refining vegetable oil?

I posted this in sci.energy, but noone seemed interested. There seem to
be some smart chemists here, so I'll ask again.....
The transesterification process used to convert vegetable oil to
biodiesel evidently breaks 20 carbon chains into 10 carbon chains. I
take it this cetane rating is what characterizes diesel fuel. My
question is, can you dump a batch of straight vegetable oil into a
crude oil refinery and catalytic crack it into gasoline like they do
with Arabian crude?? Break the cetane into octane, propane, butane,
methane?

fwiw

http://www.chemicalhouse.com:8080/nl...tter.jsp?id=94

mho
vƒe

"BobG" > wrote in message
oups.com...
> I posted this in sci.energy, but noone seemed interested. There seem to
> be some smart chemists here, so I'll ask again.....
> The transesterification process used to convert vegetable oil to
> biodiesel evidently breaks 20 carbon chains into 10 carbon chains. I
> take it this cetane rating is what characterizes diesel fuel. My
> question is, can you dump a batch of straight vegetable oil into a
> crude oil refinery and catalytic crack it into gasoline like they do
> with Arabian crude?? Break the cetane into octane, propane, butane,
> methane?

This isn't quite right. Most animal and vegetable oils are composed of
glycerine esters of fatty acids. The fatty acids commonly have chain
lengths
of C16 through C18, but both shorter and longer fatty acids also form a part
of some of these oils.

When you transesterify, you do not break the acids into 10 carbon chains.
You break the triglyceride, leaving glycerine and ethyl esters of the
original
fatty acids. For example, the ethyl ester of an 18 carbon fatty acid will
have
a total of 20 carbons in the molecule.

The cetane number is a value used for characterizing diesel fuel, similar to
the
way octane number characterizes gasoline. A 100 Octane gasoline does not
have to have any isooctane in it. It is just a test basis.¨

There are chemicals called Cetane Number Improvers which can be used in
diesel blends to raise the Cetane Number of the fuel.

A refining process could be optimized to handle vegetable oils and convert
them to other things. It would make for rather expensive fuels, most
likely.