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Quality CBD crystals begin with Quality CBD distillate
The starting material should be extracted CBD oil that has been winterized and distilled. CBD distillate should be clear. Cloudiness means there are contaminants like water, waxes and fats. If the oil is cloudy try winterizing again until the oil becomes clear.
Crystallizing oil with contamination will lead to poor yields.
CBD Crystallization Equipment
A jacketed vessel with stirring will be used to dissolve and crystallize the CBD. A heating/cooling bath is connected to the vessel jacket and will be used to control the temperature of the vessel.
ACS grade pentane will be the solvent. This can be dangerous stuff. Consult your safety officer!
Dissolving CBD Oil
Dissolve the clear CBD oil in pentane. Make sure the jacketed vessel’s vent/condenser is connected to an appropriate blower motor or fume hood for pentane vapors. The boiling point of pentane is 36 °C. Even at lower temperatures, pentane will release many vapors. BE CAREFUL AND TAKE ALL PROPER PRECAUTIONS! Make sure the vessel condenser is cooled to -20 °C. Add 1 part pentane to 2 parts CBD oil (some oils require slightly more or less pentane) in the jacketed vessel. Turn on stirring and turn on the heating bath and set to 45 °C. Wait until the solution reaches 45 °C and all the oil has dissolved.
Set the bath to 5 °C. Slow the stirring. As the solution cools it will become more viscous. Adjust the stirrer to keep the RPM above 120. CBD crystals will spontaneously form or “crash out” of the pentane solution. Keep reducing the temperature to at least -10 C. What temperatures you use and how they change over time can change the growth of the crystals.
Collect CBD Crystals
Once precipitation stops, flush or physically remove The CBD crystals from the reactor. Vacuum filter the crystal/liquid slurry to remove the mother liquor from the CBD crystals. Rinse the crystals with ice-cold pentane to rinse impurities from the crystal surfaces. More rinses with pentane can improve poor color, but losses in total yield will occur. Keeping the CBD and materials cold during this step will help give you a better yield.
Reprocess Mother Liquor
The mother liquor still contains dissolved CBD. This solution can be reprocessed! One caveat is that the mother liquor will accumulate THC over time. This sets a practical limitation to the number of crystallization.
CBD distillate with 70 – 75% CBD content can be crystallized to produce CBD isolate (crystals) with a 90+% purity or higher.
CBD distillate with less than 70% CBD can be crystallized to produce CBD isolate with 85+% purity or higher.
CDB crystals can be re-dissolved and then recrystallized to improve the potency even further.
The isolation yields between 60-80% of the CBD.
CBDA crystallization is more difficult than this process. The most success I have seen is when people crystallize it like they would THCA. Hydrocarbons and adsorbents used together seem to help.
We are able to prove vessels with 20 L up to 100 L capacity. Yields may vary from about 60-80% depending on your parameters and input purity. 20 kg of distillate in our 50 L could be turned to about 12 kg of isolate in approx 6-8 hrs.
The density of pentane at room temp is 0.626 g/mL. 40kg of of distillate into 20 litres of pentane is nearly a 4:1 ratio of distillate to pentane. I don’t recommend that kind of saturation for your first crystallization.
You really need to only use weights rather than volumes. Volume is temperature dependent so the conditions of your lab or how you run your process can really change the values.
2 parts distillate to 1 part pentane (by weight) is probably an ok starting point. For a 2:1 ratio you are correct though. 40 kg of distillate is about the max. 40kg of distillate to 20kg pentane (32ish liters of pentane) = 70 some liters total.
I don’t like to go above the lid in whatever reactor, and some reactors “total” volume includes that headspace. The headspace for a 100 liter reactor is probably 10 liters depending on shape, etc, etc.
Time is going to be dependent on a lot, but yeah if your heaters and chillers can keep up then 8 hours is pretty reasonable.
My CBD isolate smells like pentane when it comes out of the tank we use for crystalization.
The isolate will contain solvent molecules trapped within and on the surface of the crystals.
To remove residual solvent (pentane):
1) Wash the raw crystals with cold (probably around -40 C) pentane on a vacuum filter
2) Crush/Grind the crystals finely
3) Use a vacuum oven to gently purge more solvent
4) Flip the crystals in the vacuum oven to expose any trapped surfaces and continue the purge until tests indicate no pentane.
A big reason is due to the lower boiling point of pentane. The increased volatility makes handling and safety a little trickier, but with the benefit of easier removal from the final product. Since hexane and heptane require basically the same level of equipment precautions it isn’t a big deal to work with pentane.
Other reasons may come down to availability, price, and what solvents are permitted in a state or particular lab. Also, I have heard anecdotally that hexane has a lower residual ppm limit than pentane in some areas. However I am not familiar with all laws so take that with a grain of salt.
If you want to grow large single crystals you will need a modified process. Some steps would include much slower temperature changes, fewer seeds crystals/nucleation points, and a less saturated solution.
For distillate to isolate yields, the range is normally between 60-80% dependent on many factors. So if you have 1000 g of 80% CBD Distillate, you can expect between 480 and 640 grams of isolate. I have not heard of yields getting much better than 80%. It is very easy to get worse yields though!
1) 1000 mg * 0.8 = 800 mg of potential CBD.
2) 800 mg * 0.6 = 480 mg
3) 800 mg * 0.8 = 640 mg
After the initial crystallization, you must generally “wash” your crystals with cold solvent. This takes away a lot of impurities, but does take some CBD away as well. After this point the losses are mostly based on transfer from container to container.
Continue at: https://brinstrument.com/blog/cannabis-distillation/how-to-crystallize-cbd-make-cbd-isolate/
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