Crystalization of supercritical CO2 crude

I am wondering it would be possible to crystalize THCa from supercritical CO2 crude run slow and cold. No more than 2500 psi and 45°C. I cannot see why this would not be possible, if not preferable. @Photon_noir @Future @cyclopath what do you think?


@Plant2pipe @JonaaronbrayAzoth

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I’ve tried it a couple times unsuccessfully. I can’t use pentane where I am though…

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:smiley: was just coming back to call you in!

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It is possible to use the CO2 to crystallize the THCa in the extraction vessel, although, I haven’t quite perfected it yet… There’s pictures in my Instagram.


Rapid decompression is the key. You can use Co2 as the percipitation solvent or use a traditional solvent in a CXE mixture to percipitate. Regardless of the method, rapid decompression is the common thread. Ideally a high pressure filter is used to collect the percipitate but something as simple as a pressure release valve will work as a collection vessel.


Not in supercritical CO2, as that is a high temperature, high pressure, ephemeral state. It can certainly happen upon allowing the CO2 to vaporize, though, since that creates many little cold spots, nucleating THCa particles. The end result will be a budder of sorts from crude CO2 extract, but redissolving or simply making purer THCa extracts with liquid CO2, and evaporating it can totally work.


So I do understand the the intial crude you get from CO2 extraction is rather buddery and full of impurities. Is there a solvent you can dissolve it in that will either dissolve the actives but not impurities or dissolves impurities without actives? Does anybody know a solvent system that can accomplish either of these for relatively quick purification?

Just looking for a way to reduce total impurities present before entering crystalization phase

You want to flow low pressure Co2 counter current to the crude. At below 400psi the liquid Co2 will only remove the lighter compounds from the crude. At the same time the heavy less soluble compounds will drift to the lower portions of the reaction vessel.

The lower portions of the reaction vessel will contain the less soluble heavier more polar compounds (ie THC-A).

By removing the lower portions of the reaction vessel through a filter using rapidly decompression you will quickly crash out the THC-A and create snowflake crystals. The key to high purity is to insure the crude is fully dewaxed before the reaction. Any wax will fall with the THC-A in the counter current flow and end up crashing with the THC-A in the filter. You can clean up the percipitate by flushing liquid Co2 through the filter to wash them of impurities. Ideally this is done at pressures below 600psi.


How are you dewaxing? If you are dewaxing inline, how are you doing this?

Waxes crash out at pressures below 650psi, just like with the THC but at higher pressures. If you decompress through a filter the waxes can be removed inline. This only works with a CXE solvent mixture. Pure Co2 will just clog the filter and make a mesa.


What’s your solvent mixture here?

Does anyone has a list/table of what is dissolved in CO2 at different temps and pressures or at different solvent mixtures?

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1% to 3% ratio ethanol to Co2 during extraction and 10% to 30% ration ethanol to Co2 during the dewaxing filtration. The delta P comes into play also, the JT cooling of the CXE mixture is responsible for the rapid percipitation of waxes. Having a higher pressure vessel to expand lower pressure vessel using a needle valve can cool the CXE solvent mixture to below -20f in seconds.

The ethanol at this point is no longer a modifier but a process solvent and the co2 left in the CXE mixture is a antisolvent.


Are you saying you dissolve the extracted material in the 10-30% EtOH in CO2 then allow it to rapidly decompress and through the JT cooling effect the waxes percipitate and you filter that now largely EtOH solution for a mixture that is ready to have THCa crashed out of it??

No I extract at low moles and then recover most of the Co2 until I get the desired ratio in the CXE mixture. Then I simply use a delta P to create flow through a needle valve and then a filter.


Large volumes of Co2 during extraction, low volumes of Co2 during the filtration.

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Okay thank you, I believe I am clear on this part now. So after you’ve dropped pressure significantly through needle valve and filtered you are left with your filtered extract in mostly ethanol. From here how do you get the THCa to crash out as you were mentioning before?

I think I put it together, what temperatures are you running these procesess at?