FFAs / Soaps - question for chemists

[nathanrobo]

Soaps are produced in the presence of Lye, water and FFA right??

So KOH & NaOh users see more of them than those using methylate due to the lack of water in the process right??

[julianf]

As i understand it, the saphonification occurs between the triglyceride, water, and alkali as per the following -



I think that the issue with the FFA's is the "acid + base >> salt + water" reaction.  Which, of course, then gives more water for the reaction above.

I was under the impression that the reason why methylate reduced the water (hence soap) was not because it altered either of the two reactions above, but simply as, with the standard "methanol + catalyst" mix, there is water produced from the mixing of the alkali and methanol.

[Tony]

That's right. Did you see the lazyman process thread here? I'm still doing it with excess NaOH methoxide.

[nathanrobo]

You may have to bear with me a bit here, as I'm no chemist, but:

Does this mean that there might be processes that result in fuel that has higher FFA content than say the standard because the soaps aren't being produced?

[julianf]

not as i understand things -

the FFAs would still undergo the "acid + base" reaction, and produce water and their salt, regardless.  the a.methylate process would not change this.

[nathanrobo]

Searched the forum and couldn't see anything that helped other than this comment from Tony "That might be the point where breakdown to FFAs occur without the presence of water - maybe water has an effect at lower temperatures."  Seems that my understanding isn't completely correct - so what are the other conditions for the for the production of FFA's

[julianf]

Other than the post you mention, ive never read discussion of FFAs being produced in the 'standard' process (i know paul.c gets up to all sorts though!)

Their mention is generally how to deal with them in the feedstock (ie they have been produced outside of our processes)

What i mean to say is that we dont generally seem to be involved in 'creating' them, but rather 'dealing with' them. 

Im not sure of the means of production outside of our process, other than the little i know about splitting them off from the waste 'glycerol' and the brief reading ive done on the acid catalysed reaction, but, again, im not sure this is what you are asking about?

[nathanrobo]

I came across a motor industry document (can't remember which manufacturers), but bio with different methods of FFA were tested and they seem to be having a detrimental effect, perhaps either causing corrosion or reduced lubricity - can't remember, but I'll try to find it again.

Anyway that got me thinking about:

• Whether we can test for it?
• What processes lead to more or less in the final fuel
• And whether the final content % mattered more or less dependent on the fuel injection technology used (eg, mechanical di, fly-by-wire DI, Common Rail etc

[julianf]

ahh, ive just realised -

isnt that the difference between resin towers and hardwood?  hardwood removes the soaps (ie bonds them away) whilst resin towers convert the soaps back to FFAs?

(im not sure of this though)

[nathanrobo]

mate

i wasn't really thinking about that towers, as I chickened out of trying resin as there was no clear info on advantages over free HW shavings.

As I say, it seems that the motor industry were concerned about FFA % in bio a few years ago (when they reckoned that bio could be used in their cars).  The implication is that there's evidence of FFA's in bio at a level that could be an issue.  Thinking aloud, this could have been when commercial producers had gone across to resin. 

But can we test for FFA's without spectra analysis?  Are we certain that post reaction FFA's are either non-existent or at such a low level that it's not worth discussing?

It's always worth asking the questions until you can either discard the issue as irrelevant or find a solution.  Plus you can always count on me to ask the stupid question that nobody else will ask!

[julianf]

When people do the titrated water wash, they add acid to bring the product down to about neutral.  So the product is basic (alkaline) prior to that.

Can an acid 'survive' in an alkaline solution? 

Titrations test for pH, but obviously they would test for more than just FFAs.  Is the possible damage in the reports linked to acidic fuel, or specifically FFAs i wonder.



Also-

Is the commercial fuel in the reports produced in anything like the same processes we use?
Does bio go acidic over time (long term storage)?

[nathanrobo]

When people do the titrated water wash, they add acid to bring the product down to about neutral.  So the product is basic (alkaline) prior to that.

Can an acid 'survive' in an alkaline solution? 

Titrations test for pH, but obviously they would test for more than just FFAs.  Is the possible damage in the reports linked to acidic fuel, or specifically FFAs i wonder.

Also-

Is the commercial fuel in the reports produced in anything like the same processes we use?
Does bio go acidic over time (long term storage)?

More questions... so would pure FFA show up with a specific PH value? If PH is a reliable way to test for FFA, is there a way to identify FFA vs other acid in a ph test?

The report that I read talked about lubricity and corrosion.  It would seem that as bio oxidises it becomes more acidic.this would assist corrosion, but would it reduce lubricating properties?  There is not a direct correlation between viscosity and lubricity, which was the other problem reported with FFA content in Bio.  Maybe FFA's in Bio increase the propensity for fuel to oxidise and without reducing viscosity the acidic properties are reducing lubricity.  Again, could use a decent chemist's view.