Prior to distilling oil, you should follow a winterization and degassing procedure. The winterization will remove fats, waxes, and other inactive and unwanted compounds. Degassing will remove any solvents and other inactives with low boiling points to prevent foaming during distillation. These processes are imperative to successful distillation and could be considered more important than the actual distillation itself. Always use safety equipment and have proper ventilation when working with flammable chemicals.
The first step in your winterization procedure will be dissolving and emulsification of oil in an alcohol solvent. Alcohol is a solvent just like butane or propane but it is not a hydrocarbon. To dissolve oil in alcohol, you will need the following items:
- Hot Plate Magnetic Stirrer with either digital temperature readout or a submersible thermometer that will read up to 50C
- Alcohol: At minimum you want the highest proof alcohol you can aquire. A good starting place is 190 Proof Grain Alcohol. In most states, Everclear is available from most Liquor stores. You can also use organic alcohol purchased in bulk supply from some online retailers. If you can aquire 190 or 200 Proof Lab Grade Ethyl Alcohol, this will be the best option. Do not use denatured alcohol of any kind.
- Mixing Vessel: This will sit on the hot plate magnetic stirrer. A few options are Ball Jars, low form beakers, media bottles, or vacuum chamber pots.
Dissolving and Freezing Solution
It is recommended that you use as little alcohol as possible during this process. This will make alcohol recovery and filtration faster. A good starting place is filling a Ball jar a little more than half way full with alcohol. Place a magnetic stir bar in the Ball jar and place Ball jar on hot plate. You do not need high temps or high stir bar speeds. 40C on the hot plate and 200 RPM on the stir bar is a good place to start. Simply put oil into jar carefully and wait for it to completely dissolve. If the oil seems to become solidified, add a bit more alcohol to the mixture. Once all oil has been fully dissolved, it is time to freeze the solution.
Freeze your mixture overnight in a standard freezer. This will allow fats and waxes to coagulate and precipitate out of the solution. For ever faster coagulation, freeze and filter at different temps. I.e, freeze for 4 hours at 32F and filter through a fast speed filter. Freeze for 4 hours at 0F and filter through medium speed filter. Freeze for 4 hours at -40F and filter through slow speed filter. This will remove more and more mass from the mixture each time, making filtration faster.
What Kind of Filter Should I Use?
This question is both simple and difficult to answer. Simply put, you want the fastest filter you can aquire. For small personal use, a 600mL fritted disc Buchner Funnel will work fine. For larger amounts, a porcelain, polypropelene, or stainless steel filter such as our BVV Refinement Filter are recommended. As described in the paragraph above, a combination of all three speeds of filter paper will work most efficiently. You should also use some type of filtration aide. The most common is Celite 545. This will allow the mixture to flow at a constant speed, as well as create a vacuum seal across the whole surface of the funnel.
Prior to filtering, if you have activated carbon, do a basic carbon scrub by filling your media bottle with activated carbon and shaking for 1-5 minutes. To prepare Buchner Funnel for filtering, place filter paper in bottom of filter and secure with ring if using a stainless filter. Create about a half inch to inch of filter aide on top of filter paper. You can also make another 2-3 inch layer of carbon on top of the filter aide if you'd prefer to pour the solution over the carbon rather than shaking it in a media bottle. Start vac pump and slowly pour solution into filter. Try to spread liquid evenly across the whole diameter of the filter.
Alcohol Recovery via Rotovap
Once you have filtered your solution, discard fats and waxes. You can reuse filter aide by rotovapping it down but this will only work for a few uses as it does not have an infinite lifespan. Begin a rotovap procedure and reduce your solution down so that there is as little alcohol in it as possible. You might need to leave a bit of alcohol in the mixture to transfer it.
Once you have reduced your solution and recovered your alcohol, transfer your solution to a new Ball Jar or stainless steel vacuum chamber. For this example we will use a 1.5 Gallon Glass Vac. The glass lid has the best chemical resistance. If you use any other type of vacuum chamber, the lid may suffer damage from harmful degassing vapors. Place 1.5 Gallon Glass Vac on hot plate and connect to Cold Trap. Degassing will make quite a smell so it is recommended to do this under a fume hood or outside. Begin heating mixture under no vacuum. You may do this without a closed chamber or cold trap but it is recommended to have a fan blowing air over the top of the vessel to keep vapors from condensing and falling back into solution if you are not inside a fume hood. Heat the mixture to 140C. This should be a slow heat that makes the solution slightly bubble or foam. During this process you are removing solvents, unwanted compounds, and nasty terps. Once solution hits 140C, pull the vessel from the hot plate and transfer to distillation system.
Depending on first or second pass material, you may consider repeating this process again to further refine oil or distillate. There are other chemicals that can be used to pull unwanted materials from the solution. These include hexane, pentane, salt water or saline, etc. Each of these chemicals has a certain polarity and will pull residual unwanted materials such as water soluble pesticides. The use of a separatory funnel will greatly add in this process. These chemicals are highly flammable and advanced winterization should only be attempted by extremely well versed individuals with proper safety protection.