Cold Start Emissions Research Articles

Engine cold start analysis using naturalistic driving data: City level impacts on local pollutants emissions and energy consumption

The analysis of vehicle cold start emissions has become an issue of utmost importance since the cold phase occurs mainly in urban context, where most of the population lives. In this sense, this research work analyzes and quantifies the impacts of cold start in urban context using naturalistic driving data. Furthermore, an assessment of the influence of ambient temperature on the percentage of time spent on cold start was also performed.Regarding the impacts of ambient temperature on cold start duration, a higher percentage of time spent on cold start was found for lower ambient temperatures (80% of the time for 0°C and ~50% for 29°C). Results showed that, during cold start, energy consumption is >110% higher than during hot conditions while emissions are up to 910% higher. Moreover, a higher increase on both energy consumption and emissions was found for gasoline vehicles than for diesel vehicles. When assessing the impacts on a city perspective, results revealed that the impacts of cold start increase for more local streets.The main finding of this study is to provide evidence that a higher increase on emissions occurs on more local streets, where most of the population lives. This kind of knowledge is of particular relevance to urban planners in order to perform an informed definition of public policies and regulations to be implemented in the future, to achieve a cleaner and healthier urban environment.

Thermal management of newly developed non-noble metal-based catalytic converter to reduce cold start emissions of small internal combustion engine

ABSTRACTIn this study, thermal management of a newly developed non-noble metal-based catalytic converter, more suitable to smaller engines, has been investigated. Two different approaches are explored; first, use of phase change material (PCM) to keep the converter hot beyond light off temperature during shorter soak times and second, electrically heating up converter before or after engine cold start-up to reduce cold start emissions. The converter used had light off temperatures of 195 and 206°C for carbon monoxide and hydro carbons, respectively. Results showed that 1 kg of PCM was capable of keeping the converter hot beyond light off temperatures for a soak time of 2.5 h. Similarly, use of glow plugs also decreased the light off time of the converter to less than 2 min as compared to 13 min without thermal management measures.

An Isomorphously Substituted Fe-BEA Zeolite with High Fe Content: Facile Synthesis and Characterization.

An isomorphously substituted Al-free Fe-BEA zeolite with extremely high Fe content (~7 wt.%) was synthesized by a facile and industrially friendly method using an excess amount of NaOH. The obtained Fe-BEA zeolite was highly crystalline and showed a well-facetted bipyramidal morphology, similarly to beta zeolites synthesized in a fluoride medium. The chemical states of Fe in the above zeolite were investigated by diffuse reflectance ultraviolet-visible (UV-Vis) absorption spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, and X-ray absorption fine structure (XAFS) spectroscopy. The observed chemical states were similar to those of the Fe-BEA zeolite synthesized in the presence of fluoride (Fe-BEA-F). Considering the fact that more than 88% of the micropore volume of the calcined Fe-BEA zeolite was retained after hydrothermal treatment at 1000 °C for 5 h, and 53% of the tetrahedrally coordinated Fe3+ was retained after hydrothermal treatment at 700 °C for 20 h, the obtained Fe-BEA zeolite was concluded to be highly hydrothermally stable. The synthesized zeolite was evaluated in the selective catalytic reduction of NOx by ammonia (NH3-SCR), exhibiting greater catalytic activity than Fe-BEA-F throughout the reaction temperature range. Moreover, the potential of this catalyst as a hydrocarbon adsorbent for cold-start emission control was characterized by dynamic adsorption-desorption of toluene. Interestingly, only 66% of adsorbed toluene was desorbed from the Fe-BEA zeolite (cf. 96% for commercial beta zeolite), even though the gas stream did not contain oxygen, suggesting that hydrocarbon oxidation involved oxygen stored inside the Fe-BEA zeolite.

Comparison of real-world and certification emission rates for light duty gasoline vehicles

U.S. light duty vehicles are subject to the U.S. Environmental Protection Agency (EPA) emission standards. Emission compliance is determined by certification testing of selected emissions from representative vehicles on standard driving cycles using chassis dynamometers. Test results are also used in many emission inventories. The dynamometer based emission rates are adjusted to provide the certification levels (CL), which must be lower than the standards for compliance. Although standard driving cycles are based on specific observations of real-world driving, they are not necessarily real-world representative. A systematic comparison of the real-world emission rates of U.S. light duty gasoline vehicles (LDGVs) versus CL, and emission standards has not been previously reported. The purpose of this work is to compare regulatory limits (both CLs and emission standards) and the real-world emissions of LDGVs. The sensitivity of the comparisons to cold start emission was assessed.Portable Emission Measurement Systems (PEMS) were used to measure hot stabilized exhaust emissions of 122 LDGVs on a specified 110 mile test route. Cold start emissions were measured with PEMS for a selected vehicle sample of 32 vehicles. Emissions were measured for carbon dioxide (CO2), carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx). For each vehicle, a Vehicle Specific Power (VSP) modal emission rate model was developed. The VSP modal rates were weighted by the standard driving cycles and real-world driving cycles to estimate the respective cycle average emission rates (CAERs). Measured vehicles were matched with certification test vehicles for comparison. For systematic trends in comparison, vehicles were classified into four groups based on the Tier 1 and Tier 2 emission regulation, and the vehicle type such as passenger car and passenger truck.Depending on the cycle-pollutant and the vehicle groups, hot stabilized CAERs are on average either statistically significantly higher than or significantly not different from the CLs, with the exception of CO on the US06 cycle, for which real-world rates are lower than CLs. Compared to the emission standards, hot stabilized CAERs are on average significantly lower. However, comparisons of CAERs and standards are sensitive to cold start emissions. For some combinations of pollutants and vehicle groups, cold start inclusive CAERs are higher than the corresponding CLs and as high as the standards. The CLs, which are based on standard driving cycles, tend to underestimate real-world emission rates. Therefore, emission inventory estimates using certification test results are potentially underestimated.

Optimization of axial catalyst loading in transient-operated zone-structured monoliths: Reduction of cumulative emissions in automotive oxidation catalysts

A model based mathematical optimization methodology to optimize the precious metal loading profile (PGM loading) in zone-structured catalytic converters is developed. To carry out this task, a multi zone-structured optimization formulation, where the catalyst is divided into N zones axially to obtain a non uniform optimal PGM loading profile, which can be tested experimentally, is used. The effects of the PGM loading on washcoat diffusion limitations is also considered. The objective is to optimize the spatial distribution of loading for a fixed amount of precious metal to maximize the chemical conversion efficiency under transient operation. To achieve this, the transient 1D+1D model is solved with the help of implicit solver DASPKADJOINT and translated into a non-linear optimization problem that can be solved with any derivative based nonlinear programming (NLP) solvers. The model is applied to two example cases: CO oxidation on a Pt/Al2O3 based Diesel Oxidation Catalyst catalyst (minimizing cold-start emissions) and CH4 oxidation on Pd/Al2O3 (minimizing deactivation effects). In both the cases it was observed that the optimal solution with maximum PGM loading in the channel entrance region improved the performance of the catalysts. The methodology presented is generic and can be transferred to different systems with different chemistries, which may result in significantly different optimization results and loading patterns.

On-road measurement of NH3 emissions from gasoline and diesel passenger cars during real world driving conditions

NH3 is a precursor of PM2.5 which deteriorates urban air quality, affects human health and impacts the global radiation budget. Since vehicles are important sources of NH3 in urban areas, we have satisfactorily studied the possibility of measuring NH3 emissions from gasoline and SCR-equipped diesel light-duty vehicles during real driving on-road operation using a portable FTIR. The performance of the portable FTIR resulted to be comparable to that of a laboratory-based FTIR during a series of experiments performed in the Vehicle Emission Laboratory (VELA) using the World-harmonized Light-duty Test Cycle (WLTC). Higher on-road NH3 emission factors were obtained for the gasoline vehicle than for the diesel. High NOx emissions were measured from the diesel vehicle, indicating a low efficiency of the DeNOx system, SCR. On-road NH3 emission factors were ∼2 times lower than during the laboratory tests at 23 °C for both vehiclesNH3 emissions were not observed for the diesel vehicle during cold start operation. However, NH3 cold start emissions from the gasoline vehicle were up to 2 orders of magnitude higher than during the entire road trips, ranging from 45 to 134 mg km−1. Cold start emissions are of paramount importance as they commonly take place in urban areas. Hence, future urban reductions in PM2.5 might need to take into consideration the introduction of NH3 emissions limits for passenger cars.

NOx, NH3, N2O and PN real driving emissions from a Euro VI heavy-duty vehicle. Impact of regulatory on-road test conditions on emissions

Euro VI emission standards for heavy-duty vehicles (HDVs) introduced for the first time limits for solid particle number (PN) and NH3 emissions. EU regulation also includes a Portable Emissions Measurement System (PEMS) based test at type approval, followed by in-service conformity (ISC) testing. A comprehensive study on the real-time on-road emissions of NOx, NH3, N2O and PN from a Euro VI HDV equipped with a Diesel Oxidation Catalyst (DOC), a Diesel Particle Filter (DPF), a Selective Catalytic Reduction (SCR) system and an Ammonia Oxidation Catalyst (AMOX) is presented. Our analyses revealed that up to 85% of the NOx emissions measured during the tests performed are not taken into consideration if the boundary conditions for data exclusion set in the current legislation are applied. Moreover, it was found that the highest NOx emissions were measured during urban operation. Analyses show that a large fraction urban of operation is not considered when 20% power threshold as boundary condition is applied. They also show that cold start emissions account for a large fraction of the total NOx emitted. Low emissions of PN (2.8×1010 to 6.5×1010#/kWh) and NH3 (1.0 to 2.2ppm) were obtained during the on-road tests, suggesting effectiveness of the vehicle's after-treatment (DPF and AMOX). Finally, a comparison between speed-based (as currently defined by Euro VI legislation) and land-use-based (using Geographic Information System (GIS)) calculation of shares of operation was performed. Results suggest that using GIS to categorize the shares of operation could result in different interpretations depending on the criteria adopted for their definition.

Reactive Calcination Route for Synthesis of Highly Active NiCo2O4 Catalyst for Abatement of Cold-Start CO–HC Emissions from LPG Vehicles

An idea of an exotic route of reactive calcination (RC) of a precursor (co-precipitated basic carbonates of nickel and cobalt) for the synthesis of highly active NiCo2O4−δ spinel catalyst (Cat-R) for oxidation of CO and HCs emissions from LPG fueled vehicles is reported in the present paper. The route involved feed of a low concentration of chemically reactive 4.5% CO–air mixture over the precursor at low temperature of 433 K in the beginning and finally increased to 573 K. The precursor was also calcined around 573 K following two other methods: (1) conventionally in stagnant air (Cat-S) and (2) in flowing air (Cat-F) for comparative studies. The catalysts were characterized by XRD, N2 sorption techniques, TPR, SEMEDX and XPS. The formation of spinel structure is confirmed in all the catalysts. The activity measurement showed that total oxidation of lean mixture of CO–LPG occurred at the lowest temperature of 433 K over Cat-R in comparison to Cat-F (451 K) and Cat-S (458 K). The total combustion of the CO–LPG mixture at such low temperature of 433 K was never reported earlier. The remarkable activity of Cat-R over Cat-F and Cat-S in oxidation of CO–LPG mixture is due to the formation of partially reduced NiCo2O4−δ (Cat-R) oxygen deficient structure having the highest surface area smallest crystallites and highly dispersed homogeneous morphology when produced following the RC-route. The activity order of the catalysts produced by various calcination strategies for CO and LPG oxidation was as follows: RC > flowing-air > stagnant-air. Cat-R was also compared with noble metal and the catalytic activity order in the decreasing sequence was as follows: Cat-R > Cat-F > Cat-S > Cat-Pt. Stability test of the catalyst showed that the Cat-R has satisfactory catalytic stability. Thus the Cat-R is the most suitable for abatement of cold-start emissions of CO and HCs from LPG fuelled vehicles.

Numerical study of the diffusion of binary hydrocarbon blends in ZSM-12 zeolites

The experimental results for the simultaneous diffusion of toluene and ethylene in one dimensional channels of the ZSM-12 zeolite which have been reported in a previous publication are fitted with an original finite difference numerical simulation model. This system is mimicking the single file diffusion of hydrocarbons in the zeolite passive hydrocarbon trap installed at the exhaust of an internal combustion engine, prior to the catalytic muffler, to solve the hydrocarbon cold start emission problem. The study encompasses the effects of Na+, H+ and Ag+ counterions and temperature ramp on the temperature programmed desorption of the binary mixture. A simple lattice gas model is proposed to simulate the binary gas diffusion in a one dimensional pore lattice. Numerical simulations show that taking into account an Arrhenius dependence of the binary gas diffusion coefficient on temperature yielded a good fit of these experimental results, explaining many significant features of the temperature programmed desorption profile observed experimentally.

Exhaust gas treatment for reducing cold start emissions of a motorcycle engine fuelled with gasoline-ethanol blends

In countries like India, transportation by a two wheeled motorcycle is very common owing to affordable cost, easy handling and traffic congestion. Most of these bikes use single cylinder air cooled four-stroke spark ignition (SI) engines of displacement volume ranging from 100 cm3 to 250 cm3. CO and HC emissions from such engines when started after a minimum stop-time of 12 hours or more (cold-start emissions) are higher than warmed-up emissions. In the present study, a 150 cm3 single cylinder air cooled SI engine was tested for cold start emissions and exhaust gas temperature. Different gasoline-ethanol blends (E0 to E20) were used as fuel expecting better oxidation of HC and CO emissions with additional oxygen present in ethanol. The effect of glow plug assisted exhaust gas ignition (EGI) and use of catalytic converter on cold start emissions were studied separately using the same blends. Results show that with gasoline-ethanol blends, cold start CO and HC emissions were less than that with neat gasoline. And at an ambient temperature of 30±1°C, highest emission reductions were observed with E10. EGI without a catalytic converter had no significant effect on emissions except increasing the exhaust gas temperature. The catalytic converter was found to be active only after 120 seconds in converting cold start CO, HC and NOx. Use of a catalytic converter proves to be a better option than EGI in controlling cold start emissions with neat gasoline or gasoline-ethanol blends.

Analysis of upstream creeping reaction zones in catalytic monolith reactors

Monolith reactors are widely used in catalytic after-treatment systems (e.g. TWC, DOC, LNT and SCR). One major challenge in exhaust after-treatment is reducing cold-start emissions which account for a significant fraction of the total emissions. While front-end ignition is technically possible with high PGM loading and/or transient heating of the monolith, it may not be economical or feasible, especially for low exhaust gas temperature. In such cases, back-end ignition followed by a fast upstream creeping reaction zone provides a feasible way to reduce cold-start emissions. In this work, the upstream creeping reaction zone is investigated in detail using modeling approach. The influence of various design parameters (e.g. solid thermal conductivity and heat capacity) and operating conditions (gas velocity, inlet temperature/concentrations) on the creep velocity is determined and summarized. Phase diagrams and analytical criteria for reaction zones to creep upstream are also presented. The phase diagrams and criteria can provide guidance for design and control of reactors used in after-treatment systems.

Effects of CO on Pd/BEA Passive NOx Adsorbers

Cold-start emissions significantly contribute to total vehicular pollutant emission profiles. There has therefore been a significant amount of research focused on catalytic aftertreatment systems that can mitigate CO, hydrocarbon and NOx emissions at low temperatures. Recently, passive NOx adsorbers (PNAs) have been developed, and these can store or trap NOx at low temperature and are designed to release the trapped NOx at higher temperature ranges, where downstream NOx reduction catalysts are active. Pd/BEA is reported to be one such PNA. In this study its NOx storage at low temperatures and release at higher temperatures was characterized using temperature programmed (TP) experiments and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The influence of CO was investigated and was shown to improve the amount stored at low temperature and also induce higher temperature desorption, in a range that is applicable for downstream NOx reduction. Without the reductant, NOx release primarily occurred at temperatures too low to be practically relevant.

Intake air heating strategy to reduce cold-start emissions from diesel engines

ABSTRACTDiesel engine cold-start performance is influenced by the ambient temperature conditions, engine design, fuel, lubricant and engine operating conditions. This paper investigates the potential of air heating strategy in reducing the particulate emissions from the latest generation of turbocharged direct-injection diesel engines at very cold ambient temperature conditions. New European Driving Cycle (NEDC) tests were conducted at −7 °C ambient temperature conditions for the different intake air temperatures. Intake air heating reduced hydrocarbon emissions by 35 and 55% and nitrogen oxides emissions by 8 and 10% for intake air temperatures of 5 and 15 °C, respectively, during the cold-start phase of the emission driving cycle. The cold-start phase of the NEDC cycle accounted for 1/4 of the total particulates, and the use of intake air heating reduced its proportion to 1/5. More than 50% of the particulates are less than 23 nm in diameter for all the intake air temperature conditions, and the intake air heating reduced the particulate number concentration significantly. The surface area of accumulation mode particles was higher than that of the nucleation mode, and the total particle surface area decreased with the intake air heating.

Cold-Start Emission Reduction Potential and Limitations of Commercial Passive Hydrocarbon Adsorbers

Effective control of hydrocarbon (HC) emissions during cold start is critical to meeting more stringent future emission standards, and the passive HC adsorber is one possible technology to improve cold-start HC emission control. HC adsorbers for gasoline applications typically contain zeolite materials for HC storage and a noble metal-based three-way catalyst (TWC) for oxidation of stored HCs, both of which are susceptible to hydrothermal aging. In the present study, state-of-the-art HC adsorbers from two catalyst suppliers were evaluated for their cold-start HC emission reduction potential. After aging at 800 °C, the HC adsorbers tested provided reasonably high conversion efficiencies for aromatics and a moderate level of conversion for olefins but were not able to control paraffins to a significant degree. This resulted in a total HC conversion efficiency of 40–50% over the best HC adsorber for the simulated feed stream used in this study. The overall adsorber performance can be improved somewhat by increasing the noble metal loading or the O2 concentration in the feed stream and was found to be sensitive to adsorber volume (space velocity). After aging at 900 °C, however, none of the HC adsorbers tested was able to convert more than 10% of the HC in the feed.

Time Resolved Measurements of Speciated Tailpipe Emissions from Motor Vehicles: Trends with Emission Control Technology, Cold Start Effects, and Speciation.

Experiments were conducted at the California Air Resources Board Haagen-Smit Laboratory to understand changes in vehicle emissions in response to stricter emissions standards over the past 25 years. Measurements included a wide range of volatile organic compounds (VOCs) for a wide range of spark ignition gasoline vehicles meeting varying levels of emissions standards, including all certifications from Tier 0 up to Partial Zero Emission Vehicle. Standard gas chromatography (GC) and high performance liquid chromatography (HLPC) analyses were employed for drive-cycle phase emissions. A proton-transfer-reaction mass spectrometer measured time-resolved emissions for a wide range of VOCs. Cold-start emissions occur almost entirely in the first 30-60 s for newer vehicles. Cold-start emissions have compositions that are not significantly different across all vehicles tested and are markedly different from neat fuel. Hot-stabilized emissions have varying importance depending on species and may require a driving distance of 200 miles to equal the emissions from a single cold start. Average commute distances in the U.S. suggest the majority of in-use vehicles have emissions dominated by cold starts. The distribution of vehicle ages in the U.S. suggests that within several years only a few percent of vehicles will have significant driving emissions compared to cold-start emissions.

Characterizing particulate matter emissions from GDI and PFI vehicles under transient and cold start conditions

Ultrafine particle emissions from Gasoline Direct Injection (GDI) and Port Fuel Injection (PFI) vehicles under the New European Driving Cycle (NEDC) were measured by using the Differential Mobility Spectrometer 500 (DMS 500) for size distribution information and Transmission Electronic Microscopy (TEM) for morphological analysis. The first phase of the ECE 15 cycle (representing the urban driving condition) within the NEDC was examined to evaluate the cold start effect on particulate matter (PM) emissions. Even though the ECE 15 cycle1 only occupies 1/6th of the time of the NEDC, the cold start emissions accounted for more than 50% of the total particle number for GDI vehicles and approximately 70% for PFI vehicles. Further analysis in terms of the Count Medium Diameter (CMD) of the PM emissions is also discussed. A linear regression method was adopted to analyze the correlation between PM emissions and vehicle parameters. For GDI vehicles, acceleration demonstrated a strong correlation with PM emissions, particularly under warm start conditions. The effects of the after treatment device Three Way Catalyst (TWC) on PM emissions was also investigated.

Investigation of cold-start emission control strategy for a bi-fuel hydrogen/gasoline engine

For spark-ignited gasoline engine, cold start emission of hydrocarbon (HC) and carbon monoxide (CO) is a long-term concern due to a large portion of HC and CO emitted during cold start period. Starting by hydrogen or adding a fraction of hydrogen can greatly reduce the engine cold start emissions of HC and CO due to the carbonless and excellent combustion characteristics of hydrogen. However, the higher combustion speed and temperature of hydrogen tend to cause more NOx emissions. Therefore the amount of hydrogen addition to conventional fuel should be optimized at different engine operating conditions. In this paper, a spark ignited gasoline engine was retrofitted to a hydrogen gasoline flexible fuel engine by adding a set of hydrogen injection system, and the engine can be fueled with gasoline, hydrogen or both. An electronic control system was developed and applied to control the injection timings and durations of hydrogen and gasoline. In order to reduce cold start emissions of HC and CO, the engine started with hydrogen and then changed to run on gasoline with hydrogen addition or on pure gasoline to avoid high NOx generation. The basic composition of the control system was introduced and the cold-start emission control strategy for the hydrogen gasoline flexible fuel engine was investigated. And finally the emission of the vehicle running on the hybrid hydrogen and gasoline fuel mode was tested over the New European Driving Cycle (NEDC), and compared with that of the original gasoline car. The experimental results showed that the cold start emissions of HC and CO greatly decreased when the vehicle engine operating on hybrid hydrogen gasoline mode.

Experimental Analysis of Telescopic Catalytic Converter in a Petrol Engine to Reduce Cold Start Emission

Control of harmful emissions during cold start of the engine has become a challenging task over the years due to the ever increasing stringent emission norms. Positioning of the catalytic converter closer to the exhaust manifold is an efficient way of achieving rapid light-off temperature. On the other hand, the resulting higher thermal loading under high-load engine operation may substantially cause thermal degradation and accelerate catalyst ageing. The objective of the present work is to reduce the light-off time of the catalyst and at the same time to reduce the thermal degradation and ageing of the catalyst to the minimum possible extent. In the present work two innovative approaches namely Parallel Catalytic Converter System (PCCS) and Telescopic Catalytic Converter System (TCCS) have been adopted to reduce the light-off time of the catalyst. The tests were conducted on a 4 cylinder Spark Ignition Engine under cold start condition. It was established that considerable reduction in the light-off time was achieved by using TCCS. Further reduction in the light-off time was achieved by using pre catalysts (40%vol. & 20%vol.) and hot air injection. It has been found that 13% reduction in CO light-off time was achieved with pre-catalyst (40%vol.), 50% reduction with pre-catalyst (20%vol.) and 66% reduction with hot air injector system, when compared to TCCS. Also 14% reduction in HC light-off time was achieved with pre-catalyst (40%vol.), 43% reduction with pre-catalyst (20%vol.) and 63% reduction with hot air injection system, when compared to TCCS. It was also established that light-off time of TCCS can be brought down to 10 seconds using hot air injection.

Effect of ethanol–gasoline blends on CO and HC emissions in last generation SI engines within the cold-start transient: An experimental investigation

Urban areas in developed countries are characterized by an increasing decline in air quality state mainly due to the exhaust emissions from vehicles. Besides, due to catalyst improvements and electronic mixture control of last generation engines, nowadays CO and HC cold start extra-emissions are heavily higher than emissions exhausted in hot conditions, with a clear consequence on air quality of the urban contexts. Ethanol combined with gasoline can be widely used as an alternative fuel due to the benefit of its high octane number and its self-sustaining characteristics. Ethanol, in fact, is well known as potential alcohol alternative fuel for SI engines, since it can be blended with gasoline to increase oxygen content, then decreasing CO and HC emissions and the depletion of fossil fuels.Literature data about cold emissive behaviour of SI engines powered with ethanol/gasoline blended fuels are rather limited. For this reason, the aim of this study is to experimentally investigate the effect of ethanol/gasoline blends on CO and HC cold start emissions of four-stroke SI engines: a last generation motorcycle was operated on the chassis dynamometer for exhaust emission measurements without change to the engine design, while the ethanol was mixed with unleaded gasoline in different percentages (10, 20 and 30vol.%). Results of the experimental tests and the application of a new calculation procedure, designed and optimised to model the cold transient behaviour of SI engines using different ethanol–gasoline blends, indicate that CO and HC cold start emissions decrease compared to the use of commercial gasoline, with the 20% v/v ethanol blend achieving the highest emission reduction. Moreover, in this paper a review of the recent scientific literatures was performed on the emissive behaviour of SI engines fuelled with ethanol–gasoline blended fuels.

Effect of Diverse Hydrocarbons on the Cold Start Behavior of Three-Way Catalysts

A new experimental setup is introduced, enabling a preheated exhaust gas mixture to abruptly heat up an initially cold monolith catalyst and, thus, reproduce transient catalyst light-off behavior. With this setup, cold start experiments have been carried out on an aged monolithic Pd three-way catalyst (TWC). This study aims at systematically investigating the effect of diverse hydrocarbons, including methane, acetylene, ethene, ethanol, acetaldehyde, propane, propene, toluene, and xylene in TWC exhaust. It was shown that the commonly used model components propane and propene do not represent the behavior of aromatics and other hydrocarbons present in a typical TWC exhaust very well, since they do not account for their variability in inhibition strength and reactivity. Among the studied hydrocarbons, acetylene proved to be the strongest inhibitor; even at low concentrations of 70 ppm (a typical value found in TWC exhaust), acetylene inhibition increases CO cold-start emissions by 40 %. Furthermore, aromatic and liquid hydrocarbon species (like ethanol) first condense on the initially cold catalyst surface and evaporate again as the catalyst heats up, resulting in a desorption peak at the catalyst outlet.