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Name: Ken J.
Status: Other
Age: 20s
Location: N/A
Country: N/A
Date: April 2003

A once popular TV show called "Mr. Wizard's World" aired a program where "Mr. Wizard" (Don Herbert) showed a child how to refine oil from crude using a very simple-looking, science fair-like rig. Since that program, the boiler method of producing gasoline has been altered dramatically with the advent of chemical catalysts.

Even though it is not recommended for one to do even small amounts of gasoline refinement, could you at least tell how gasoline is currently being made...if not tell of resources so that very small amounts could be made for research/science fair/demonstration purposes?

Crude oil is made up of a large variety of hydrocarbons. They are usually classified by molecular weight (how many carbons). Here is a VERY simplified example;

C=1 --> CH4 (methane)
C=2 --> C2H6 (ethane)
C=3 --> C3H8 (propane)
C=8 --> C8H18 (octane) ... and so on.

This large variety or spectrum of hydrocarbons gives rise to many different boiling point temperatures for each molecule type. This is where the FRACTIONATING DISTILLATION COLUMN comes into play. Chemical engineers and process engineers design huge fractionation towers that have product outlet ports every "x number of feet", up from the bottom. They heat the bottom of the tower and run coolant through the inside of the tower BUT NOT IN CONTACT WITH THE OIL. The coolant line is isolated from the process line (oil line). They run the coolant to create a temperature profile along the height of this tower. Each type of hydrocarbon has its own specific boiling point, b.p. (methane's bp is lower than octane's b.p.). As the "mix" moves up the column (temp. profile getting colder) the lower molecular weight molecules will start to "dew" out and exit at each point. At the very top you will have lower molecular weight fractions such as CH4, C2H6, etc...

Keep in mind that this is not very precise. They are many other compounds in crude oil than just simple straight chained hydrocarbons. There is aromatic hydrocarbons, there can be some sulphur compounds, etc...

You may ask, "OK, Fine. I want to have 1 litre of 99.999% pure hexane (C6H14)" You would have to go to the product outlet port on the tower that is producing the highest fraction of C6H14 (which will also contain relatively high quantities of C5 and C7). Collect all of this product and then run a separate continual fractionation of that until you get the desired purity of, in this case, C6H14. It is this additional time and energy that explains why you might pay quite a bit more for 99.999% product vs. 97% product.

Darin Wagner

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