Getting at the gasoline, part two

Fractional distillation is a process that separates the individual components of a chemical mixture, by heating the mixture to the various boiling points of the components.

Gasoline is extracted from crude oil (petroleum) by fractional distillation.

If you have 5 gallons of water and a bottle of whiskey, it is easy to combine those chemicals: simply dump the whiskey into the water and stir.

But how do you get the alcohol back out again? Not quite so easy.

Not very hard either: simply heat the water until it is above the boiling point of the alcohol (174 degrees F.) and collect the alcohol vapor as it rises off the top of the mixture. Then, run the alcohol vapor through a tube whose other end is hanging over an empty contatiner, and BOOM! the alcohol will cool back to a liquid in the tube (assuming you made the tube long enough) and the liquid will drip into the empty container. The water will remain in the first container, since you didn't heat it enough for water to boil (212 degrees F.)

Actually, there is no BOOM! when this happens. I just threw that in there.

Neglecting little real-life details, such as you are unlikely to get all the alcohol out of the water the first go-around, that's basically how fractional distillation works.

Want a more practical example? OK:

1. Put some (human edible) carbohydrate into a kettle and add some water and yeast and mix it up. Put an airtight lid on the kettle. Run some coiled copper tubing from the airtight lid up to the ceiling and down the wall so the other end of the tube is hanging over an empty catch container. Put a little on-off valve in the copper tubing as it comes out of the kettle lid. Turn the valve to the "off" position.

2. Wait for about 2 weeks so your mix (let's call it "mash" or "wash") can ferment.

3. At the end of the 2 weeks, come back and turn the little valve in the copper tubing to "on" so the vapor can escape out of the kettle and build a fire under the kettle. Slowly heat the mixture. Not too hot. Hot enough. 174 degrees F. If you really do this, you will want to rig up a thermometer so you can see how hot it is inside the kettle.

4. Put the liquid that drips out of the other end of the copper tube into bottles. Or jugs.

5. Don't light a match while you put it in bottles.

This is fractional distillation. Alcohol (ethanol) is created by the action of your mash mixture fermenting, and heating the mixture separates the alcohol from the water and goop, as described at the top of this post.

Caveat: make sure the carbohydrate you use is edible by humans. Corn. Rye. Potato peelings. Cactus (agave.) ApplesPeachesPlumsCherriesBerriesPears. Molasses. Grapes. Sugar water. Like that.

Important: make sure your carbohydrate is clean and pure and edible by humans. Don't drink the stuff we talked about yesterday which was made by wood pyrolysis (destructive distillation.) That is methanol. Methyl alcohol. Wood alcohol. OK? Wood alcohol will make you drunk, but it will also make you blind. Stick to corn and other grains. Ethanol is the name of the alcohol you want to produce in this example. Not only can you get drunk on it, you can also burn it in your car (and probably already are). Unless you drive a diesel car.

We are sneaking up slowly on how we "make" gasoline. (Tomorrow)

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Disclaimers:

1. Don't do this.

2. Remember that pressure cookers can explode if they are not vented. An on-off valve is needed.

3. Remember that alcohol which is not still mixed with water is flamable.

4. Ethanol is made from EDIBLE carbohydrate. Clean. Not rotten. Pure.

5. It is not legal (in the U.S.) to distill spirits. It is especially not legal to sell the bounty of your mash. Unless you get a permit to do so from the government and put tax stamps on all your bottles. Good luck with that permit.

6. You CAN make up to 100 gallons of wine and 100 gallons of beer per person per household for personal consumption. You still can't sell it.

7. If you filter the fermented goop and drink the liquid (without distilling it) it is called wine. Or beer, if you use malt and add hops, I guess. But that has nothing to do with fractional distillation, so I don't know why I told you that.

8. Don't do this.

Getting at the gasoline, part one

Distillation is a chemical process that separates a substance into it's constituent chemical components.

Generally, there are two methods of doing this, depending upon the nature of the substance being broken down: "destructive distillation" and "fractional distillation".

Destructive distillation is done when solids need to be deconstructed for their individual contents. For example, if you heat wood in a closed container without oxygen present, then you can collect the methane gas that is given off. The wood is forever changed, though, and becomes charcoal.

Most of us are more familiar with the other process, called "fractional distillation" which is used mainly to separate liquids. Fractional distillation is possible because various liquids boil at different temperatures.

A person who makes whiskey back in the woods is using the chemical principle of fractional distillation. He is after only one chemical - ethanol - so he doesn't need to have apparatus that is too precise with regards to temperature, as long as his fire is just hot enough to boil off the alcohol in his mixture.

Usually fractional distillation is more precise than that, and great attention is paid to the various boiling temperatures of the components that make up the substance being distilled. Perhaps the most common example is the fractional distillation (refining) of crude oil.

We will take a closer look at the process of fractional distillation next time.