Decarboxylation and Cannabis
Decarboxylation of Cannabis in Your Ethanol Extraction Process
Decarboxylation is, in my professional opinion, the most important step in producing cannabis distillate extract of premium quality. While the quality of the biomass, the rigor of the extraction, and the sensitivity of the distillation are also crucial, the only chemistry in the entire cannabis purification process occurs in the decarboxylation reactor.
But first, what is Decarboxylation and why is it needed?
The two most well-known plant cannabinoids are THC (tetrahydrocannabinol) and CBD (cannabidiol) but they are barely present in their desired form when the plant is unprocessed. In the ‘raw’ plant these cannabinoids are known as either THCA or CBDA. Decarboxylation (or “decarbing”) involves using heat so that the chemical structure of the acid cannabinoids change to a neutral (non-acid) form of THC or CBD. So ultimately, by decarboxylating the raw cannabis plant biomass, you are able to produce quality cannabis end product—either THC or CBD or a mixture of both.
How to Produce Near-Perfect Cannabis Decarboxylation
Why is decarboxylation so important for cannabis purification? Because all other stages of the cannabis extraction and distillation process are mere manipulations of thermodynamic properties; this includes the effect heat has on solvency, or how the application of a vacuum will affect the boiling point of a substance in question. As such, it is my intention to provide any budding cannabis chemists with a tried and true technique for a near-perfect decarboxylation.
Start with the Right Vessel
To begin, an appropriate vessel is essential. My recommendation is a glass vessel, as while a steel variant will prove sturdier, viewing your crude oil as it releases CO2 is a vital metric. To that end, the more of the vessel visible during operation, the better. A liquid jacketed reactor is ideal as it provides full visibility of the extract throughout the reaction, and also allows for unparalleled control of the heat level within the vessel. The capability to increase the temperature incrementally is most desirable.
Budget reactors will often come with a jacket heating mantle that will be temperamental, and often overshoot the heat it delivers to the chamber if not handled very carefully. This can be catastrophic as overheating cannabis oil can convert desired products or even carbonize it, complicating downstream processing.
Now, the technique. For the transfer of cannabis oil, I find the mitigation of transfer loss is best accomplished with about a 1/10 dilution of Ethanol (EtOH). Install a gooseneck condensing coil along the vapor path of your vacuum, so that you can condense the residual ethanol from your tincture. Load your tincture into your reactor and be sure to leave at least ⅓ of the graduated capacity as a headspace to ensure the crude oil will have space to rise as it muffins up.
Pull a vacuum on your vessel and incrementally raise the temperature of your reactor to 90°C (194°F). Notice you’ll have a hard time passing the 85°C (185°F) mark. This is because a thermodynamic property dictates that the temperature of a mixture will remain at the boiling point of the least stable component of said mixture until that component has fully evaporated. In the case of the tincture, that would be our Ethanol. If you place a stopcock before the collection flask of the condenser coil where you EtOH will return, you can then close it once the flow across the condenser is thinning. In doing so, you can monitor the small amount that will collect in the condenser and await a yellow color change indicating the distillation of high volatile terpenes, and the absence of EtOH in the reactant.
Once it is confirmed you are pulling terpenes, you can then raise the jacket temperature until the thermometer in your mixture reaches 120°C (248°F) and allow one hour for all of the acidic forms to be converted into CO2. After your newly decarboxylated oil has sat at temp for an hour, lower the temperature setting of the jacket to 85°C (185°F) and allow the mixture to cool to at least 90°C (194°F) before discharging the oil from the vessel. You can then introduce atmosphere and drain the oil into your tertiary container. The purpose of this step is to avoid atmospheric oxygen making contact with the cannabinoids while they are at a high enough temperature to cause conversion or carbonization of the sugars.
Hopefully the information found in this post will be of use to those of you just getting into cannabis extraction and processing, and also those who are trying to perfect their decarb process.