the reaction between FFA and methanol is an equlibrium when catalysed by an
acid
FFA + methanol <==> Me ester + water
so the reaction is driven to the right by an excess of methanol (the
reaction you want) but is driven to the left by an excess of water, so my
guess is that you need to get rid of water in your oil to make the FFA go to
Me ester, and more methanol will help push the reaction the way you want.
cheers, Tim
>From: Keith Addison <[EMAIL PROTECTED]>
>Reply-To: biofuel@yahoogroups.com
>To: biofuel@yahoogroups.com
>Subject: [biofuel] Fwd: Re: reducing ffa's
>Date: Mon, 11 Aug 2003 19:50:13 +0900
>
>Fwd from Biofuels-biz.
>
>
> >To: biofuels-biz@yahoogroups.com
> >From: Michael Allen <[EMAIL PROTECTED]>
> >Date: Mon, 11 Aug 2003 14:19:24 +0700
> >Subject: Re: [biofuels-biz] reducing ffa's
> >
> >Dear Colton (and indirectly Girl Mark),
> >
> >I think pH meters are very stable and reliable instruments these days.
>But
> >you have to rememebr that they measure the hydrogen ion concentration in
>a
> >solvent that allows ionisation such as water. (Indeed, the pH scale is
> >devised so that pH 7 is as neutral as water is supposed to be). Methyl
> >ester and vegetable oils are not such solvents. If you put the electrodes
> >of a pH meter into oil or an oil/water mix, the lack of an ionisable
> >solvent between them causes the apparent pH value to wander all over the
> >place. You can even damage some pH meters.
> >
> >I think that is also part of the answer for Girl Mark too: You can soon
> >test what Todd is saying by dropping some sodium hydroxide pellets or
> >flakes into some vegetable oil. You will see that it slowly reacts with
>the
> >glycerides to give sodium soaps which encase the pellets. This would make
> >ppoor hand-soap because the unreacted pellets would be quite dangerous.
>But
> >add some water and a little heat and the reaction is much faster and more
> >complete. The sodium salt of the fatty acid so formed can be skimmed off
>or
> >separated out with a strong brine solution (including calcium chloride
> >solutions just like emulsion breaking mentioned elsewhere). It may then
>be
> >washed with fresh brine at this time to remove unreacted sodium
>hudroxide.
> >The pH of the soap made in this way is usually then lowered by adding
>resin
> >(wood resins such as pine and kauri have been used for yonks) and
>buffered
> >by adding something like borax (sodium tetraborate) or a phosphate (which
> >also counters scum-formation in calcium-containing "hard" waters). The
>soap
> >is then left to harden ("aging") so that water evaporates and any sodium
> >hydroxide (lye) left gets a chance to react with carbon dioxide in the
>air
> >to make the less skin-aggressive sodium carbonate. (This is basically how
> >laundry soaps and soap powders were once made -- and still are in some
> >sustainable-technology countries). Some of these crude soaps are then re-
> >milled, heated with colouring, perfumes, resin, buffers, glycerol etc. to
> >make toilet soaps. (Incidentally, I think there are many more good
>recipes
> >on the net for soap-making than there are for ester-making. Here are just
> >three of the thousands presented by google:
> >http://candleandsoap.about.com/mbody.htm,
> >http://waltonfeed.com/old/soaphome.html,
> >http://members.aol.com/oelaineo/soapmaking.html)
> >
> >I'm sure you can see the similarities of this saponification reaction to
> >the transesterification reaction. And you can also see how the presence
>of
> >water can quickly turn one into the other!
> >
> >But to return to Colton's enquiry:
> >For the reasons given in the first paragraph, we measure the pH of the
> >wash-water in contact with the methyl ester. Of course it takes some time
> >for the two phases to come to equilibrium depending on how much mixing is
> >going on, surface area exposed etc. Strictly speaking, we are not trying
>to
> >make the oil pH neutral by washing so much as trying to remove sodium
>soaps
> >and methoxide. If these remain in the ester, they could be deposited in
>the
> >engine and may cause damage. (Whether such damage is more dangerous to a
> >diesel engine that a long drive down a spume-covered coast road I cannot
> >say ..... but it's an interesting thought!)
> >
> >Hope this is some help
> >
> >Michael Allen
> >Thailand
> >
> >On Thu, 07 Aug 2003 03:01:07 +0000, <[EMAIL PROTECTED]> wrote:
> >
> > > We are using a pH meter (& visual) methods during our titration to
> > > determine the ffa%. It is very frustrating since the pH meter readings
> > > are very inconsistant. Our current ffa% is 1.6% and we are trying to
> > > reduce it to .5% by acidification. Any comments on methods for
>determing
> > > the ffa%?
> > > Thanks
> > > Colton
> > >> How were you able to know that your ffa's increase?
> > >> If you are just using a pH meter, it is but natural that the pH will
> > >> fall
> > >> since you are using a strong acid H2SO4.
> > >> If you are titrating with NaOH, H2SO4 will eat up a considerable
>amount
> > >> of
> > >> lye.
> > >>
> > >> Christopher
> > >>
> > >> =>-----Original Message-----
> > >> =>From: Orion Polinsky [mailto:[EMAIL PROTECTED]
> > >> =>Sent: Tuesday, August 05, 2003 8:53 AM
> > >> =>To: biofuels-biz@yahoogroups.com
> > >> =>Subject: [biofuels-biz] reducing ffa's
> > >> =>
> > >> =>
> > >> =>hi all,
> > >> =>
> > >> =>I am trying to convert my free fatty acids to
> > >> =>esters by acidification using methanol and
> > >> =>H2SO4. Unfortunately, each time I try it, my
> > >> =>ffa level increases.
> > >> =>Is there anyone out there with a good
> > >> =>acidification recipe?
> > >> =>thanks,
> > >> =>Orion
>
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