Sunday, October 28, 2012

Making Biodiesel

Making Biodiesel
Last time, I talked about the raw materials needed for this, and the (very) basic chemistry behind our reaction. Now, we're going to move on to the fun stuff- let's make some biodiesel!

To begin, we need 1 Liter of vegetable oil (above)

In order to have a successful reaction, that proceeds at a decent rate (chemical kinetics is a bit beyond the scope of this blog/project), we need to heat the oil to 130 degrees F.

Heated oil at 130 degrees F

While waiting for the oil to heat, you can prepare the sodium methoxide. This is done by measuring 200 mL of methanol (Heet) and adding ~5.5 g (capfull) of NaOH (Drano/lye). I did  this by pouring the methanol into a glass home canning jar, and then adding the NaOH.

~5.5 g lye (NaOH)

Adding NaOH to methanol

You want to make sure ALL of the lye dissolves. I found that there were some inert compounds that didn't dissolve- I strained those solids out using a small-holed colander (don't use it for food preparation afterwards!). During the methoxide reaction, it is important to be in a well-ventilated area. There won't be any seriously toxic gases given off, since we're dealing with small amounts, but it is always good practice to have a kitchen fan on and a few windows open. 

After the oil is heated up, it is time to pour it into the mixing (and later separating) vessel (above). Make sure to use a funnel so you're not spilling hot oil and/or sodium methoxide all over the place.

Adding the sodium methoxide to the heated oil

Here is where the chemical "magic" happens- You can see the liquids are slightly miscible, and bubbles are forming. This is good- it means the reaction is going! After all the liquids are poured, it is time to mix.

Mixing. And shaking. Like a salt shaker.

You'll want to shake the mixture for a good 5-10 minutes. This will ensure a thorough reaction, and that most of the oil/methoxide will go to completion (that means almost all of it will react- we want that). After this is done, store the vessel cap down and let it sit for around 48 hours (using a glass to balance works great) so it can readily be separated.

Now What?
Now, you have made a very crude and impure one liter batch of biodiesel! Something that is important to understand (and helps explain why we'll need to separate the mixture) is that the reactants ("ingredients") made the product (biodiesel) that we wanted, but also something called glycerine (also known as glycerol). Basically, when the methoxide breaks apart the oil (lipid) molecules to make the fatty acid methyl ester (see previous post for more chemistry talk), the "backbone" portion doesn't just disappear, and it becomes glycerine. We'll need to separate this from our biodiesel, so our new biofuel will be less crude, and more pure, which means it will run better in our diesel engine. But for right now, we'll need to let it sit so the two liquids can separate. 

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