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In 2008-2009, EPA and DOE tested fifteen 2008 model year Tier 2 vehicles on 27 fuels. The fuels were match-blended to specific fuel parameter targets. The fuel parameter targets were pre-selected to represent the range of fuel properties from fuel survey data from the Alliance of Automobile Manufacturers for 2006. EPA's analysis of the EPAct data showed that higher aromatics, ethanol, and T90 increase particulate matter (PM) emissions. EPA focused their analysis only on the targeted fuel properties and their impacts on emissions, namely RVP, T50, T90, aromatics, and ethanol. However, in the process of fuel blending, at least one non-targeted fuel property, the T70 distillation parameter, significantly exceeded 2006 Alliance survey parameters for two of the E10 test fuels. These two test fuels had very high PM emissions. In this study, we examine the impacts of adding T70 as an explanatory variable to the analysis of fuel effects on PM.

This paper is the fourth and final paper in a series providing fuel blending and analysis data for the Auto/Oil Air Quality Improvement Research Program (AQIRP), essentially detailing the work of the Fuels Blending Subcommittee (FBSC) and portions of the work of the Fuels Analysis Subcommittee (FASC). This paper covers fuels for the final follow up projects in Phase II. Blending procedures, feedstock preparation and analytical techniques are explained, and blend recipes, full physical properties and compositional data are given. In addition, a survey of commercial gasolines carried out in cooperation with the MVMA (Motor Vehicle Manufacturers Association) is reported. Regional and national fuel sampling and subsequent derivation of composite fuels is explained briefly, and fuel analysis data produced by the FBSC are presented. Papers by Pahl and McNally (1)*, Gerry et al. (2), and Kopp et al. (3), have presented the corresponding data for the forerunning Phase I and II AQIRP work.

This study was undertaken to determine the vapor pressure characteristics of M85 fuel, a mixture of 85 percent methanol and 15 percent gasoline or other hydrocarbons. For M85 fuels made with full-boiling-range gasolines, the vapor pressure of the M85 fuel at 37.8°C increased linearly with an increase in the vapor pressure of the gasoline. A different linear relationship was obtained for M85 fuels made with pure hydrocarbons rather than with gasolines. The vapor pressure of an M85 fuel was higher when the hydrocarbon component was a pure hydrocarbon or simple hydrocarbon mixture rather than a gasoline of the same vapor pressure. Vapor pressure vs. temperature characteristics were measured for a number of M85 fuels and the hydrocarbons from which they were made. In most cases, a change in temperature caused a greater change in the vapor pressure of the M85 fuel than in the vapor pressure of the hydrocarbon component of the M85.

We have developed and validated a simple, quick, in-expensive method for determining the methanol or hydrocarbon content of a methanol blend fuel (a mixture of methanol and gasoline). The method exploits the insolubility of water in hydrocarbons. Briefly, 50 mL of fuel is mixed with a like amount of water and allowed to settle; the volume of the upper phase is directly correlated to the amount of hydrocarbon in the fuel. Equations and graphs are provided which translate between the hydrocarbon volume measured and the methanol content or the hydrocarbon content of the fuel. This method and the graphs and equations in this report are valid for methanol fuels made with any gasoline or virtually any hydrocarbon mixture, provided there are not oxygenates such as ethanol or MTBE present in the hydrocarbon fraction. The accuracy and precision of the method are excellent, for mixtures of dry methanol and oxygenate free gasoline.

Laboratory bench tests were conducted to simulate both the diurnal and the hot-soak (carburetor only) parts of an evaporative emissions test with gasolines containing various alcohols and ethers. The mass of vapor generated during each test and the detailed composition of the vapor were determined for each fuel. Using published atmospheric reactivity scales, the ozone-forming potential of the vapor was estimated. Based on the scale of maximum incremental reactivities, which the California Air Resources Board has proposed for future emissions standards, the diurnal test results showed that the addition of methyl tertiary-butyl ether (MTBE) or ethyl tertiary-butyl ether (ETBE) to gasoline resulted in about the same or lower total vapor reactivity compared to the gasoline alone.

Ethyl tertiary-butyl ether (ETBE), a reaction product of ethanol and isobutylene, has been proposed as a high-octane blending component for gasoline. Laboratory studies have been conducted to determine how the addition of ETBE to gasoline affects the volatility characteristics of the fuel, and how the effects of ETBE compare with those of the commonly used oxygenates, ethanol and MTBE. The amount of vapor generated in bench-scale simulated evaporative emissions tests with each of those three oxygenates was also determined. The vapor pressures of gasoline-ETBE blends decreased linearly as the concentration of ETBE was increased. In contrast, ethanol addition raises the vapor pressure of gasoline, although in a nonlinear fashion. ETBE increased the mid-range volatility of the fuel, in the same way as a pure hydrocarbon of similar vapor pressure and boiling point.

An investigation was conducted to determine the change in Reid vapor pressure (RVP) which results when gasoline and various gasoline-alcohol blends are mixed. Such mixing occurs in vehicle fuel tanks when a motorist buys gasolines and blends alternately. When mixing a gasoline with a gasoline-alcohol blend of the same RVP, the resulting mixture always had a higher RVP, due to the non-linear effect of alcohol concentration in gasoline on RVP. Even when a blend had a much lower RVP than gasoline, some mixtures of the two still had higher RVP's than the gasoline. When two common commercial blends, 10 percent ethanol and 10 percent Oxinol™ 50, both having the same RVP, were mixed in various proportions there was essentially no change in RVP. The results of this study suggest that the presence of both gasolines and blends in the marketplace can lead to higher in-use evaporative emissions from vehicles, even if the blends meet the same volatility standards as gasoline.

An experimental test program was conducted to determine the detailed hydrocarbon composition of the vapor emitted from a vehicle fuel tank during refueling with gasoline. The composition of the equilibrium vapor in the tank was strongly dependent on the composition of the liquid gasoline, but, as expected, the vapor was composed primarily of the more volatile components of the gasoline. The composition of the vapor could be calculated satisfactorily from the liquid composition, using ideal solution theory. In the refueling tests in which the tank fuel and dispensed fuel were the same, there was little difference in the composition of the equilibrium vapor in the tank before refueling and the vapor expelled during refueling. When the tank fuel and dispensed fuel had different compositions, the vapor expelled during refueling was composed of about two-thirds dispensed fuel vapor and about one-third tank fuel vapor.

During several test programs involving evaporative emissions and driveability, the vapor pressures and distillation characteristics of a large number of gasoline-alcohol and gasoline-ether fuel blends were measured. The maximum increases in Reid vapor pressure (RVP) above that of the gasoline alone ranged from 1.0 kPa (0.2 psi) for tertiary-butyl alcohol to 23.4 kPa (3.1 psi) for methanol. As little as 0.25 percent methanol, ethanol, or Oxinol ™ 50 (a 1:1 mixture of methanol and gasoline-grade tertiary-butyl alcohol) produced measurable increases in RVP. Because of the nonlinear response of RVP to alcohol concentration, mixing a gasoline and a gasoline-alcohol blend of the same RVP can produce a fuel with a higher RVP. The vapor pressures of fifteen gasolines and gasoline-alcohol blends were measured at several vapor-to-liquid ratios (V/L), With an increase in V/L, the vapor pressures of the gasolines were reduced more than the vapor pressures of the blends.

The immediate effects of methanol-gasoline blends on vehicle emissions, fuel economy, and driveability were investigated. The addition of a 2:1 mixture of methyl and butyl alcohols to gasoline, to provide a total alcohol concentration of either 10 percent or 18 percent, resulted in higher evaporative emissions, lower carbon monoxide emissions, lower volumetric fuel economy, and poorer driveability. Exhaust hydrocarbon and nitrogen oxide emissions decreased with some cars and increased with others. The closed-loop fuel metering systems, with which some of the test cars were equipped, could not completely compensate for the leaning effect of the alcohols. Consequently, the results of this test program suggest that these alcohol-gasoline blends would not be satisfactory for use in many cars either with or without closed-loop systems.

Vehicle exhaust emissions tests, using the Federal Test Procedure, were conducted to determine the effect of gasoline sulfur content on the performance of three-way catalysts. The test fuels had sulfur concentrations of 0.01, 0.03, and 0.09 percent. An increase in the fuel sulfur content from 0.01 to 0.09 percent reduced the conversion of hydrocarbons, carbon monoxide, and oxides of nitrogen, resulting in higher tailpipe emissions. The effects were generally small, but statistically significant. The lower conversion was due to poisoning of the catalyst by sulfur species in the exhaust. The poisoning was reversible.

Vehicle tests showed that evaporative emissions were increased significantly by adding 10 percent ethanol to gasoline, but were increased less with 15 percent MTBE in gasoline. The quantity of ethanol or MTBE in evaporative emissions was investigated in laboratory tests. Exhaust HC, CO, and NOx emissions from a car without closed-loop fuel control were significantly lower with the ethanol and MTBE fuel blends than with gasoline. For cars equipped with closed-loop carburetors, the absolute differences in exhaust emissions among the fuels were small. Fuel economy and drive-ability were worse with ethanol and MTBE fuel blends than with gasoline.

Monolithic oxidation converters can become plugged with manganese oxide deposits when the gasoline contains the antiknock additive MMT. Engine dynamometer studies showed that the rate of converter plugging depended on the catalyst inlet temperature and the concentration of MMT in the fuel. Converter plugging was not affected by base fuel or engine oil composition, and it occurred as readily with a bare monolithic support containing no catalytic material as with a production catalyst. Monolithic converter plugging appears to be a physical, rather than a chemical phenomenon, in which the manganese oxide collects primarily on the inlet edge of the converter.