Distilling Limonene

[Ryan Carlyle]

Is anyone attempting to recycle limonene used for dissolving HIPS? At ~$40/gal (Amazon), it might be a good idea.

It seems like it would be pretty straightforward to distill if I had the right lab glassware and a fume hood, but the vapor flammability is a bit concerning for home chemistry purposes. There are two low-temp distillation options I'm looking at to reduce the flame hazard.

The obvious solution is vacuum distilling, to get the boiling temp down and produce a controlled vapor exhaust stream that I can route outside. Limonene should boil at 100C at about 0.1 bar (1.5 psia). But explosion-proof vacuum pumps are expensive.

The other option is steam distilling. You can bubble steam through the limonene and it will carry some limonene vapor with the steam. Then both vapors recondense as two immiscible phases and you can just decant clean limonene off the top of the water. This really appeals to me, because it doesn't require any pumps. All you need is a hot plate, distilled water, and some glassware. Unfortunately, to distill a liter of limonene, you'll have to co-distill over 10 liters of water! This means either doing a ton of small batches (labor-intensive) or using very large distillation vessels (expensive). It's workable, but kind of a pain.

The idea I'm tinkering around with is building a semi-batch still that recirculates the water phase via gravity feed -- U-tubing. This would allow the use of smaller glassware as well as re-capturing some of the heat lost at the condenser, thereby making it more energy efficient. See picture:

Is this ridiculous? Yes, absolutely. I think that's kind of the point.

[notstarman]

explosion-proof vacuum pumps ?_? expensive...why?

Have you considered an asperator for this purpose.
http://en.wikipedia.org/wiki/Aspirator_%28pump%29

[Ryan Carlyle]

I think a water aspirator would waste a ton of water and put a fair bit of water vapor into the system. Getting down to 0.1 bar is kind of low for a single-stage ejector type pump. It might work though.

[Greg Fisk]

I dont know anything about limonene or is safety, but just in case something I do is helpful, I sell distilling equipment.  In particular, a boiler with a flat, concealed element that may reduce risk?
http://puredistilling.com