To the suggestion:
>glycerin settles slower in a poorly completed reaction.
Tom: "I wonder why"
To which Joe Street replied:
"Well I'm no chemist but my guess would be that the large Mono and Di and
triglyceride molecules that are left are jammed in between the ester molecules
and the glycerine has to jostle its way through it all on its way to the
bottom. Having just the light ester molecules in a highly complete scenario
makes it a little easier ride cause they get out of the way of the big heavy
glycerin more readily?"
An answer based on physical properties; nice
Let me try to add to that:
Glycerine has regions of charge at the -OH groups.
While Triglycerides probably wouldn't have such regions of charge, Mono- and
Di- glycerides would.
The uncharged fatty acid chains of the Mono- and Di- glycerides might interact
with the uncharged hydrocarbon chains of the BD while the charged regions of
the Mono- and Di- glycerides are associating with the charged regions of
glycerine. Sort of like the way one end of soap (uncharged) interacts with
grease/oils while the other end (charged) of the soap interacts with water.
Then again, maybe not. I thought I'd give it a try.
Tom
----- Original Message -----
From: Joe Street
To: biofuel@sustainablelists.org
Sent: Tuesday, August 07, 2007 4:38 PM
Subject: Re: [Biofuel] Biofuel Quality Test
Thomas Kelly wrote:
Hi Joe,
>glycerin settles slower in a poorly completed reaction.
I wonder why
Well I'm no chemist but my guess would be that the large Mono and Di and
triglyceride molecules that are left are jammed in between the ester molecules
and the glycerine has to jostle its way through it all on its way to the
bottom. Having just the light ester molecules in a highly complete scenario
makes it a little easier ride cause they get out of the way of the big heavy
glycerin more readily?
Interesting experiment.
I make two grades of BD
Good: passes quality test; used for car
Not so good: fails QT used for boiler (heat)
I could take a separate sample from each after 6 - 8 hrs settling and
note whether more glycerine drops out of one or the other.
(I'll have to make a note of this and try it when I get some time)
Yes this is a good idea. Let me know what you find out.
Do you agree that settling does not remove unreacted oil?
Yes oil is soluble in esters.
I guess I could do a quality test on "Not so good" BD after 6 - 8 hrs
of settling, repeat the test after 7 days of settling and see if less residue
dropped out.
(Make another note of this).
No I don't think this will give meaningful data because it is the mono/di and
triglycerides that settle out of the methanol test ( and soap) but the glycerol
will stay in solution in the methanol.
Joe
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