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Thread: Minus 7 deg C Biodiesel Reaction

  1. #1
    Join Date
    Jan 2006
    ลึก ประเทศอินเด&

    Minus 7 deg C Biodiesel Reaction

    -7deg C Biodiesel Reaction

    Hi Everyone,

    There has been some discussion lately about making biodiesel at ambient temperature- without heating.

    Many years ago I did a number of experiments to sort out the truth from the well meaning nonsense that was posted concerning whether it is required to heat the reaction.
    One of the experiments I performed was to do the reaction at 4deg C which did make biodiesel

    As it is raining this morning, I decided to have another look at low temperature reactions.
    I took a litre of my current production WVO, poured it in a 2 litre Dr Pepper bottle and placed it in a freezer with a thermometer in the WVO.

    I made the required methoxide by mixing 9g KOH into 140ml methanol in a coffee cup, stirred until the KOH was dissolved and then placed the coffee cup in the freezer with a thermometer.

    I kept checking back and to my very great surprise the WVO was still liquid at -7C. At this point I decided that was cold enough. The methoxide had already dropped passed -7C so I allowed the methoxide to warm back up to -7C, added it to the bottle of WVO, screwed the top down tight and shook hard for around 30 seconds.

    The contents of the bottle went white and thickened.
    At the time I thought it was probably a failure but I did notice that while the sides of the Dr Pepper bottle initially contracted with the shaking, the sides did start to fill back out which suggested there was a reaction going on.

    So I set the bottle back in the freezer and when I checked back a few minutes later the contents of the bottle had changed colour back to an oil colour.
    Of course, it had gone through the initial main part of the reaction where the viscosity increases and then reduces. However at this low temperature, instead of taking 10- 15 seconds to do it took several minutes

    Over the next five minutes or so, I left the Dr Pepper bottle in the freezer and I came back several times and re-shook the bottle.

    I then removed the top of the bottle and there was a release of pressure. Then I put a thermometer in the bottle and noted the temperature had increased to around -4C. These were both sure signs that the reaction was occurring.

    I then let the bottle sit in the freezer for a few hours, making sure the Temperature stayed around -7C.
    I now have a Dr Pepper bottle with biodiesel sitting on top a layer of by-product- all at -7 deg C
    Last edited by tillyfromparadise; 14th October 2017 at 12:24 PM.

  2. #2
    Join Date
    Sep 2009
    Brisbane (North Side)

    Re: Minus 7 deg C Biodiesel Reaction

    would love a photo mate, thats very cool. it goes to show how robust the reaction really is.

    I have been watching this discussion with much interest as I have always heated the brew as I believed that was required. I do 200 litre batches of oil and 40l meth, so I am pretty keen to save the energy and time if it isnt needed. need a bit of confidence though before I risk wasting a big brew!


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  3. #3
    Join Date
    Dec 2016
    York UK

    Re: Minus 7 deg C Biodiesel Reaction

    Hi Tilly, as I have mentioned to you before I do not agree with the rule of thumb principle regarding temperature versus processing time. According to my rough calculations, applying the rule of thumb, your experiment should have taken in excess of 30 hours to complete and yet it only took a 'few' hours. Well done.

    I have been processing 'on and off' at ambient for several years, using normal processing times. It does work. Not quite as simple as it sounds for those who water wash but that is a discussion for another thread.

  4. #4
    Join Date
    Jan 2006
    ลึก ประเทศอินเด&

    Re: Minus 7 deg C Biodiesel Reaction

    Hi Smithy,

    Quote Originally Posted by smithy View Post
    your experiment should have taken in excess of 30 hours to complete and yet it only took a 'few' hours.
    You are confusing the initial part of the reaction where most (but not all) of the reaction occurs very quickly, with the reaction going as far as it can go which typically takes much longer.
    The aim of this experiment was only to verify whether the reaction will occur at very cold temperatures and not how long it takes for the reaction to go as far as it could go at this very low temperature using any particular reactor design
    I am quite sure that if I had continued shaking, the reaction would have gone further but that was not what I was testing for.

    Well done.
    Thank you

    I have been processing 'on and off' at ambient for several years, using normal processing times. It does work.
    Yes, the reaction will go at ambient temperture. That has been known for as long as people have been making biodiesel- with the exception of one person on the forum who apparently did not know that the reaction will proceed at ambient temperature. As I put it, As long as everything remains liquid, temperature is not a limiting factor in the biodiesel reaction
    Last edited by tillyfromparadise; 16th October 2017 at 07:57 AM.


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