Well I followed the advice of many saynig that when you start working with Biodiesel to start with small batches, and work your way up. I printed off all of the material on the Dr. Pepper method, purchased all of the material, and went to work. For some reason, all of the NaOH is not disolving in the methanol, some crystals get left behind even after lots of shaking. I proceeded to mix the ingredients after I got as much disolved as I could. The instructions said that the amount of Glycerine left should be slightly more than the ammount of Methanol used. It appears that after using 250 ml of methanol, I have between 150-200 ml of glycerine @ the bottom, and the biodiesel is pretty cloudy after sitting overnight. there is some precipitate on the bottom, looks like crystals of NaOH. Shook the bottle up a few more cycles to see if I could get a more complete reaction, but still no change.
I made another batch of methoxide to use later, and tried crushing the crystals of NaOH in the solution this time, but still am not getting it to completely disolve.
Did I just get a bad batch of NaOH that had somehow absorbed water along the way before I got it?
Last edited by Rushmore X; 01-25-2007 at 11:53 AM.
Reason: I need to use spell check?
How much remains undissolved? Some drain cleaner type materials contain Aluminum or magnesium. Does it look like grey or silver particles? You may have poor quality NaOH. The undissolved material may be silicates or ???. It is also possible that it is carbonates. NaOH will absorb both water and carbon dioxide from the air. Trace amounts should not be a problem. You don't say whether you are using pellets or prills. Prills are much easier to dissolve. Some people combine the methanol and NaOH in a closed glass container overnight. For safety do this in an uninhabited area (unattached garage), relieve pressure and open carefully with full face shield and gloves. Have running water available to wash yourself down as a precaution. If you suspect the NaOH try a test batch using new vegetable oil. The transesterification reaction is usually very straight forward especially with virgin vegetable oil. Phase seperation will occur within 15-30 minutes and be essentially complete in 1 hour (at 120 deg F). Water contamiation of either the NaOH or the methanol makes it much easier to dissolve the NaOH so I don't think this is a problem.
Good Luck, take care as these chemicals can be quite dangerous!
It does look like there are some metallic particles in the precipitate. I was wondering where that stuff was coming from. there is quite a bit of white stuff in the bottom of the methoxide. I mixed it in a glass bottle, and am thinking of heating it up (both the methoxide for the next batch, and the 2 liter bottle of Biodiesel mix) to see if that will help the reaction go to more of a completion.
Do Not Heat methoxide!!!!!
The "white stuff" is probably carbonates. Nothing you can do at this stage will make it reactive. Don't worry about getting it completely dissolved. Pour off the methoxide and estimate the undissolved material. If it is significant (greater than say 5%) simply use 5-6% more NaOH. Remember to keep your NaOH (& methanol) tightly sealed during storage. Buy fresh and good quality materials. There are enough good suppliers to find good materials.
If you are concerned that the quality of the NaOH is effecting your reaction run a small test batch with virgin vegetable oil. I use 18oz jam jars for this purpose and rountinely run a test batch before every 50 gal. batch. Clean and dry the jam jar and cover. Depending on the titration of the oil add the appropiate amount of NaOH. I have previously determined that for my NaOH (red devil lye) one -1/8th teaspoon contains about 0.8 grams of NaOH. So for virgin vegetable oil which you would use 5g NaOH per liter of oil to make a 250 mLtest batch you need 1.25 grams NaOH (5/4). Measure 1&1/2 1/8th measures NaOH (a little more won't hurt) into your jam jar. Then add 50 mL dry methanol, cover and swirl vigorously until dissolve (as much as it will). Hold the jar away from you face and open the container slightly to relieve any pressure. Measure 250 mL oil in measuring cup and warm in a microwave. Warm it just above body temperature, no more than 120 deg F. If you get it too high all the methanol will boil when you try to add it to the methoxide. You should be able to hold your hand on the container. Carefully add the oil to the methoxide allow the temperature to equilibrate and cover. Mix by inverting once and again relieve the pressure. When no more pressure builds rotate the jar and mix the contents. The sample should mix easily. Let it set with in about 30 min you should begin to see the glycerol layer begin to form on the bottom. It will start slowly then much more rapidly. The reaction will be essentially complete within one hour. If it doesn't go there is probably something wrong with your materials and no amount of fussing will help. Discard the test and figure out what the problem with the materials is.
Be careful, these chemicals can be dangerous!!!
I think I will try to wash what I have and see what it looks like, use the remainder of the drain cleaner to clean out my sinks (they were starting to drain slow anyway), and head to Menards to see if I can find some KOH and try the whole thing again. Guess this the whole reason behind starting small.
How did you first trial batch come out? In case you haven't yet started your workup let me suggest something.
By now (depending on how much methanol you used) the glycerol layer should be quite firm. Prepare another batch of methoxide only use one half the original amount of methanol and lye in another suitable container. Carefully pour off the BD (top) layer into this newly prepared methoxide, mix and allow to react. (It may be necessary to re-warm the BD layer but do not use a microwave or stove due to the methanol in the BD, it might explode.)
If the original reaction was incomplete you will see additional glycerol layer form.
Take care and good luck.
with the 2 liter bottle, would it be easiest to seperate the glycerine from the bio diesel by removing the cap, putting my thumb over the hole, and slowly turning the bottle upside-down, then letting the glygerine drain out slowly? I haven't seen any clear instructions for the decanting process.
Unless your lye was KOH (not likely) the glycerol layer should be stiff. If it isn't, cool it to 50-60 deg F. and just pour the BD (top) layer off. You've never said whether the vegetable oil you're using is used or new. If it is used oil the cloudness could just be soap. The BD from new oil should be very clear. The cloudness could also be because the methanol and the unreacted oil (triglycerides) don't mix very well (if your reaction was substantially incomplete).
I would think it would be much easier just to carefully pour off the top layer than trying the thumb trick. Pouring off just requires patience and a steady hand.
My suggestion about the second reaction is meant to help you understand whether you achieved a fairly complete reaction the first time or not. Practice with small test batches until you have some feel for how things work & what it should look like. Even then when you move up to 40-50 gal. batches things don't always go as you'd expect.
Chemistry is an art as well as a science. Good Luck.
ok, finally got around to seperating it out. Added a fresh batch of methoxide to the biodiesel to see if there was just an incomplete reaction. So far no precipitate or glygerine, maybe the new oil that I was using didn't produce as much? Anyway, proply need to wash it next to see if it clears up? Fabman said that there is a chemical wash that he uses instead of washing with water, since water = contamination. What is the process for this?
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