Gasoline: How Does It Power My Car?

Gasoline, main fuel to power automobiles.

Gasoline, or commonly known as petrol, is the main fuel that use to power automobiles. 


Ever wonder how gasoline, which is mainly made up of hydrocarbons could power and move a huge car? Find out more here.

What is gasoline? What does it consist of?

Gasoline consists of a complex mixture of 500 hydrocarbons and is known as an aliphatic hydrocarbon. In other words, gasoline is made up of molecules composed of nothing but hydrogen and carbon arranged in chains. Most of the gasoline are hydrocarbons that may have 5 to 12 carbons. Smaller amount of alkane cyclic and aromatic compounds are present. Virtually, there are no alkenes or alkynes can be found in gasoline.   

The typical composition of gasoline:

 


  

Typical
  Composition of Gasoline

 

  

 General
  Name

  

 Examples

  

 Percentage

 

  

Aliphatic - straight chain

  

 heptane

  

 30-50

 

  

Aliphatic - branched

  

 isooctane

 

  

Aliphatic - cyclic

  

 cyclopentane

  

 20-30

 

  

Aromatic

  

 ethyl
  benzene

  

 20-30

 

Where does gasoline come from?

Gasoline is made from crude oil. The crude oil pumped out of the ground is a black liquid called petroleum. This liquid contains hydrocarbons, and the carbon atoms in crude oil link together in chains of different lengths. Hydrocarbon molecules of different lengths have different properties and behaviors. For example, a chain with just one carbon atom in it (CH4) is the lightest chain, known as methane. Methane is a gas so light that it floats like helium. As the chains get longer, they get heavier. 

An oil refinery plant.

The different chain lengths have progressively higher boiling points, and therefore they can be separated out by distillation. 

This is what happens in an oil refinery -- crude oil is heated and the different chains are pulled out by their vaporization temperatures. 

Naphthas, gasoline, kerosene, diesel, lubricating oils, paraffin wax are examples of different substances come from crude oil. The only difference is the length of the carbon chains!

How to increase the yield of gasoline?

The yield of gasoline is favored by converting higher or lower boiling point fractions into hydrocarbons in the gasoline range.  Two of the main processes used to perform this conversion: 

Cracking 

In cracking, high molecular weight fractions and catalysts are heated to the point where the carbon-carbon bonds break. Products of the reaction include alkenes and alkanes of lower molecular weight than were present in the original fraction. The alkanes from the cracking reaction are added to the straight-run gasoline to increase the gasoline yield from the crude oil. An example of a cracking reaction is:

alkane C13H28 (l) → alkane C8H18 (l) + alkene C2H4(g) + alkene C3H6 (g) 

Isomerization 

In the isomerization process, straight chain alkanes are converted into branched chainisomers, which burn more efficiently. For example, pentane and a catalyst may react to yield 2-methylbutane and 2,2-dimethylpropane. Also, some isomerization occurs during the cracking process, which increases the gasoline quality.


Octane Number?

I guess you have come across with this term when purchasing fuel. 
What is octane number refer to?

The octane number of gasoline is a measure of its resistance to 'knock'. 'Knock' refers to the detonation in engine of a car. Generally, octane number is determined by comparing the characteristics of a gasoline to isooctane (2,2,4-trimethylpentane) and heptane. Isooctane is assigned an octane number of 100. It is a highly branched compound that burns smoothly, with little knock. On the other hand, heptane, a straight chain, unbranched molecule is given an octane rating of zero because of its bad knocking properties.

Octane rating versus type of compound:

Octane ratings decrease with increasing carbon chain length.

Octane ratings increase with carbon chain branching.

Octane ratings increase in aromatics with same number of carbons.


So I suppose you have this question in mind: 

Which octane gasoline is suitable and should you purchase to run your car? 

Generally, for most of the automobiles, a lowest grade of 87 octane is sufficient to power and move the engine, unless the automobile is specifically said to use a higher octane gasoline. Also, keep in mind that using higher octane grades does not provide any extra power or extra mileage! Spend your money wisely! :)

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After the reading, you will sure have some ideas on what is gasoline about, how do we obtain it as well as information associated when purchasing gasoline. Well, let's get back to the main question. How does gasoline power my car? 

A gasoline engine uses internal combustion to generate power. Pistons in the engine compress air mixed with fuel, which ignites and creates the energy that powers your car. The amount of power your car's engine can produce is determined by how much gasoline and air are igniting within your engine. By stepping on the gas pedal, which opens the valves that let the air and gasoline in, you are actually regulating how much gasoline and air are igniting within your engine, then, your car is ready to move!