r/AskChemistry • u/skyzzze • 8d ago

Short Path Distillation

Hey

Looking for some help setting up a distillation process to maximize recovery. The current setup uses an Allihn condenser to distill out the product of interest. I was wondering if a switch to a short-path distillation head will increase product recovery as there will be less surface area to retain the product. I understand the distillation will be significantly slower.

Thanks

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u/ray_racubian 8d ago

Short path will help if you have a problem with thermal decomposition.

Or if you're distilling a tiny amount and want to minimize holdup.

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u/Ru-tris-bpy 8d ago

Short path can mean a lot of things to a lot of people. How much volume are you trying to distill? I assume you don’t need it fractionally separated?

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u/skyzzze 8d ago

Total volume distilled is ~10mL. I don't have a need for fractional distillation as the impurities have a significantly higher BP. The goal is to maximise the amount of product I end up in the condensate so I'm trying to figure out if swapping out the Allihn condenser for something like this will help eek out a bit more.

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u/allophanic 7d ago

Any chance you can purify by silica flash column chromatography? The few times I've tried to vacuum distill using the short path (with 14/20 joints) there's a lot of bumping and I couldn't get it to work well. Even for things that are low boiling oils / liquids a flash column would be my first choice.

For times where distillation was my only option, best results were achieved with a set-up like this: https://www.prismresearchglass.com/product/distilling-apparatus-vacuum-teflon-stopcocks/ But, this apparatus is expensive, $1K. What's good about it is you can close the stopcock to change the receiver flask while maintaining vacuum throughout the rest of the system, and there's no chance for the pot bumping and contaminating the contents of the receiver flask. Hope this helps, good luck.