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Thread: bio diesel wash

  1. #11
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    Re: bio diesel wash

    Hi smithy,

    Quote Originally Posted by smithy View Post
    The use of acid also leaves the biodiesel slightly darker in colour...After reading your post I'm wondering if the slightly darker colour left in the bio after an acid wash is simply due to the mono's being left in the mix.
    After reading your first post, I did some testing this weekend.
    One part of the testing was to compare the color of biodiesel that was Acid washed with biodiesel that was not acid washed.
    I do not know what acid you are using, but the acid mentioned in this thread was vinegar.

    Part of my testing was to do two "Shake-em-up tests" using two Dr Pepper bottles, each containing one litre of low conversion biodiesel that had not been water washed and had sit for 2 years in a sealed drum. I added about 500ml Rain water for the test.
    After performing the "shake-em-up" test, I added a good "glug" of vinegar to one of the batches, again shook it hard, and have allowed them to both sit over the weekend.
    I just had a look at both of the test batches. There was no discernible difference in color.

    It is "common knowledge" that biodiesel produced using the two stage A/E procedure that passes the 3/27 test is significantly darker than biodiesel that passes the 3/27 test using a base only procedure. This assumes that both batches of biodiesel are made from identical WVO.

    "Conc sulphuric acid burns organic compounds." was Neutral's explanation for the darker colour when using acid.

  2. #12
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    Re: bio diesel wash

    Hi Tilly,
    Thank you for your reply. It doesn't suprise me that when you did your test that you found no colour change. Even though your biodiesel isn't initially water washed, I doubt that after being settled for that amount of time that there is little or no soap present for the acid to convert to ffa's. As to the prescence of mono's, without GC analysis it's anyones guess.

    I do indeed use acetic acid.

    I did a test a while ago where I 'split' a 200 litre batch 50/50 One half was water washed with no acid and the other half washed with acid water, very diluted. I took some photo's of the finished bio in cubies and the difference is there to see.

    I posted a thread on our Biopowered Forum which I will link on here with photo's when the biopowered forum is running again (it is down at the moment)
    Last edited by smithy; 28th February 2017 at 04:06 AM.

  3. #13
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    Re: bio diesel wash

    Hi Smithy,
    In your previous post you had speculated that the change in colour was "simply due to the mono's being left in the mix." I must admit that I was scratching my head over that one because as far as I know Acid and water have no affect on the monoglycerides remaining in the biodiesel after it is water washed.

    Now you seem to be suggesting the change in colour is due to converting soap back into FFA's.
    I wonder what colour FFA's are?

  4. #14
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    Re: bio diesel wash

    The reason I mention mono's is that when I have used acid I sometimes have soap tested between each wash and haven't added acid water (probably 15mls glacial acetic 1n 10 litres of tap water) until the soap level is less than 100ppm and still the bio ends up slightly darker.

  5. #15
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    Re: bio diesel wash

    The brown color resulting from concentrated sulfuric acid contacting biodiesel in the Fischer Esterification is due to the organic chemistry reaction called electrophilic addition. Electrophile means electron loving. Sulfuric acid is two hydrogens bonded to four oxygens plus a sulfur central atom. The hydrogens have I believe single bonds to a single oxygen atom. The molecule turns into a charged ion easily. The hydrogen one or both of them detach, break their bond with oxygen, so a plus charged proton an ion without an electron on it approaches the phi bond, the second bond of a double bond between carbon atoms in the fatty acid chain. Since the positive charge proton has no electron with it, it goes to the electrons of the second bond between carbon atoms. The positive proton can bond with two of the electrons that make the phi bond between a double bond in the fatty acid chain. So the proton forms a single bond with one of the two carbon atoms that had the double bond between two carbon atoms. I've forgotten which carbon the positive charge is set up on when this occurs, which side of the carbon atom that just formed a bond with the proton making a new hydrogen attached to one of the carbons that had a double bond. You might look it up on the internet if you care to understand why it happens. So , a positive charge forms on a carbon adjacent to the carbon that just had a proton add to it forming a single bond. One of the two carbon atoms in the double bond is deficient in electrons, giving it a positive charge, so when a sulfuric acid molecule loses a hydrogen, ionizes, it has a negative charge. The negatively charged sulfuric acid, one hydrogen, four oxygen, and one sulfur atom , attacks the positively charged carbon atom in the fatty acid chain and forms a bond with the carbon chain of the fatty acid. So you get sulfuric acid bonded to the fatty acid carbon chain. Sulfur involved in being bonded to carbon can produce a brown colored material that smells bad, it stinks. The brown material is very polar, a big charge difference , a big variance in electron density from one spot in the molecule when compared to another spot in the molecule, so I expect Magnesol, magnesium silicate would adhere to the brown crud (brown stuff) and then filter the Magnesol out. If I'm right about this issue then Magnesol would lower sulfur content of biodiesel made in part with the Fischer Esterification using strong concentrated sulfuric acid (minberal acid).
    Last edited by WesleyB; 1st March 2017 at 05:19 AM. Reason: left a word out

  6. #16
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    Re: bio diesel wash

    In simple terms Wesley, does this mean that the use of Magnesol would lighten the colour of biodiesel derived from the acid esterification process.

  7. #17
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    Re: bio diesel wash

    Yes, I expect magnesium silicate will remove the brown colored portion of biodiesel from the not brown colored biodiesel liquid. I'm not sure that Magnesol is 99% magnesium silicate. The brown color is due to a sulfuric acid molecule attaching to (bonding with) a biodiesel molecule, A chemist told me sulfur bonded to carbon can produce a brown colored product. The long carbon chain on fatty acids is non-polar. If sulfuric acid attaches to a non-polar carbon chain, then around that part of the molecule it's polar. The word polar indicates a significant charge difference from one part of the molecule relative to a different part of the molecule. One part of the molecule would be relatively negative compared to another part (another atom in the same molecule) of the molecule which would be relatively positive. Polar or polar covalent molecules hold to magnesium silicate, and can be removed from a solution of nonpolar molecules that are biodiesel (fatty acid methyl esters). Also, magnesium silicate is a white solid. If a brown material adheres to the white solid and the solid is filtered out, you will be able to see a color change in the white magnesium silicate. If you have a beaker and a magnetic stirring hot plate, then do an experiment. Put 500 milliliters of your biodiesel with brown crud liquid in it. Heat biodiesel in an adequately ventillated area to 95 degrees centigrade with fast stirring for about thirty minutes with say 5 grams of magnesium silicate. Shut down the stirring hot plate. Allow most of the magnesium silicate to settle out. Vaccum filter the biodiesel through a 20 micron paper filter. Then vacuum filter through a 1 micron paper filter. Decant the biodiesel off the settled magnesium silicate solid material (gently pour off the top liquid, while minimally disturbing the magnesium silicate on the bottom of the beaker). You will be able to see that the white solid has taken on a brown color (probably). In this way you can remove most of the sulfuric acid catalyst that reacted with fatty acid esters in the biodiesel. Which would lower the sulfur content of biodiesel made using sulfuric acid esterification as part of the process. A Buchner filtration funnel is the right type of funnel to use in this vaccum filtration and a vacuum filtration flask. Vacuum filtration is a lot faster in this application. A regular filtration funnel at atmospheric pressure might take a very long time to do, if it worked at all for 1/2 a litre of biodiesel.
    Last edited by WesleyB; 3rd March 2017 at 09:28 PM. Reason: wrote it backwards

  8. #18
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    Re: bio diesel wash

    Hi WesleyB,

    Quote Originally Posted by WesleyB View Post
    The brown color is due to a sulfuric acid molecule attaching to (bonding with) a biodiesel molecule,
    Can you please be more specific about why this causes the oil to change in colour. For instance, what chemical change has occurred to produce the change in colour




    [A chemist told me sulfur bonded to carbon can produce a brown colored product.
    Did the chemist say what this brown coloured product is and the chemical reaction that caused it?

    For instance, about an hour ago I dipped a strip of cardboard taken from a Dr Pepper 6 pack into some concentrated H2SO4. The Cardboard immediately started going black. I then got a cotton bud and rubbed the blackened area of the cardboard and it feels "gooey".
    Now an hour later the cardboard is still black and falls apart easily

    It looks like there is probably a more significant chemical reaction occurring than just colouring the paper black.
    Last edited by tillyfromparadise; 3rd March 2017 at 12:54 PM.

  9. #19
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    Re: bio diesel wash

    Tilly; I explained it in this thread. The protons produced from sulfuric acid in reaction solution form a bond on one of the two carbon atoms in a double bond in the long carbon chain of a fatty acid leaving the carbon atom next to or two carbon atoms away aqacent to the new bond electron deficient (poisitive) so the sulfuric acid ion with one hydrogen removed (negative) attacks the positive carbon, bonding with it. So you get sulfuric acid bonded to the long fatty acid carbon chain in roughly the middle of the twelve to twenty two long carbon chain that are fatty acids. The product molecule has a brown color due to the sulfur being present. I probably never wrote that biological produced moleculeces have an even number of carbon atoms in multiples of two. So fatty acids have 12, 14, 16, 18, 20 and 22 carbon atoms bonded to each other in a chain. I don't know why this occurs in even numbers.

  10. #20
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    Re: bio diesel wash

    Hi Wesley,
    I am sorry, I do not understand your explanation- I am not a chemist.

    I have read that H2SO4 is a strong oxidizing agent.
    " It will char wood and most other organic matter on contact, but is unlikely to cause a fire."

    The Chemist Neutral explained that the reason for the darker colour was that "Conc sulphuric acid burns organic compounds."
    If this is not what you are trying to say, To quote smithy "In simple terms Wesley," please explain what you mean without going into detail of the chemistry involved
    Last edited by tillyfromparadise; 4th March 2017 at 12:42 AM.

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