Does all the catalyst drop with the glyc?

[Tony]

Running an experimental two stage today:

• stage one 12% meth and excess catalyst (enough to react the whole batch and then some)
• drained the glycerol
• stage two 4% meth with NO catalyst

Stage one mixed for three hours at 65C (had other things on the go today) and reacted well, leaving very approximately 10% unreacted oil.
So I expected an stage two easy clear pass with twice as much meth present as necessary, though this time I didn't add extra catalyst.

After an hour, no further reaction appears to have taken place.

So I am mixing up some methoxide with enough catalyst to cover the unreacted oil.

I can only assume when the stage one glycerol was removed, all the catalyst went with it.  I assumed some would remain in suspension, especially given the excessive quantity I added - but clearly not.  Perhaps that only happens when there is methanol/methoxide still present?

[Julian]

I'd tend to agree, I recon it stays in the glycerin as does much of the methanol.

The last couple of batches have been buggers to get a full conversion.  On both I used about 18 - 20% methanol and under dosed the catalyst (as I normally do).  Often you can get away with sticking ASM in a bio sample and wacking that in the processor just to convert the last knockings.

But this trick wouldn't work on the last two batches which failed a 3/27 after the second stage and I had to add quite a bit more methanol to get a clear pass.

[Tony]

Added catalyst and almost immediately got a clear pass.  Definitely stalled on catalyst rather than meth for stage 2 in this case.

[Manfred]

Interesting that. So it's safe to overdose on catalyst without it gelling on you so long as you under dose the methanol.  What's the soap content like and did you loose any bio due to manufacturing soap ?

 Was that with Koh.

[Tony]

NaOH - which it is safe to overdose so long as the oil is bone dry (no water).  The methanol amount is unimportant unless you have water present, in which case increasing methanol will reduce the occurrence of jelly soaps.

No yield loss so long as everything is dry (beyond that which is lost to water created by mixing your own methoxide anyway).

[Jamesrl]

I was always under the impression that all the catalyst not used in neutralizing FFAs was removed with the Glyc.

I  go for 15% methanol on both stages and under dose the catalyst, ASM is too expensive to prat around with, I never go above the equivalent of 3g (NaOH) on either stage and as I demeth I'd rather stall stage 0ne on catalyst than Methanol.

I know saponification takes place due to the neutralization of FFAs but haven't seen excess soap for a few years now. Glyc washing is a standard first stage in my production regime to neutralize as much FFA and remove as much of any remaining H2O as possible.

Fist stage reaction normally returns 95-97% conversion so very little meth and ASM is required to complete stage two, my second stage runs until demeth temperature is reached 85C.   

[Julian]

Been thinking about this, well, speculating really ... glycerin is of no use in the process, other than allowing us to do a pre-wash.

I've no idea if this is possible, most likely not, but how about adding a chemical which has no effect on the transesterification reaction, but will react with glycerin as soon as it's produced, converting it into something innocuous that won't hold on to methanol or unreacted catalyst?

Call for a chemist!

[Jamesrl]

Considering this Transesterification lark has been going on now for close to 150yrs I'd have thought a chemist type person would have come up with a solution to the glyc problem by now.

You never know the answer cold be buried somewhere in scientific papers on the subject.

[Julian]

We've been using ceramic wall tiles for over 1500 years, but have only recently devised a tool ....

[Jamesrl]

We've been using ceramic wall tiles for over 1500 years, but have only recently devised a tool ....

I'll bet Archimedes had one in his toolbox or Leonardo invented one years ago.


Nuffin' new in this world.