I am sure this idea has been discussed but I could not turn up search results...

It was touched up on in the Methanol managment thread here:
http://biodiesel.infopop.cc/eve/forums/a/tpc/f/629605551/m/585600516

but the idea was in reverse...

Instead of trying to use minimal methanol ...why not use a massive excess of methanol in the acid stage...like 200% (or more).
In this case any water formed would end up in the methanol and float with the methanol above the oil after acid reaction, no?

The higher the ratio of methanol to oil, the lower the ratio of water to methanol.

Oil is drained post acid reaction (and settling) and move along to base stage.

Acid and makeup methanol could be added to the methanol "bath" with each batch as needed.

New batch of high FFA oil added to Methanol/Acid bath.

Over time the water would accumulate in the methanol layer and this layer could then be dealt with when needed (fractional distil/zeolite/corngrits,whatever).

Does water in the methanol even affect acid esterification? If not it only becomes problematic when the methanol/water layer no longer wants to float on the oil,making separation difficult.

I imagine there are people here doing something like this.

quote:

Originally posted by vegenergy:
Instead of trying to use minimal methanol ...why not use a massive excess of methanol in the acid stage...like 200% (or more).
In this case any water formed would end up in the methanol and float with the methanol above the oil after acid reaction, no?

The higher the ratio of methanol to oil, the lower the ratio of water to methanol.

Oil is drained post acid reaction (and settling) and move along to base stage.

Are you sure the oil will settle?

For that matter, are you talking about oil as in "unreacted triglycerides" or oil as in "methyl esters"?

The methyl esters will not settle. They are soluble in large amounts of methanol. Their solubility in large amounts of methanol is the basis for the 3/27 test.

Most of the unreacted triglycerides will probably settle, but some may stay dissolved in the methanol because of the co-solvent effect of the methyl esters and any mono- and di- glycerides that may be present.

that sound similar to the ISU method of acid/base processing with a few twists...
interesting thoughts..are the geared toward home brewing or commercial production?

also the FFA will dissolve into the methanol. TG will not. this is known.

sorry if this seems like rambling, but but there is alot of new territory in acid/base processing that will be important in the future. since it allows using 'bad' oils. eventually the price the 'good' used oil will be beyond home brewing.


-dkenny

In ISU method the oil either floats or sinks depending on the percentage of water formed, and yes, what you're describing is exactly what they do. The question is how to purify that methanol to remove water, without the purification method being affected by the sulfuric acid that's now in the methanol.


The homebrew holy grail has been to do easy esterification without having to purify methanol afterwards, Dkenny's process seems to be the best we have so far. I've been experimenting over the last couple of years with a process where I just get as much of the 'homebrew' amount of methanol into the first stage as possible. This requires a mechanical KOH/methanol mixer for the second stage as you're making quite a concentrated methoxide there and the KOH doesn't dissolve passively as easily. I'll do more experiments this winter as apparently I've got access to Dkenny's awful oil source so I finally have reason to do this full-size, and I'll post any results.
In the meantime, what you're suggesting is a good idea, but we don't quite know what all the purification possibilities are.
Mark

This isn't as easy as it seems. For instance, simple math suggests that 5% water in methanol has a density of 0.8005 but Perry's Chemical Engineer's Handbook shows it at 0.824.