[Stoves] Vegetable oil or biodiesel?

[Crispin Pemberton-Pigott]

Dear Andrew

It must be in a heck of a lot of ethanol! Wow. 

I never look at it closely. Have you examined what is in oil that is just
heated? Perhaps with a catalyst (metal) in the pot?

If it is well insulated, maybe it will affect it. I know marula oil is
difficult to treat this way which is why it is used in cosmetics. It is very
resistant to heat degradation. 

Regards
Crispin


On Wednesday 09 November 2011 21:44:09 Crispin Pemberton-Pigott wrote:
> I think if you want to make a fuel you will have to avoid 
> saponification and I had not given it any thought, but if you add the 
> lye directly to the oil it will turn some of it into soap immediately 
> so they must have a method of keeping it pretty thin to avoid that.

That's why the caustic is added to dry methanol, to keep the water out, the
mixture of pure methanol and caustic makes sodium methoxide which splits the
triglyceride and the methyl radical immediately attaches to each of the
three fatty acid strings to make a single chain fatty acid ester which is
similar to diesel. Plainly the methanol contributes about 10% of the energy
in the biodiesel.

If water is present it catalyses the splitting and a sodium salt combines
with the ester instead.

AJH