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A methoxide mixing tank mixes dangerous chemicals safely.

Most commercial methoxide mixing tanks are made from stainless steel. There is a good reason why - the chemicals are corrosive as well as toxic and flammable.

What is Methoxide?

Methoxide is the chemical that is made by mixing methanol with either Potassium Hydroxide (KOH) or Sodium Hydroxide.

Actually the are properly known as Potassium Methylate or Sodium Methylate.

Mixing the Methoxide is an intermediate step in biodiesel production. The methylate is mixed and then added to the vegetable oil. The methylate reacts with the oil and converts it into glycerine and biodiesel.


A 304 or better grade stainless steel is rated for use with methanol and caustic soda, it is a good, safe choice for dealing with them.

conical methoxide tank
Biodiesel plant with methoxide tank in the middle


Most home biodiesel plants use a plastic methoxide mixing tank, a carbouy is often used (the typical 25 litre methanol container is a carbouy). This is not necessarily a bad thing but you need to be aware of the issues that you can have.

  1. Plastic offers no protection from a biodiesel fire or heat. If you use plastic you are better off putting the tank outside or in an area where it will do no harm if it catches fire.
  2. A lot of these plastic tanks are not vented into a safe area (outside). Again, this is a good reason to mix the methoxide outside.
  3. A lot of these plastic tanks are not sealed and will leak vapor into the area. Again (perhaps there is a pattern developing here?) mix outside.
  4. Do not use PVC.
  5. Use PE (Polyethylene) or PP (Polypropylene) or even better PEX (Cross linked PolyEthylene) for the tank. You can buy these tanks from Duda Biodiesel

These plastic tanks can be used safely, be aware of the methanol and caustic chemicals and work safely.

methanol carbouy

When using a carbouy or a non sealed tank for methoxide mixing:

  1. Mix the chemicals outside close to running water so that you can rinse in the event of a spill
  2. Always wear gloves and eye protection.
  3. Wear a mask, this will not protect you from the methanol but it will protect you against any caustic dust.
  4. Fill the carboy/tank with methanol and then weigh out the catalyst and add it to the methanol. Never add the methanol to the caustic. It is like the old rhyme - may his rest be long and placid, he added water to the acid. The same danger holds here. Putting methanol onto the caustic may cause excess heat and a fire.
  5. Always lable the carbouy, you may know what is in it but others may not.

Whenever mixing methoxide have a fire extinguisher close by, also running water. Remember you can put out a methanol fire with water.

The methoxide should be sucked into the processor through the pump. In our processor it gets sucked in via valve 2. Leaving valve 4 partially open sucks the oil from the bottom of the processor at the same time and mixes the methanol into it.


Return from Methoxide Mixing to Biodiesel Equipment


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