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WaterGates: ISTF Project #01-0224



ISTF Contest



Fuels and Additives

What is gasoline?

Gasoline is made up of different hydrocarbon compounds, including aromatics, olefins, and benzene, all of which contribute to ozone and toxic air pollution. The levels at which these components are present in reformulated gasoline (RFG) are lower, resulting in fewer harmful emissions. Gasoline comes from crude oil pumped out of the ground in the form of a black liquid called petroleum. This oil contains aliphatic hydrocarbons composed of hydrogen and carbon. The carbons link together to form different hydrocarbon links of various sizes. The longer the chain, the heavier and harder the link is to boil. Chain links of C7H16 through C11H24 are blended together to form gasoline. All of them vaporize at levels below the boiling point of water. Though gasoline is an aliphatic hydrocarbon, it does not burn cleanly to form only CO2 and H2O. If gasoline is burned as a vapor with a hot flame and plenty of oxygen, the products of the reaction would be CO2 and H2O that are nearly pure. But automobile exhaust contains a lot more than just carbon dioxide and water, and carbon monoxide is formed because combustion is incomplete. Oxygen is not available fast enough to react completely with all of the carbon monoxide present, and because of the pressure and temperature inside a cylinder, nitrogen and oxygen combine in various ways to form nitrogen oxide. Not all hydrocarbons participate in the reaction because of the small amount of time available during the combustion phase.

What is motor gasoline?

Motor gasoline is a complex mixture of relatively volatile hydrocarbons that sometimes contains small quantities of additives to form a fuel suitable for use in spark-ignition engines. As defined by ASTM Specification D 4814 or Federal Specification VV-G-1690C, motor gasoline is said to have a boiling range of 122 F to 158 F at the 10 percent recovery point. The recovery point at 90 percent is 365 F to 374 F. Motor gasoline includes conventional gasoline, oxygenated gasoline, including gasohol, and reformulated gasoline, but it does not include aviation gasoline. To produce finished motor gasoline, the mechanical mixing of motor gasoline, blending products, and oxygenates are required. Finished motor gasoline may be further mixed with other motor gasoline blending components or oxygenates, which results in increased volumes of finished motor gasoline and changes in the formulation of finished motor gasoline.

There are five blends of gasoline marketed in the United States.

  • Conventional gasoline is the most widely available gasoline. It is sold where air quality is satisfactory. Since 1992, it has been formulated to evaporate more slowly in hot weather to reduce smog, and it now contains detergent additives to reduce engine deposits.

  • Winter Oxygenated gasoline as of 1992, is formulated as conventional gasoline with oxygen-rich chemicals added, such as MTBE or ethanol. The oxygen promotes cleaner burning, reduces carbon monoxide, and is generally sold from November to March because cold engines operate less efficiently and produce more carbon monoxide.

  • Reformulated gasoline (RFG) was introduced in 1995 and is mandated in areas where toxins in the air are a constant problem. It contains oxygen-rich chemicals in lesser concentrations than conventional and winter oxygenated gasoline. It is also formulated from certain toxic chemicals found in the gasolines below.

  • Oxygenated Reformulated Gasoline is a wintertime gasoline exclusive to the New York City area due to the heavy carbon monoxide pollution.

  • California Reformulated Gasoline (CaRFG) was introduced in 1996. It has a different formulation and burns more cleanly than regular reformulated gasoline. MTBE has been implicated as a pollutant of groundwater, and in 1999 California ruled that MTBE must be phased out of CaRFG by December 31, 2002.

Conventional, oxygenated, and reformulated gasolines are classified by three grades:

  • Regular Gasoline: having an antiknock index (octane rating) greater than or equal to 85 and less than 88.

  • Mid-grade Gasoline: having an antiknock index greater than or equal to 88 and less than or equal to 90.

  • Premium Gasoline: having an antiknock index, i.e., octane rating, greater than 90.

What is octane?

Since 1912 the spark ignition internal combustion engine's compression ratio has been constrained by the unwanted "knock" that could rapidly destroy engines. "Knocking" is a very good description of the sound heard from an engine using fuel of too low octane. The engineers had blamed the "knock" on the battery ignition system that was added to cars along with the electric self-starter. The engine developers knew that they could improve power and efficiency if knock could be overcome. In 1927 Graham Edgar suggested using two hydrocarbons that could be produced in sufficient purity and quantity. These were "normal heptane" and they were already obtainable in sufficient purity from the distillation of Jeffrey pine oil, and " an octane, named 2,4,4-trimethyl pentane " that he first synthesized. Today we call it " iso-octane " or 2,2,4-trimethyl pentane. The octane had a high antiknock value, and he suggested using the ratio of the two as a reference fuel number. He demonstrated that all the commercially available gasolines could be bracketed between 60:40 and 40:60 parts by volume heptane:iso-octane. The reason for using normal heptane and iso-octane was because they both have similar volatility properties, specifically boiling point, thus the varying ratios 0:100 to 100:0 should not exhibit large differences in volatility that could affect the rating test."

What is reformulated gasoline?

The concept of RFG was originally generated, developed, and endorsed by industry, not by the EPA or other federal government agencies. Arco Petroleum was the first to successfully market RFG in California in the 1980's to help reduce motor vehicle emissions. Their formula, "EC-1", was formulated as a replacement for leaded gasoline. MTBE was an additive.

In 1990 President Bush sent the Clean Air Act legislation to Congress, which included a number of provisions that would lead to the introduction of non- petroleum fuels. Petroleum and oxygenate industries argued that a significant fleet turnover would need to occur if emission reductions were to be achieved, but RFG, on the other hand, would be effective immediately on the existing fleet. These industries now offer RFG programs as a substitute for most of the provisions for alternative fuels. The final Clean Air Act legislation included a mandate for RFG to contain oxygenates.

Throughout 1991, the EPA participated in regulatory negotiation process with industries and organizations representing the public in order to develop the framework for the RFG rulemaking. Vehicle manufacturers and the oil companies invested millions of dollars in a research program called Auto/Oil Air Quality Improvement Research Program. The results of this program and many other studies conducted by EPA revealed that large emission benefits of RFG were possible and cost effective. Now as a result emissions standards for RFG in 2000 surpass the minimum requirements of the Clean Air Act.

What is in reformulated gasoline?

The ingredients used to make RFG are not different from the ingredients used to make conventional gasoline. They only differ in the levels at which the ingredients are used, thereby reducing the use of ingredients that contribute to air pollution. Formulations of RFG suit the power requirements of vehicles in which it is used. Although vehicle performance has always been considered when choosing fuel formulation, emissions performance in fuel formulation has not. But because of a mandate in the reduction of vehicle emissions, emissions performance is now considered in the production of high quality, reformulated gasoline. Therefore, in terms of RFG's effect on driving, vehicle owners should notice little change, if any at all, in performance while dramatically reducing harmful emissions.

What are the differences between reformulated gasoline and conventional gasoline?

There are three main differences between reformulated gasoline and conventional gasoline. RFG has lower levels of certain compounds that contribute to air pollution, will not evaporate as easily as conventional gasoline, and contains oxygenates. Conventional gasoline is made up of different hydrocarbon compounds, including aromatics, olefins, and benzene, all of which contribute to ozone and toxic air pollution. The levels at which gasoline hydrocarbon components are present in RFG are lower, resulting in fewer harmful emissions. RFG has lower volatility in the summer months, meaning that it does not evaporate as easily as conventional gasoline, thereby reducing the ability of gasoline to evaporate and in turn reducing the amount of ozone-forming hydrocarbons released into the air. RFG also contains oxygenates which are added to fuels for purposes of octane enhancement. The EPA claims that the presence of oxygenates in RFG may result in a 1 to 2 percent reduction in gas mileage in some vehicles when compared to fuel without oxygenates, although gas mileage is more effected by the type of engine, driving habits, weather conditions, and vehicle maintenance. The reformulated gasoline program will result in a consistently better gasoline that burns more efficiently, has reduced evaporative tendencies, and contains fewer impurities, which is a benefit to human health and the environment.

Why choose Ethanol over MTBE?

Ethanol is the most likely replacement of MTBE in reformulated gasoline. It behaves better in groundwater and has fewer public health concerns, although ethanol has encountered issues with its effects on air quality, supply and distribution, and economics. In respect to protecting water resources, ethanol has several advantages over MTBE. Like MTBE, ethanol/ gasoline blends are absorbed into the groundwater, but ethanol is highly biodegradable and transforms into harmless byproducts before potential receptors are invaded by plumes. It also does not exhibit a taste or odor when present in water, unlike MTBE. In respect to air quality, ethanol has several disadvantages when compared to MTBE. One particular disadvantage is that ethanol may retard biodegradation of benzene, a known carcinogen, thus allowing benzene plumes to spread further when gasoline is spilled. Ethanol use can also increase VOC emissions and overall toxic air emissions when compared to RFG containing MTBE. It also increases emissions of a toxic air combustion by-product of ethanol, acetaldehyde, in RFG by diluting lesser quantities of toxic compounds in gasoline. The significant toxic dilution benefit of oxygenates is decreased with ethanol because only 5.7 percent ethanol, by volume, is necessary as opposed to 11 percent MTBE to meet minimum oxygen content required for RFG. Production capacity of ethanol does not currently exist to meet the demand if both California and the Northeast ( two regions whom are currently thinking of switching to the use of ethanol instead of MTBE in RFG) were to substitute ethanol for MTBE. The transportation of ethanol is a problem because it is highly soluble in water, and the typical transportation of fuel via pipeline is unable to transport ethanol. Therefore, the current ethanol production would have to be transported from the Midwest ( where it is predominate) to California and the Northeast via truck, rail, or ship. A possible solution for this supply and distribution problem is to construct biomass based ethanol production facilities in those areas. Ethanol will also increase the cost of RFG by 2.5 cents per gallon.

ETHANOL Reduces toxic air emissions not a cancer threat 

cost of making is to high compared to other additives
BIOMASS ETHANOL Reduces toxic air emissions, made from agricultural waste

MMT increase gasoline octane levels

inhibits proper functioning of emission-control sensors in later model cars. Manganese air pollution
MTHF increases oxygenate levels in gas without adversely affecting engine performance, and boasts octane rating  
TBA replaced tetra ethyl lead in gas

harder to remove from water than MTBE
ETBE reduces evaporative emissions and can be blended in the refinery. Also a slight octane boast

more expensive than MTBE, has problems with coldstarting, and low energy content
TAME increases octane rating

METHANOL directly as a fuel with modifications to the engine.

corrosive and poisonous
GTA FUEL ENHANCER increases horse power, reduces harmful emissions, makes cold starting easier, increases octane rating, and cost very little

MTBE can be shipped through existing pipelines, low volatility makes it easier to meet the emission standards.

cancer causing high solubility in water



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