DPF+CuZ-SCR+AMOX. Mechanisms responsible for the reduction, and, in some cases, the formation of PAH and nitro-PAH compounds are discussed in detail, and suggestions are provided to minimize the formation of nitro-PAH compounds through aftertreatment design optimizations. Potency equivalency factors (PEFs) developed by the California Environmental Protection Agency are then applied to determine the impact of aftertreatment on PAH-derived exhaust toxicity. Finally, a comprehensive set of exhaust emissions including criteria pollutants, NO2, total hydrocarbons (THC), n-alkanes, branched alkanes, saturated cycloalkanes, aromatics, aldehydes, hopanes and steranes, and metals is provided, and the overall efficacy of the aftertreatment configurations is described. This detailed summary of emissions from a current nonroad diesel engine equipped with advanced aftertreatment can be used to more accurately model the impact of anthropogenic emissions on the atmosphere.

Vanadium and tungsten release from V-based selective catalytic reduction diesel aftertreatment

Vanadium-based selective catalytic reduction (V-SCR) catalysts are currently used for the reduction of nitrogen oxides (NOx) in worldwide diesel applications including Euro IV, V, and VI as well as U.S. nonroad Tier 4 Final. Although V-SCR catalysts are attractive because of their high NOx conversion, low cost, resistance to sulfur poisoning, and ability to reduce hydrocarbon emissions, there is concern that V-SCR washcoat material (e.g., vanadium and tungsten) and its derivatives may be released into the atmosphere, potentially harming human health and the environment. In this study, vanadium and tungsten release measurements are made with both a reactor- and engine-based approach in order to determine the potential release of these metals from diesel exhaust aftertreatment systems that contain a V-SCR catalyst. Results for a commercially available V-SCR reveal that both V and W release begin at 500 °C, and both reactor- and engine-based methods are capable of measuring qualitatively similar release. Emissions with the engine-based method are higher at all temperatures evaluated, likely due to this method's ability to capture particle-phase and vapor-phase emissions which become particle-bound after their evolution from the catalyst surface. Certification relevant data (NRTC and NRSC) from a nonroad engine is used to understand probable emissions from V-SCR aftertreatment architectures. Finally, results from a V-SCR catalyst formulated for improved thermal durability illustrate that it is possible to increase the maximum temperature for V-SCR catalysts. This comprehensive understanding of the temperature dependence of vanadium and tungsten volatility can be used to further analyze the full impact of diesel aftertreatment on exhaust emissions and their impact on human health and environmental toxicity.

Ammonia Storage and Slip in a Urea Selective Catalytic Reduction Catalyst under Steady and Transient Conditions

This paper aims to investigate quantitatively the characteristics of the storage and slip of ammonia in a full-size vanadium-based selective catalytic reduction (SCR) catalyst under typical steady and transient conditions on a diesel engine test bench. The effect of space velocity (SV) and exhaust temperature on the ammonia storage process and the storage capacity of the catalyst was studied. The ammonia slip in various transient processes was also investigated. The experimental results indicate that the increase of SV causes early appearance of ammonia slip. Then, the ammonia storage time is shorten to avoid the ammonia slip and the ammonia storage amount is consequently reduced which has an effect on the NOx conversion efficiency. The exhaust temperature is the key factor affecting the ammonia storage capacity of the catalyst which sharply decreases with the increase of temperature. The NOx conversion efficiency strongly depends on the amount of ammonia storage when the temperature is lower than 280 °C, and it is nearly linear to the amount of ammonia storage at 200 °C. If the ammonia storage is not controlled properly ammonia slip will occur under various transient conditions. Rapid heating of the catalyst at low temperature can cause serious ammonia slip. The initial temperature of the heating process is crucial to causing ammonia slip in transient processes while SV is not the key factor. The saturation level of the ammonia storage has a significant effect on ammonia slip in transient processes. There is an appropriate amount of ammonia storage which can be defined as the “slip-preventing limit” that maximizes the NOx conversion efficiency while keeping ammonia slip under 10 ppm to comply with the Euro 6 legislation for heavy-duty diesel engines.

Metals emitted from heavy-duty diesel vehicles equipped with advanced PM and NO X emission controls

Emission factors for elemental metals were determined from several heavy-duty diesel vehicles (HDDV) of 1998–2007 vintage, operating with advanced PM and/or NO X emissions control retrofits on a heavy-duty chassis dynamometer, under steady state cruise, transient, and idle conditions. The emission control retrofits included diesel particulate filters (DPF): catalyzed and uncatalyzed, passive and active prototype vanadium- or zeolite-based selective catalytic reduction (SCR) systems, and a catalyzed DPF fitted on a hybrid diesel electric drive vehicle. The prototype SCR systems in combination with DPF retrofits are of particular interest because they represent the expected emissions controls for compliance with PM and NO X regulations in 2010. PM samples from a full-exhaust dilution tunnel were collected on bulk filters, and on a Personal Cascade Impactor Sampler (PCIS) for total and water-soluble elemental analysis. All the DPFs significantly reduced emissions of total trace elements (>85% and >95% for cruise and for the Urban Dynamometer Driving Schedule (UDDS), respectively). However, we observed differences in the post-retrofit metals emissions due to driving cycle effects (i.e., exhaust temperature) and type of retrofit. In general, the metals emissions over cruise conditions (which leads to higher exhaust temperatures) were substantially different from the emissions over a transient cycle or while idling. For instance, during cruise, we observed higher levels of platinum (1.1 ± 0.6–4.2 ± 3.6 ng km −1) for most of the retrofit-equipped vehicle tests compared to the baseline configuration (0.3 ± 0.1 ng km −1). The vanadium-based DPF + SCR vehicle during cruise operation exhibited emissions of vanadium (562 ± 265 ng km −1) and titanium (5841 ± 3050 ng km −1), suggesting the possible release of actual SCR wash-coat (V 2O 5/TiO 2) from the catalyst under the higher temperatures characteristic of cruise operation. The vanadium emissions exhibited a bi-modal mass size distribution, with modes at <0.25 μm and 1.0–2.5 μm size ranges for the vanadium-based SCR system. For the DPF + SCR systems, a greater fraction of the metal emissions from the zeolite-based system is water-soluble compared to emissions from the vanadium-based system.

Characterization of Particle Bound Organic Carbon from Diesel Vehicles Equipped with Advanced Emission Control Technologies

A chassis dynamometer study was carried out by the University of Southern California in collaboration with the Air Resources Board (CARB) to investigate the physical, chemical, and toxicological characteristics of diesel emissions of particulate matter (PM) from heavy-duty vehicles. These heavy-duty diesel vehicles (HDDV) were equipped with advanced emission control technologies, designed to meet CARB retrofit regulations. A HDDV without any emission control devices was used as the baseline vehicle. Three advanced emission control technologies; continuously regenerating technology (CRT), zeolite- and vanadium-based selective catalytic reduction technologies (Z-SCRT and V-SCRT), were tested under transient (UDDS) (1) and cruise (80 kmph) driving cycles to simulate real-world driving conditions. This paper focuses on the characterization of the particle bound organic species from the vehicle exhaust. Physical and chemical properties of PM emissions have been reported by Biswas et al. Atmos. Environ. 2008, 42, 5622-5634) and Hu et al. (Atmos. Environ. 2008, submitted) Significant reductions in the emission factors (microg/mile) of particle bound organic compounds were observed in HDDV equipped with advanced emission control technologies. V-SCRT and Z-SCRT effectively reduced PAHs, hopanes and steranes, n-alkanes and acids by more than 99%, and often to levels below detection limits for both cruise and UDDS cycles. The CRT technology also showed similar reductions with SCRT for medium and high molecular weight PAHs, acids, but with slightly lower removal efficiencies for other organic compounds. Ratios of particle bound organics-to-OC mass (microg/g) from the baseline exhaust were compared with their respective ratios in diesel fuel and lubricating oil, which revealed that hopanes and steranes originate from lubricating oil, whereas PAHs can either form during the combustion process or originate from diesel fuel itself. With the introduction of emission control technologies, the particle bound organics-to-OC ratios (microg/g) decreased considerably for PAHs, while the reduction was insignificant for hopanes and steranes, implying that fuel and lubricating oil have substantially different contributions to the total OC emitted by vehicles operating with after-treatment control devices compared to the baseline vehicle since these control technologies had a much larger impact on PAH OC than hopanes and steranes OC.