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Thread: caustic soda

  1. #1
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    caustic soda

    I just read an article in the Hobart mercury where a bloke says he uses caustic soda and methanol to make BD. Does anyone have any knowledge about this as there were no references in the article.

  2. #2
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    Re: caustic soda

    I think the bit that was missing from that article was the oil! Methanol and caustic soda (or KOH) are both used during the process of making biodiesel (also called "reacting" or "transesterification"). Just check in the making biodiesel forum, you'll find loads of info there.
    Robert.
    Site Admin.

  3. #3
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    Re: caustic soda

    Thanks Robert, I did go through the making bd thread but must have missed the definiton of koh. I must admit to having problems deciding which way to go with all this, is there a fool proof simple diagramatic design for processors.

    I'm one of those people challenged by technological descriptions, but once I see the practical operation can make it then put it into action. Maybe its because I'm 60 and used to making things from mind pictures. I have a large workshop fully equiped to make just about anything.

  4. #4
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    Re: caustic soda

    A foolproof design for a processor - I'm sure there are a thousand varieties. Many people will swear by different designs, but the most common one seems to be the "appleseed" processor, which is made from an old hot water heater.
    I have seen people posting up designs, or links to other sites offering them, so have a trawl through the making biodiesel section (or use the search function) and I'm sure you'll come across a few options. If not, Im sure if you post a message in there, someone will point you in the right direction.
    I've personally never made any biodiesel myself, or looked into the processor options, but I just read what people post in here, which I guess makes me a bit of an expert in theory

    As for KOH/NaOH, both can be used.
    NaOH, or Sodium Hydroxide is also known as caustic soda (or the Americans also call it "lye"). It is most typically found as drain cleaner.
    KOH, or
    Potassium Hydroxide is also sometimes known as caustic potash, potassa, potash lye, and potassium hydrate. I believe this is the preferred option to make biodiesel with. I know it might also be a little bit harder to get as it can also be used in explosives. I think that perhaps the waste product from the reaction with KOH slightly better than NaOH, but I'm not sure. I know that most of the big commercial producers just use NaOH. Like I said earlier though, I'm no expert in this and this sort of discussion is probably best left to the clever chemists in the making biodiesel forum
    Robert.
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  5. #5
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    Re: caustic soda

    Hi Robert,

    Re KOH:
    I know it might also be a little bit harder to get as it can also be used in explosives.
    Are you sure about this? I think you might be confusing this with Potassium Nitrate KNO3 which is used in gun powder.

    KOH is used to make household cleaning products, so try cleaning product manufacturers.

  6. #6
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    Re: caustic soda

    You could be right geewizztoo - like I said, I'm no expert, so I appreciate people who can correct me .
    Robert.
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  7. #7
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    Re: caustic soda

    hi robert,
    pottasium hydroxide(koh) is freely available and is not used to make explosives. Ammoniun nitrate on the other hand mixed with diesel can.
    cheers brian.

  8. #8
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    Re: caustic soda

    Thanks everyone, learned a lot from that. Just for interest sake, could you substitute ethanol for methanol.

    Thanks again
    Alga

  9. #9
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    Re: caustic soda

    And, can anyone explain also the reasons why KOH is preferred over NaOH?
    Robert.
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  10. #10
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    Re: caustic soda

    Two main reasons:

    1. KOH dissolves in methanol much faster than NaOH
    2. The KOH glycerine by-product stays liquid, NaOH by-product solidifies. This can be a problem if left to cool in the processor.

    This one is purely subjective....shoot me down if you like,
    3. IMHO, the KOH seems more tolerant of poorer grade oils and SMALL quanities of water in the oil.

    Alga,

    Yes you can use Ethanol instead of Methanol, but I've read that it's harder to use unless it's really dry. Ethanol naturally forms an azeotrope of roughly 95% ethanol and 5% water. You need to use a molecular sieve, such as Zeolite, to remove the remaining water first.
    Last edited by geewizztoo; 8th June 2006 at 11:37 AM.

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