This is a topic which is very hard to pursue using the search facility. Searching for re-process finds all "re". So it seems good to start a new thread with easily found words in the subject line like "reprocess" without the hyphen.

First, do you want an exact measure of unreacted oil or just an indication?

For an indication, add 1g NaOH in 50ml methanol per litre of washed and dried biodiesel. If you use too much methanol the density of the glycerine may be too low to settle. Warm, shake and settle, as for making biodiesel. Separate the glycerine and evaporate the methanol from it and weigh the residue.

[For description of an experiment on this - see post below]

To obtain an exact measure would requires more steps including acidifying the glycerine and extracting any oils that were present.

In determining the amount of methanol to use one has to think about how much unreacted oil is likely to be present. Even a poor reaction will be 85% converted if it has managed to settle. So at the most 15% of the oil will still be there hence 50ml methanol per litre should be very ample. If you get a cloudy reaction which will not settle, try another sample with less methanol. If you do the test on unwashed biodiesel there will already be about 25ml methanol present so the NaOH should be dissolved in only 25ml methanol.

This message has been edited. Last edited by: neutral,

Just waiting to capture your advise again. As reading this about too much methanol in the glycerine brings me back to the subject of feeding cattle the left over glycerine. Is there any chemical that I could add to the spent glycerine that would render any excess methanol harmless ?

Not that I know of but evaporation costs nothing but effort. I suggest you start a new thread on feeding glycerine to ruminants. Might turn up some good info.

just a thought: does anyone know what the potential ecological impact of evaporating methanol is? for small scale operations it is obviously a common practice.... i dont think any of the cheaper kits include any meth recovery part , nor do a lot of homebrew rigs. in this common scenario the methanol in the fuel gets burnt in the fuel, goes into wash water, or evaporates. the methanol in the byproduct phase is probably left to evaporate by most homebrewers. but just how bad is this? anybody got any research or insights?

Reprocessing washed biodiesel.

Part of this thread was lost recently. It contained some debate about what you would see if you performed a reprocess test, which started me thinking.

There are two situations, washed and unwashed, and one would expect them to behave differently. With washed and dried biodiesel there would be no soap or methanol in with the esters.

I prepared a sample with new oil, using excessive KOH, 11g per litre of oil, and plenty of methanol, 250ml. Previous expts have shown by gc that this treatment gives over 99.5% conversion. I then treated it a second time and got a little more glycerine out. The upper layer was then washed and dried. The resultant material could be thought of as being virtually pure esters. This was divided into three parts and some veg oil was added to two of them, and then all were treated with KOH in methanol at the rate of 1.4g KOH (equivalent to 1g NaOH) in 50ml methanol per litre of oil. Results as follows:

Oil%__glycerine% by volume
0______0
2______trace
4______2

The first sample, with no oil added, of course showed no glycerine. The interesting thing about this one was that it did not even go cloudy, as the others did initially, just stayed perfectly clear. So that is an instant test for a very high conversion oil. The following day I added 4% oil to it and heated and shook. No glycerine appeared. The conclusion is that the catalyst had totally reacted overnight with the esters to form soap and was no longer available to react with the oil, and the soap produced remained in solution in the esters. This shows that we need never worry about unreacted caustic in biodiesel as it will all be soap before we can use it.

The second sample with 2% oil would be approximately equivalent to ASTM standard. This went cloudy initially showing that some reaction occurred. No significant glycerine was produced. Apparently, at that level, the methanol added in the test is sufficient to keep the glycerine produced in solution.

The third sample, equivalent to a 96% conversion, perfectly good biodiesel as judged by reports on this forum, showed some glycerine. It is clear that this reprocess test can show up quite low levels of unconverted material. The amount produced is augmented by the methanol so its volume will not be a good indicator of reaction, but if the methanol was evaporated and the residue weighed this would give a useful indication. You can judge how successful the original reaction was by noting that a complete reaction should give about 10% glycerine by weight after evaporation of the methanol from it. So if you got say 1% glycerine by weight, after evaporaton of methanol, in a reprocess test the original reaction must have been about 90% converted.

This message has been edited. Last edited by: neutral,

Look here for my experience of this topic:
http://forums.biodieselnow.com/topic.asp?TOPIC_ID=5667

Chris E.

maybe this has been done before, and if it has i'd love to see the results, but it seems like a series of test batches could sort this out. like, 1 L WVO + 0.5 g KOH + 50 ml MeOH, then 1 L WVO + 1.0g KOH + 50 mL MeOH, then 1 L WVO + 1.5 g KOH + 50 ml MeOH, etc. the point is, you use the same amount of WVO and methanol and vary the amount of KOH (or NaOH). and then graph the volume of glycerine produced against the amount the catalyst used.

i imagine that with too-low catalyst loadings you'll still get under converted fuel and thus too little glycerine. but too much catalyst will give the same amount of glycerine as just the right amount of catalyst. so the graph would sort of level out and the inflection point would correspond to the optimal amount of catalyst--just enough to give full converstion.

of course in practice things are never as simple as they "ought" to be according to theory. at any rate, the point is that not all under-processed oil is created equal. just becuase 1 g KOH + 50 ml MeOH per liter WVO works well for one batch, doesn't mean it'll work well for another batch, since the two batches probably have different amounts of under reacted oil in them.

I am currently studying for a major in chemistry and had a recent project involving biodiesel. I would like to answer some of the questions you have asked. First, the ecological impact of methanol evaporation is none, as the oxidation reaction methanol + oxygen -> carbon dioxide + water is spontaneous and has a short life. Nonetheless, if animals were to breath the methanol while it is in the atmosphere it would cause intoxication because of its partial oxidation to formaldehyde in the animal's liver. Second, as it was pointed out in the last post, there is a precise amount of catalyst which would provide the highest convertion ratio, but this amount, is based on many different variables. The two most important, are the equilibriumm (NaOH+alcohol-> methoxide + water), which, if pushed too far into the products can encourge soap formation and the free fatty acid content of the oil which would indeed, consume catalyst to form soap. In our study, our goal was to develop a solid catalyst, which could be used by a home producer, and would take care of all this complications. One of our most promising catalysts was made from CaCO3 and BaOH. From which we achieved 98% convertion and complete reutilization of the catalyst.

Danielfp,

Remarkable! What was your yield and what were your reaction conditions? You should start a new thread for this topic.

Deja Vu

There now seem to be two Reprocess threads going.
I will repost the following information onto this thread too.

World Famous Dr Pepper ASTM Reprocess test (Pat Pend) Revised

If you reprocess a litre of washed and dried biodiesel using the standard 1g NaOH in 50 ml methanol at room temp by putting the biodiesel in a 2 litre Dr Pepper bottle and giving it 20 good shakes and it forms a full gel within 5 minutes you have very high, probably ASTM conversion biodiesel.

I noticed that when I reprocessed a batch of high conversion biodiesel using the standard 1g NaOH in 50 ml methanol it often quickly forms a gel.
To further pin this down, I recently had my good friend Mickey and Billy run some tests.
This is their latest test series just as they teletyped it to me earlier today.

"Four- 1 litre batches of biodiesel were made from WVO titrating arount 0.5. The label said it was Vegetable oil with some soy content.

Each batch was processed, washed, dried viscosity checked with average of three runs, and then reprocessed at 30deg C.
The calibration of the viscosimeter showed that 1g additional triglycerides= an increase run-time of 1.16 seconds.

Batch A 250ml methanol 7.5g NaOH.
Viscosity run-time 2min 3.41sec.
Full Gel within a few minutes of re-processing.

Batch B 200ml methanol 5.5g NaOH
Viscosity run-time 2min 4.14sec.
Full Gell within a few minutes of re-processing.

Batch C 200ml methanol, 4g NaOH
Viscosity run time 2min 6.34 seconds.
Reprocess dropped further glycerine when left to settle over night.
Washed, dried and performed second reprocess; full gel formed within a few minutes

Batch D 180ml methanol 4g NaOH
Viscosity run-time 2min 6.86 seconds
Reprocess dropped further glycerine overnight.
Washed, dried and checked viscosity.
Viscosity run-time 2min 3.62seconds
Reprocessed, formed immediate gel.

Conclusions

Batch A was at near maximum conversion and almost certainly ASTM conversion quality.

Batch B was less than 1% lower in conversion and almost certainly ASTM quality.

Both Batch A and B formed an almost immediate full gel when reprocessed, however the gel in batch A was "Firmer"

Batches C and D both dropped more glycerine overnight, batch D producing more glycerine than batch C.
The reprocess viscosity of batch D was virtually identical to the viscosity of batch A.
Both batches formed an immediate gel when re-processed a second time.

By the slight difference in viscosity between batch C and D it appears that the NaOH drives the reaction "Harder " than the methanol does. I have noticed this before.

Re-processing is very accurate in determining an incomplete reaction.

I have randomly reprocessed Washed and dried litres of of "Production biodiesel" produced using 180ml methanol. They have all dropped further glycerine over night.
When I then Wash, dry and re-process a second time they form an immediate gel.

You can easily Try it yourself."

Thank you Mickey and Billy

Mickey also said that all four batches passed the "Shake-um up" test using warm water and all four failed it using cold water.

This message has been edited. Last edited by: Tilly,

quote:

Originally posted by danielfp:
In our study, our goal was to develop a solid catalyst, which could be used by a home producer, and would take care of all this complications. One of our most promising catalysts was made from CaCO3 and BaOH. From which we achieved 98% convertion and complete reutilization of the catalyst.

Danielfp, you have to tell us more!

Did you mix the two catalysts? How so?

And do you still use methanol? I figure you must?

How is the cost of this catalyst amalgum vs. KOH?

Time to share, dude!

Since you have showed so much interest, I will gladly answer your questions. First of all, and to have a clear definition, a catalyst is a substance which provides an alternative path for a chemical reaction without being changed in the overall process. Normally, the function of a catalyst is to achieve equilibriumm quicker in an espontaneous reaction. To understand the mecanism by which the catalyst works in a base-catalyzed transesterification reaction (biodiesel production) gives us the key for the development of an heterogenous catalyst (solid). We found various catalysts that could work for a home producer, the most appropiate, in my own opinion, would be one made with calcium carbonate and dopped with barium hydroxide monohydrate.Now, the efectiveness of the catalyst is widely determined by its surface area. So, the catalyst is very porous, nothing I guess, that can be easily done with home equipment. We used mainly methanol in our experimentation, though some trials were made with ethanol with unstatisfying results. Remember that the catalyst does not intervene in the net result of a reaction, so both products and reactants remain the same. I am not aware of KOH's price where you live. But I can assure you the catalyst would last for at least 1500 gallons of oil, at a price of no more than 50 us dollars. It is important, that the catalyst is poisoned by free fatty acids in the reaction, so WVO must be made neutral with another base before the solid catalyst makes contact with the solution. We also found a path, which didn't require these steps of neutralization with WVO, using the acid-catalyzed reaction. The catalyst we used were zeolites (aluminum-silicates) which proved to be very effective chemically, but not economically. If that path was to be used, and the reaction was to occur at the same rate, pressures and temperatures had to be incremented beyond the scope of the home producer.As for the reaction conditions, for the CaCO3 BaOH catalyst, we worked at 65°C and atmospheric pressure, achieving yields between 90 and 98%. Hope I answered your questions.

quote:

Originally posted by danielfp:
the most appropiate, in my own opinion, would be one made with calcium carbonate and dopped with barium hydroxide monohydrate.Now, the efectiveness of the catalyst is widely determined by its surface area. So, the catalyst is very porous, nothing I guess, that can be easily done with home equipment.

Well, you answered many. I am a little unclear about the above. Are you saying that making the catalyst porous is what is difficult about producing this at home?

I would imagine the "doping" of the CaCO3 would be a little tricky to do properly as well. What special equipment was used to make this?

Finally, how did you actually process using this stuff? Run the neutralized WVO + x% Meth through a Y" long tube filled with the solid, porous CB Cat?

Your work is really interesting and I thank you for sharing.

Ok.

1. The process for making the catalyst cannot be done at home, for many reasons, including but not limited to the texture and the doping. I would glandly send information regarding catalyst doping to anyone interested, though I cannot send the complete project due to patent issues.

2. The process we used is somehow similar to what you described. Though it would work by simply stiring and heating as it is usually done by the hobbyst.

Also to note, that i would appreciate any suggestions regarding what an hetergoneous catalyst should have in order for you to buy it. You should also know that our work is not revolutionary but a special application for home users of currently developed catalysts for industrial transesterification applications.

Well, I don't want you spilling any patent secrets.

As to "what it should have" is a clear and friendly MSDS sheet and not be too hygroscopic if that is possible. I suppose it should be available in solid and flake for consumers.

Any chance I can get a sample with which to play?

If you compare my results, using KOH, with Tilly's, using NaOH, you will see a difference in outcome. KOH produces soaps which are more soluble and I did not observe a gel forming. In this case the amount of glycerine dropping out is the only indicator. Tilly found that a gel is produced quickly if the biodiesel was of high conversion. The degree of conversion was later confirmed by the amount of glycerine dropping out. Both methods give a good indication of degree of conversion but Tilly's method appears to have the advantage that some information is obtained quicker. However my method does give an instant indication in the case of very high conversion material.

This message has been edited. Last edited by: neutral,

In our study, our goal was to develop a solid catalyst, which could be used by a home producer, and would take care of all this complications. One of our most promising catalysts was made from CaCO3 and BaOH. From which we achieved 98% convertion and complete reutilization of the catalyst.

Could you tell me a lot more about this?
thanks,Ron

When I did my first test batch I used canola oil. It made about 60% bio juice. The glycerin at the bottom was real dark, like dark honey. So far so good. BUT! there was a real thin layer of real dark brown "stuff"
floating on top of the bio juice. What was this and what should I do to it?

My next batch was with corn oil. It made a LOT more bio fuel ans less glycerin Is this right? Also, there was a thin film on the top that was like foamy plastic wrap. When it cooled i just skimmed it off in one peace. What was that?

Also, there is a formaldehyde smell, is that OK?

Ron

bump

Bump? What bump? I don't see no camel so what bump?????