"Methacid" method

[dodge50]

Being a newbie to this Forum I've been catching up on old posts. Instead of adding acid to methanol, add the methanol to the oil, mix and while mixing slowly pour in the acid. It's a lot safer.

[Julian]

No oil at this stage it's a method for neutralising soap in bio.

The methanol is used as a carrier for the acid.  I'm not sufficiently knowledgeable to say if adding neat conc. acid to bio is safe, but the method I tried with the methanol, as suggested by PC, seemed to work.

I'm sure I've read neat acid on oil will carbonise it ... would that also be the case with bio?

[dodge50]

Hi Julian. I'm no chemist but I've been reading up on 2 stage reactions with conc Sulphuric acid as the first stage and adding the acid after mixing in the methanol seems to be acceptable.

[Julian]

Ah, are you talking about acid esterifiucation?

Having made a heated stirrer, I've been intending to have a small scale play with that, but work keeps getting in the way!

[dgs]

As I'm sure a lot of you know that I am not adversed to trying new things, so well done to Julian and the guy that first tried this.
However, I am not a great lover of acid washing. The question I ask myself is why convert an unknown amount of soap to FFA's, one of the things we are trying to remove from the oil in the first place.

I realise FFA's can be a good source of fuel in the right circumstances, but in an HDI engine?

[Julian]

I'm not a sufficiently good chemist to know if it makes FFA, but the sole aim of this process was to neutralise the soap in biodiesel to "something" in order to get rid of it.  I believe Paul said it converted to sodium sulfate, but don't quote me on that ... there may be more info on the wiki.

As stated above, converting FFAs to usable fuel is something totally different and an area I've yet to blunder my way into!  Given time I'm sure I can add it to my list of heroic failures.

[dgs]

I'm not a sufficiently good chemist to know if it makes FFA, but the sole aim of this process was to neutralise the soap in biodiesel to "something" in order to get rid of it.  I believe Paul said it converted to sodium sulfate, but don't quote me on that ... there may be more info on the wiki.
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I am pretty sure the soap is converted to FFA's, but on any biodiesel spec sheets I cannot find a max for FFA's in finished fuel, does anyone know?
This is the way that ion exchange works, by replacing the Na or K ion at the end of the molecule with a H ion. The ion exchange beads are coated with an acid (from memory I think it is sulphonic acid)

[Julian]

Found a couple of pages which agree with your statement ... soap + acid = FFA.


This methacid wash was just an experiment to keep the bio water free and obviate drying.

Logically though, wouldn't the same thing happen with an acid/water wash?  If so, would the FFAs get washed away in the water or stay in the bio?

Perhaps the standards were drawn up before the common use of dry media, hence no FFA content limits.

[dgs]

Yes, an acid wash does the same thing.
I'm reasonably sure that they stay with the bio.

Maybe its not really bad, I don't know, but if a batch had been really over-chemicaled ( i know thats not a proper word) the soap level could be sky high.

One of the most efficient ways I have found of getting rid of soap is to wash the bio with pure glycerine.
This can be done preferably after de-mething and whether you water wash or not. It's expensive, but can be used many times, until it gets towards saturation. I have had the soap level of non de-methed bio down to 10ppm in the processor by using this method.

Maybe the subject of a new thread sometime.

[Julian]

So acid esterification, to get shot of FFAs without forming soap in the first place could, theoretically have it's merits.

I've tended to hear more bad things about acid esterification than good.

[Julian]

One of the most efficient ways I have found of getting rid of soap is to wash the bio with pure glycerine.
This can be done preferably after de-mething and whether you water wash or not. It's expensive, but can be used many times, until it gets towards saturation. I have had the soap level of non de-methed bio down to 10ppm in the processor by using this method.

Maybe the subject of a new thread sometime.

It would be most interesting to have a thread on the subject, or even a wiki page it you fancy it.

To that end I've just given you wiki editing rights!

[high compression ii]

Found a couple of pages which agree with your statement ... soap + acid = FFA.


This methacid wash was just an experiment to keep the bio water free and obviate drying.

Logically though, wouldn't the same thing happen with an acid/water wash?  If so, would the FFAs get washed away in the water or stay in the bio?

Perhaps the standards were drawn up before the common use of dry media, hence no FFA content limits.

Yet Another Innovation to BioDiesel Process, YAIBP!


Yes--Soap neutralisation will form FFA'a....

But In the presence of Methanol--the (Remaining Acid not consumed in neutralisation) will act as Catalyst and Esterify the FFA into esters.....

--As an observation/experiment--Add approx 2.5-3.5mL Extra Acid in addition to your titrated quantity per L of Biodiesel--So there's sufficient left over to Esterify the FFA liberated, and Maybe increase the yield just slightly....

The Esterification stage--when done on raw oil though is a rather long time-consuming process stage--Maybe the extra heat during the De-meth after the 'methacid' stage is sufficient to shorten this into the usual de-meth time....