Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Refining Oil Made Simple
Name: Ken J.
Status: Other
Age: 20s
Location: N/A
Country: N/A
Date: April 2003


Question:
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?



Replies:
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.

Regards,
Darin Wagner



Click here to return to the Engineering Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory