Exhaust Emission Control Research Articles

Optimal Speed Ranges for Different Vehicle Types for Exhaust Emission Control

Controlling vehicle speed is crucial for reducing exhaust emissions and ensuring the sustainable development of road transportation. Currently, speed limits on expressways are primarily set from a safety perspective, with limited research addressing speed limits from an environmental protection standpoint. In this study, based on real-world vehicle experiments and a vehicle flow exhaust emission model, we investigated the exhaust emission characteristics of light passenger vehicles (categorized as M1) and freight vehicles (categorized as N, including N1-minivans, N2-light heavy-duty vehicles, N3-medium heavy-duty vehicles, and N4-large heavy-duty vehicles) both individually and in traffic flows at varying speeds. We take carbon monoxide (CO), nitrogen oxides (NOx), particular matter (PM), and hydrocarbons (HCs) as representative emission components. The emission rate ranking of typical exhaust factors differs between M1-light passenger vehicles and N-freight vehicles. For M1-light passenger vehicles, the order is CO > HC > NOx > PM2.5, while for N-freight vehicles, it is NOx > CO > PM2.5 > HC. Conversely, for freight vehicles, higher speeds correlate with increased exhaust emissions in general, although carbon emissions specifically decrease as the speed increases. The results indicate the following speed limits conducive to sustainable road transportation development and low exhaust and carbon emissions: 90–110 km/h for light passenger vehicles and 80–100 km/h for freight vehicles.

The response of daytime nitrate formation to source emissions reduction based on chemical kinetic and thermodynamic model

Particulate nitrate is an important component of particulate matter and poses a significant threat to the ecosystem and human health. The gas-phase formation pathway of nitrate is extremely important, which mainly comprises the NO2 oxidation process triggered by OH radicals and the nitrate partitioning process. The response of nitrate to source emission reduction during different pollution periods remains unclear. Here, we applied the chemical kinetic and thermodynamics model to explore the importance oxidation process and partitioning process during different pollution periods based on high-time resolution observation data. The result indicated that with the aggravation of pollution, the partitioning process gradually ceases to be a limiting step in the formation of nitrates. The results of the influencing factor analysis indicate that NO2 concentration and aerosol pH values play a more significant role in the formation of nitrates. Specifically, during the clean period, nitrate formation is sensitive to both NO2 concentration and pH values, but during the pollution period, it becomes sensitive only to NO2 concentration. By combining source apportionment, we explored the response of nitrate formation to source emission reduction, and the results showed that the control of vehicle exhaust emissions and coal combustion sources is more effective in mitigating nitrate pollution. Additionally, this study also emphasized the importance of early prevention and control of pollution sources. This research provides scientific evidence for the precise management and control of nitrates.

Analysis of energy consumption efficiency and emissions according to urban driving of hybrid electric vehicles in Korea

Internal combustion engines contribute significantly to global warming and air pollution in urban areas with high population densities and abundant vehicular movement. Alternative energy vehicle, such as hybrid and electric vehicles, are being developed to address these concerns. However, a gradual transition to electrification while maintaining the existing fuel infrastructure appears more feasible than the rapid proliferation of battery-powered electric vehicles. Hybrid electric vehicles are recognized as an important means of improving vehicle fuel efficiency and reducing carbon emissions by introducing changes in driving modes to enhance energy consumption efficiency. Catalyst activation does not occur in cold starts, making it challenging to control exhaust emissions. In Korea, urban driving patterns characterized by speeds below 60 km/h often results in insufficient catalyst activation. Therefore, research on the characteristics of urban driving and cold-start conditions is essential. This study analyzed the urban driving characteristics of domestic hybrid vehicles reflecting urban conditions through chassis tests and examined the variations in the external temperature and engine contribution to assess the control capability of the hybrid system. Confirming that minimizing the engine preheating time during cold starts and efficiently utilizing energy stored in the motor can enhance fuel efficiency and reduce exhaust emission rates.

Manganese-substituted strontium ferrite catalyst on honeycomb structured cordierite support for oxidation of diesel particulate matter

Perovskite-based catalysts have been explored as low-cost substitutes for platinum (Pt)- based catalysts for diesel particulate matter (DPM) oxidation. In this work, manganese (Mn)-substituted strontium ferrite (SrFeMnO3-δ) (SFM) as a catalyst was coated on the honeycomb structure of cordierite support and tested for its catalytic performance for DPM oxidation using a real-world engine. The characteristic diffraction peaks due to the presence of the perovskite structure of SFM were observed for the cordierite-supported SFM. Mn was substituted in the lattice of un-substituted strontium ferrite and no other impurities were formed upon the Mn-substitution. Highly agglomerated SFM particles were formed solely due to the perovskite phase formation temperature (900 °C). The SFM catalyst enhanced catalytic Printex-V oxidation performance compared to its oxidation without the catalyst, where Printex V was used as the model DPM. The SFM catalyst showed high CO2 selectivity upon the oxidation of DPM. These results infer that the SFM catalyst possesses promise as an alternative to commercially available DOC catalysts based on PGM for DPM oxidation. SFM-coated cordierite support performed much better in terms of particle number, mass and surface area than commercial diesel oxidation catalyst (DOC) or without DOC at no engine load. The performance is substantially higher even at moderate engine loads of up to 40% and comparable at very high engine loads of 100%. Detailed investigations on a real engine exhaust and measurement of crucial parameters like particle number, mass and surface area suggest convincing and relatively rare evidence for its potential as a catalyst for diesel exhaust emission control catalyst.

Exhaust Emission Control in Sport Motorcycles: A Comparison of Catalytic Converters with Alternative Metal Materials

In this modern era, motor vehicles have brought significant changes in human life. Faster and more efficient mobility has increased connectivity between regions, supported economic growth, and improved quality of life. However, increased mobility also means an increase in vehicle exhaust emissions, which contribute to climate change and air pollution. One effective technology for controlling exhaust emissions is the use of catalytic converters. Metal catalytic converters, such as copper, brass, and chrome-plated copper, have been researched as more affordable and effective catalyst alternatives. This research aims to analyze the optimal design of exhaust systems with catalytic converters among three types of alternative materials (copper, brass, and chrome-plated copper) as well as standard exhaust systems without catalysts (STD NC) and standard platinum group metal exhaust systems (STD PGM) in maximizing the reduction of motor vehicle exhaust emissions. An experimental research design was used by utilizing a 2015 Yamaha Vixion Lightning as the research object. Catalytic converters were prepared with specific specifications to ensure consistency and accuracy in measurements. CO (carbon monoxide), HC (hydrocarbons), CO2 (carbon dioxide), and O2 (oxygen) emissions were analyzed using an Exhaust Gas Analyzer. The research results indicate that the CuCr sample exhibits excellent performance in reducing CO and HC emissions. The CuCr sample has an average CO emission of 4.09% Vol with a standard deviation of 1.46, demonstrating good consistency in CO emissions. Meanwhile, the average HC emissions from the CuCr sample are 320 ppmVol with a standard deviation of 106, indicating good consistency in HC emissions. All samples meet the emission standards set by the government, except for the STD NC sample, which exceeds the CO emission threshold.

Biogas intake pressure and port air swirl optimization to enhance the diesel RCCI engine characteristics for low environmental emissions

Exhaust emission and combustion control in RCCI (reactivity-controlled compression ignition) focused mainly on the direct-injected fuel parameters, urging to investigate the advantages of port-fuel intake parameters. The engine was modified for port injection of Biogas at the valve and RCCI mode. The influence of port swirl ratio (PSR, 0 – 80%) and biogas injection pressure (BIP, 1 – 4 bar) on the diesel RCCI combustion and emissions was tested and optimized at varied loads and 1600 rpm in a port injection at the valve (PIVE) approach. Established kinetic mechanisms were combined with multi-objective optimization to further investigate, predict, and analyze emissions occurrence and trade-offs for reduced environmental impacts. The results show that the radiation absorption triggered by increased CO2 lowers combustion temperature, resulting in prolonged ignition. Setting the airflow to swirl lowers the in-cylinder pressure at elevated BIP while raising the heat generated across the BIPs. Increasing the PSR slows the combustion while BIP speeds up the process. BIP and PSR show great trade-off reduction ability among all emission parameters. The optimum unburned hydrocarbon, nitrogen oxide, particulate, and carbon monoxide emissions for the injection at the valve were found to be 109.58, 0.577, and 2.336 ppm, and 0.103%, respectively, at low-load, low-BIP, and high-PSR. The emissions were lowered by 6.58, 91.26, 80.65, and 13.45% compared to the premixed RCCI mode, respectively. Therefore, introducing low-pressure biogas amid high swirling air at the valve elevates the in-cylinder condition while lowering the emissions, mitigating their environmental implications.

Energy, exergy, sustainability, thermoeconomic, exergoeconomic, environmental and environmental-economic effects of novel boron-containing open cell geopolymer filter of a diesel engine on exhaust emissions

In this study, the energy, exergy, sustainability, thermoeconomic, exergoeconomic, environmental and environmental-economic based analyses are applied to the experimentally developed (3 % boric acid based) boron-doped geopolymer filter used for the diesel engine to assess it in a large engineering point of view. In this context, novel boron-doped filter exhaust after treatment system (BDF EAS) is compared with catalytic exhaust after treatment system (catalytic EAS) and unfiltered option (filterless) with engine loads of 50 Nm, 75 Nm and 100 Nm, while engine speeds are 1500 rpm, 1700 rpm, and 1900 rpm. The utilization of the newly developed BDF EAS has a significant effect on the exhaust emission particles. It effectively filters the particles compared to the original catalytic EAS of the engine. On the other hand, the developed BDF EAS has effective oxidation process for the emissions. So, the newly developed boron-doped filter can be used as a single device that has both of the Diesel Oxidation Catalyst (DOC) and Diesel Particulate Filter (DPF) specifications together. Hence, the new product of BDF EAS is environmentally benign system for the diesel engines and boron-doped geopolymer material can be used as an innovative material in the automotive industry's exhaust emission control system.

The Effect of Catalyst Composition on Electric Field-Mediated Catalytic Reactions for Exhaust Emission Control

The Effect of Catalyst Composition on Electric Field-Mediated Catalytic Reactions for Exhaust Emission Control

A comprehensive observation on the pollution characteristics of peroxyacetyl nitrate (PAN) in Beijing, China

Peroxyacetyl nitrate (PAN) is a typical secondary photochemical product in the atmospheric environment with significant adverse effects on human health and plant growth. In this study, PAN and other pollutants, as well as meteorological conditions were observed intensively from August to September in 2022 at a typical urban sampling site in Beijing, China. The mean and maximum PAN concentrations during the observation period were 1.00 ± 0.97 ppb and 4.84 ppb, respectively. Severe photochemical pollution occurred during the observation period, with the mean PAN concentration about 3.1 times higher than that during the clean period. There was a good positive correlation between O3 and PAN, and their correlation was higher during the O3 exposure period than that during the clean period. The simulated results by box-model coupled with the Master Chemical Mechanism (MCM v3.3.1) showed that the O3-related reactions were the largest sources of OH radicals during O3 exposure period, which was conducive to the co-contamination of PAN and O3. Acetaldehyde (CH3CHO) and methylglyoxal (MGLY) were the largest OVOCs precursors of peroxyacetyl radicals (PA), with the contributions to the total PA generated by OVOCs about 67 % – 83 % and 17 % – 30 %, respectively. The reduction of emissions from liquefied petroleum gas (LPG) and solvent usage has the highest reduction effect on PAN and O3, followed by the control of gasoline vehicle exhaust emissions. This study deepens the understanding of the PAN photochemistry in urban areas with high O3 background conditions and the impact of anthropogenic activities on the photochemical pollution. Meanwhile, the findings of this study highlight the necessity of strengthening anthropogenic emissions control to effectively reduce the co-contamination of PAN and O3 in Beijing in the future.

Direct NO decomposition over Rh-supported catalysts for exhaust emission control

Direct nitrogen oxide decomposition (DND) is a promising alternative to the selective catalytic reduction (SCR) of nitrogen oxides for emissions control, as it eliminates the need to inject reductants such as urea/ammonia. The present study investigates the implementation of Rh-supported metal oxides for the DND reaction. Rh supported on each of PrOX, TiO2, Al2O3, and CeO2 were characterized, and we found that initially the catalytic activity on Rh/PrOX and Rh/TiO2 was very high, though it deactivated over time due to strong poisoning by adsorbed oxygen. This deactivation by oxygen poisoning was verified through in-situ DRIFTS, XPS, NEXAFS, O2-TPD measurements and density functional theory (DFT) calculations, respectively. This catalytic deactivation was positively regenerated by reductive treatments with CO or H2. This study discovers the mechanism of DND deactivation and regeneration over Rh-supported metal oxides, which will provide significant insight into further development of DND.

Utilization of Aerial Drone Technology in Logistics

In order to create a supply chain that is both economically and ecologically sustainable and complies with contemporary standards, the logistics chain must be modernized and should rely on new technology. In this article, the authors will attempt to elaborate the development direction of delivery systems through examples of technology-oriented companies such as Amazon, focusing on the use of unmanned aerial vehicles (drones) for delivering smaller packages within urban and suburban environments. The main goal of using drones in urban logistics is to reduce the burden on city roads and the use of road vehicles that generate the highest gaseous emissions footprint. The use of drones has proven to be extremely flexible and useful in port logistics as well, eliminating the need to send supply vessels into rough seas or putting people in danger during exhaust emission control. However, drones are a relatively new technology, and they have their own limitations, which are still being discovered. The main constraints of the devices themselves are power sources and the power of the aircraft, which currently and likely in the future won’t be able to transport heavier commercial loads. Increased use leads to congestion in airspace, posing risks to other modes of transportation such as road or air. Research shows that the current use of drones mainly revolves around test flights or limited applications within a regulated environment.

Parametric optimization with Biodiesel-water emulsion under premixed lean combustion to achieve high efficiency and clean combustion

Advanced low temperature combustion (LTC) aids in simultaneously controlling exhaust emissions of oxides of nitrogen (NOx) and particulate matter (PM). However, LTC strategies are constrained by achievable load range restriction and higher levels of unburned hydrocarbon (HC) and carbon monoxide (CO). The present investigation envisages combining renewable biodiesel-water emulsions and an advanced premixed lean combustion strategy to curtail the higher HC and CO emissions without sacrificing engine performance. Non-edible Karanja oil was the source of biodiesel and the emulsion stabilizer. A production light-duty diesel engine is modified to run under premixed lean combustion conditions based on late injection using a fully-flexible electronic fuel injection system. The engine operating parameters were optimized, including fuel injection timing, EGR flow rate, and emulsion water concentration. Emulsions of neat biodiesel were prepared to contain 6, 12, and 18% water on a mass basis using 1 and 2% surfactant by mass. The fuel injection timing was varied from 2 to 4 degrees after the top dead centre, and up to 15% EGR flow rate was utilized. Design of experiments aided in minimizing the number of engine tests. The performance and emission parameters were the output responses. Taguchi Grey Relational Analysis established the optimal combination of input factors to improve engine performance and reduce exhaust emissions. Engine experiments at optimized operating conditions revealed that compared to conventional diesel combustion, the brake thermal efficiency and brake specific fuel consumption improved by 33 and 16%, respectively, at 5.08 bar BMEP. The NOx, smoke and HC emissions were reduced by 68, 73 and 46%, while CO emissions increased nearly two-fold.

Exhaust emission control of SI engines using ZSM-5 zeolite supported bimetals as a catalyst synthesized from coal fly ash

This paper synthesizes ZSM-5 zeolite from coal fly ash and uses it as a catalyst for reduction of NOx emissions in gasoline powered engine. It suggests a mono and bimetallic doped zeolite coated in honeycomb structure cordierite monolith for effectively reducing the NOx emissions. The synthesized ZSM-5 zeolite was subjected to SEM, XRF and XRD analysis and compared with commercial ZSM-5 zeolite. The experimental study of measuring emissions using AVL DI-gas analyzer on a Tata nano twin-cylinder spark ignition engine clearly indicated that in-house made bimetallic of Ce.Cu-ZSM5 and Ce.Fe-ZSM5 were able to reduce the NOx by 69 % and 75 % at 16 kW. The NOx reductions were much better than those of the commercial catalytic converters.

Experimental Investigations on Control of Exhaust Emissions of a Semi-Adiabatic Diesel Engine with Plastic Oil

This paper concentrates on alternative fuel technology for diesel engine and environmental protection. The exhaust emissions from diesel engine cause severe health hazards when they are inhaled in.. They also cause environmental disorders. Hence control of these emissions is an immediate step. Vegetable oils and alcohols are important substitutes for diesel fuel, as they are renewable in nature. Though vegetable oils have comparable properties with diesel fuel, they have high viscosity and low volatility causing combustion problems in diesel engines. Alcohols have high volatility but low Cetane number (a measure of combustion quality in diesel engine). Plastic oil derived from waste plastic by the process of pyrolysis has equitant calorific value with diesel fuel. However, its viscosity is higher than diesel fuel calls for semi adiabatic diesel engine (SADE). The concept of semi adiabatic diesel engine is to reduce heat flow to the coolant there by providing hot combustion chamber used for burning high viscous fuels like plastic oil. Semi adiabatic engine consisted of air gap insulated piston with stainless steel crown and stainless steel gasket. The exhaust emissionsof particulate matter (PM), carbon monoxide (CO), nitrogen oxide levels (NOx ) and Un-burnt hydrocarbons (UBHC), with plastic oil were determined with conventional engine (CE) and SADE with varied injection timing at full load operation of the engine. Injection timing was varied with an electronic sensor. PM was determined by AVL Smoke meter, while NOx , CO and UBHC were measured by Netel Chromatograph multi gas analyzer at full load operation of the engine. Exhaust gas recirculation (EGR) at optimum value of 10% flow rate was provided to control the emissions. The data were compared with neat diesel operation on conventional engine with and without EGR.

Control exhaust emissions of insulated diesel engine fuelled with biogas and cottonseed biodiesel

Gaseous fuels have many advantages than liquid fuels, as their calorific values of fuels are high, pollutants emitted by gaseous fuels are low and less dangerous when compared with liquid fuels. The drawbacks associated with use of vegetable oils in diesel engines such as high viscosity and low volatility can be reduced to some extent by converting them into biodiesel. However, they (biodiesel) cause combustion problems in diesel engine, due to their moderate viscosity, and hence call for low heat rejection (LHR) engine, which can burn low calorific value fuel, give high heat release rate and faster rate of combustion. The concept of LHR engine is to minimize heat loss to the coolant, thereby increasing thermal efficiency. LHR engine in this investigation consisted of ceramic coated diesel engine. They are many methods toinduct gaseous fuels such as port injection, carburetion technique, injection of gaseous fuel at the near endof compression stroke etc,. Investigations were carried out with biogas gas as primary fuel inducted by port injection and cottonseed biodiesel was injected into the engine in conventional manner, as India is second large producer of cottonseed oil in the world. Particulate matter (PM), oxides of nitrogen (NOx), carbon mono oxide (CO) levels and un-burnt hydro carbons (UBHC) are the exhaust emissions from a diesel engine. They cause health hazards, once they are inhaled in. They also cause environmental effects like Green-house effect and Global Warming. Hence control of these emissions is an immediate effect and an urgent step. The pollutants of PM, NOx ,CO and UBHC were determined at full load operation of the engine with varied injection timing such as recommended injection timing and optimum injection timing. NOx levels were reduced with provision of exhaust gas recirculation (EGR) at optimum flow rate of 10%. The maximum induction of biogas with conventional engine (CE) was 35% of total mass of biodiesel as full load operation, while it was 45% with LHR engine. Particulate emissions were determined by AVL Smoke meter, while other emissions were measured by Netel Chromatograph multi-gas analyzer at full load operation. These pollutants were drastically reduced with induction of biogas and further reduced with advanced injection timing. NOx levels drastically reduced with EGR.

Service Based Practical Technology Drinking Water Heater with Heat Smoke Recovery of Multipurpose Diesel Motorcycle Exhaust for Wooden Fisherman Boat Power

The gas power cycle of a four-stroke combustion engine is obtained from a mixture of diesel injection+compressed hot air as the working fluid, which in this case is taken from a versatile type of diesel engine from all kinds of fishing communities on the north coast of Java Island, it can be said that in general the use of multipurpose diesel engines used as a propulsion engine for fishing boats. A common sight for Pantura fishermen is hot smoke exhaust from the exhaust of a multipurpose diesel motor driving a wooden fishing boat released into the air. Eventually, it becomes a source of air pollution around the ship, especially nitrogen oxides, which are toxic to human respiration; hot smoke waste resulting from the combustion process released through the piston engine exhaust system still contains valuable energy potential in the form of hot gas released by the exhaust which if attempted to heat the hot gas energy before being discharged into the ambient air, the heat energy can be recovered by installing additional heat exchangers as a benefit of heat sources for heat exchange heaters or heaters the result is cold drinking water turns into hot drinking water. Heat balance is the calculation of the heat released in the combustion of fuel+air in the combustion chamber and its utilization in the transfer of cold fluids to hot fluids, which is the heat energy content of explosion in compression combustion engines based on fossil fuels. All heat products of combustion cannot be converted 100% into practical motor work or power; energy transfer is lost from the combustion motor, such as 25%, to cooling water 32%, in the exhaust gas 34%, pumping losses, 3%, losses -friction loss between parts due to lousy machining inaccuracy 6% and radiation to the air environment. A drinking water heater with hot smoke recovery from a versatile diesel motor exhaust driving a wooden fishing boat works by recovering or recovering heat energy from the exhaust gas in the exhaust directly from the combustion process cycle in a piston-type combustion engine. The hot flue gas flow is forced into direct contact with the wall of the heat exchanger tube before exiting the exhaust. As long as the piston combustion motor is running, the hot stream from the exhaust gas flows into the shell & tube heat exchanger shell. This experiment aims to get clean hot water 70OC with a linked cold water mass = 0.0064 kg/s at 28OC. Another effect of this experiment is to control exhaust emissions into the atmosphere from internal combustion engines.

Pr-rich cerium-zirconium-praseodymium mixed oxides for automotive exhaust emission control

This study describes the textural, structural, redox properties, oxygen reactivity of two Pr-rich cerium-zirconium-praseodymium (CZP) oxides (Ce0.45Zr0.10Pr0.45O2−x and Ce0.475Zr0.05Pr0.475O2−x) and their catalytic activity for propane and CO oxidation in both stoichiometric and lean conditions, two important reactions for automotive exhaust emission control. The concentration of oxygen vacancies can be tuned by the quantity of Pr3+ cations which depend both on the preparation method and the composition. The Pr4+(4 f1)/Pr3+(4 f2) ratio was accurately determined by magnetic measurement. A highly energetic grinding step was found to double this Pr3+ concentration, resulting in a strong enhancement of the low-temperature reducibility, bulk oxygen mobility and catalytic activity for propane deep oxidation. Pr-rich CZP oxides seem to be less relevant for CO oxidation, which is mainly driven by the specific surface areas. These Pr-rich CZP mixed oxides present better performances for lean conditions, suggesting their possible role in diesel oxidation catalysts applications.

Ammonia in urban atmosphere can be substantially reduced by vehicle emission control: A case study in Shanghai, China

To investigate the impact of emission controls on ammonia (NH3) pollution in urban atmosphere, observation on NH3 (1 hr interval) was performed in Shanghai before, during and after the 2019 China International Import Expo (CIIE) event, along with measurements on inorganic ions, organic tracers and stable nitrogen isotope compositions of ammonium in PM2.5. NH3 during the CIIE period was 6.5±1.0 µg/m3, which is 41% and 32% lower than that before and after the event, respectively. Such a decrease was largely ascribed to the emission controls in nonagricultural sources, of which contribution for measured NH3 in control phase abated by ∼20% compared to that during uncontrol period. Molecular compositions of PAHs and hopanes further suggested a dominant role of the reduced vehicle emissions in the urban NH3 abatement during the CIIE period. Our results revealed that vehicle exhaust emission control is an effective way to mitigate NH3 pollution and improve air quality in Chinese urban areas.

Characteristics and Source Apportionment of Vehicular VOCs Emissions in a Tunnel Study

To explore the emission characteristics of volatile organic compounds (VOCs) from vehicular exhaust sources and evaporative sources with ethanol gasoline (E10) as the main fuel, VOCs sampling campaigns were carried out in the north third ring tunnel of Zhengzhou city for two consecutive weeks in December 2019. In addition, the characteristics of traffic flow and environmental information were also monitored in the tunnel. Firstly, 106 VOCs were quantified using gas chromatography/mass spectrometry (GC/MS), and then source apportionment of VOCs in the tunnel was carried out using a positive matrix factorization (PMF5.0)-chemical mass balance (CMB8.2) composite model. Finally, the ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAFP) of vehicle exhaust sources and evaporative sources were analyzed using the maximum incremental reactivity (MIR) and fractional aerosol coefficient (FAC). The results showed that ρ(VOCs) in the tunnel was (2794.5±147.4) μg·m-3 during the experiment, among which halogenated hydrocarbons[(32.4±2.0)%] accounted for the highest proportion, followed by aromatic hydrocarbons[(27.5±0.6)%] and alkanes[(23.3±0.8)%]. Source apportionment of vehicular VOCs showed that exhaust emissions (62.5%)>evaporative emissions (37.5%), whereas the contribution of OFP was that exhaust emissions (71.9%)>evaporative emissions (28.1%), and the contribution of SOAFP was that exhaust emissions (75.8%)>evaporative emissions (24.2%). The dominant components of OFP in evaporative sources were m,p-diethylbenzene, isoprene, and trans-2-pentene, whereas m,p-diethylbenzene, m,p-xylene, and 1,2,3-trimethylbenzene were the dominant components of SOAFP. The major components of OFP in exhaust sources were m,p-xylene, 1,2,4-trimethylbenzene, and 1,3,5-trimethylbenzene, whereas m,p-xylene, m,p-diethylbenzene, and 1,3,5-trimethylbenzene were the dominant components of SOAFP. In regions where ethanol gasoline is used, special attention should be paid not only to the exhaust emissions control but also to strengthening the emissions reduction of VOCs from vehicle evaporative sources, especially the high active components such as aromatic hydrocarbons and alkenes.

Low-temperature NOx reduction over hydrothermally stable SCR catalysts by engineering low-coordinated Mn active sites

Low-temperature selective catalytic reduction (SCR) of NOx over hydrothermally stable metal oxide catalysts is still a great challenge in heavy-duty diesel exhaust purification. Herein, hydrothermally stable MnOx/Al2O3 catalysts with highly dispersed low-coordinated Mn active sites were originally demonstrated for low-temperature NOx reduction. The catalyst exhibited greater than 90 % NOx conversion within 200–360 °C even after a 24 h aging treatment at 650 °C with a flow of 10 % H2O. A series of characterization revealed that the developed catalysts with more active low-coordinated Mn species possessed reactive redox sites and Lewis acid sites. Thus, the successive adsorption and activation of NH3 and NOx species would be efficiently accelerated and proceeded with the subsequent SCR reaction over hydrothermally stable MnOx/Al2O3 catalysts. This work discovered hydrothermally stable manganese oxide catalyst for low-temperature NOx reduction which would provide new opportunities for the application of metal oxide catalysts among diesel engine exhaust emission control.