Rotary Evaporators

SquattingBull · Apr 8, 2015

It seems like perhaps one advantage to spinning on its side like a roto would be that when the fluid got thicker towards the end of the recovery you could still get a pretty good spread of material along the sides of the flask. SH perhaps this could be achieved in your design by altering the pitch or speed of the rotation as you progress through the cycle? Maybe this wouldn't be an issue at all I just thought about it while watching a video of some decarbed oil that was being done and how thick and viscous is was at the end compared to the water you used for your initial swing test.

SkyHighLer · Apr 8, 2015

Thanks for allowing me the space to completely present my idea, I'll shut up now. :biggrin:

Siskiyou Sam · Apr 8, 2015

At max volume the Rotovape Maximus holds about one liter, that requires about 4 hours to remove and recover the alcohol and last few drops of water.

Siskiyou Sam · Apr 8, 2015

SkyHighLer said:
I totally agree Sam's device is kicker, just way too much work if there's a simpler way.

Agree. It's simply my expression of artistic engineering. An off the shelf rotovap would be way simpler http://www.ebay.com/itm/5L-Rotary-E...9c5906&pid=100204&rk=1&rkt=28&sd=371240791065

SkyHighLer · Apr 9, 2015

Siskiyou Sam said:
Agree. It's simply my expression of artistic engineering. An off the shelf rotovap would be way simpler http://www.ebay.com/itm/5L-Rotary-E...9c5906&pid=100204&rk=1&rkt=28&sd=371240791065

No, you misunderstood me, you're device probably kicks the butt of a traditional rotovap, the whole side wall is continuously evenly heated, and you've eliminated the glassware. Slick.

I don't know who's going to have the skills to build it themselves from scratch, but it's the way to go. I hope someone produces it, and you and your family profits from the patent rights for generations.

Siskiyou Sam · Apr 9, 2015

LOL, yea I would be stoked if somebody produced it, but it's in the public domain now, so I don't expect to see any more profit than the real gold of paying it forward.

SquattingBull · Apr 11, 2015

As a general rotovape question, do you require a fractioning still in order to renew your alcohol back to 190 proof as with just a basic recollection still? I know you pick up water from the atmosphere and the plant when using ethanol but can a roto keep the parameters tight enough to fraction ethanol first and then the remaining moisture in the oil second?

Gray Wolf · Apr 11, 2015

SquattingBull said:
As a general rotovape question, do you require a fractioning still in order to renew your alcohol back to 190 proof as with just a basic recollection still? I know you pick up water from the atmosphere and the plant when using ethanol but can a roto keep the parameters tight enough to fraction ethanol first and then the remaining moisture in the oil second?

The alcohol picks up water where ever it can find it, so to return to 190 proof will require a refluxing still, but if you are using it for winterizing, it shouldn't be picking up huge amounts of water, like it can using it for QWET.

SquattingBull · Apr 11, 2015

Thanks GW thats what I thought you would say but I was hopeful that I was wrong ha. Guess we will be building a reflux still soon because even if we get a bunch of uses out of our ethanol it would be nice not to have to waste solvent even after numerous uses.

APK47 · Apr 11, 2015

With accurate vacuum control you can distill just the ethanol while leaving most if not all water behind. Water takes quite a bit more vacuum and heat to boil than ethanol. With a decent vacuum controller, and accurate heated bath, you should rather easily have the ability to fractionally distill the ethanol while leaving behind water and concentrate in the evaporating flask.
I use an old buchi rotovap but have a newer KNF vac controller that has the ability to do this. I surmise that this is what's taking place, please correct me if I am wrong.

SquattingBull · Apr 11, 2015

I do not think this is the case actually. I had to refresh on some long lost chemistry but due to the fact that water and ethanol form an azeotrope a simple distillation cannot renew the solvent mixture back to pure ethanol but rather can get it closer to the azeotropic point. Each distillation of the water/ethanol mixture will take it closer to the azeotropic point (ie 190 proof) but never exceeding it. Another question on that front is could our ethanol that has been diluted over time be run through the roto several times to get us back to the baseline azeotropic point GW (or another chemistry guru)? Would this be silly in time consumption to the point of us just needing to invest in a fractioning column even if it is possible ha?

SquattingBull · Apr 11, 2015

Also, does the azeotropic form of ethanol not stop occurring under high enough vacuum allowing pure ethanol to be distilled where normally it could not? At least theoretically? Can a roto not achieve a vacuum substantial enough to shift the azeotropic form enough to ethanols favor to achieve 190 proof? (Running solvent alone not laden with hash oil in this particular case)

MEMED · Apr 11, 2015

squatting bull, dude you guys need to do some r&d. Its worth it. You will drive yourself mad with all this questioning. Everyone is different. Im a dick, i kno.

fwiw, I use zeolite, and carbon in my flask when I recycle, rectify, and store etoh, er any liquor.

you can tell how dry it is with a proof meter

MEMED · Apr 11, 2015

you can totally dry it w/o distilling. However, I find theres dust no matter how low I filter to, so I distill it over for clarity.

SquattingBull · Apr 12, 2015

You're not a dick sir you just don't know our circumstances which is why our questions might seem usual/ strangely specific in nature. I can assure you that I am doing everything in my power you can do both theoretically and in reality but the parameters of my work situation are controlled by unyielding forces. However this is the "R" in R&D brother and I make it work. It is not so simple that I can go out and figure it out for myself... yet. But soon. We'll share in our great gratitude and humility to this forum when that happens.

I have thought about using zeolite in this application which is a cool idea and may be how we end up doing drying ethanol so thanks for the input on that regard you answered one of my questions without me having to ask so for that :tiphat:

Honestly, I am a chemistry nerd from back in the day and found myself enthralled by the question since I haven't gotten to think about things like that in a long time and look forward to an answer from someone who knows better than myself regardless. As usual thank you for your help MEMED.

MEMED · Apr 12, 2015

yes you are doing research bro. I dont mean to be degrading. Respect.

G.O. Joe · Apr 12, 2015

Don't buy the Yugo of rotavaps when a new Buchi R-210 base model is on sale delivered for under $3500. If you do cheap out, get a Buchi and make your own bath.

SquattingBull said:
can a roto keep the parameters tight enough to fraction ethanol first and then the remaining moisture in the oil second?

Any distillation would do that. The distillation would start out ethanol-rich and the water content would gradually increase.

SquattingBull said:
Also, does the azeotropic form of ethanol not stop occurring under high enough vacuum allowing pure ethanol to be distilled where normally it could not?

Whether the azeotrope exists at certain pressures won't matter without a column.

SquattingBull · Apr 12, 2015

MEMED said:
yes you are doing research bro. I dont mean to be degrading. Respect.

I know brother and I appreciate your help and input always.

Joe, I did a bit of reading between that first post and the second (I know, should have done it before the first post) so I realize now why a simple distillation won't simply separate the water and leave pure ethanol regardless of parameter, hence the azeotropic nature of ethanol and water. Duh on my part.

Agree on the Buchi its what we are getting but it was more of an academic question because I wanted to know sooner rather than later whether or not to be including materials for a fractioning column to renew the state of our ethanol over time. MEMED brought up a good point that zeolite could remove the water and then a distillation could be done to ensure no fine particles remained prior to its next use with product. However, I also read that vacuum distillation can be used to produce pure ethanol because it pushes the azeotropic nature of the mixture more to the favor or EtOH rather than water so I was curious why this seemingly doesn't happen with a rotovape. When you said column in your last post were you referring to a fractioning column?

G.O. Joe · Apr 12, 2015

SquattingBull said:
When you said column in your last post were you referring to a fractioning column?

Yes. If you search hard enough you can find references to losing the azeotrope with vacuum, but when you read the fine print you find that it's difficult in practice, enough that it's just a novelty. You will need a good column. You need a good column to get the azeotrope at atmospheric pressure from low-ethanol mixture - closer to the azeotrope it will be easier to get close to the azeotrope. Even some simple industrial practice like drying with corn cobs comes with fine print. 3A molecular sieves on the other hand is not a problem. Dust can be dealt with but it's better to distill again after drying. Add water because the 95% ABV is best for winterization. 95 volumes anhydrous ethanol, 6.18 volumes water to be exact.

SquattingBull · Apr 12, 2015

G.O. Joe said:
Yes. If you search hard enough you can find references to losing the azeotrope with vacuum, but when you read the fine print you find that it's difficult in practice, enough that it's just a novelty. You will need a good column. You need a good column to get the azeotrope at atmospheric pressure from low-ethanol mixture - closer to the azeotrope it will be easier to get close to the azeotrope. Even some simple industrial practice like drying with corn cobs comes with fine print. 3A molecular sieves on the other hand is not a problem. Dust can be dealt with but it's better to distill again after drying. Add water because the 95% ABV is best for winterization. 95 volumes anhydrous ethanol, 6.18 volumes water to be exact.

Ahhhhhh I see. That makes an incredible amount of sense thank you very much for the help. Chemistry does tend to have lots of the "fine print" as you say. Lots of novel concepts to be waded through a much fewer that can be practically applied. At least with the money and resources that warrant being thrown at them.

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