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CO2 supercritical fluid extraction on the cheap

3dDream

Matter that Appreciates Matter
Veteran
BTW if people have access to papers:

I don't wanna buy it.

Dry ice-originated supercritical and liquid carbon dioxide extraction of organic pollutants from environmental samples
Purchase the full-text article



References and further reading may be available for this article. To view references and further reading you must purchase this article.

Kong-Hwa Chiua, Hwa-Kwang Yakb, Chien M. Waic and Qingyong LangCorresponding Author Contact Information, E-mail The Corresponding Author, d

a Department of Natural Sciences, National Science Council, Taipei 10636, Taiwan, ROC

b Department of Chemistry, Chung Yuan Christian University, Chung-Li 320, Taiwan, ROC

c Department of Chemistry, University of Idaho, Moscow, ID 83844-2343, USA

d Nutritional Laboratories International, 1001 S 3rd West, Missoula, MT 59801, USA
Received 2 December 2003;
Revised 25 May 2004;
accepted 25 May 2004.
Available online 15 July 2004.

Abstract

Packed in a high-pressure vessel and under calculated conditions, dry ice can be used as a source of carbon dioxide for supercritical CO2 extraction or liquid CO2 of organic compounds from environmental samples. Coupled with a fluid modifier such as toluene, dry ice-originated supercritical CO2 (Sc CO2) achieves quantitative extraction of many volatile organic compounds (VOCs) and semivolatile organic compounds (SOCs) including polycyclic aromatic hydrocarbons (PAHs), n-alkanes, and polychlorinated biphenyls (PCBs) from solid matrices. Compared to contemporary manual or automated supercritical fluid extraction (SFE) technologies, this novel technique simplifies SFE to a minimum requirement by eliminating the need of a high-pressure pump and any electrical peripherals associated with it. This technique is highly suitable to analytical areas where sample preservation is essential but difficult in the sampling field, or where sample collection, sample preparation, and analysis are to be done in the field.
 
M

medi-useA

So you'd need pressurized chamber for the CO2-Dry-Ice, the CO2 'evaporates' and is fed through the weed to deposit oil @the bottom of the chamber before it is 'bled off'?...would you heat the chamber?

muA
 

3dDream

Matter that Appreciates Matter
Veteran
You would put it in 112 degree f water like the video. I am thinking you could have the release valve set at the top pressure to make sure you don't go over. The next thing to figure out is:

Can I get a high enough pressure w/ just dry ice? I am thinking 8000 psi or so? It looks like 5000 psi max is a more common vessel.

Is there such a thing as too small a container where the yield is not worth it?

What is the best way to collect the resin? Scraping the bottom is not an option.

This is interesting:

http://www.patentstorm.us/patents/7344736/description.html

In PCT/GB02/00620 the applicant discloses a method of preparing a herbal drug extract (botanical drug substance) from medicinal cannabis. The process comprises: 1. a heating step to decarboxylate the acid form of the cannabinoids to theirneutral form; 2. a first extraction with a specified volume of liquid carbon dioxide for 6 8 hours; and 3. a step to reduce the proportion of non-target materials, referred to as winterisation, which step precipitates out waxes.

More specifically, PCT/GB02/00620 describes a process wherein: step 1 comprises heating chopped cannabis (2 3 mm) at 100 150° C. for sufficient time to allow decarboxylation; step 2 comprises CO2 extraction using: a) a coarse powder(the particles are passed through a 3 mm mesh); b) a packing density of 0.3; and c) supercritical conditions of 600 bar at 35° C. for 4 hours, although other combinations of temp and pressure ranging from 10 35° C. and 60 600 bar (bothsuper critical and sub critical conditions) could, it is acknowledged, be used; and step 3 comprises conducting an ethanolic precipitation at -20° C. for 24 hours and removing the waxy material by filtration.

The supercritical method disclosed in PCT/GB02/00620 produced: a) a high THC extract containing: 60% THC (Δ9-tetrahydrocannabinol) 1 2% CBD (cannabidiol) 4 5% other minor cannabinoids including CBN (cannabinol) (Quantative yields were9% wt/wt based on dry weight of medicinal cannabis); and b) a high CBD extract containing: 60% CBD 4% THC 2% other cannabinoids (Quantative yields were 9% wt/wt based on dry weight of medicinal cannabis).
 
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3dDream

Matter that Appreciates Matter
Veteran
stink.whistler - thanks for the fear. That's why I would want to use something that is meant for the high psi.
 

3dDream

Matter that Appreciates Matter
Veteran
Hmm so 20g of dry ice in a 50ml tube should be 203.4 atm or 2,989 psi? That's at room temp?
 

Ryoko_The_Demon

New member
If you are able to build a supercritical extraction setup, it'd be much easier to just hook up a tank of CO2 instead of messing around sublimating dry ice.
 

Gray Wolf

A Posse ad Esse. From Possibility to realization.
Mentor
ICMag Donor
Veteran
As my memory serves me, CO2 becomes super critical in the neighborhood of 1100 psi and 89F. Actually pretty low and easily achievable.

At the cryogenic temperatures reached as the pressure is released, carbon steel becomes a grenade, so typically 300 series stainless is used.

A piece of 4" Schedule 160 stainless pipe is more than adequate for a 1500 psi operating pressure, and still maintain a 3X safety factor.

Liquid C02 at atmospheric pressure is called dry ice, so some pressure is required to just keep it liquid.

A 50 gallon Dewar of liquid C02 with a dip tube, would allow you to pre-pressurize your vessel to ~150psi with the 250psi gaseous head pressure to keep it liquid, and still have transfer pressure using the liquid dip tube.

Per Boyles ideal gas law:

The state of an amount of gas is determined by its pressure, volume, and temperature. The modern form of the equation is:
43fa535941b0be935b3b173e1ce20338.png
where p is the absolute pressure of the gas; V is the volume of the gas; n is the amount of substance of the gas, usually measured in moles; R is the gas constant (which is 8.314472 J·K−1·mol−1 in SI units[4]); and T is the absolute temperature.


You can heat the reaction vessel with simple pipe heaters, to hit whatever operating pressure you wish. If a back pressure regulator is placed in the system that limits backpressure to 1500psi before venting to atmosphere, you can operate in super critical range without overpressuring and exploding the vessel.

By starting with liquid C02, it eliminates the need for pumps and a refrigeration system.

GW
 

hades

Member
I am about 3/4th of the way through that patent. I'm not sure if you all have taken the time to actually read it, but it is amazing. It is a step by step guide on how to do this process at its utmost efficiency. Here is a link to the full document available for download:
http://www.google.com/patents?vid=USPAT7344736

It says that they found the optimal pressure for the CO2 extraction was actually sub-critical, not super-critical, and it goes into detail why. It's basically the same as making quality dry sift, where softer/longer = better quality and harder/faster = lower quality. Quality being determined by percentage of cannabinoids to residual plant matter in this case, though, whereas for dry sift it would be trichome heads to plant matter.

That is the most detailed and thorough document I have ever read in my life, and it just so happens to be about something I am very interested in. As I was reading I was thinking in my head that I'm sure this could be pulled off DIY style....if you were very careful and had some cash to spend. I am already picturing a little laboratory, would probably be a lot of fun. Very interesting thread.
 

3dDream

Matter that Appreciates Matter
Veteran
Nice find hades. This info plus eden labs notes about sub-critial being better for botanical extractions should seal the deal. I guess we don't have to extract with a pipe bomb (well not a very strong one anyways). I think I want to have the option anyways. I will let you guys know what I put together.

Thanks for all the input.

Gray Wolf, hades, and cannabowl - you rock!
 

hades

Member
I'm sorry I didn't get through that whole article before I posted. It turns out that they did an experiment, which is at the very end of the document, which actually does find that super-critical levels with 2% ethanol added to the liquid CO2 is actually the most efficient method. They used a high CBD strain for this experiment, but the same applies if it were a high THC strain:
The results illustrate that changing the extraction conditions from sub-critical to super-critical increases the solvating power of the CO2 and results in a higher recovery of the available CBD. However, the supercritical CO2 can now solubilise a wider range of compounds and the extraction of these additional compound has the effect of diluting the concentration of CBD in the extract to such an extent that it is now lower than that obtained for the sub-critical extraction. Consequently, the marginal additional recovery of available CBD from the raw material would not outweigh this disadvantage and demonstrates the use of supercritical conditions is not desirable.
This coincides with the method they present in the paper, but it goes on to dispute their own claim....
The addition of 2% w/w absolute ethanol to supercritical CO2 as a modifier increases the recovery of the available CBD to >90%. Presumably the relatively polar cannabinoid is more soluble in the extract of increased polarity.

Interestingly, the concentration of CBD in the extract is increased slightly by the addition of polar modifier. This would seem to indicate that the co-extractable non-cannabinoid material present in the plant material is less polar than the target cannabinoid and hence the extraction of this material (the "ballast") is deselected when polarity is increased.

Thus, extraction of cannabis plant material with supercritical CO2 2% w/w ethanol provides an increase in recovery of the target active with no attendant penalty of loss of selectivity.

In Summary:

1. A switch from sub-critical to super-critical conditions produces little advantage in terms of overall recovery of cannabinoid from the raw material but does result in the disadvantage of reducing the active content of the extract.

2. The addition of 2% absolute ethanol modifier to supercritical CO2 results in a significant improvement in the recovery of cannabinoid from the raw material with no penalty of dilution of active content by co-extracted material.
 
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Dendrite

New member
BTW if people have access to papers:

I don't wanna buy it.
I was thinking about designing and building some sort extractor.

I uploaded the paper plus most of its references, which includes a book, as well as two other papers that are related to C02 extraction. I can't vouch for the usefullness of these since I don't have the time to read them yet.

A high volume approach would be to buy a CO2 tank that connects to a bunch of fittings, a pressure regulator, a heating section, and a collector.

These are the critical properties of CO2

304.21 K
31.06 C
87.91 F

7.383 MPa
72.86 atm
1070.81 psi

To reach the critical point of CO2, class 600 fittings are required as per ASME B16.5. Don't know how much those cost but they aren't cheap. I'd guess you could build the project for $100-$300, but I'm not sure.

I like the idea of just using dry ice in a 15 ml centrifuge tube. It wouldn't be critical C02, but I guess that isn't a problem if you aren't supplementing with ethanol.

I need to study for exams tho. The links below are mirrors of each other. If you find another article you need just post the DOI—this one for example is doi:10.1016/j.talanta.2004.05.049—or the next best thing is the author, title, year.
I made an email if you want to get a hold of me. It's dendrite210 [at] gmail.com


 

ZEROorDIE

Member
i only dabbled into the articles so far but as i get further i will make a decision as to whether i will pursue an at home DIY version

at the moment i have a whole bunch of left over paintball co2 tanks and all kinds of fittings and steel braided line most of which is rated in excess of 3000psi

i just wanna plan out a setup before i try anything and blow something up.

im thinkin that the 12-20oz co2 tanks are going to be the best as they are cheap to fill so recovery of the intitial solvent isnt necessary. im just wondering if it would contain enough actual liquid co2 as i haveno clue as to the volume necessary.

lets keep this thread goin guys i wanna get away from the ethanol based solvents and see what i can do with this.

ill be back when im more educated on the processes already discussed
 

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