Natural Gas Vehicles Research Articles

Analysis of Retrofit and Scrappage Policies for the Indian Road Transport Sector in 2030

In India, the road transport sector contributed around 90% of total transport CO2 emissions in 2018. Air pollution from the road transport sector has detrimental effects on both air quality and human health. The policies implemented have a long-term impact on the amount of vehicle emissions and characteristics of fleet vehicles. The present study analyzes emissions from India’s road transport sector using the bottom-up activity approach model. Future vehicle stocks in India are projected up to 2030 using a hybrid growth model approach. Vehicle emissions of CO2, CO, particulate matter (PM), and NOx are analyzed for India's reference (2020) and projected years fleet (2030). The emissions from the projected fleet are subjected to different mitigation scenarios such as retrofit and scrappage policies to estimate the emission reduction potentials of these scenarios from the future fleet of India. The analysis of the study indicates that the retrofit policies are more effective in reducing vehicle emissions than the scrappage policies. Retrofit policies such as the advancement in emission norms (shift to Bharat Stage (BS)-VI from BS-IV), the increased share of compressed natural gas (CNG) vehicles, and fuel efficiency (FE) improvements have reduced vehicle emissions significantly compared to the scrappage of old vehicles from the fleet. The low impact of scrappage policies is attributed to the projected fleet’s lower share of old vehicles (10–15%). While retrofit policies have a significant impact as they largely affect 85% to 90% of young vehicles (less than ten years of age) in 2030. A combination of both policies is suggested to control future fleet emissions. The study also conducts sensitivity analysis, which indicates a significant influence of the emission factors in the vehicle emission analysis and GDP growth rates in the vehicle fleet projection.

Thermodynamic Analysis of CNG Fast Filling Process of Composite Cylinder Type IV

Due to ecological and economic advantages, natural gas is used as an alternative fuel in the transportation sector in the form of compressed natural gas (CNG) and liquefied natural gas (LNG). Development of infrastructure is necessary to popularize vehicles that use alternative fuels. Selected positive factors from EU countries supporting the development of the CNG market were discussed. The process of natural gas vehicle (NGV) fast filling is related to thermodynamic phenomena occurring in a tank. In this study, the first law of thermodynamics and continuity equations were applied to develop a theoretical model to investigate the effects of natural gas composition on the filling process and the final in-cylinder conditions of NGV on-board composite cylinder (type IV). Peng–Robinson equation of state (P-R EOS) was applied, and a lightweight composite tank (type IV) was considered as an adiabatic system. The authors have devised a model to determine the influence of natural gas composition on the selected thermodynamic parameters during fast filling: Joule–Thomson (J-T) coefficient, in-cylinder gas temperature, mass flow rate profiles, in-cylinder mass increase, natural gas density change, ambient temperature on the final natural gas temperature, influence of an ambient temperature on the amount of refueled natural gas mass. Results emphasize the importance of natural gas composition as an important parameter for the filling process of the NGV on-board composite tank (type IV).

Real-world gaseous emission characteristics of natural gas heavy-duty sanitation trucks

As compared to conventional diesel heavy-duty vehicles, natural gas vehicles have been proved to be more eco-friendly due to their lower production of greenhouse gas and pollutant emissions, which are causing enormous adverse effects on global warming and air pollution. However, natural gas vehicles were rarely studied before, especially through on-road measurements. In this study, a portable emission measurement system (PEMS) was employed to investigate the real-world emissions of nitrogen oxides (NOx) (nitrogen monoxide (NO), nitrogen dioxide (NO2)), total hydrocarbons (THC), carbon monoxide (CO), and carbon dioxide (CO2) from two liquified natural gas (LNG) China V heavy-duty cleaning sanitation trucks with different weight. Associated with the more aggressive driving behaviors, the vehicle with lower weight exhibited higher CO2 (3%) but lower NOx (48.3%) (NO2 (78.2%) and NO (29.4%)), CO (44.8%), and THC (3.7%) emission factors. Aggressive driving behaviors were also favorable to the production of THC, especially those in the medium-speed range but significantly negative to the production of CO and NO2, especially those in the low-speed range with high engine load. In particular, the emission rate ratio of NO2/NO decreased with the increase of speed/scaled tractive power in different speed ranges.

Alternative-energy-vehicles deployment delivers climate, air quality, and health co-benefits when coupled with decarbonizing power generation in China

<h2>Summary</h2> China is the world's largest carbon emitter and suffers from severe air pollution, which results in approximately one million premature deaths/year. Alternative energy vehicles (AEVs) (electric, hydrogen fuel cell, and natural gas vehicles) can reduce carbon emissions and improve air quality. However, climate, air quality, and health benefits of AEVs powered with deeply decarbonized power generation are poorly quantified. Here, we quantitatively estimate the air quality, health, carbon emission, and economic benefits of replacing internal combustion engine vehicles with various AEVs. We find co-benefits increase dramatically as the electricity grid decarbonizes and hydrogen is produced from non-fossil fuels. Relative to 2015, a conversion to AEVs using largely non-fossil power can reduce air pollution and associated premature mortalities and years of life lost by ∼329,000 persons/year and ∼1,611,000 life years/year. Thus, maximizing climate, air quality, and health benefits of AEV deployment in China requires rapid decarbonization of the power system.

Life cycle assessment of mid-range passenger cars powered by liquid and gaseous biofuels: Comparison with greenhouse gas emissions of electric vehicles and forecast to 2030

• Biofuels can provide significant GHG emissions benefits in a short period of time. • The current trend to increase the size of batteries is detrimental to GHG impacts. • With an adapted battery size, PHEVs seem to be another relevant solution. • Electrification and biofuels can together reach the European Green Deal targets. Electrification of the transport sector is a relevant measure to decarbonize, but the massive electrification approach can be questioned since another interesting low-carbon solutions are available. Current and future forecast comparative analysis of the greenhouse gas emissions of mid-range passenger cars, obtained using life cycle assessment (LCA) methodology, are presented. Two important factors are addressed by assessing the use of biofuels suitable for internal combustion engines (including bio natural gas vehicles) and forecasting the LCA results in 2030 with updated vehicle weight, battery technology, and CO 2 electricity content. The synthesis shows that conventional engines powered with biofuels complement electrified powertrains. Plug-in hybrid electric vehicles seem to be the ideal solution owing to the limited size of their batteries. The current trend of expanding the battery size to improve the range of electric vehicles is detrimental to greenhouse gas (GHG) impacts. Biofuels can provide significant GHG emission benefits in a short time as vehicle powertrains can already accommodate up to 85% ethanol or 100% biodiesel without engine changes.

Effect of support on Pd-catalyzed methane-lean combustion in the presence of water: Review

The exhaust stream from a lean-burn natural gas vehicle (NGV) typically has a maximum temperature of about 550 °C, a low concentration of methane (500–1000 ppmv) and a large amount of water vapor (around 15% by volume) which is a major cause of Pd catalyst deactivation. Such conditions pose significant challenges in the development of a small footprint catalytic converter to mitigate methane emissions. In this review, we address how the choice of support material can affect the Pd catalyst tolerance to water. Support hydrophobicity, its ability to serve as a sink for the hydroxyls, and oxygen mobility are some of the crucial factors that have contributed to improved catalyst stability and activity. In addition to the summary of the most recent advances in the field, we provide recommendations for catalyst testing and characterization techniques that are specific to the application of interest.

Economically feasible production of green methane from vegetable and fruit-rich food waste

Increasing food waste (FW) generation is a major obstacle to achieving sustainable development by emitting greenhouse gas and wasting resources. The conventional FW treatment technologies cause environmental pollution and waste the potential energy of FW. Notably, the production of green methane (CH4) from FW has been proposed as a promising approach to overcome the environmental challenges associated with typical FW treatment and transportation technologies. The generated CH4 could be utilized as a fuel for natural gas vehicles (NGVs). The present study involved the development of a large scale process for the production of green CH4 from FW based on anaerobic digestion using pressure swing adsorption. Additionally, the economic feasibility of the process was evaluated by considering appropriate economic parameters and assumptions. Treatment of 50 t/d of FW in China resulted in the generation of 0.3 t of green CH4, and its minimum selling price was calculated at US$ 0.991/kWh. The benefits of scale-up as well as the developed FW treatment method were demonstrated by successful energy recovery and conversion of FW to green CH4. Importantly, the minimum selling price could be decreased to US$ 0.069/kWh, which is comparable to the current NGV fuel prices.

Risk-based scheduling of an off-grid hybrid electricity/hydrogen/gas/ refueling station powered by renewable energy

Making full use of renewable energy to supply clean energy for transportation sector can effectively reduce environmental pollution and realize the sustainable development. A hybrid electricity/hydrogen/gas/refueling station (EHGRS) powered by renewable energy in an off-grid region is proposed. It supplies electricity for electric vehicles (EVs), and hydrogen for hydrogen fuel cell vehicles (HFCVs) and produces natural gas for natural gas vehicles (NGVs) simultaneously. A hybrid stochastic/information gap decision theory (IGDT) optimization method is employed for the scheduling problem of the hybrid EHGRS in an uncertain environment. The uncertainties of wind and photovoltaic (PV) power is modelled via scenarios, while the uncertainties of the demands of EVs, HFCVs and NGVs, depending on human behavior, are formulated with a bi-level IGDT method without knowing the accurate distribution information. The work aims to find the maximum expected profits of the hybrid EHGRS. Two different scheduling strategies, i.e. risk-averse and risk-seeker, with two contradictory attitudes under the uncertain demands are proposed. Results indicate that 1) The proposed hybrid EHGRS can simultaneously provide different fuels to EVs, HFCVs and NGVs. 2) Under the same condition, the profit for the risk-averse scheduling is decreased and the risk-seeker scheduling is increased, compared to the results obtained by the pure stochastic optimization.

Selection of alternative fuel taxis: a hybridized approach of life cycle sustainability assessment and multi-criteria decision making with neutrosophic sets

This study presents a combined application of hybrid life cycle sustainability assessment and multi-criteria decision-making, aiming to further advance an integrated sustainability assessment and decision-making for the selection of alternative-fuel taxis. First, a multiregional hybrid life cycle sustainability assessment model is built to evaluate macro-level sustainability impacts of various vehicle types: conventional gasoline vehicles, compressed natural gas vehicles, hybrid, and battery electric vehicles. Second, considering the subjective nature of the evaluation process, the interval-valued neutrosophic sets-based analytic hierarchy process is suggested to assess the results obtained from the life cycle model to determine the weight of each evaluation criterion. Then, the technique for order preference by similarity to the ideal solution is used to rank the sustainability performance. Two different charging scenarios are also tested. The results show that solar-powered BEVs are the best in the environmental impacts with the exceptions of water consumption and land use. Solar-powered BEVs are superior in human health impact, while, ICVs are the best in compensation and employment generations. The ranking results reveal that solar-powered BEVs are the best alternatives when all indicators are considered, followed by CNG vehicles. The proposed method provides a practical and life cycle-based decision-making approach to support and prioritize effective policies for more sustainable transportation.

Life-Cycle Greenhouse Gas Emission Benefits of Natural Gas Vehicles

Abundant supply, low prices, and low carbon content may result in an increased use of natural gas (NG) as an alternative transportation fuel. Assessments of the associated climate benefits are sensitive to the climate metric and time horizon selected to equate methane to equivalent CO2 emissions and to the assumptions of methane emissions during NG production, distribution, and use. We report life-cycle greenhouse gas (GHG) emissions from cars, light-duty trucks (LDTs), and heavy-duty trucks (HDTs) that are powered directly or indirectly using NG as a function of methane emission rates. We show that whether internal combustion engine vehicles (ICEVs) powered by fossil compressed natural gas (CNG) have GHG benefits over their gasoline and diesel counterparts depends on a value judgment of using either an integrated or end-point climate metric (e.g., global warming potential [GWP] or global temperature change potential [GTP]) and a short or long time horizon (e.g., 20 or 100 years). Conversion of NG into electricity or hydrogen for use in battery electric vehicles (BEVs) or fuel-cell vehicles (FCVs) has clear GHG benefits for cars and LDTs. Benefits are less clear for HDTs where heavy batteries and CNG tanks lead to a relatively poor GHG performance of BEVs and CNG_ICEVs compared to the incumbent diesel technology.

Factors influencing the payment of costs of converting oil-to CNG-fuelled cars in a market dominated by used-cars

This paper examines the relationship between economic factors and car-owners’ willingness to incur full costs of converting their cars to natural gas vehicles (NGVs) or to secure commercial loans to supplement their savings for meeting the attendant costs. The paper applies logit models on data generated from 429 randomly selected vehicle-owners, who had visited three big oil refuelling stations in Kinondoni district of Dar es Salaam city in Tanzania. The results show that the better the vehicle condition in terms of mileage, the newness or near-newness, the higher the number of car-cylinders, the more likely the car-owners would be willing to incur conversion-to-NGVs costs and use commercial loans to foot the bills. Private/family- and male-car-owners were more willing to incur these costs or use commercial loans to finance such conversion relative to taxi-car- or female-car-owners. Policy instruments such as the creation of awareness of the benefits of utilising NGVs, and provision of commercial loans emerged to be important in enticing car-owners to convert their cars to NGVs and incur the conversion costs. For quick response, the policy instruments should target newly bought cars which are in good condition and with bigger engine capacity, male- and private/family car-owners.

A comparison of light-duty vehicles' high emitters fractions obtained from an emission remote sensing campaign and emission inspection program for policy recommendation

Urban transportation is one of the leading causes of air pollution in big cities. In-use emissions of vehicles are higher than the emission control certification levels. The current study uses a roadside remote sensing emission monitoring campaign to investigate (a) fraction of high emitters in the light-duty vehicle (LDV) fleet and their contributions to the total emissions, (b) emission inspection (I/M) programs' effectiveness, and (c) alternate fuel (natural gas) encouragement policy. LDVs consist of passenger or freight transport vehicles with four wheels equivalent to classes M1 and N1 of European union vehicle classifications. The motivation is to assess the current emission inspection program's success rate and study the impact of the increased natural gas vehicle market share policy. It is also meant to present and validate remote sensing as a possible backup method to the current I/M program.The emission remote sensing campaign was conducted to measure emissions of CO, HC, and NO of the LDV fleet. Fleet age, engine size, and fuel type (gasoline or natural gas) were extracted and correlated with emissions. It was found that CO and HC emissions are five times higher for cars more than fifteen years old of age compared to those less than five years old. Analyses of high-emitters showed that almost 20% of the fleet were high-emitters and responsible for roughly half of CO, HC, and NO emissions.The correlation between the I/M program and the remote sensing to identify high-emitters was weak. Which indicates the need for an improved I/M program. It shows that even a limited remote sensing campaign is beneficial as a complementary monitoring tool to the I/M program. The study showed the same fraction of high-emitters in natural gas (methane) vehicles, despite the national policies to increase natural gas vehicle fraction in the market for reduced emissions.

Tuning the interactions among Ce, Pd and Rh over Ce-modified Pd-Rh three-way catalyst for exhaust treatment of natural gas vehicles

Three Ce-modified Pd-Rh bimetallic catalysts for exhaust purification of natural gas vehicles (NGVs) under stoichiometric conditions were prepared by deposition-precipitation (DP), stepwise impregnation (SI) and co-impregnation (CI) methods, respectively. It demonstrated that before and after aging the catalyst prepared by DP technique displayed much higher activity for the conversions of CH4 and NO than the other two catalysts, especially at high temperatures (about 410–550 °C). X-ray diffraction, CO-chemisorption, hydrogen temperature-programmed reduction and X-ray photoelectron spectroscopy analyzes demonstrated that there were smaller CeO2 particles, higher metal dispersion, stronger reducibility and more surface metallic Pd species over the catalyst prepared by DP method. This might be due to the stronger Pd-Ce but weaker Pd-Rh interactions over the catalyst prepared by DP mean. Moreover, in situ diffuse reflectance infrared Fourier transform spectroscopy of CO adsorption analysis implied that the electronic structures of Pd in the three catalysts were different, which may be also induced by the different interactions among Rh, Ce and Pd in these catalysts. The results indicated that the performance of Pd-Rh three-way catalyst for NGVs exhaust purification can be enhanced by modulating the interactions of Pd-Rh and Pd-Ce. Our work may provide a new strategy for the preparation of three-way catalyst with high efficiency for NGVs.

Real-world NOx emissions from heavy-duty diesel, natural gas, and diesel hybrid electric vehicles of different vocations on California roadways

This study assessed the real-world nitrogen oxide (NOx) emissions from 50 heavy-duty vehicles of different vocations and engine technologies using portable emissions measurement systems (PEMS). This is one of the most comprehensive in-use emissions studies conducted to date, which played a key role in the development of CARB's (California Air Recourses Board) updated EMission FACtor (EMFAC) model, especially for natural gas vehicles. In-use emissions testing was performed on school and transit buses, refuse haulers, goods movement vehicles, and delivery vehicles while were driven over their normal operating routes in the South Coast Air Basin. Engine technologies included diesel engines with and without selective catalytic reduction (SCR) systems, compressed natural gas (CNG) engines and liquified petroleum gas (LPG) engines, and SCR-equipped diesel hybrid electric vehicles. For most vehicles, the in-use NOx emissions were higher than the certification standards for the engine. Diesel vehicles generally showed higher brake-specific NOx emissions compared to the CNG vehicles. NOx emissions were strongly dependent on the SCR temperature, with SCR temperatures below 200 °C resulting in elevate brake-specific NOx. The 0.02 g/bhp-hr certified CNG vehicles showed the largest reductions in NOx emissions. The diesel hybrid electric vehicles showed important distance-specific NOx benefits compared to the conventional diesel vehicles, but higher emissions compared to the CNG and LPG vehicles. Overall, average NOx reductions were 75%, 94%, 65%, 79%, respectively, for the 0.2 CNG, 0.02 CNG, diesel hybrid electric, and LPG vehicles compared to diesel vehicles, due in part to some diesel vehicles with particularly high emissions, indicating that the widespread implementation of advanced technology and alternative fuel vehicles could provide important NOx reductions and a path for meeting air quality targets in California and elsewhere.

Chemical characterization of PM2.5 emitted from China IV and China V light-duty vehicles in China

This study reported the emission factors (EFs) and detailed chemical compositions of PM2.5 collected from China IV and China V light-duty vehicles (LDVs) through dynamometer test. The China IV LDVs containing 4 gasoline vehicles (GVs) and 4 natural gas vehicles (NGVs) had port fuel injection (PFI) engines, while the China V LDVs included 2 GVs with PFI engines and 2 GVs with gasoline direct injection (GDI) engines. The average EFs of PM2.5 were 1.90 ± 0.70 mg km−1, 1.44 ± 0.29 mg km−1, and 0.56 ± 0.05 mg km−1 for China IV GVs, China IV NGVs, and China V GVs, respectively. PM2.5 profiles of LDVs were characterized by abundant carbon species (60.59–68.58%) with low amounts of water soluble ions (WSIs, 6.96–16.37%) and elements (5.20–7.53%). In general, the EFs of PM2.5 constituents including organic carbon (OC), elemental carbon (EC), WSIs, and elements were reduced obviously by strengthening emission standards from China IV to China V. While the contributions of most WSIs and elements to PM2.5 increased as vehicle technology improved. Furthermore, the EFs of PM2.5 components from China IV LDVs also decreased when shifting fuels from gasoline to natural gas. While the fractions of OC, WSIs and most elements in PM2.5 increased due to the highest reduction rate of EC mass. For China V LDVs, GDI vehicles emitted less OC but more EC compared to PFI vehicles, and the EFs of most WSIs and elements also increased. Overall, GDI vehicles exhibited lower fractions OC and WSIs but higher contents of EC and elements in PM2.5. Besides, PM2.5 and its chemical species were heavily dependent on vehicle's driving patterns. The average EFs of PM2.5 components under aggressive driving pattern increased significantly compared to those under moderate driving pattern.

Pd/SiO2 as an active and durable CH4 oxidation catalyst for vehicle applications

The removal of CH4 is critical to address environmental concerns for developing natural gas vehicles (NGVs), because CH4 has a 20-fold-greater contribution to the greenhouse effect than CO2. Alumina supported Pd catalysts are widely used for CH4 oxidation due to their superior catalytic activity and durability compared to other CH4 oxidation catalysts. However, the continuous deactivation of Pd-based catalysts during vehicle applications needs further development of active and durable catalysts. Here, we report that Pd/SiO2 can be active and durable catalysts for CH4 oxidation in practically relevant condition via a simple reductive regeneration. CH4 oxidation light-off curves of freshly prepared Pd/SiO2 (air, 550°C) present higher activity than those of Pd/Al2O3, but severe deactivation was observed after hydrothermal aging (HTA, air with 10% H2O) at 850°C. However, X-ray diffraction (XRD), scanning transmission electron microscopy (STEM) and volumetric CO adsorption suggest that Pd/SiO2 has similar particle sizes as Pd/Al2O3 even after HTA, indicating that Pd/PdO particle sintering is not the origin of the deactivation of Pd/SiO2. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) shows that the CO was not adsorbed on Pd/SiO2 after HTA, whereas it was adsorbed on Pd/Al2O3 after HTA. These results demonstrate that the deactivation of Pd/SiO2 originates mainly from the blockage of the Pd/PdO surface by the SiO2 overlayer formed during HTA. The Pd/PdO surfaces are re-exposed by a simple H2 treatment at 500°C, resulting in CO adsorption on the Pd/PdO surface and regeneration for CH4 oxidation activity, which suggests that the Pd/PdO surface was re-exposed by a reduction treatment. This work also demonstrates that SiO2-supported Pd catalysts can be a good candidate for active and durable CH4 oxidation catalysts by using the proper regeneration protocols.

Unregulated Emissions from Natural Gas Taxi Based on IVE Model

Emissions from motor vehicles have gained the attention of government agencies. To alleviate air pollution and reduce the petroleum demand from vehicles in China, the policy of “oil to gas” was vigorously carried out. Qingdao began to promote the use of natural gas vehicles (NGVs) in 2003. By the end of 2016, there were 9460 natural gas (NG) taxis in Qingdao, which accounted for 80% of the total taxis. An understanding of policy implementation for emission reductions is required. Experiments to obtain the taxi driving conditions and local parameters were investigated and an international vehicle emissions (IVE) localization model was established. Combined with vehicle mass analysis system (VMAS) experiments, the IVE localization model was amended and included the taxi pollutant emission factors. The result indicates that annual total carbon monoxide (CO) emissions from actual taxis are 6411.87 t, carbureted hydrogen (HC) emissions are 124.85 t, nitrogen oxide (NOx) emissions are 1397.44 t and particulate matter (PM) emissions are 8.9 t. When the taxis are running on pure natural gas, the annual emissions of CO, HC, NOx and PM are 4942.3 t, 48.15 t, 1496.01 t and 5.13 t, respectively. Unregulated emissions of annual total formaldehydes, benzene, acetaldehyde, 1,3-butadience emissions from an actual taxi are 65.99 t, 4.68 t, 1.04 t and 8.83 t. When the taxi is running on pure natural gas, the above unregulated emissions are 12.11 t, 1.27 t, 1.5 t and 0.02 t, respectively.

Environmental and health risks of VOCs in the longest inner–city tunnel in Xi’an, Northwest China: Implication of impact from new energy vehicles

Traffic source–dominated volatile organic compound (VOC) samples were collected during four time-intervals in a day (Ⅰ: 7:30–10:30, Ⅱ: 11:00–14:00, Ⅲ: 16:30–19:30, and Ⅳ: 20:00–23:00) in a tunnel in summer, 2019, in Xi’an, China. The total measured VOC (TVOC) in periods Ⅰ and Ⅲ (rush hours, 107.2 ± 8.2 parts per billion by volume [ppbv]) was 1.8 times that in periods Ⅱ and Ⅳ (non-rush hours, 58.6 ± 13.8 ppbv), consistent with the variation in vehicle numbers in the tunnel. The considerably elevated ethane and ethylbenzene levels could have been attributed to emissions from compressed natural gas vehicles and the rapid development of methanol-fueled taxis in Xi’an in 2019. The mixing ratios of benzene, toluene, ethylbenzene, and xylenes (BTEX) contributed 9.4%–12.7% to TVOCs, and the contributions were nearly 40% higher in periods Ⅰ and Ⅲ than in Ⅱ and Ⅳ, indicating that BTEX levels were strongly affected by vehicle emissions. The indicators of motor vehicle emission, namely ethylene, propylene, toluene, m/p-xylenes, o-xylene, and propane, contributed to more than half of the ozone formation potential in this study. The noncarcinogenic risks of VOCs in this study were within the international safety standard, whereas the carcinogenic risks exceeded the standard by 2.3–4.6 times, suggesting that carcinogenic risks were more serious than noncarcinogenic risks. VOCs presented 2.2 and 1.4 times noncarcinogenic and carcinogenic risks during rush hours than during non-rush hours, respectively. Notably, the carcinogenic risk in period Ⅳ was comparable with that in period Ⅲ; however, the vehicle numbers and VOC mixing ratios were the lowest at night, which may have attributed to the increasing number and proportion of methanol M100-fueled vehicles in the tunnel. Therefore, VOCs emitted by new energy vehicles should also be seriously considered while evaluating fossil fuel vehicle emissions.

Pd-Based Catalyst on Alumina with Perovskite (La0.67Fe0.83Cu0.17O3) to Reduce Ammonia Content in Natural Gas Exhaust

La0.67Fe0.83Cu0.17O3 with perovskite structure was prepared by sol–gel method, and 1.5 wt% Pd/Al2O3 was prepared by initial wet impregnation method. Pd/Al2O3 and perovskite prepared above were mixed by mechanical ball-milling with mass ratios of 10:1, 5:1 and 3:1, respectively, and represented by 10Pd/Al-La, 5Pd/Al-La and 3Pd/Al-La. Pd/Al refers to Pd/Al2O3 catalyst. In theoretical air–fuel ratio conditions ( $$\lambda$$ =1), the simulation of chemical metering of natural gas vehicle exhaust gas mixture on the catalysts were tested. The results showed that the perovskite could significantly reduce the ammonia formation in the exhaust gas. Moreover, the three-way catalytic performance of Pd/Al and 3Pd/Al-La were also tested in the feeds without water, CH4 or CO. The results demonstrated that the perovskite greatly reduced the ammonia content in the three exhaust gases. However, the ammonia content over bare Pd/Al was much higher in the presence of CO, and almost no ammonia was generated in the absence of CH4. The catalysts were also investigated by N2-physisorption, CO-chemisorption, XRD, EDX mapping and XPS techniques. The results showed that the perovskite may promote the reaction of NO and CO towards high N2 selection in the presence of CH4 and H2O, resulting in lower ammonia formation. Our work provided a new method for reducing ammonia formation over TWC catalysts for stoichiometric natural gas vehicles.

Assessment of Petrol and Natural Gas Vehicle Carbon Oxides Emissions in the Laboratory and On-Road Tests

The problem of global warming and the related climate change requires solutions to reduce greenhouse gas emissions, in particular CO2. As a result, newly manufactured cars consume less fuel and emit lower amounts of CO2. In terms of exhaust emissions and fuel consumption, old cars are significantly inferior to the more recent models. In Poland, for instance, the average age of passenger cars is approximately 13 years. Therefore, apart from developing new solutions in the cars produced today, it is important to focus on measures that enable the reduction in CO2 emissions in older vehicles. These methods include the adaptation of used cars to run on gaseous fuels. Natural gas is a hydrocarbon fuel that is particularly preferred in terms of CO2 emissions. The article presents the results of research of carbon oxides emission (CO, CO2) in the exhaust gas of a passenger car fueled by petrol and natural gas. The emissions were measured under the conditions of the New European Driving Cycle (NEDC) test and in real road tests. The test results confirm that compared to petrol, a CNG vehicle allows for a significant reduction in CO2 and CO emissions in a car that is several years old, especially in urban traffic conditions.