The optimal formulation of gasoline fuel for spark ignition engines, to guarantee the best performances and minimal pollutant emissions, has always been one of the relevant challenges in the long history of this wellestablished technology 1. Due to the increase of the economic activities and the wider use of vehicles especially in developing countries, the demand for transport fuels is increasing. On the other hand, stricter rules for the control of both pollutant and climatealtering emissions induce to improve the conventional fuel performance and to use alternative fuels in conventional internal combustion engines. Automotive manufacturers have centered their engine calibrations and designs on meeting greenhouse gas (GHG) emissions targets using all available combinations of enginetechnologies and fuelblends. The modeling results performed by Han et al. 2, suggest that refineries that process relatively heavier crude inputs have higher yields of heavy products, lower energy efficiencies and higher greenhouse emissions than refineries that run lighter crudes. Mexicos refining system operates to process light crude, but now needs to adapt to heavier oil as lighter deposits decrease steadily. In the first’s months of 2019, Mexico imported 676,600 barrels per day of gasoline representing about 70% of the fuel sold in the country 3. Moreover, last year a new gasoline standard raises the ethanol blend wall from 5.8% to 10% volume, in an effort to stimulate a growth in domestic production. It will exclude the use of ethanol in ozone nonattainments areas, where the use of reformulated gasoline (RFG) is mandated. RFG requires containing a minimum of 2.0% by weight oxygen that in Mexico is achieved by adding methyl tertbutyl ether, now banned in 25 states of USA due to concerns about groundwater contamination 4,5. As the efficiency of engines increases with the engine’s compression ratio 6, which demands a fuel with high octane number, the use of ethanol improves combustion and overall engine operation under partload conditions 7, and under knocklimited higher load conditions 8. In the United States the vast majority of the fuelgrade EtOH is blended into gasoline at 10 vol.% (volume %), also known as E10, and represents over 95% of the domestic gasoline market 9. The United States Environmental Protection Agency (USEPA) issued a partial waiver to allow the use of up to 15% EtOH in gasoline (E15) for vehicles model year 2001 and newer, however, denied the waiver for E15 use in all heavyduty gasoline engines and vehicles, motorcycles, and nonroad engine vehicles 10. Future blending options for EtOH in gasoline include continuation of lowlevel blends (E0–E15), greater use of E85 in flexible fuel vehicles (FFVs), or new use of midlevel blends (E20–E40) in FFVs, or in new vehicles designed with midlevel blendcapability 11. Clearly, there are many considerations for determining the best future fuel strategy, including the context of the current modern naturally aspirated SI (spark ignition) vehicle fleet, which must operate effectively and efficiently on the E15 blend without major modifications 12. Ethanol have a higher heat of vaporization and octane number than typical gasoline this aspect makes the temperature of the intake manifold lower, which increases airfuel mixture density, therefore increasing the engine’s volumetric efficiency 13,14. Unfortunately, EtOH exhibits some negative attributes, such as significantly lower energy content, hygroscopic behavior and chemical toxicity. Moreover, addition of EtOH to gasoline also comes with some challenges, potentially increasing (or decreasing) Reid vapor pressure (RVP), and altering distillation properties 15. To produce gasolineethanol blends, ethanol is mixed with a hydrocarbon blendstock for oxygenate blending also known as a “BOB”. The BOB is used to produce reformulated gasoline after blending with ethanol (commonly known as an RBOB or may produce conventional oxygenated gasoline (CBOB) to be sold outside of areas requiring reformulated gasoline. Refineries reduce the octane of the BOB, lowering the aromatic content, to take advantage of the highoctane blend characteristics of ethanol. Oxygenates like ethanol are not allowed in product pipelines because of corrosion problems; they are therefore typically added at product terminals. Consequently, refineries typically blend neat RBOB, and CBOB, without EtOH 16. Several studies have been carried out, to understand how different compounds or a different percentage of typical hydrocarbon families (olefins, aromatics, etc.) can improve the knock resistance for SI engine applications using EtOH free gasoline 17,18. The socalled ethanol boost effect on the final blended gasoline’s properties is both recipedependent and nonlinear because the addition of EtOH to a BOB changes various fuel qualities including the octane, vapor pressure and density. The ratio of olefins to aromatics used in the neat blendstock significantly determines the final product 17. Schifter et al. 19 investigated the combustion and emissions using four ethanol–gasoline blends ranging from 10% to 85% volume, and performance was compared with two Tier I vehicles in a chassis dynamometer. An increase in total hydrocarbon emissions and a decrease in benzene, toluene, xylenes and ethylbenzene compounds (BTEX) was detected as the ethanol in the fuel increased. The engine could be started stably up to E45. However, for E85 the engine idling became unstable making impossible the reduction reactions that are necessary for NOx emission control in the catalytic converter 19. Shen et al. 20 studied effects of hydrocarbon compositions on raw exhaust emissions and combustion processes on an engine test bench. As olefins increased from 10% to 25% in volume, the combustion duration was shortened, and hydrocarbons emission reduced by about 15%. Moreover, as aromatics changed from 35% to 45%, the engineout nitrogen oxides (NOx) emissions increased by 4%. Karavalakis et al. tested with 15%, 25% and 35% aromatics by volume on a fleet of light duty vehicles, and found increases in carbon monoxide (CO), total hydrocarbons (THC) and particulate matter mass, with increasing aromatics content. Changes in fuel composition had no effect on the emissions NOx, formaldehyde, or acetaldehyde 21. Zhu et al. 22 evaluate the effects of aromatic, olefin contents and T50 (temperature for 50% volume D86 distillation) tailpipe emissions from gasoline direct injection, and found that changing aromatic and olefin contents had relatively small impacts on fuel consumption. Compared with olefins and T90, the regulated gaseous emissions were impacted more by aromatics and T50 saw the opposite results in a different study where lower aromatics in gasoline caused increased nonmethane hydrocarbons and CO emissions, but reduced NOx emissions 22. Yang et al. 23 study the impacts of varying aromatic (20 and 30%) and EtOH levels (from 0% to 20%) on direct injection exhaust emissions of five 2016–7 model year vehicles, and found that total aromatics played an important role in the emissions. Increasing EtOH led to significant reductions in CO but neither aromatics nor ethanol showed effect in NOx emissions. Currently, a source of uncertainty in Mexico is how the increased demand of gasoline by the transport sector will be satisfied, taking into consideration the deficit in domestic production. Additional imports of fuel would certainly be required; therefore increasing in the future the ethanol content to E15 in gasoline could provide greatest benefits 24. In this work, we report the effects of varying aromatic, olefins in gasoline blends with and without ethanol added, on regulated and toxic tailpipe emissions of four recent models vehicles tested on a chassis dynamometer.
Fuel 265 (2020) 116950 Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel Full Length Article Influence of gasoline olefin and aromatic content on exhaust emissions of 15% ethanol blends T ⁎ I Schifter , L Díaz, G Sánchez-Reyna, C González-Macías, U González, R Rodríguez Instituto Mexicano del Petróleo, Eje Central Lázaro Cárdenas No 152, San Bartolo Atepehuacan, México, D.F 07730, Mexico G R A P H I C A L A B S T R A C T A R T I C LE I N FO A B S T R A C T Keywords: Gasoline aromatics and olefins Ethanol blends Vehicles Tailpipe emissions Ozone formation This research focused on the determination of relationships between aromatic and olefins in fuels with constant concentration of ethanol compared with blends without the oxygenate compound Nine fuels were used for testing prepared by match blending, four of them were non-oxygenate with high and low levels of aromatics and olefins, another four were fuels with 15% volume of ethanol and similar levels of aromatic and olefins The ninth fuel was oxygenated with 7% volume ethanol to monitor differences in vehicle performance This study evaluated the tailpipe emissions of four-model year 2017–2018 light-duty gasoline vehicles subjected to the EPA protocol related to FTP-75 During cold start period CO contribution to emissions increase in the ethanol blends, being greater with the low olefins blends, while, NOx emissions are reduced in the low aromatic fuels without ethanol compared with the high aromatic blends Principal components analysis was used to investigate the relationship between formulated fuels Non-oxygenated fuels with high aromatic and olefin content shows higher values of the ozone formation The aromatic content is positively related with hydrocarbons and CO2 emissions Additionally the aromatic content is related with 3-methylpentane and the BTEX compounds NOx emissions are related with ethanol content, but inversely associated with the carbon fraction of fuels ⁎ Corresponding author E-mail address: ishifter@imp.mx (I Schifter) https://doi.org/10.1016/j.fuel.2019.116950 Received 11 August 2019; Received in revised form 11 December 2019; Accepted 22 December 2019 0016-2361/ © 2019 Elsevier Ltd All rights reserved Fuel 265 (2020) 116950 I Schifter, et al Introduction oxygenated gasoline (CBOB) to be sold outside of areas requiring reformulated gasoline Refineries reduce the octane of the BOB, lowering the aromatic content, to take advantage of the high-octane blend characteristics of ethanol Oxygenates like ethanol are not allowed in product pipelines because of corrosion problems; they are therefore typically added at product terminals Consequently, refineries typically blend neat RBOB, and CBOB, without EtOH [16] Several studies have been carried out, to understand how different compounds or a different percentage of typical hydrocarbon families (olefins, aromatics, etc.) can improve the knock resistance for SI engine applications using EtOH free gasoline [17,18] The so-called ethanol boost effect on the final blended gasoline’s properties is both recipe-dependent and non-linear because the addition of EtOH to a BOB changes various fuel qualities including the octane, vapor pressure and density The ratio of olefins to aromatics used in the neat blendstock significantly determines the final product [17] Schifter et al [19] investigated the combustion and emissions using four ethanol–gasoline blends ranging from 10% to 85% volume, and performance was compared with two Tier I vehicles in a chassis dynamometer An increase in total hydrocarbon emissions and a decrease in benzene, toluene, xylenes and ethylbenzene compounds (BTEX) was detected as the ethanol in the fuel increased The engine could be started stably up to E45 However, for E85 the engine idling became unstable making impossible the reduction reactions that are necessary for NOx emission control in the catalytic converter [19] Shen et al [20] studied effects of hydrocarbon compositions on raw exhaust emissions and combustion processes on an engine test bench As olefins increased from 10% to 25% in volume, the combustion duration was shortened, and hydrocarbons emission reduced by about 15% Moreover, as aromatics changed from 35% to 45%, the engine-out nitrogen oxides (NOx) emissions increased by 4% Karavalakis et al tested with 15%, 25% and 35% aromatics by volume on a fleet of light duty vehicles, and found increases in carbon monoxide (CO), total hydrocarbons (THC) and particulate matter mass, with increasing aromatics content Changes in fuel composition had no effect on the emissions NOx, formaldehyde, or acetaldehyde [21] Zhu et al [22] evaluate the effects of aromatic, olefin contents and T50 (temperature for 50% volume D-86 distillation) tailpipe emissions from gasoline direct injection, and found that changing aromatic and olefin contents had relatively small impacts on fuel consumption Compared with olefins and T90, the regulated gaseous emissions were impacted more by aromatics and T50 saw the opposite results in a different study where lower aromatics in gasoline caused increased non-methane hydrocarbons and CO emissions, but reduced NOx emissions [22] Yang et al [23] study the impacts of varying aromatic (20 and 30%) and EtOH levels (from 0% to 20%) on direct injection exhaust emissions of five 2016–7 model year vehicles, and found that total aromatics played an important role in the emissions Increasing EtOH led to significant reductions in CO but neither aromatics nor ethanol showed effect in NOx emissions Currently, a source of uncertainty in Mexico is how the increased demand of gasoline by the transport sector will be satisfied, taking into consideration the deficit in domestic production Additional imports of fuel would certainly be required; therefore increasing in the future the ethanol content to E15 in gasoline could provide greatest benefits [24] In this work, we report the effects of varying aromatic, olefins in gasoline blends with and without ethanol added, on regulated and toxic tailpipe emissions of four recent models vehicles tested on a chassis dynamometer Four fuels were prepared with and without ethanol (15% volume) with nominal aromatics content of 16% and 36% volume, and olefins content ranging from 3.6% to 14.8% volume all of them by the match blending technique When the match blending technique is used, the The optimal formulation of gasoline fuel for spark ignition engines, to guarantee the best performances and minimal pollutant emissions, has always been one of the relevant challenges in the long history of this well-established technology [1] Due to the increase of the economic activities and the wider use of vehicles especially in developing countries, the demand for transport fuels is increasing On the other hand, stricter rules for the control of both pollutant and climate-altering emissions induce to improve the conventional fuel performance and to use alternative fuels in conventional internal combustion engines Automotive manufacturers have centered their engine calibrations and designs on meeting greenhouse gas (GHG) emissions targets using all available combinations of engine-technologies and fuel-blends The modeling results performed by Han et al [2], suggest that refineries that process relatively heavier crude inputs have higher yields of heavy products, lower energy efficiencies and higher greenhouse emissions than refineries that run lighter crudes Mexico's refining system operates to process light crude, but now needs to adapt to heavier oil as lighter deposits decrease steadily In the first’s months of 2019, Mexico imported 676,600 barrels per day of gasoline representing about 70% of the fuel sold in the country [3] Moreover, last year a new gasoline standard raises the ethanol blend wall from 5.8% to 10% volume, in an effort to stimulate a growth in domestic production It will exclude the use of ethanol in ozone nonattainments areas, where the use of reformulated gasoline (RFG) is mandated RFG requires containing a minimum of 2.0% by weight oxygen that in Mexico is achieved by adding methyl tert-butyl ether, now banned in 25 states of USA due to concerns about groundwater contamination [4,5] As the efficiency of engines increases with the engine’s compression ratio [6], which demands a fuel with high octane number, the use of ethanol improves combustion and overall engine operation under partload conditions [7], and under knock-limited higher load conditions [8] In the United States the vast majority of the fuel-grade EtOH is blended into gasoline at 10 vol.% (volume %), also known as E10, and represents over 95% of the domestic gasoline market [9] The United States Environmental Protection Agency (USEPA) issued a partial waiver to allow the use of up to 15% EtOH in gasoline (E15) for vehicles model year 2001 and newer, however, denied the waiver for E15 use in all heavy-duty gasoline engines and vehicles, motorcycles, and nonroad engine vehicles [10] Future blending options for EtOH in gasoline include continuation of low-level blends (E0–E15), greater use of E85 in flexible fuel vehicles (FFVs), or new use of midlevel blends (E20–E40) in FFVs, or in new vehicles designed with midlevel blend-capability [11] Clearly, there are many considerations for determining the best future fuel strategy, including the context of the current modern naturally aspirated SI (spark ignition) vehicle fleet, which must operate effectively and efficiently on the E15 blend without major modifications [12] Ethanol have a higher heat of vaporization and octane number than typical gasoline this aspect makes the temperature of the intake manifold lower, which increases air-fuel mixture density, therefore increasing the engine’s volumetric efficiency [13,14] Unfortunately, EtOH exhibits some negative attributes, such as significantly lower energy content, hygroscopic behavior and chemical toxicity Moreover, addition of EtOH to gasoline also comes with some challenges, potentially increasing (or decreasing) Reid vapor pressure (RVP), and altering distillation properties [15] To produce gasoline/ethanol blends, ethanol is mixed with a hydrocarbon blendstock for oxygenate blending also known as a “BOB” The BOB is used to produce reformulated gasoline after blending with ethanol (commonly known as an RBOB or may produce conventional Fuel 265 (2020) 116950 I Schifter, et al Table Properties of test fuels Property F1 F2 F3 F4 FE5 FE6 FE7 FE8 REF Aromatics, vol % Olefins, vol % Paraffins, vol % Isoparaffins, vol % Naphtenes, vol % Ethanol, vol % RVP, psi Distillation (°C) Distillation 50% (°C) Distillation 90% (°C) Motor Octane Number Research Octane Number Octane Rating (AKI) Carbon Fraction Sensitivity AFR Stoich HoV, kJ/kg LHV (kJ/kg) HoV/LHV 17.03 4.70 11.71 62.04 4.05 7.38 16.25 14.83 12.59 50.92 3.97 10.46 36.46 3.67 15.63 39.62 4.27 7.69 31.31 11.32 14.09 38.71 3.21 10.18 19.37 4.08 15.31 39.25 6.11 15.21 7.07 16.7 7.77 13.68 41.04 5.26 14.73 10.11 32.77 2.32 15.25 29.11 4.71 15.24 7.72 31.47 5.57 13.04 30.64 3.02 15.55 9.78 25.78 5.65 12.95 43.91 4.63 6.57 8.62 105.9 167.5 83.2 90.1 86.7 0.8598 6.9 14.9 328.4 43.82 7.470 77.4 158.0 83.0 90.8 86.9 0.8549 7.8 14.7 327.7 42.73 9.425 110.4 170.6 82.0 90.3 86.2 0.8679 8.3 15.0 358.1 43.26 7.577 96.4 167.9 82.0 91.7 86.8 0.8654 9.7 14.7 349.0 43.03 8.986 91.5 161.8 83.4 91.7 87.6 0.7943 8.3 13.3 396.6 40.65 8.833 69.2 161.2 83.2 92.6 87.9 0.8026 9.4 13.5 381.3 41.1 9.804 108.6 167.1 82.5 92.5 87.5 0.8144 10.0 13.5 405.7 40.43 9.965 74.2 163.1 85.3 96.6 91 0.8115 11.3 13.5 403.5 40.91 8.530 106.3 168.6 83.2 91.6 87.4 0.8383 8.4 14.4 365.3 42.48 8.578 High aromatics, high olefins blends, no EtOH (F4); EtOH (FE8) High aromatics, low olefins blends, no EtOH (F3); EtOH (FE7) Low aromatics, high olefins blends, no EtOH (F2); EtOH (FE6) Low aromatics, low olefins blends, no EtOH (F1); EtOH (FE5) gasoline fuel is altered such that the finished blend matches target values for one or more fuel properties prepared fuels Additionally a reference fuel containing approximately 6.5% volume ethanol was prepared Tailpipe emissions were studied on four-model year 2017–2018 vehicles subjected to the EPA protocol related to FTP-75, and the weighted exhaust hydrocarbon emissions were used to estimate their potential to form ozone ratio and carbureted for the determination of Octane Number Both indexes were designed to be representative of the most mild (RON) and severe (MON) operating conditions encountered in SI engines In both tests, the highly reactive n-heptane and highly stable isooctane were used as surrogate fuels, spanning the octane scale from zero to 100 The air-to-fuel ratios were calculated as described by Pearson et al [27], while the latent heat of vaporization (HoV) of individual compounds was calculated using the equation described by Chupka et al [14] following the method proposed by Reid et al [28] As described by Yawns [29] the predicted HoV values of individual compounds were multiplied by the % mole of each component, and then totalized The value was divided by the total mole percent of the sample (after removal of the minor components), and then, divided by the average molecular weight of the fuel Materials and methods 2.1 Test fuels Table shows physical and chemical properties of the formulated blends prepared with refinery streams, and analyzed following American Society for Testing Materials (ASTM) procedures [25] As shown in Table 1, two blends (F4 and F3 contains high aromatics and high and low olefins, respectively, while fuels F1 and F2 contains low aromatics and low and high olefins, respectively, all of them with no ethanol added The cut point criteria for high-low olefins was stablished in accordance with Fuel Trends Report: Gasoline 1995–2005 published by EPA for summer gasoline as the lowest value no mattering the District In a similar way, another two blends with EtOH (FE8 and FE7) contains high aromatics and high and low olefins, respectively, while fuels FE6 and FE5 contains low aromatics and high and low olefins, respectively Moreover, a fuel denoted FR was used as reference containing 6.5% volume EtOH Ethanol (Sigma-Aldrich, México, 99.5%), complies with the ASTM D-4806-08 standards [26] Form the six vapor pressure/distillation classes of gasoline contempt USA named AA, A, B, C, D, and E AA is the least volatile while E is the most volatile For the test fuels, AA volatility class was selected in order to reflect fuel volatility EPA regulations The fuels were stored in a temperature-controlled facility, and separate fuel pumps employed to avoid any possibility of cross contamination between fuels A Cooperative Fuels Research Engine (Waukesha Engine Division, Model CFR F-1) determined the Research Octane Number (RON) and the Motor Octane Number (MON) of the fuels The test engine was a standardized single cylinder, four-stroke cycle, variable compression 2.2 Test vehicles Potential test vehicles received an incoming inspection upon arrival at the laboratory The inspection documents and the physical condition of the vehicle was used to determine if it is safe to test Four-passenger light duty gasoline vehicles from 2017 to 2018 model years were selected to represent a subset of technologies and range of emissions from the previous study [19] A summary of each vehicle and their technologies is shown in Table Vehicle odometer readings ranged in the order of 22,000 km, and complied with federal emissions requirements for Tier I federal certification level Each vehicle received a chassis road-load derivation using the EPA Test Car database to select the inertia weight and roadload coefficients In order to minimize fuel carryover effects, the vehicle fuel preconditioning procedure incorporated multiple drains and fills to ensure complete changeover of the fuel and to minimize or eliminate carryover effects between the test fuels [30] 2.3 Dynamometer emissions testing The experiments were performed in our facilities on a standardized dynamometer system (Horiba) in which the selected vehicles were tested at least twice on the chassis dynamometer operating over the Fuel 265 (2020) 116950 I Schifter, et al Table Test vehicles Model year Maker Model Displacement (L) HP Specific power (Hp/L) Cylinders Fuel Supply Transmission Odometer (km) 2017 2018 2018 2017 Chevrolet VW Dodge Toyota Aveo Vento Pick up RAM Matrix 1.6 1.6 3.7 1.8 103 105 213 130 64 66 58 72 4 MPFI* MPFI MPFI MPFI Standard Automatic Standard Standard 25,466 26,946 25,813 21,603 * MPFI multi-port fuel injected 2.4 Cold start emissions Federal Test Procedure FTP-75 Urban Dynamometer Driving Schedule [30], which is the emission certification cycle for new light-duty vehicles in México The vehicles operated on a Horiba-ECDM-48 single-roll electric dynamometer coupled to a constant-volume sampler unit (Horiba CVS45) Total hydrocarbons, CO, NOx, and carbon dioxide (CO2) concentrations were measured using a Horiba MEXA-9200D gas analyzer system The test is divided in three phases: The cold-start phase lasting 505 s, a hot transient operating phase lasting 864 s, and a hot start period lasting 505 s that repeats the driving pattern of phase but starts with the warmed-up engine During a 10-min cool-down, between the second and third phases, the engine is turned off Additionally, fuel consumption calculations based on the FTP-75 test method required the knowledge of fuel composition in terms of C/H/O elemental content Exhaust samples, taken at the end of each individual phase as well as the end of the entire cycle of the FTP-75, were analyzed for CO, THC, NOx and CO2 by auto-monitors (HORIBA MEXA-9200) Emissions levels of late model year vehicles are low and difficult to measure, and studies have used very high difference criteria between two repeat runs to initiate an additional test The criterion to determine whether a repeat-test was necessary was performed when FTP-75 emissions ratio between the larger value divided by the smaller value, was greater than 1.17 for THC, 1.33 for CO, and 1.40 for NOx The overall test result, expressed in mg/km, was calculated using USEPA-defined weighting factors (0.43, 1.0, and 0.57, respectively) applied to the emissions collected in each bag To determine the fuel mass supplying for vehicle, a Fuel Balance AVL 733S that is based on the gravimetrical method was used Total hydrocarbons were analyzed by a Rosemount heated 248 FID (Horiba FIA-120) CO and CO2 by NDIR using Horiba AIA-120 instruments, and NOx by a chemiluminescence detector using a Rosemount Horiba CLA Hydrocarbons from exhaust emissions of each cycle of the test were sampled according to the methodology described in [25] In the present case, samples were first concentrated in Entech 7100A 3-Stage equipment and later identified using two Agilent 6890 N FID chromatographs, one equipped with a methyl-phenyl silicone column and the other with a Plot/Q column to analyze C1-C2 hydrocarbons Carbonyl emissions were collected in Bags 1, 2, and of the FTP A small amount of diluted exhaust gas was diverted through a Horiba collection system to trap aldehydes and ketones in silica gel cartridges, with 2,4-dinitrophenylhydrazine (Waters Corp USA) as the derivative reagent, and subsequent extraction with acetonitrile After the extracts were analyzed on an Agilent Hewlett Packard1100 gas chromatograph equipped with an ultraviolet–visible detector following the methodology described by Siegl et al [31] In accordance with cartridges manufacturer, collection efficiency is higher than 95% when the sampling flow is up to L/min Each carbonyl compound was quantified by its liquid standard calibration curve (Supelco) The r2 of the carbonyl calibration curves was higher than 0.9999; standard deviation was less than 5%; the accuracy ranged from 100 ± 2% to 103 ± 1%, and the method detection limit ranged from 6.46 μg/m3 (acetone) to 222 μg/m3 (2,5-dimethylbenzene- aldehyde) Environmental planning uses emission factor models to calculate vehicle emissions based on their behavior at normal operating temperatures The temporary ineffectiveness of motor vehicle emission controls at startup causes emission rates to be much higher for a short period after starting than during fully warmed, or stabilized, vehicle operation [32] As described in other studies [33,34], the absolute excess cold start emissions is defined as the additional emission value obtained under cold conditions compared to the emission value that could have been recorded for the same period (cycle) under hot conditions The methodology to estimate cold start emissions is based on bag data, e.g the mass difference of the phase I and phase III emissions from the FTP-75 driving cycle is taken as a measure for the cold start emission 2.5 Ozone forming potential (OFP) The data of the weighted exhaust hydrocarbon emissions were used to estimate their potential to form ozone According to Carter [35], the Maximal Incremental Reactivity (MIR) scale represents a dimensionless coefficient that indicates how much the compound may contribute to ozone formation in the air mass Ozone forming potential for a specific fuel was computed first by incorporating the MIR values expressed as grams of ozone per gram of the constituent measured in the exhaust from a particular fuel Each compound was assigned a MIR value, which was multiplied by the mass of that compound to yield potential mass of ozone formed calculated in units of mass of ozone per kilometer traveled 2.6 Statistical analysis The database, consisting of fuel properties and gaseous exhaust emissions, was constructed with average values of the repeated tests of each vehicle and fuel combination The calculations of descriptive statistics and multivariate methods were run using the STATISTICA software For the Factor Analysis (FA) technique, a logarithmic transformation was applied prior running the analysis, since the variables are measured in different units This is a multivariate technique widely used for detecting structure and associations among variables in large databases; also, it is possible to identify variables that have no significant effect on the study, thus they can be excluded without losing information, making it suitable for our purposes [36] The FA was run using the principal component method of extraction and the varimax rotation factor for the final solution The number of factors to retain for further interpretation was based on the screen plot test A t-paired test (p = 0.05) was used to determine whether the means of the measurements were statistically different Results 3.1 Fuel properties A summary of the properties of the blends is shown in Table Fuel 265 (2020) 116950 I Schifter, et al fuel The results indicate that in blends with and without ethanol containing high aromatics, THC decrease when the olefin content is low (F4-FE8, F3-FE7) On the contrary, in the low aromatic blends, THC emissions increase for low olefin content fuels (F2-FE6, F1-FE5) Blend FE5 presents the highest THC emissions of all fuels According to Hajbabaei et al [41], reducing the olefin content of a fuel and substituting with paraffins, can reduce emissions photochemical reactivity Olefins improve anti-knock performance and fuel octane number, nevertheless, increase ozone forming potential of the combustion processes emissions [41] Fig shows weighted CO tailpipe emissions per fuels In general, the highest emissions are related to the non-ethanol blends, particularly the low aromatic/high olefins blend (F2) Concerning the set of EtOH fuels, high aromatic blends decrease with lower olefins, while low aromatic fuels increase with the aromatic content The lower fractions of carbon available in the ethanol fuels to form CO during combustion was an important contributing factor for the lower CO emissions for the ethanol blends Yang et al [23] found that fuels with the same levels of aromatics but higher ethanol concentrations results in statistically significant lower CO emissions The lower fractions of carbon available in the ethanol fuels to form CO during combustion is another contributing factor for the lower CO emissions for the ethanol blends Fig shows that the weighted NOx tailpipe emissions per fuels are greater for the ethanol blends, particularly FE7 (high aromatic, low olefins) and FE5 (low aromatics, low olefins) As the ethanol is incorporated into the fuels some enleanment takes place, producing high NOx emissions Guerrieri at al reported that on vehicles tested with gasoline only, and gasoline/ethanol blends, there was an increase in tailpipe NOx emissions for fuels with 12–17% ethanol addition Below 12% ethanol, the NOx emissions were virtually unchanged from the base level [42] Fig shows that weighted CO2 tailpipe emissions per fuels decreases with the ethanol blends Only the FE6 blend (low aromatic, high olefins) increases in 7% with respect to the non-ethanol blend Concerning the non-ethanol blends, the highest emissions are observed for the F4 fuel (high aromatics, high olefins) The results are in accordance with those of Yang et al [23] who suggest that CO2 emissions increase with the C/H ratio of the fuels For the ethanol/gasoline blends, the latent heat of evaporation values were higher than that of gasoline without EtOH which would provide a better mixture, lower temperature intake manifold and improve volumetric efficiency Fuel economy results are shown in Fig Theoretically, the fuel economy reduces when oxygenates are Concerning RVP, it is observed that the low proportion of olefins in blends with (FE5-FE7) and without (F1-F3) ethanol produce fuels that comply with USA gasoline class AA specifications, while high olefins content with (FE6-FE8) and without (F2-F4) ethanol generates USA gasoline class B These results are in agreement with those found by the American Petroleum Institute, which concludes that the range of vapor pressure impacts for the same concentration of ethanol in different base hydrocarbons is much larger than the range in vapor pressure impact caused by changing the ethanol content from 10% to 30% using the same base hydrocarbon [37] This is attributed to the proportion of different compounds in the base gasoline, each of which will be more or less repelled by the polar ethanol molecules Moreover, Totten et al [38] found that the higher the paraffin content, the higher the vapor pressure of the resultant alcohol-hydrocarbon blend; however, in this work the higher content of paraffins + iso-paraffins (F1 and FE5) lead to the lower RVP values Not surprisingly, the results show that fuels with ethanol containing high olefins have lower values for the distillation temperature for 50% volume (T50) than similar blends without ethanol, but no clear trend is observed between the all set of blends with the T90 distillation temperature The T50 characterizes the fuel capacity to ensure a proper functioning of the engine at different loads Moreover, the T50 influences the engine warm-up time and operating stability The distillation temperature of 90% volume (T90) affects the complete burning, the fuel consumption, the engine wear, and deposits inside the engine [39] The Octane Rating (AKI), i.e the arithmetic average of RON and MON, has historically been used to describe gasoline octane ratings [19] The AKI quality of a fuel in a given vehicle and operating condition are in these days defined by its octane index OI = RON − KS, where K is a constant for that condition and S is the sensitivity, (RONMON) Table shows that the AKI value of the blends with and without ethanol, are in general very similar, however RON numbers are greater with the ethanol blends, particularly FE8 of high aromatic and olefin content Foong et al [40] reported non-linear behavior by volume and by mole increases of RON when ethanol is blended with gasoline, suggesting a synergistic effect (a further increase from the linear volume or molar model) 3.2 Exhaust emissions results Fig shows weighted total hydrocarbons tailpipe emissions per THC 0.060 0.049 0.050 0.042 (g km-1) 0.040 0.040 0.037 0.037 0.034 0.040 0.032 0.030 0.030 0.020 0.010 0.000 F4 FE8 F3 FE7 F2 −1 Fig Weighted total hydrocarbons (THC) exhaust emissions per fuel (g.km vehicles FE6 F1 FE5 REF ) Error bars representing the mean ± pooled standard deviation for the fleet of Fuel 265 (2020) 116950 I Schifter, et al CO 1.600 1.435 1.400 1.287 1.200 1.121 0.967 (g.km-1) 1.000 0.920 0.946 FE6 F1 1.024 1.083 0.784 0.800 0.600 0.400 0.200 0.000 F4 FE8 F3 FE7 F2 FE5 REF −1 ) Error bars representing the mean ± pooled standard deviation for the fleet of vehicles Fig Weighted carbon monoxide (CO) exhaust emissions per fuel (g.km This trend is not followed in the case of benzene and xylenes, which raise in both the ethanol blends containing low olefins and high aromatics The carbonyl compounds are known for their impact on air quality, as they are precursors of ozone and peroxyacetyl nitrates, which are secondary products of urban air pollution and significant oxidants in the atmosphere The two most abundant carbonyls, formaldehyde and acetaldehyde together average for 46% of the total carbonyls in the ethanol blends The results of Table shows that formaldehyde emissions tend to be higher in the high aromatic blends regardless ethanol content, which is in agreement with [23] who found that emissions of this hydrocarbon showed statistically significant increase for higher aromatic content fuels compared to lower aromatic blends Moreover, acetaldehyde emissions are greater in the ethanol blends compared to the blends without the alcohol added On the other hand, for ethanol-fueled engines, it has been observed that emissions of acetaldehyde dominate over formaldehyde [19] Moreover, studies conducted with old technology vehicles have generally reported lower aldehyde emissions with increasing gasoline aromatics, suggesting that aromatic species are not major precursors to their formation [21] blended with gasoline due the lower energy content of the oxygenate The calorific power diminish between 4% and 7% for 15% ethanol fuels In the other hand, fuel economy decreases between 3% and 7% for the same ethanol contents, suggesting no differences in thermal efficiency for tested fuels This performance can be associated with the absence of full power conditions in FTP-75 for relatively high power to weight ratio of the actual light duty vehicles that mimic the improvements in volumetric efficiency at full load related to ethanol-gasoline blends 3.3 Speciated hydrocarbons emissions Table shows the calculated weighted tailpipe emissions of selected hydrocarbons per fuel Methane emissions are higher in the ethanol blends, while the lowest emissions correspond to low olefins/low-aromatic fuels, F1 and FE5 A similar trend is found in 1, 3-butadiene emissions that decrease in the ethanol blends, and the lowest emissions are observed also in the low olefins F1-FE5 blends According to Zhang et al [43] the 1, 3-butadiene emission comes mainly from the incomplete combustion of minor fuel fractions of olefins and cyclohexane The BTEX fraction declines in the ethanol blends, while the highest values are those of the high aromatic concentration These results are in agreement with those obtained by Karavalakis et al [21] that found BTEX and emissions increase with higher aromatic content in gasoline NOx 0.160 0.135 0.140 0.114 (g km-1) 0.120 0.133 0.111 0.105 0.121 0.102 0.100 0.080 0.081 0.074 0.060 0.040 0.020 0.000 F4 FE8 F3 FE7 Fig Weighted nitrogen oxides (NOx) exhaust emissions per fuel (g.km F2 −1 FE6 F1 FE5 REF ) Error bars representing the mean ± pooled standard deviation for the fleet of vehicles Fuel 265 (2020) 116950 I Schifter, et al CO2 300.0 241.9 250.0 228.3 229.0 FE8 F3 232.5 219.1 217.0 FE7 F2 231.5 225.5 224.5 (g km-1) 200.0 150.0 100.0 50.0 0.0 F4 −1 Fig Weighted carbon dioxide (CO2) exhaust emissions per fuel (g.km FE6 F1 FE5 REF ) Error bars representing the mean ± pooled standard deviation for the fleet of vehicles emissions of toxic compounds Concerning methane, the highest percentage of emissions is related to the blends with high aromatic content and ethanol; while butadiene shows high values with all the blends, particularly with the FE5 fuel that has low aromatics and olefins In a similar way, the BTEX group shows the highest concentration in the FE5 blend Emissions of acetaldehyde and formaldehyde increase in blends with ethanol in view that they are partial oxidation products of ethanol The highest percentage of emissions of these carbonyls are related to blends FE8 and FE7 of high aromatic content 3.4 Cold start results Engine cold-start high emissions are related to both low catalytic efficiency and low lambda control effectiveness Table presents the calculated contribution of cold start to the emissions of THC, CO and NOx The cold-start portion of phase of the FTP cycle contributes greatly to THC emissions in blends, independently of ethanol content, since only marginally differences are observed between the two types of fuels Chen et al [44], reported the effects of ethanol–gasoline blended fuel on cold-start emissions of an SI engine and found also that the hydrocarbons emissions decreased significantly when more than 20% ethanol was blended During the cold start period, CO contribution to emissions raise in the ethanol blends, being greater in the low olefins blends (F3-F1 and FE7-FE5) Moreover, during engine cold start, NOx emissions are reduced in the low aromatic fuels without ethanol (F2-F1) compared with the high aromatic blends Concerning blends with ethanol, cold start contribution of NOx is significantly lower with respect to the EtOH blends, perhaps due to the effect of low temperature at the combustion chamber with a rich fuel-air mixture Table shows also the calculated contribution of cold start to the 3.5 Ozone forming potential Table shows calculated ozone formation potential (OFP) obtained with the set of tested vehicles In general, the OFPs are lower for the ethanol blends, as reported in previous studies [19,45] Fuels with high aromatic and olefin content produce higher OFP values, but differences are related with vehicle technology The results indicate that the major contributors to the OFP are low molecular weight olefins (ethylene, propylene, butenes), alkanes (2,2,4trimethylpentane, and aromatic hydrocarbon species (i.e toluene, xylenes trimethylbenzenes) The contribution of formaldehyde and acetaldehyde is almost negligible Fuel economy 12.00 9.79 10.00 9.31 9.64 9.39 9.79 9.29 F2 FE6 9.95 9.27 10.10 (km L-1) 8.00 6.00 4.00 2.00 0.00 F4 FE8 F3 Fig Weighted carbon balance fuel economy per fuel (km.L FE7 −1 F1 FE5 REF ) Error bars representing the mean ± pooled standard deviation for the fleet of vehicles Fuel 265 (2020) 116950 I Schifter, et al Table Weighted total toxic exhaust emissions per fuel (mg.km−1) representing the mean ± pooled standard deviation for the fleet of vehicles Fuel Methane 1,3-Butadiene Benzene Toluene Ethylbenzene Xylenes Formaldehyde Acetaldehyde Total Carbonyls F4 FE8 9.37 ± 1.5 10.56 ± 3.4 0.12 ± 0.05 0.11 ± 0.04 1.56 ± 0.5 1.43 ± 0.4 3.12 ± 0.6 2.30 ± 0.5 0.53 ± 0.5 0.46 ± 0.2 3.18 ± 0.4 2.14 ± 0.5 0.27 ± 0.2 0.30 ± 0.2 0.19 ± 0.4 0.33 ± 0.1 0.94 ± 0.2 1.156 ± 0.7 F3 FE7 6.80 ± 0.8 9.54 ± 4.1 0.14 ± 0.02 0.08 ± 0.06 1.90 ± 0.3 0.81 ± 0.1 3.05 ± 0.5 2.53 ± 0.4 0.63 ± 0.2 0.19 ± 0.2 3.07 ± 0.5 1.06 ± 0.2 0.31 ± 0.04 0.27 ± 0.3 0.20 ± 0.3 0.28 ± 0.1 0.60 ± 0.3 0.80 ± 0.2 F2 FE6 8.89 ± 1.0 11.09 ± 2.6 0.14 ± 0.03 0.12 ± 0.05 0.93 ± 0.2 0.77 ± 0.3 1.39 ± 0.3 1.14 ± 0.1 0.24 ± 0.2 0.21 ± 0.04 1.12 ± 0.2 0.92 ± 0.1 0.11 ± 0.1 0.13 ± 0.1 0.21 ± 0.3 0.26 ± 0.1 0.69 ± 0.1 0.84 ± 0.6 F1 FE5 7.19 ± 3.4 7.51 ± 2.2 0.11 ± 0.04 0.08 ± 0.04 0.74 ± 0.2 1.33 ± 0.5 1.32 ± 0.3 1.13 ± 0.3 0.23 ± 0.1 0.41 ± 0.2 1.06 ± 0.2 1.36 ± 0.3 0.15 ± 0.01 0.21 ± 0.1 0.22 ± 0.1 0.30 ± 0.1 0.71 ± 0.2 1.08 ± 0.4 REF 9.18 ± 3.9 0.11 ± 0.04 1.04 ± 0.2 1.88 ± 0.4 0.31 ± 0.2 1.76 ± 0.1 0.13 ± 0.1 0.28 ± 0.1 1.02 ± 0.2 3.6 Statistical analysis results Table Estimated ozone forming potential (mg ozone km−1) for the weighted exhaust emissions The fuel properties and tailpipe emissions data were arranged in a matrix for its evaluation by Factor analysis (FA) The analysis was performed testing different number of factors, from to 6; the optimal solution was found with three factors that together explain 79.5% of the total variability of the study The results are shown in Table The factor 1, which explains 37.3% of the total variability of the study, indicates that the aromatic content is strongly and positively associated with the emissions of most of the pollutants (e.g., total HC, CO2, benzene, toluene, 3-methylpentane, ethylbenzene and xylenes) and with the ozone forming potential Results in factor (28.2% of the total variability) suggest that NOx emissions are associated with ethanol content, heat of vaporization and research octane number of the blend On the contrary, emissions of these pollutants are inversely related with the carbon fraction, latent heat of vaporization, air fuel ratio and iso-paraffins content It is also observed that these four blend properties have direct influence on the propylene and 1,3-butadiene emissions Factor loadings on factor (representing 13.9% of the variability) point out that isopentane emissions are directly associated with olefin content and Reid vapor pressure, while the T50°C showed inverse relationship From results in Table it can be concluded that paraffin, and naphthene content, T90 and MON have no significant influence on the gaseous emissions The emission of carbon monoxide, methane and acetaldehyde are almost independent of any gasoline property Based on the FA results, that highlight the influence of aromatic content over gaseous emissions, a t test was run to support this observation For this analysis, the gasolines were classified into two groups: 1) gasolines with aromatic content lower than 30% (F1, F2, FE5 and FE6), and 2) gasolines with aromatic content higher than 30% (F3, F4, FE7, FE8) The general trend was lower emissions for group 1, nevertheless only carbon dioxide, ozone forming potential, methylhexane, methylhexane, pentane, toluene, ethylbenzene, and xylenes exhibited statistical significance (p = 0.05) Fuel RAM Toyota Versa Vento Average F4 FE8 F3 FE7 F2 FE6 F1 FE5 REF 97.90 78.77 121.43 46.99 86.20 53.48 65.64 56.51 77.09 100.91 85.05 86.96 80.89 85.21 70.57 112.66 96.31 80.14 145.51 91.37 120.12 66.49 83.78 84.41 95.11 96.24 103.62 152.57 152.40 166.21 127.63 93.60 102.85 140.35 90.61 116.52 124.22 101.90 123.68 80.50 87.20 77.83 103.44 84.92 94.34 Conclusions The results obtained in this work proved that exist significant differences between blends with and without EtOH that depend also on the aromatic and olefin content In blends with and without ethanol containing high aromatics, THC decrease when the olefin content is low while in the low aromatic blends, THC increase lowering the olefin content CO emissions show higher values in the blends with 0% ethanol, low aromatics and high olefins Weighted NOx tailpipe emissions are greater for the ethanol blends The results indicate that CO2 emissions increase with the C/H ratio of the fuels The BTEX fraction decrease in the ethanol blends, moreover, the highest values are for those with high aromatic concentration Formaldehyde emissions appear to be higher in the high aromatic blends, regardless ethanol percentage Furthermore, acetaldehyde emissions are greater in the ethanol blends compared to the blends without the alcohol added Fuels with high aromatic and olefin content exhibit higher values of ozone formation, but differences are related with vehicle technology CRediT authorship contribution statement I Schifter: Conceptualization, Supervision, Validation L Díaz: Table Tailpipe excess cold start emissions expressed as percentage Fuel THC CO NOx Methane 1,3-Butadiene Benzene Toluene Ethylbenzene Xylenes Formaldehyde Acetaldehyde F4 FE8 F3 FE7 F2 FE6 F1 FE5 REF 86.7 84.9 80.5 78.2 79.7 80.2 84.1 85.2 84.4 29.3 42.6 32.7 54.9 28.7 44.1 35.3 59.4 47.9 43.3 24.8 45.2 22.8 31.9 20.5 35.1 15.6 9.4 41.6 38.7 41.9 41.2 37.9 28.8 38.8 30.4 36.4 88.4 89.1 89.8 83.5 83.1 88.6 86.8 95.0 89.0 90.2 93.7 88.7 84.9 85.5 88.6 86.6 95.9 86.7 93.6 94.6 92.9 89.7 89.5 91.6 87.1 94.8 89.6 95.7 95.7 94.8 92.7 94.3 93.7 94.2 97.4 94.7 96.2 96.8 95.4 95.6 94.9 95.6 94.5 98.4 95.5 46.8 71.7 75.5 78.0 79.8 81.1 66.4 65.6 75.8 56.6 95.4 38.6 92.2 35.9 89.3 33.2 77.5 49.5 Fuel 265 (2020) 116950 I Schifter, et al Table Factor analysis results showing in bold values greater than ± 0.70 Property Factor Factor Factor Aromatics, vol % Olefins, vol % Paraffins, vol % Isoparaffins, vol % Naphtenes, vol % Ethanol, vol % RVP, psi T50, °C T90, °C MON RON RON + MON/2 Carbon Fraction AFR STOICH HoV, kJ/kg LHV, kJ/kg 0.844 −0.146 0.635 −0.593 −0.442 −0.104 0.111 0.419 0.601 −0.393 0.181 −0.028 0.274 0.081 0.220 −0.001 −0.172 0.371 −0.227 0.754 −0.178 −0.933 −0.066 0.457 0.293 −0.607 −0.824 −0.792 0.889 0.924 −0.930 0.920 −0.329 0.872 −0.282 0.079 −0.394 −0.125 0.927 −0.750 −0.569 0.151 0.281 0.233 0.032 0.000 0.008 0.023 Emissions THC CO NOx CO2 Fuel economy Ozone Methane Propylene 1,3-Butadiene Isopentane 3-Methylpentane Benzene Toluene Ethylbenzene Xylenes Acetaldehyde Explained variance Cumulative variance 0.817 0.270 −0.100 0.922 −0.146 0.963 0.193 0.071 0.220 0.234 0.768 0.950 0.983 0.978 0.988 0.298 37.338 37.338 −0.478 0.616 −0.781 −0.103 0.924 0.182 0.385 0.805 0.803 −0.126 0.260 0.120 −0.034 0.099 −0.072 −0.118 28.241 65.579 0.035 0.254 0.530 −0.267 0.077 0.039 −0.612 −0.119 0.008 0.929 0.535 0.177 0.058 0.064 0.032 −0.060 13.876 79.455 [9] US Energy Information Administration U.S ethanol exports exceed 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No 142/Monday, July 25, 2011/Rules and Regulations [11] Hubbard CP, Anderson JE, Wallington TJ Ethanol and air quality: influence of fuel ethanol content on emissions and fuel economy of flexible... effects of aromatic, olefin contents and T50 (temperature for 50% volume D-86 distillation) tailpipe emissions from gasoline direct injection, and found that changing aromatic and olefin contents... inverse relationship From results in Table it can be concluded that paraffin, and naphthene content, T90 and MON have no significant influence on the gaseous emissions The emission of carbon monoxide,