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Thread: Separating ethyl biodiesel

  1. #1
    Join Date
    Nov 2010
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    Fort Worth, Texas, USA
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    Separating ethyl biodiesel

    I'll try to make this short. Put 500 ml new corn oil 144 ml dry ethanol with 3.5 grams KOH (potassium ethoxide) into a flask. Heated at 56 to 84 degrees centigrade with magnetic stirring for three hours. Two layers (phases) did not form. Heated an additional 6 hours with magnetic stirring at about 75 degrees centigrade. A separation of two layers did not occur. Added 71 ml dry ethanol mixed with 3.5 grams KOH (85%) to the flask. Heated an additional 9 hours with magnetic stirring in a sealed flask at 70 to 75 degrees centigrade. Two phases did not form, a glycerine layer did not form. Put the reaction product into a 1 litre separatory funnel. Extracted 6 times with salt water at room temperature about 70 degrees farenheight, then extracted 3 times with boiling distilled water. Removed the top ethyl biodiesel layer. Put 2 teaspoons of anhydrous sodium sulfate into the biodiesel in a 250 ml flask. Did magnetic stirring for 8 hours. After 8 hours let the drying agent settle out a few minutes. Decanted off the partially dried ethyl biodiesel into another 250 ml flask. Added 1 teaspoon anhydrous sodium sulfate let it sit undisturbed for about 15 hours. Decanted off 125 milliliters of clear, transparent yellow ethyl biodiesel. I got the product out even though it never dropped out glycerine. The reaction liquid didn't separate. I haven't done any quality control tests on it.
    Last edited by WesleyB; 6th June 2012 at 01:41 PM.

  2. #2
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    ลึก ประเทศอินเด&
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    Re: Separating ethyl biodiesel

    Hi Wesley,
    That is a major problem when you use ethanol. Ethanol will act as a cosolvent and not allow the glycerine to fall out of the biodiesel.
    Some people have found that if you add a bit of water to the mix after the reaction has finished this will force separation.

  3. #3
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    Re: Separating ethyl biodiesel

    When I gently poured salt mixed with distilled water into the reaction product liquid, part of it turned a color like milk. It didn't do much then ( like last time with propyl biodiesel). That's why I used salt water. I don't know exactly how much water is is the ethanol I used ( maybe 1/2 of 1%). I expect the salt water and hot distilled water washings removed most of the glycerine and alcohol and catalyst and soap.

  4. #4
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    Re: Separating ethyl biodiesel

    Why are you mixing for 6 - 9 hrs with such a small amount? Just put the lid on and give it a good shake for a minute. It probably converted in the first 10minutes and the remaining 8 hrs forming an emulsion or moving the reaction backwards. Also it sounds like you mixed all the ingredients at once- "Put 500 ml new corn oil 144 ml dry ethanol with 3.5 grams KOH (potassium ethoxide) into a flask." Please tell me you didn't do that.
    Johnnojack
    4WD Isuzu Jackaroo 3.1 170,000km on WVO,(2017) 2 tank home built system 6 solenoids. Mk. 9 version. Improvements under investigation

  5. #5
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    Nov 2010
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    Re: Separating ethyl biodiesel

    I asked my chemistry professor about getting a more complete conversion in transesterification. He said to heat it longer. I dissolved the KOH in the ethanol before adding it to the new corn oil. I'll do this again using more KOH to start.

  6. #6
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    Re: Separating ethyl biodiesel

    I made the ethyl biodiesel again but used 7 grams of KOH dissolved in 145 milliliters dry ethanol, instead of 3.5 grams KOH to start, in 500 milliliters new corn oil. Heated with magnetic stirring for about 4 hours at 72 to 77 degrees centigrade. Extracted 8 times with 200 milliliter portions salt water then twice with 200 milliliters of distilled water. Three layers formed. An upper biodiesel layer a middle white organic layer and a lower salt water layer. I don't know what the middle layer in the separatory funnel was. For the salt water washings (extractions) I dissolved about 7 grams sodium chloride in each 200 millilitres of distilled water. The theoretical stoiciometric volume of ethyl biodiesel from 500 milliliters new corn oil is about 587 milliliters if no soap was made (no free fatty acids, no water). Dried with anhydrous sodium sulfate and magnesium silicate. Vacuum filtered through a 1 micron retention filter paper.to get 381 millilitres of clear transparent, yellow ethyl biodiesel.The density of this ethyl biodiesel is 0.8984 grams per millilitre. I got the transparent yellow, ethyl biodiesel after treating with magnesium silicate and vacuum filtering, but it turned cloudy in a sealed storage bottle after sitting overnight at about 20 degrees C.
    Last edited by WesleyB; 27th June 2012 at 03:23 AM.

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