Large Scale Extraction with Hexane/Heptane

It seems like everyone is talking about using ethanol for large scale processing operations. I am starting to wonder if this is really the best route and wanted to describe an alternative approach. This idea came about when I was investigating nanofiltration for solvent recovery, and learned that hexane can be sent through a membrane up to 3x faster than ethanol.

The process would go something like this: use room temperature heptane to extract cannabis, perhaps in a centrifuge like used for ethanol, modified for all materials to be compatible with hydrocarbons. A centrifuge should actually recover more effectively for hydrocarbons because of their lower viscosity and polarity. Or extraction could be done in a continuous fashion, maybe with a screw-type extractor.

Then the product can be dewaxed and desolvated at room temperature with membrane systems. You could perhaps even decarb the plant material in advance of the process, cut the solvent down to a equal ratio with oil, and move directly into a crystallization reactor with no need for distillation. Considering the great leaps made in the CRC thread, it seems scrubbing + membrane dewaxing would likely give a product pure enough to crystallize without trouble.

This would pretty much eliminate all need for heating and cooling in the process, cutting operating expenses. Heptane will not pick up any water, so there would be no need for reproofing and recovered solvent could be recirculated back into extraction immediately. It could even be used to extract freshly harvested plant material without drying first.

Has anyone implemented something like this?


The reason people use ethanol is to skip winterization. It also gives you the best color when cryo extracted. Id use hexane over heptane. Hexane requires half the ethrapy to change state from a liquid to gas, i can recover twice as much hexane as i can ethanol with my roto in the ammount of time. I think the problem is with heptane or hexane youll have to use a polar solvent to winterize. I don’t see you being able to filter out all the fats and lipids using a membrane filter in a non polar solvent. I could be wrong though.


I agree with you that that was the problem with hexane extraction. If you did have to switch solvents, I wouldn’t think this was great idea. But using nanofiltration membranes will allow dewaxing regardless of the solvent being used, as it’s primarily based on molecular size. Evonik too has demonstrated this in trials. As far as color goes, nobody using cryo ethanol has shown color as good as what people are doing using bleaching clay + butane extraction, which can be completely water clear.


If your starting material is light enough bleaching clay will make it water clear, it doesnt matter how its extracted. I can make you water clear distillate with cryo ethanol crude, hexane or heptane. Its not hard. I dont see how nanofiltration will grab fat particles bigger AND smaller then the cannabinoids.


I didn’t say water clear distillate. It’s whether you can make the crude water clear with just wet scrubbing.

As far as the membranes, it is done in two stages; the first a larger membrane and the second a smaller one.


I would love to see someone make their crude water clear by just scrubbing with t5, i know people doing chromatography AND scrubbing prior to first pass and there crude isnt water clear. It takes silica in the CRC thread to make water clear shatter so idk about that one. Id have to see it to believe it. They should be using just t5 in the CRC thread then and they’re not.


OK I admit I misstated it earlier. I meant in CRC they are getting water clear with just wet scrubbing. They do indeed use a variety of sorbents. But nobody has got water clear from wet scrubbing ethanol no matter what sorbents they use.

That wasn’t even my point. My point was just that wet scrubbing is more effective in hexane, so it can be used to help purify the product and prepare it for direct crystallization without distillation.


You do realize theyre basically doing chromatography with silica in there? They even said silica is the key to water clear shatter and without it you cant make it. I wouldnt consider chromatography a “scrub”. If it is then yes i can make water clear ethanol crude if i “scrub” with silica in a column lol theres a reason why theyre now looking into the PR abilities of the CRC, because its chromatography more or less


You think you are going to get good separation running normal phase chromatography with a polar solvent? I would like to see you do it. Reverse phase media is a thing for a reason. In any case if you look at the EHO thread and see plenty of examples of people running their ethanol through silica with less than impressive results.


Woot woot ^

Also i would think bottom filling a column with a non polar and draining out of the top would work better since aqueous phase is heavier. But hey what do i know


Anyway that is the least important point I was trying to make. Using scrubs is like 1% of what I was trying to start a discussion on.

What everyone is really looking for is a way not have waxes while avoiding changing solvent. Right now everyone has picked cryo ethanol as the best way to do this, but I would like us to think outside the box. I don’t think cryo is perfect and I think there must be better solutions out there. For one, cryo is an energy hog, and two, water pickup will always be an ongoing problem.

I flagged nanofiltration as a way to remove waxes because I saw trial data from ecosce and evonik where they both demonstrated and quantified wax removal with membranes, and because the transmittance rates through a membrane with hexane are very very high. Like well over 1000 L/hr on a ~250k unit. You can choose to doubt whether it works. Within this year these will be pretty widely diffused, and i’ll either look smart or I won’t.

But that is still not the point. There could be other ways to remove waxes. At the indo expo I saw a seminar where a man said he had got good results removing waxes via direct centrifugation of the crude oil. In another thread on here, people are hard at work trying to use adsorbents to dewax in a nonpolar solvent. Yet again, in another thread people discussed room temperature methanol as an extraction solvent (which removes need for cryo, but water pickup would still be an issue).

What i’m really trying to discuss is methods for removing wax besides cryo ethanol. I suggest membranes because I really believe they are the most effective technology in this area. But i’d love to hear other ideas too.


You said no one can get as good of results “scrubbing” with silica as in the CRC thread, youre not scrubbing first of all youre doing chromatography so maybe if youd actually use proper terminology we wouldnt have to figure out what youre trying to say.

Tell me what your definition of scrubbing is that would allow a column of bleaching earth to count, but not a column of silica. The definition of chromatography allows any solid with any affinity for a compound to be used as the stationary phase. Furthermore, chromatography in chemistry is generally applied to a technique that elutes every compound through the media in bands. However in this case people do not want the color compounds to elute; they want them to be 100% retained by the media, which makes this decidedly more of a adsorption scrub than a chromatography run.

There is nothing magical about silica. Silica is a convenient adsorbent to use for normal phase chromatography. What you’re describing isn’t even normal phase. Normal phase uses a nonpolar solvent with a polar stationary phase (silica). You are suggesting using a polar solvent with a polar phase. If you knew how chromatography works you would see that’s not a winning combination.


Scrubbing isn’t a technical chemistry term. People use it informally here to mean purification by adsorption. Silica is an adsorbent. Silica in a column is also an adsorbent. It could be used for chromatography. Or you could run everything through it and hope it just completely blocks the bad stuff, in which case, it’s being used as an adsorbent only.


This is going to keep me up all night tonight, and makes me want to see if I can convince my business partners to spend some more R&D money.

This kind of system would be a bit of a bother from a regulatory perspective, but really no more so than any other hydrocarbon based system.

To go from ethanol to heptane/hexane you shouldn’t need to change much actually, many of the common materials that are used for ethanol are also reasonably resistant to alkanes. I’d probably add in a nitrogen blanketing system, and some other minor modifications, but not much else off the top of my head.


Don’t these nanofiltration membrane systems still leave some solvent in with the separated oil? I’ve seen talk of 1:1 ish ratios on the output. If so, you’d still need some sort of other system for removing the final portion of solvent. And with heptane having an even higher BP than ethanol you’re likely to lose even more terps than with a standard ethanol extraction.


Yeah, you need either a secondary evaporator or the direct crystallization approach. As far as BP, hexane would be better.


Im with ya on the membranes. I too have seen the data, and will get to experience first hand in the next month or so, and will be comparing to centrifugal separation. I’m betting neither will be “perfect”, but confident that one or the other will be better than the traditional cold sep tek we’ve all been doing for yrs.


Tell me a little about centrifugal separation. I was just talking to someone who mentioned it.

Centrifugal seperation works Ok on polishing of extract
I have done Some test runs with ethanol extracted cbd oil and Brine water ph swing
So more of a LLE function

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