Hi all,
I made a 25-gallon batch of Biodiesel using some partially hydrogenated oil I got from a sandwich shop. It titrated at 12 mL, I pretreated it with acid to 10 mL, and then processed it using the recipe for a titration of 10 mL (around 1700 g KOH total I think).

The next day, the batch has only cooled somewhat (down to 130F from 165F), and I see a small layer of clear-looking, light colored biodiesel at the top, and an extremely tall layer on the bottom, which I hope is a mixture of glyerine and biodiesel.

So, my question is, is my yield very very poor, or do I need to wait for the mixture to cool down more before the glycerine will settle out? Right now, I cannot tell any difference between a glycerine layer and a layer of darker Biodiesel on top, just a quite thin layer of light biodiesel on the very top. I'm hoping there is biodiesel in there that I can seperate out from the glycerine, but I'm not sure how if they don't seperate naturally. Is this common for partially hydrogenated WVO? Does anyone have any tips?

Thanks very much!

Brownhousechris,
If you can donate a bit more info, a diagnosis would be a little easier.

How much methanol did you use?
How much H2SO4?
How long did you mix, and by what means?
It could be that it needs to settle longer.

Is your reactor sealed to prevent methanol evaporation? 165 degF is above methanol's boiling point. If it is sealed, I suspect the very small layer could be methanol that's condensed and "floating" on top of the oil.
If that sounds right, heat the mixture back up to 130 and remix for two hours then let it settle overnight.

If your reactor is not selaed, then we have a little more work to do, but it's still salvagable.

Let us know if it's not sealed and we'll walk you through.
Give as much info as possible.

-Dave-

Hey Dave et al.
OK, here's some more numbers. I did the acid pre-treat by mixing 3.5 gallons methanol with 120 mL H2SO4, then processing that at about 150 for an hour. The mixture then sat in the processor for two days, before I mixed 2.5 gallons methanol with the 1700 g KOH.

The processor is the standard Appleseed, which incidentally seems to retain heat extremely well! There are three 3/4" ports on the top, two are sealed and the third is open to the air, so I imagine the methanol could eventually boil off.

Also, one thing I neglected in the first post is that while most of the WVO I used was the nasty hydrogenated stuff, I did use maybe 3 gallons of very nice, lightly and lighter colored used oil to get the batch up to 25 gallons. So, I'm wondering if the lighter stuff on top could be the results from that WVO? I would be pretty surprised, though, if it would separate out that clearly, I've used the pump the mix it all quite a lot.

Anyway, there are some more details, and I'd be very thankful for any more insight anyone has.

Chris,
Your problems stem from high titrating oil and not from the fact that it was partially hydrogenated.
When doing the acid-base you should make sure that your oil is extremely dry. This is because water is produced during the acid reaction. This water really hinders things.
I am a little curious as to if you drained the batch out of the processor? My more direct question is how you came up with the description of:
"The next day, the batch has only cooled somewhat (down to 130F from 165F), and I see a small layer of clear-looking, light colored biodiesel at the top, and an extremely tall layer on the bottom, which I hope is a mixture of glyerine and biodiesel." If this observation is from the site tube, it is unreliable.
You were a little on the warm side at 165F. I would expect a yield of between 50-70% with a transesterification reaction with a starting titration of 10.
DD

Last night I drained out the batch, and after about 9 gallons of glycerine I got some really nice looking biodiesel. I think Don was right, and it just needed more time to settle, and what was in the sight-tube probably was not a reliable indicator of the whole batch. That is good to know about making sure the WVO s dry before using the acid-base technique. I've had limited success using the acid to bring down the titration, so that might be a big help. Now it's on the the washing. Thanks!

I've had 2 acid/base batches that needed an extra 8 hours (over and above the ususal 8 hours) of settling time. I have not yet figured out why, but they just seemed to take longer to separate. They both burned with no problems, after washing.