[schmidling]

Made a few small batches of biodiesel and have a few questions about the chemistry involved.

There is lots of info out there on the subject but it's sort of like matter and antimatter.  For every "fact" there are as many factoids and it's hard to sort out what to believe.

First of all, "methanol is preferred, ethanol is very difficult for beginners and denatured will not work".

The only readily available source of methanol is Heet but at $5 for enough to process a liter of oil, it's not very practical.

Having a gallon of hardware store denatured alcohol on hand I had to try it.  I made two batches with Heet and two with denatured and I can't tell the difference.

I used both NaOh and KOH with the Heet but only KOH with the denatured as it is the preferred catalyst for ethanol processing.

For the record, I don't own a diesel engine and my interest is making fuel for an oil lamp that burns something like typical lamp oil.  My feed stock is  used oil from our deep fryer.  I already make liquid soap from this so I thought this would be a fun project also.

One is supposed to titrate used oil to determine how much lye to add to the standard recipe for new oil.  That's fun to do but having a good pH meter seems it like that would be a lot easier.

Problem is what I measure does not make any sense.  The assumption is that used oil has more fatty acids so it takes more lye to process this.

New corn oil has a pH of about 5.6 and my used stuff is about 6.2 so it seems to be going the wrong way.

The other problem is that the only number I could find with regard to the pH desired is 8.5 but no info on what that means.

One adds .1% lye to the oil sample and for every ml of lye added to make the Phth stay pink for 15 seconds, we add 1 gram of lye to the basic recipe.

Question is:  how do I translate that into a procedure using a pH meter.

Thanks,

Jack Schmidling

[Borek]

What is the general procedure you follow to make the biodiesel?

What is the exact procedure of titration? Presence of oil in the titrated mixture means it will attach itself to the pH electrode, pH electrode is designed to work in water - if it is covered with oil what it shows will be unpredictable.

[Arkcon]

You've asked a dozen questions, and its hard to know what to answer.  Let me start with this one -- why are you making biodiesel for an oil lamp?  An oil lamp can easily burn vegetable oil.  If your used oil is impure for lamp use, then you must purify it first to get suitable feedstock for an organic reaction.

We need your recipe, and we need to take it step by step.  IMHO, I see nothing terribly wrong with denatured alcohol.  Its ethanol, methanol and isopropanol.  So you'll get ethers formed from all three.  But you must scrupulously avoid water, or you'll make soap instead.  But you must do that for all your ingredients.   So even your recipe isn't clear from a chemical stand point.

[schmidling]

-- why are you making biodiesel for an oil lamp?  An oil lamp can easily burn vegetable oil.

One can make lamps that burn veg oil but I have yet to see a kerosene type lamp burn it.  The viscosity is too great for wicking up far enough to work.

 Biodiesel barely works and then only with a fiberglass wick.

 
As far as the process is concerned, it is too well described elsewhere to repeat it here so this link is  as good as any..

  http://makezine.com/projects/make-03/backyard-biodiesel/

Roger on the oil on the pH probe. 


>We need your recipe, and we need to take it step by step.  IMHO, I see nothing terribly wrong with denatured alcohol.

That plus the fact that it seems to work but it might not work in an engine?  This is what it's all about for most folks.

My recipe for new oil  is 10 g KOH in 275 ml denatured alcohol mixed into 1 L of corn oil at 130F.

I scale this down to 100 or 200 ml batches.

I shake this vigorously for about 5 minutes and then hold at 130F for two hours, stirring regularly.

It then is allowed to cool and rest for 12 hours.  After an hour or so, the glycerine settles out but I leave it for 12 hours anyway.

The fuel is decanted off and washed with water until the water remains clear. 

This is done in a separator funnel so it's easy to run off the water.

The fuel is then dried  in a beaker on a hot plate and again held at 130F.  "They say" when it clears it is done but I still smell alcohol so I dry until I can't smell it.

Question:

Again they say you can dry it simply letting it sit in a good air flow in an open container but they also say that biodiesel is hygroscopic so it will pick up water from the air.  This seem a bit contradictory.

Jack