The no titration two stage process.

[DavidA]

Just been reading the above in the wiki.
Could someone elaborate on the following instructions,

Determine the amount of unprocessed oil in your batch from the dropout.
Make up the second stage methoxide by mixing "unprocessed oil volume x 20%" methanol with "unprocessed oil volume x base" catalyst.

Dave.

[nigelb]

2 stage process.
Undercook stage one by using 5g per litre of oil
Allow it to settle and take a 10ml sample. Put this into 90ml of methanol and mix. See what drops out. For me typically 2ml of oil sits at the bottom.  This means you have 20% unreacted oil.
Drain the glyc.
Stage 2:
Add 5g NaOH per litre unreacted plus a bit of methanol. This should take the batch to full reaction.

[dgs]

IMO the typical 80/20 two stage reaction leaves the crude bio too far from the reaction end point to get accurate process results if water washing. I now like to get about 0.3mls dropout before the penultimate reaction (even though this can mean 3 stages)

Only by having a really small final stage can the slight over-chemical addition be determined accurately. This avoids the mono's when water washing.

Remember mono's are present with a clear 10/90 if the test is just on the cusp of clear.

The 10/90 test does not work the way most people think. It is not a case of the dropout being all oil, it's more like 50/50 oil/biodiesel.

[countrypaul]

The solubility test should be carried out with both components at 20C for best results. The methanol should be very pure - if there is significant water present you will always get dropout even from just bio.
o
The test was never designed to be quantitative, though it is usually accurate enough for determining the quantity of reagents needed.

If using the 2 stage non titration method it is often possibe to use much less methanol, 16% for example, but it is best to make sure you have mastered the porcess before trying to optimise the use of reagents.

if your oil is very acidic, or you are unsure, then it is worth titrating first regardless. If the oil titrates above 5 for example, you are unlikely to get any conversion as all the caustic will be used in neutralising the FFA.

[DavidA]

Thanks for those replies.
I'll give the two stage method a try. I don't have much trouble with my oil, it's quite clean. But always good to try something else.

At the moment I'm wrestling with these soap tests. Things are not going to plan.

Paul,

..if your oil is very acidic, or you are unsure, then it is worth titrating first regardless. If the oil titrates above 5 for example, you are unlikely to get any conversion as all the caustic will be used in neutralising the FFA...

Would that mean you will get a large drop-out on the first try, and will have to do maybe three stages ?

[countrypaul]

David,

It depends on how acidic the oil is, yes you would get a large dropout, but you could even need 4 or 5 stages. Some people have reported getting UCO that titrates at 20+ 

I use the 2 stage no titration normally, but if the oil is suspect, I titrate, or try a Dr Pepper test to check.

Neutralising the FFA will produce water that will catalyse more soap formation (neutralising FFA produces soap), so you may gets lots of soap with little glycerol and find it difficut to find the glycerol as it may take a long time to drop out (days) or may not drop out at all thanks to all the soap. This can result in creating a huge mess and little to no bio..

[dgs]

The solubility test should be carried out with both components at 20C for best results.

Hi Paul, from many tests I have done the recommended temp of 20degs isn't low enough. The test can remain clear is Summer overnight (temps between 15 and 20 degs) for days, then we get a night of 12 or so and bobs your uncle, yes you got it, theres the dropout.

For more accurate results I use down to 10.

[countrypaul]

Dave,

I seem to remember that the test is only vaid for an hour os so after being carried out and leaving it longer can show false results (not sure where I go that from though) - so leaving it a few days might not be accurate though I don't know why.

Found a reference: https://www.utahbiodieselsupply.com/biodieseltutorial/methanoltest/

[dgs]

Thanks for those replies.
I'll give the two stage method a try. I don't have much trouble with my oil, it's quite clean. But always good to try something else.

At the moment I'm wrestling with these soap tests. Things are not going to plan.

Paul,

..if your oil is very acidic, or you are unsure, then it is worth titrating first regardless. If the oil titrates above 5 for example, you are unlikely to get any conversion as all the caustic will be used in neutralising the FFA...

Would that mean you will get a large drop-out on the first try, and will have to do maybe three stages ?

     

Excess amounts of soap means more glycerol, there is only about 7% glycerine in veg oil. Calling the by-product glycerol is a little misleading.

If you ever have high titrating oil there is an easy way around it. in your glycerol pre-wash add an amount of catalyst that will neutralise the ffs's. As the neutralisation is then done in the presence of glycerol any water produced is absorbed by the glycerol, making the oil dry and ready for conversion.

[dgs]

Years ago someone on here reported that after processing oil that titrated at 25 (yes, 25) the yield was 62%, After using the enhanced pre-wash method the yield went up to 82% with the same oil.

[dgs]

Dave,

I seem to remember that the test is only vaid for an hour os so after being carried out and leaving it longer can show false results (not sure where I go that from though) - so leaving it a few days might not be accurate though I don't know why.

I think the only time a false result can occur is if the test is so cold that a residue can form at the tube base. I have had this when leaving the test in the fridge for extended periods.

I did dozens of tests years ago when I was doing the dropout v oil comparison. I couldn't understand why adding 1ml of oil to a clear test gave about 2mls dropout. i will see if I can find the thread although the graphs i did at the time will have disappeared.

[dgs]

Here it is and the graph is still there.

http://biopowered.co.uk/forum/index.php?topic=2523.0

There is also a comment from Chug in the thread mentioning Neutrals findings on the 3.5 v 5gms of NaOH.

[countrypaul]

Been thinking about why there is a supposed time limit on the test, the one thing that has crossed my mind is whether the bio is likely to polymerise at all (since most of the oils we use are unsaturated). Even just if dimers were formed these would have a much higher MW and therefore would likely be less soluble. the results would vary from oil to oil depending on source, linseed might well go off very quickly, whereas a saturated one like stearin would not polymerise at all. The main problem with this theory is that polymerisation slows down as temperature drops which does not appear to equate with obsevations.

I can't find an original paper at present so why Jan suggested 20C for consistency is not clear to me.

I have to admit to doing the tests with methanol at whatever temperature it happens to be at (roughly 10C last week) and when that gives a pass I am quite happy.

[DavidA]

Now here is something different.

I did a sample litre as per the wiki.

Here are the results.

Make your first stage methoxide solution with base amounts 3.5g/l for NaOH or 5g/l KOH x full batch size + 80% of normal methanol amount.

I normally use 240Mll/Litre. So I made up a 192 mL + 3.5g mix.


Put this first stage methoxide mix into the processor at normal reaction temperature, and mix for an hour.
Stand for 20 minutes ..

Added this to 1 litre of oil at 50C, shook vigorously, then repeated the shakes for an hour (my usual method).

..and drain off the glycerol into a clean container, and seal.

Here is where things went strange.

There was no glyc drop out. Just about 30cc of (apparently) bio sitting on top of the rest which appears to be a very cloudy (but stable) liquid.


Do your 3/27, 5/45 or 10/90 test and measure the amount of drop out.
Determine the amount of unprocessed oil in your batch from the dropout.

What happens if there is no drop-out ?

Dave.

p.s.  I've made a few test samples by the old  titration method over the last day or two with no problem. They are in the car tank.

NigelB,

..Undercook stage one by using 5g per litre of oil

Yes, I did read that and am going to do it. Just wanted to see what the method as per  wiki worked like.

[dgs]

But if your oil titrates and you have added only 3.5gms you will have hardly processed any oil into bio. Try a 10/90 you maybe surprised.

I must admit IMO those wiki instructions are to say the least not very good. That 80/20 split of the 2 stages just isn't accurate enough if you water wash. No wonder people end up with emulsions!