One-step hydrothermal synthesis of Cu-SAPO-34/cordierite and its catalytic performance on NO_x removal from diesel vehicles

Cu-SAPO-34/cordierite catalysts were prepared via one-step hydrothermal synthesis method and their performances to remove NO x from the diesel vehicle exhaust were evaluated. The morphology, structure, Cu content and valence state were characterized by SEM, XRD, ICP and XPS, respectively. The experimental results show the active component Cu of the catalysts via in situ synthesis could significantly improve the selective catalytic reduction （SCR） activities of NOx and the optimal Cu content is in the range of 0.30%-0.40%（mass fraction）. No N 2 O is detected by gas chromatograph （GC） during the evaluation process, which implies that NOx is almost entirely converted to N2 over Cu-SAPO-34/cordierite catalyst. The conversion rate of NOx to N2 by NH3 over catalyst could almost be up to 100%in the temperature range of 300-670 ℃with a space velocity of 12000 h-1 and it is still more than 60% at 300-620 ℃ under 36000 h-1. The catalysts also show the good hydrothermal and chemical stability at the atmosphere with H 2 O.

A Brief Account of Domestic Vehicle Diesel Engines and Their Emission Control

Ⅰ. Briefing domestic vehicle diesel engines Before the 1970s, domestic vehicle diesel engines were mainly applied to heavy vehicles, while medium and light vehicles were powered chiefly with gasoline engines.

Analysis of diffusion behavior of harmful emissions from trackless rubber-wheel diesel vehicles in underground coal mines

To define the diffusion behavior of harmful exhaust substances from diesel vehicles and support safety risk assessments of underground coal mines,we performed a multi-species coupling calculation of the emission and diffusion of harmful substances from a trackless rubber-wheel diesel vehicle.A computational fluid dynamics(CFD)model of the diffusion of harmful emissions was hence established and verified.From the perspective of risk analysis,the diffusion behavior and distribution of hazardous substances emitted by the diesel vehicle were studied under 4 different conditions;moreover,we identified areas characterized by hazardous levels of emissions.When the vehicle idled upwind in the roadway,high-risk areas formed behind and to the right of the vehicle:particularly high concentrations of pollutants were measured near the rear floor of the vehicle and within 5 m behind the vehicle.When the vehicle idled downwind,high-risk areas formed in front of it:particularly high concentrations of pollutants were measured near the floor and within 5 m from the front of the vehicle.In the above cases,the driver would not breathe highly polluted air and would be relatively safe.When the vehicle idled into the chamber,however,high-risk areas formed on both sides of the vehicle and near the upper roof.Forward entry of the vehicle caused a greater increase in the concentration of pollutants in the chamber and in the driver’s breathing zone compared with reverse entry.

Carbonyl emissions from heavy-duty diesel vehicle exhaust in China and the contribution to ozone formation potential

Fifteen heavy-duty diesel vehicles were tested on chassis dynamometer by using typical heavy duty driving cycle and fuel economy cycle. The air from the exhaust was sampled by 2,4- dinitrophenyhydrazine cartridge and 23 carbonyl compounds were analyzed by high performance liquid chromatography. The average emission factor of carbonyls was 97.2 mg/km, higher than that of light-duty diesel vehicles and gasoline-powered vehicles. Formaldehyde, acetaldehyde, acetone and propionaidehyde were the species with the highest emission factors. Main influencing factors for carbonyl emissions were vehicle type, average speed and regulated emission standard, and the impact of vehicle loading was not evident in this study. National emission of carbonyls from diesel vehicles exhaust was calculated for China, 2011, based on both vehicle miles traveled and fuel consumption. Carbonyl emission of diesel vehicle was estimated to be 45.8 Gg, and was comparable to gasolinepowered vehicles （58.4 Gg）. The emissions of formaldehyde, acetaldehyde and acetone were 12.6, 6.9, 3.8 Gg, respectively. The ozone formation potential of carbonyls from diesel vehicles exhaust was 537 mg O3/km, higher than 497 mg O3/km of none-methane hydrocarbons emitted from diesel vehicles.

Advances in emission control of diesel vehicles in China

Diesel vehicles have caused serious environmental problems in China.Hence,the Chinese government has launched serious actions against air pollution and imposed more stringent regulations on diesel vehicle emissions in the latest China VI standard.To fulfill this stringent legislation,two major technical routes,including the exhaust gas recirculation(EGR)and high-efficiency selective catalytic reduction(SCR)routes,have been developed for diesel engines.Moreover,complicated aftertreatment technologies have also been developed,including use of a diesel oxidation catalyst(DOC)for controlling carbon monoxide(CO)and hydrocarbon(HC)emissions,diesel particulate filter(DPF)for particle mass(PM)emission control,SCR for the control of NOx emission,and an ammonia slip catalyst(ASC)for the control of unreacted NH3.Due to the stringent requirements of the China VI standard,the aftertreatment system needs to be more deeply integrated with the engine system.In the future,aftertreatment technologies will need further upgrades to fulfill the requirements of the near-zero emission target for diesel vehicles.

Development of database of real-world diesel vehicle emission factors for China

A database of real-world diesel vehicle emission factors, based on type and technology, has been developed following tests on more than 300 diesel vehicles in China using a portable emission measurement system. The database provides better understanding of diesel vehicle emissions under actual driving conditions. We found that although new regulations have reduced real-world emission levels of diesel trucks and buses significantly for most pollutants in China, NOx emissions have been inadequately controlled by the current standards, especially for diesel buses, because of bad driving conditions in the real world. We also compared the emission factors in the database with those calculated by emission factor models and used in inventory studies. The emission factors derived from COPERT（Computer Programmer to calculate Emissions from Road Transport） and MOBILE may both underestimate real emission factors, whereas the updated COPERT and PART5（Highway Vehicle Particulate Emission Modeling Software） models may overestimate emission factors in China. Real-world measurement results and emission factors used in recent emission inventory studies are inconsistent,which has led to inaccurate estimates of emissions from diesel trucks and buses over recent years. This suggests that emission factors derived from European or US-based models will not truly represent real-world emissions in China. Therefore, it is useful and necessary to conduct systematic real-world measurements of vehicle emissions in China in order to obtain the optimum inputs for emission inventory models.

On-board measurements of gaseous pollutant emission characteristics under real driving conditions from light-duty diesel vehicles in Chinese cities

A total of 15 light-duty diesel vehicles（LDDVs） were tested with the goal of understanding the emission factors of real-world vehicles by conducting on-board emission measurements. The emission characteristics of hydrocarbons（HC） and nitrogen oxides（NOx） at different speeds, chemical species profiles and ozone formation potential（OFP） of volatile organic compounds（VOCs） emitted from diesel vehicles with different emission standards were analyzed. The results demonstrated that emission reductions of HC and NOxhad been achieved as the control technology became more rigorous from Stage I to Stage IV. It was also found that the HC and NOxemissions and percentage of O2 dropped with the increase of speed, while the percentage of CO2 increased. The abundance of alkanes was significantly higher in diesel vehicle emissions, approximately accounting for 41.1%–45.2%, followed by aromatics and alkenes. The most abundant species were propene,ethane, n-decane, n-undecane, and n-dodecane. The maximum incremental reactivity（MIR）method was adopted to evaluate the contributions of individual VOCs to OFP. The results indicated that the largest contributors to O3 production were alkenes and aromatics, which accounted for 87.7%–91.5%. Propene, ethene, 1,2,4-trimethylbenzene, 1-butene, and1,2,3-trimethylbenzene were the top five VOC species based on their OFP, and accounted for 54.0%-64.8% of the total OFP. The threshold dilution factor was applied to analyze the possibility of VOC stench pollution. The majority of stench components emitted from vehicle exhaust were aromatics, especially p-diethylbenzene, propylbenzene, m-ethyltoluene, and p-ethyltoluene.

Variation characteristics of fine particulate matter and its components in diesel vehicle emission plumes

A rapid reaction occurs near the exhaust nozzle when vehicle emissions contact the air.Twenty diesel vehicles were studied using a new multipoint sampling system that is suitable for studying the exhaust plume near the exhaust nozzle.The variation characteristics of fine particle matter(PM_(2.5)) and its components in diesel vehicle exhaust plumes were analyzed.The PM_(2.5) emissions gradually increased with increasing distance from the nozzle in the plume.Elemental carbon emissions remained basically unchanged, organic carbon and total carbon(TC) increased with increasing distance.The concentrations of SO_(4)^(2-),NO_(3)^(-) and NH_(4)^(+) (SNA) directly emitted by the vehicles were very low but increased rapidly in the exhaust plume.The selective catalytic reduction(SCR) reduced 42.7% TC, 40% NO_(3)^(-) emissions, but increased 104% SO_(4)^(2-) and 36% NH_(4)^(+) emissions, respectively.In summary,the SCR reduced 29% primary PM_(2.5) emissions for the tested diesel vehicles.The NH_(4)NO_(3) particle formation maybe more important in the plume, and there maybe other forms of formation of NH_(4)^(+) (eg.NH4Cl).The generation of secondary organic carbon(SOC) plays a leading role in the generation of secondary PM_(2.5).The SCR enhanced the formation of SOC and SNA in the plume, but comprehensive analysis shows that the SCR more enhanced the SNA formation in the plume, which is mainly new particles formation process.The inconsistency between secondary organic aerosol(SOA) and primary organic aerosol definitions is one of the important reasons for the difference between SOA simulation and observation.

An estimation of vehicle kilometer traveled and on-road emissions using the traffic volume and travel speed on road links in Incheon City

The objective of this study is to estimate the vehicle kilometer traveled（VKT） and on-road emissions using the traffic volume in urban. We estimated two VKT; one is based on registered vehicles and the other is based on traffic volumes. VKT for registered vehicles was 2.11 times greater than that of the applied traffic volumes because each VKT estimation method is different. Therefore, we had to define the inner VKT is moved VKT inner in urban to compare two values. Also, we focused on freight modes because these are discharged much air pollutant emissions. From analysis results, we found middle and large trucks registered in other regions traveled to target city in order to carry freight, target city has included many industrial and logistics areas. Freight is transferred through the harbors,large logistics centers, or via locations before being moved to the final destination. During this process, most freight is moved by middle and large trucks, and trailers rather than small trucks for freight import and export. Therefore, these trucks from other areas are inflow more than registered vehicles. Most emissions from diesel trucks had been overestimated in comparison to VKT from applied traffic volumes in target city. From these findings, VKT is essential based on traffic volume and travel speed on road links in order to estimate accurately the emissions of diesel trucks in target city. Our findings support the estimation of the effect of on-road emissions on urban air quality in Korea.