What is Ethanol Combustion?

Image Credit: 
Main Image: 
Ethanol combustion.

Ethanol fuel is ethanol (ethyl alcohol), the same type of alcohol found in alcoholic beverages. It is most often used as a motor fuel, mainly as a bio-fuel additive for gasoline. World ethanol production for transport fuel tripled between 2000 and 2007 from 17 billion to more than 52 billion liters. From 2007 to 2008, the share of ethanol in global gasoline type fuel use increased from 3.7% to 5.4%. In 2009 worldwide ethanol fuel production reached 19.5 billion gallons (73.9 billion liters). Most cars on the road today in the U.S. can run on blends of up to 10% ethanol, and the use of 10% ethanol gasoline is mandated in some U.S. states and cities. Bio-ethanol is a form of renewable energy that can be produced from agricultural feed stocks. It can be made from very common crops such as sugar cane, potato, manioc and corn.


What is Combustion?

Combustion or burning is the sequence of exothermic (a process or reaction that releases energy from the system, usually in the form of heat, but also in the form of light) chemical reactions between a fuel and an oxidant (compound that transfers electrons) accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame. Fuels of interest often include organic compounds (especially hydrocarbons) in the gas, liquid or solid phase. Combustion is a term that simply means the ‘burning of things’. It occurs all of the time surrounding us, from the flame of a lighter to the controlled explosion that powers a muscle car’s engine. Various substances for combustion are commonly being considered for various reasons, including the abundance of the substance being burned and what is produced when that happens. One such substance which is frequently utilized for combustion is ethanol, also known as ethyl alcohol or grain alcohol. Combustion is very important; it is the basis of the internal combustion engine, for example.


What are the properties of Ethanol?

  • The molecular formula for Ethanol is C2H6O.
  • Ethanol is a volatile, colorless liquid that has a slight odor.
  • The Melting Point is -1150C
  • The Boiling Point is 780C
  • The Specific Gravity 0.79.
  • It is completely miscible with water and organic solvents and is very hydroscopic.
  • The physical properties of ethanol stem primarily from the presence of its hydroxyl (OH) group and the shortness of its carbon chain. Ethanol’s hydroxyl group is able to participate in hydrogen bonding, rendering it more viscous and less volatile than less polar organic compounds of similar molecular weight.
  • Ethanol is a versatile solvent, miscible with water and with many organic solvents, including acetic acid, acetone, benzene, carbon tetrachloride, chloroform, etc.


How is Ethanol Produced?

Ethanol is produced in 3 ways:

  • Ethanol is produced both as a petrochemical (chemical products derived from petroleum), through the hydration of ethylene.
  • Biologically, by fermenting sugars with yeast. Fermentation is the process of deriving energy from the oxidation of organic compounds, such as carbohydrates, and using an endogenous electron acceptor, which is usually an organic compound.
  • Ethanol may also be produced industrially from ethene (ethylene). Addition of water to the double bond converts ethene to ethanol:

C2H4 + H2O --> CH3CH2OH

This is done in the presence of an acid which catalyzes the reaction, but is not consumed. The process which is more economical depends on prevailing prices of petroleum and grain feed stocks.


What is the Combustion reaction of Ethanol?

Ethanol combustion is quite a simple process. Ethanol and oxygen combine in a chemical reaction with the help of a little bit of energy. The reaction results in a significant release of energy in the form of heat and light, as well as the formation of carbon dioxide and water. Complete combustion of ethanol forms carbon dioxide and water vapor with a specific heat of 2.44 kJ. The chemical reaction of combustion of Ethanol is given as below:

C2H5OH (l) + 3 O2 (g) --> 2 CO2 (g) + 3 H2O (g) ; where, l, g stands for liquid and gaseous phases.

With the help of molecular formulas, Ethanol combustion can be characterized chemically. Ethanol, represented by C2H5OH, combines with six oxygen atoms denoted as ‘3O2’. When the reaction is commenced through the addition of energy in the form of heat or a spark, 2CO2 and 3H2O (two carbon dioxides and three water molecules) are formed. Energy is also released when the reaction occurs.


What are the benefits of Ethanol and combustion of Ethanol?

  • The heat of the combustion of ethanol is used to drive the piston in the engine by expanding heated gases. It can be said that sunlight is used to run the engine (as is the case with any renewable energy source, as sunlight is the only way energy enters the planet).
  • Ethanol fuel is widely used in Brazil and in the United States, and together both countries were responsible for 86 percent of the world's ethanol fuel production in 2009.
  • Ethanol may also be utilized as a rocket fuel, and is currently in lightweight rocket-powered racing aircraft.
  • The largest single use of ethanol is as a motor fuel and fuel additive.
  • Ethanol combustion in an internal combustion engine yields many of the products of incomplete combustion produced by gasoline.
  • Hydrous ethanol (about 95% ethanol and 5% water) can be used as fuel in more than 90% of new cars sold in the country.
  • There is also potential for bio-ethanol replacing some kerosene use in domestic lighting from feed stocks grown locally.
  • Ethyl alcohol is also relatively easily made from fermenting plant materials, while other fuels require significantly more difficult processes to create.
  • Ethanol combustion, however, produces less heat energy than many other commonly used combustible materials.
  • The most common places where ethanol combustion occurs is in vehicle engines and It is not unusual for some farm machines and other lightweight vehicles to be powered only by ethanol fuel.


What are the Negative aspects of Ethanol?

External References
Related Videos: 
See video
Related Images: