CO2 as a Crystallization solvent

Another one of co2 many superpowers is recrystallization and nanocrystal formulations. pressure facilitated recrystallization have something that other forms of recrystallization don’t, and thats the ability to instantly (well speed of sound) affect the polarity of the entire mixture causing saturation precisely and controllable. and its compatible with the cycling methods just like heat cycling but with direct control.

“If the supercritical or near-critical fluid is used as the anti-solvent, its dissolution into the solvent is typically accompanied by a change in polarity of the solvent mixture, and consequently, a reduction of the fluid’s solvation power relative to a particular substance. Density may also decrease, resulting in further reduction in solvation capacity. As a result, the mixture becomes supersaturated, which causes nucleation at the molecular level and the formation of well-ordered and highly pure crystals. In certain cases, the mixture density may actually be greater than that of the neat solvent. In this case, crystallization is caused primarily by the polarity change of the mixture.”

“First, a solution is
made of the solute in an organic solvent. The solution is then pressurized with CO2. Unlike
oxygen and hydrogen, pressurized CO2 is very soluble in many liquid organic solvents
(Beckman, 2004). The dissolved CO2 expands the liquid phase, reducing the density and
reducing the solvent strength of the solution. Due to the resulting supersaturation, pure
solute particles precipitate out of solution (Subramaniam et al., 1997). The particle size and
morphology can be controlled by the rate and method of CO2 addition (Gallagher et al.,
co2scienceCrystal.pdf (1.3 MB)

co2 is so flexible there’s no way this cant be made to work with thca. But fucking chemistry is crazy, looking through the literature and its just a shit show. the effects of co2 being a quadrupole solvent have crazy extremely nonlinear behaviors lik points where heating a solution up cause it a solute crystallize or where cooling down will cause will cause the substance to dissolve.
I have basically all the equipment here i need to do the crystallization once the info is known but for me to experimentally figure it out on my machine is never gonna happen i may get close and get some kind of procedure working but we need real data in order to design a proper one lol
"There is no single parameter such as polarity, density or CO2 solubility which determines
how binary expanded solvents behave. Taking an example of each it is possible to
find an exception to what the predicted result may be. "

“In order to optimize such a separation scheme, fundamental thermodynamic studies
are required to better understand the equilibrium phase behavior of the ternary antisolvent/solvent-nutraceutical solute system and the three binary systems that it comprises”
CO2-EXPANDED SOLVENTS 2008mistryrphd.pdf (4.7 MB)


We throw dry ice in the pressure vessel…


Below 350psi is the sweet spot, the thca crashes out like a blizzard. Any THCA rich crude that has been dewaxed will work, just a co2 soluble solvent and blast it with liquid co2 out of a Dewar. The rub is you need a pressure vessel rated to at least 1000 psi for safety.


so im confused about ur procedure. dissolve dewaxed high thca extract in a solvent the put solvent+extract in the machine and pressurize to x psi then wait for short time then lower the psi to just below 350psi and wait? or just depressurize? r u doing this all in one vessel?
I could see this working if u were using neat SFCO2 with two pressure vessels and u put extract solution in one thats higher pressure one introduce co2 containing extract from 800 psi to a 350 psi system.
that would definitely precipitate thca but i think that seems oversimplified. Temperature also has very nonlinear and unintuitive effect on the system and if u get water in the systems all the parameters could change or the whole solvent system could break. and u couldnt know if ud messed up and salt out ur organic phases making a biphasic system that won’t crystallize.
I make co2 oil and ive used Paradigm Supercritical Innovation’s fractionating system to get 90% cannabinoids but never large crystals. so my pressure vessel is tested at 8000psi (i never go above 3k psi) so thats no problem. I know there r seemingly easier ways to achieve crystallization but I dont think you realize how powerful this technique is when u have the necessary info

what they r doing here is on another level. manipulating VLE orVLSE phase equilibrium’s can be used for so many things like breaking water ethanol aezotropes or Ionic liquid extractions. you could problably extract the butane out of bho or the ethanol out of rso without needing vacuum.


You are taking a supersaturate solution and introducing a antisolvent. The liquid Co2 is the antisolvent and is introduced at 300psi from a Dewar not a high pressure cylinder. The 300psi liquid co2 will load the already supersaturated solution causing the least soluble compounds in the solution to crash out. This is why you must winterize the solution first, otherwise you will have lipids crash out with the THCA. The key is the ratio of supersaturated mother (winterized solution) and antisolvent (co2).

This has nothing to do with supercritical Co2 or depressurizing into separators. The cascading separators don’t work well for cannabis separations and will never produce crystals.


co2 is not always an antisolvent ur kinda missing the whole point. thca dissolved in co2 expanded ethanol and crystalized thru controlled variations in the pressure and temperature is different then injecting cryogenic co2 into a low-pressure vessel
if u read the provided information ull see that there more to what im talking about. and yes adding any cryogenic liquid added to not cryogenic ethanol extract will cause tons of stuff to precipitate just due to the cold and if the ethanol is already that cold then the fats and waxes would hav already precipitated or at least will if kept that cold. and im sure ur right that there is a simple way to get some amount of crystals to form in a simple way for extracts that could be crystallized by other methods. but that’s not what im talking about.

"it is possible to see from Figure 5.13 and Figure 5.14 that GXLs can act as both pro- and
anti solvents, and can therefore can be used to induce miscibility (for example PTC
applications), or be used in phase separations studies such as the precipitation of
solids, in extractions, separations and to replace distillation methods. "

and fractionation systems lik work great separating terps from cannabinoids from fats/waxes just not great and separating cannabinoids from each other. this patent showed how 90% cannabinoid extract was obtained. it also uses a stage of adsorbents but still.

"The pressure in GAS precipitation can be carefully controlled to allow fractionation
of a solution of mixed solutes by exploiting the difference in solubility of the various
fractions in the gas-expanded liquid phase. "

“They found that at a given temperature, the pressure that a solute precipitates from a solution
that has a mixture of solutes does not correspond to the pressure that the solute precipitates
from the pure solvent. The difference in precipitation pressures is much lower for solutes
when they are in the mixture.”

Not to be a dick… but your writing is impossible to follow. I can barely make heads or tails of it and I am sure I am not the only one.

Let me ask you this. Have you ever extracted using CXE or precipitated crystals using co2? It is rather simple and you seem to want to make it complicated.


"Winters and coworkers used GAS precipitation
to separate protein mixtures, achieving fractional crystallization of mixtures of lysozyme
and ribonuclease, alkaline phosphase and insulin, and trypsin and catalase from CO2-
expanded DMSO (Winters et al., 1999). Chang and coworkers used GAS precipitation to
separate β-carotene from oxides (Chang et al., 1991); they further separated the cis and
trans-β-carotene isomers, indicating the potential for using GAS fractionation to separate
subtly-different molecules. "

this controlled fractional crystallization is what im talking about

I do CO2 SFE extraction and the line between ethanol as a modifier vs CXE extraction is kind of blurry. dont usually use it to crystalize cause u get a better yield from THC then THCa when using co2 dominated extractions.
ur right the method u describe is simple but its not the only or the best way cause it will only crystallize if the starting ethanolic solution could be crystallized itself and u cant control size or morphology
thats why im researching it
but if u think this is simple you abviously havent read enough lol

If the perception is all about temperature and pressure then why doesn’t winterizing crude in alcohol at -50f crash out THCa?

Solvents have preferences, some solvents are more attracted to other solvents than the solutes they solublize. Alcohol and Co2 are more attracted to one another than the THCA that is dissolved in the Alcohol. As the Alcohol loads with the co2 the least soluble compounds start to crash out. The process is much like creating a hydrosol by loading Alcohol with water. The water loads the Alcohol and the compounds that were in suspension fall out and float to the top of the hydrosol.


THCa does crystalize out when u winterize lol u didnt know that?
not all of it obviously but yes cannabinoids precipitate during winterization especially if u go colder then -50
“least soluble” is a varible that can be modified
do u know what quadrupole moment is?

I have never seen THCa cold precipitate out of ethanol. Please enlighten us on this procedure?


ru talking to me or the other guy?

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And I’m sure that a supersaturated EtOh solution can crystallize with the right method, just havent seen anyone doing it. I spoke with an Ag chemist that was kind of weirded out that we aren’t crystallizing in EtOh but he didn’t feel like sharing any insight on the method he was thinking of.

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well the point of the post was my assurtion that it is possible to crystallize thca from ethanol using co2 but that this type of separation, while simple in execution, would require granular details about co2-ethanol-thca(+) ternary(+) mixtures and their phase equilibria in order to accomplish it. If ur talking about winterization then im not talking about crystalline thca just saying some can co-precipitate at very low <-60c temperatures. i hav multiple mentions of it in different patents and whitepaper but Im trying to find some academic reference cause i know alot of stuff written in patents isnt true but its hard to find a 100 % reliable source.
here’s one that uses ethanol
“We found that a semi-solid CO­2 oil (75% total cannabinoids) will form localized crystals at the bottom of a small glass beaker over several days under slight heat. The experiment was repeated and controlled using an ethanol solution highly saturated with CO2 oil, filtered through a 0.2 um nylon filter, and winterized. The results were pleasing: much larger and more numerous crystals!”

I have, under vacuum in a pyrex dish. Just one gorgeous, acyclic seed.


Under vaccum? Was this recrystalazation by evaporation? I doubt etoh would last long under most vaccum.

vacuum evaporation would both decrease the amount solvent and make it colder so it would be a combination