The critical point for methane is 673 psi and -82.6 C. It’s actually lower pressure than needed for co2. You ought to be same to use it in a co2 machine.
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The only thing better than super high pressure, is highly flammable under super high pressure 
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Yeah I saw that, thats wild, Throw a Huber 815 or 915 on a co2 machine and ensure all exposed gaskets are viton and youd be in business as long as your pumps are suitable
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@Roguelab are you any closer to getting the revco online so you can test extraction with ethane?
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Viton isn’t approved for uses below -60C. Usually I don’t have issues pushing those boundaries but on something like this i’d rather be sure!
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So the ethyl or methyl groups don’t affect cannabanoid affinity? Obviously there’s no inherent comparison base here. But methanol and ethanol have higher cannabanoid affinity compared to other alcohols don’t they?
Or are alcohols entirely different in solvent properties?
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The alcohols do have entirely different properties. The hydroxyl group dominates their intermolecular interactions. I’m not even sure it’s true that ethanol and methanol are far above other alcohols. Isopropyl alcohol is also a very active solvent for cannabinoids. I haven’t heard of anyone using a butyl alcohol, but I suspect it would work good too.
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Nice, figured that was right, hoping it wasn’t. Lol.
This is an interesting concept, but I am not sure how it would play out. Methane and ethane are about as non-polar as CO2, and they are similarly small inflexible molecules. Running liquid methane or ethane would be similar to running liquid CO2… they would extract terpenes and, vicariously, cannabinoid acids dissolved in those terpenes, and they would also strip out vegetable oils and epicuticular wax to some degree, just like CO2 and other alkanes.
One would simply need more molecules of solvent to extract the same amount of oleoresin as the longer alkanes, and with their low boiling points, more terpenes would be left behind in the oleoresin product. At those temperatures, THCa would very likely quickly precipitate out of the solution, so these could be used to make the ultimate live resin… probably with higher yields than butane or propane, as long as enough solvent was used, due to their lower surface tension and therefore high permeability into the small spaces around the frozen plant matter.
I would not recommend using these small alkanes in supercritical phase, for the same reasons supercritical CO2 is ill advised… the solvent does not need to penetrate through any cell walls to extract cannabinoids. Supercritical phase matter is used to penetrate every part of the biomass in order to reach hard-to-get molecules inside cells and tough cellulosic and lignacious materials, which is entirely unnecessary to get through the thin membranes of glandular trichomes.
Finally, there are the inherent safety problems of working with methane and ethane. They are extremely inflammable, and require high pressures and low temperatures to compress them and keep them in liquid state. Their NFPA hazard class is probably at least one step higher than the LP gases like propane and butane.
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The potential for there to be so little residual solvent because of the super low boiling point gets me pretty stoked though. None of that 3 days in the oven I’d assume.
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What piping and fittings would you use to contain the pressure?
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Was just thinking something like a classic or modified soxhlet style, or perhaps a reflux column with the weed as packing.
Was gonna go stainless with a ln2 condenser at the top. Probably run whatever system at around 100psi or something? Bring the boiling point up a bit (-120 or something?). I think the key is gonna be a plethora of solvent interaction since it has a relatively low affinity for cannabinoids.
All stainless I think. I got a welder that owes me a couple favours. 304 and 316 are fine for super low temps.
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If your cooling fails the whole system goes boom. Tri clamp fittings aren’t meant for very high pressures.
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No, I was gonna use higher pressure fittings I think. Probably build my prototype outside 
Yeah, I was thinking of using a liquid nitrogen generator with a resevoir, or a cooling system with a larger reservoir just to make sure there’s always enough coolant available to keep things under control.
This is all very hypothetical at the moment 
I’ve actually got a high pressure tube & fittings here I forgot about. Rated for 600psi I think. Off to a good start at least
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What sort of pipes and fittings are used for supercritical co2 extraction?
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That’s some pieces I got kicking around. The end cap is wrapped in Saran in the picture.
Could probably fit 2-3lb in there I’d guess
I would look into how co2 extractors are constructed. But just keep in mind the far colder temperatures of this system which will affect the seals used.
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Yeah absolutely, gaskets are gonna be a bitch lol
the thar works with metal gaskets that deform pretty wild
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Yeah that might be the ticket. Even those can be problematic though because of size contraction from temperature change. I mean I’m sure it could work just be careful.