Ozone-Forming Potential of Reformulated Gasoline (1999) / Chapter Skim
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5 Reformulation of Gasoline
5 Reformulation of Gasoline
Pages 101-130
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From page 101... ...
with respect to the amount of ozone precursor emissions (volatile organic compounds GIOCs) , oxides of nitrogen (NOX)
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From page 103... ...
Increased concern about air pollution and health effects from the use of motor-vehicle fuels have brought the federal and some state governments, through their en~ronmental regulatory agencies, into an increasingly prominent role in determining fuel composition. Within this regulatory context, fuel composition has typically been defined by specifications set as a range of properties, each having a maximum or minimum or both stipulated.
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From page 104... ...
% of ethanol and MTBE that correspond to a range of At % oxygen contents that are typical of RFG blends. Note that because ethanol contains more oxygen on a per-gram basis than TABLE 5-1 Test Parameters for Octane Measurement Research Octane Number (R)
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From page 105... ...
is required to produce a given % wt of oxygen in a fuel than in the case of MTBE. As discussed later in this chapter, the federal RFG program mandates a minimum 2 wt % oxygen in all RFG blends.
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From page 106... ...
The presence of oxygenates in reformulated gasoline has been mandated by law and regulation, and this provides the incentive for using oxygenates to boost octane number instead of using components produced by conventional processes. All things being equal, the choice of which specific oxygenate to use would be dictated by economic factors; that is, which oxygenate can produce the desired gasoline characteristics (e.g., high-octane number)
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From page 107... ...
However, in the United States, tax subsidies have made ethanol production via fermentation competitive with MTBE production. Because the committee was not asked to address this aspect of the RFG issue, the economic implications of using MTBE versus ethanol as an oxygenated additive are not discussed in this report.
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From page 108... ...
The ozone excursions led to speculation that evaporation of the then-common high-volatility summer gasoline, in use and in bulk storage, was a major contributor to the mass of VOC emissions giving rise to these ozone episodes. A seminal compendium of peer-reviewed research results, at that time, identified reduction of gasoline volatility as the most effective means then available to reduce anthropogenic VOC emissions attributable to mobile-source activity (NAPAP 1991)
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From page 109... ...
to reduce air pollution, and will also meet the requirements of the federal RFG program some 3 to 4 years earlier than that mandated in the CAA Amendments of 1990. Motorvehicle-exhaust emissions standards were further specified under California's Low Emission Vehicles and Clean Fuels Program.
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From page 110... ...
The program was motivated in part by the perception that the crafting of gasoline should be completely rethought, such that the entire range of its potentially health-harmful constituents, including sulfur, aromatics, and reactive olefins, should be subject to limits. The AQIRP findings have served as the cornerstone for the design of both the federal and California RFG programs, and are discussed in depth in Chapter 6.
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From page 111... ...
By contrast, the RFG programs tend to prescribe content and volatility of gasoline sold during the summer ozone season. Federal RFG Program In general terms, the federal concept of RFG, as of January I, 199S, is gasoline blended such that, on average, the exhaust and evaporative emissions of VOCs and air taxies (chiefly benzene, I,3-butadiene, polycyclic organic matter (POM)
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From page 112... ...
112 to ILL .
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From page 114... ...
114 Cat ._ or Cay Ids .
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From page 115... ...
115 -1 Cat ~n o In a, ED o CO a' LO m C ='= ~ em or ~ Do al ·- O ~ ~t_ i E ~ ~ |
From page 116... ...
~21. Further, as part of the federal RFG program, the EPA Administrator was instructed by CAA Section 211 (k)
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From page 117... ...
As indicated in Table 5-3 Part I, California Phase 2 RFG was required to limit specific fuel properties: RVP to reduce evaporative VOCs; sulfur content to avoid catalyst poisoning and thereby reduce VOCs, NOx, CO, and toxic emissions; aromatics content to reduce the atmospheric loading of mono- and polycyclic hydrocarbons linked to ozone formation; olefins to reduce VOC emissions reactivity; and benzene content to decrease emissions of this regulated toxic substance.
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From page 118... ...
In principle and in contrast to the federal Phase II RFG requirements, a fuel can be certified for Phase 2 of the California RFG program through emissions testing without having any oxygenates. FEDERAL REQUIREMENTS FOR RFG UNDER TH E COMPLEX MODEL In a final rule of February 16, 1994 (EPA 1994)
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From page 119... ...
The regulation defines both summer and winter baseline fuel properties with respect to eight content variables, and from these derives baseline exhaust emissions of VOCs, NOX, tonics, and polycyclic organic matter, and evaporative emissions of VOCs and benzene as the basis of comparison for both federal Phase ~ and Phase IT RFG. There is further allowance for the difference between normal and high emitters, such that emissions-reduction credit for each season and RFG phase must be weighted between them.
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From page 120... ...
120 an a)
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From page 121... ...
121 Cal ~ ^1 _ O Q ~ O Q ~ O2 ~ m~ g by' Al -- - ~ _ _ .
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From page 122... ...
The models are used to certify a candidate fuel for the federal RFG program (Complex Model) or California RFG program (Predictive Model)
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From page 123... ...
In Chapter 7 of this report, the Complex and Predictive Models were used to evaluate the relative benefits of RFG with and without oxygenates and with various amounts and types of oxygenates. For these reasons, some discussion of the reliability of the models and their attendant uncertainties is in order.
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From page 124... ...
There are also some more-general concerns that need to be borne in mind. The use of the Complex and Predictive Models requires a substantial extrapolation of measured emissions from a sample set of motor vehicles operating under controlled test conditions to real-worId emissions from a fleet of motor vehicles using one or more RUG blends.
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From page 125... ...
VOC art 10 20 30 Complex "Predictive l 40 50 60 70 % Reduction from Federal Base FIGURE 5-1 Recent reductions in the mobile-source emissions from four illustrative RFG blends relative to the federal base fuel (see Table ~1) as predicted by the EPA Complex Model and the California Predictive Model.
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From page 126... ...
SPECIFICATION FLEXIBILITY AN D DOWNSTREAM CONTROL IN FEDERAL PHASE I! RFG In the year 2000, Phase ~ RFG blends sold under the federal RFG program in the nine severe nonattainment areas and all present and future opt-in areas will be replaced by Phase lI RFG.
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From page 127... ...
In fact, the demonstrated consistency of refining practice year-round has prompted EPA to remove the distinction between gasolines designated as "oxygenated fuels program reformulated gasoline" (OPRG) and those designated as non-OPRG, effective November 6, 1997 (EPA 1997b)
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From page 128... ...
gasoline-property results obtained from refiners for the gasoline sold locally. For purposes of complying with planning requirements for attainment of the ambient ozone standard, the values of the key variables needed for computation of evaporative VOC emissions in MOBILE (ambient temperature and gasoline RVP)
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From page 129... ...
Certainly, as discussed in Chapter 4, high ambient temperature (and the magnitude of daily temperature rise) plays a role in the quantity of evaporative VOC emissions produced, and it is possible that current emissions-certification procedures underestimate the contribution of hot soaks to total evaporative emissions.
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From page 130... ...
However, the methods used in those models to predict the in-use performance of gasolines reformulated to meet the criteria of the reformulated gasoline programs, are based on results from large and diverse, but nonetheless limited, data bases. They might not accurately represent what actually occurs in specific nonattainment areas, especially where a high summertemperature rise produces relatively high evaporative VOC emissions.
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