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Module 2:

Chemical and Physical Characteristics of Ethanol and

Hydrocarbon Fuels

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Objective• Upon the completion of this module,

participants will be able to describe the chemical & physical differences between gasoline & ethanol-blended fuels.

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Introduction• Characteristics of polar solvents &

hydrocarbons, their differences, & how they interact

• Conditions under which ethanol-blended fuels will retain popular solvent characteristics as compared to all hydrocarbon characteristics

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Characteristics of Gasoline

• Insoluble in water• Produced from crude oil by fractional distillation• Not considered poisonous:

– Harmful effects after long-term & high-level exposure

• Smoke from burning gasoline is black & has toxic components

• Greatest hazard is flammability:– Fairly narrow range of flammability

• 1.4% - 7.2% by volume in air

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Gasoline Production

David Parsons/NREL

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Characteristics of Ethanol• Renewable fuel source produced by fermentation

& distillation processes• Most common feedstock in U.S. is corn• Ethanol used with motor fuels must be denatured

with 2% - 5% gasoline or similar hydrocarbon before transport to a bulk storage facilities

• Denaturant has minimal effects on characteristic

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Feed Stock

Cooking

Cooling

Saccharification

Cooling

Yeast Propagation Fermentation

Beer Stripping

Beer Rectification

Dehydration

Denature

Storage & Transportation

Steam

Cooling Water

Cooling Water

Alpha Amylase Enzyme

Gluco Amylase Enzyme

Yeast

Cooling Water

Steam

Cooling Water

Cooling WaterSteam

Natural Gasoline Rust Inhibitor

190 Proof

200 Proof

Cooling Water

CO2

Non volatiles

Ethanol Production

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Characteristics of Ethanol • Ethanol is produced by fermenting corn,

conversion of corn starch into ethanol– Sophisticated grain handling equipment present

at ethanol production facilities

– Co-products from ethanol production include distillers dried grains, a high protein animal feed & CO2

• Future feedstocks will expand to include corn cobs & stover, switchgrass, sugar cane

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Characteristics of Denatured Fuel Ethanol

• Polar solvent• Totally miscible in water• Less toxic than gasoline/methanol• Toxic compounds not present in ethanol• Greatest hazard as motor fuel component is

flammability– Wider flammable range than gasoline:

• 3% - 19% by volume in air

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Characteristics of Ethanol

• In neat form, no visible smoke or visible flame• In denatured form, little to no smoke & slight

orange flame will be visible• Ethanol & some ethanol-blends can conduct

electricity• Large amounts of water required to dilute

ethanol to no longer support combustion

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Chemical Properties Comparison

Property Gasoline Denatured Fuel Ethanol

Flash Point -450F -50F

Ignition Temp 530 - 8530F 6890F

Specific Gravity 0.72 – 0.76 0.79

Vapor Density 3 - 4 1.5

Vapor Pressure 38 - 300mmHg 4.5mmHg

Boiling Point 100 - 4000F 165 - 1750F

Flammable Range 1.4% - 7.6% 3% - 19%

Conductivity None Good

Smoke Characteristics Black None - Slight

Solubility None High

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Invisible Flames - Ethanol

• Thermal imaging

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Activity 2.1: Comparison of Gasoline and Ethanol• Purpose:

– To allow participants to discuss the differences & similarities in the chemical & physical properties of ethanol & gasoline.

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Characteristics of Ethanol-Blended Fuels• Ethanol increases the ability of gasoline to burn

cleaner:– Lower emissions from unburned hydrocarbons

• Water contamination of ethanol gasoline fuel blends may cause phase separation:– Phase separation will introduce a water layer in

the bottom that consists of water & ethanol – All hydrocarbon gasoline will remain in the top

layer

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Characteristics of Ethanol-Blended Fuels• Water contamination of ethanol gasoline fuel

blends may cause phase separation:– Gasoline floating on layer of ethanol/water solution– Resulting ethanol/water solution still flammable

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Characteristics of Ethanol-Blended Fuels• Blending fuels alters physical & chemical

characteristics of original fuels:– Visual difference of smoke & flame

characteristics:

• Higher content of ethanol, less visible black smoke content & orange flame production

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Characteristics of Ethanol-Blended Fuels• Blending fuels alters physical & chemical

characteristics of original fuels:– When foam/water flowed on burning product,

gasoline tends to burn off first:• May have no visible smoke as the hydrocarbon

burns off leaving only the ethanol burning

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Activity 2.2: Definitions• Purpose:

– To allow participants to identify the definitions related to ethanol & ethanol-blended fuels.

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Worksheet 2.2: Definitions• Polar solvent• Oleophilic• Toxicity• Ethanol• Boiling point• Vapor density• Flammable range

– Upper explosive limit (UEL)

– Lower explosive limit (LEL)

• Hydrophilic– Water miscible

• Flash point• Combustible liquid• Flammable liquid• Hydrocarbon• Hydrophobic

– Non-water miscible• Specific gravity• Auto-ignition temperature

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Summary

• Ethanol is a polar solvent, miscible with water, & flammable

• Higher content of ethanol, less visible black smoke content, & orange flame production

• Blend of gasoline & ethanol can easily go unnoticed by emergency responders:– Ethanol will be last fuel to burn – Ethanol can burn without visible smoke