December 07, 2022, 02:50:42 AM
Forum Rules: Read This Before Posting


Topic: Equipment question: Metered addition to a reaction flask under vacuum  (Read 994 times)

0 Members and 1 Guest are viewing this topic.

Offline Reddart

  • Regular Member
  • ***
  • Posts: 51
  • Mole Snacks: +3/-0
  • Gender: Male
Hi,

I was wanting to help semi automate a particular reaction by replacing an addition funnel with a pump to meter in reagent. One of the problems with this particular reaction is I am adding reagent solution while vacuum distilling off solvent. The reaction requires an overhead stirrer for thorough mixing, otherwise I would try to do this on a rotovap.

The scale I am running this requires ~ 1mL/min of almost 1L of solution (so a ~10hr procedure), hence desiring to get away from the addition funnel (and fiddling with the valve every 15 minutes or so to keep the correct addition rate).

I was thinking peristaltic pump since the reaction vessel is under vacuum and the volumes being pumped. Any other solutions that come to mind?


Offline Reddart

  • Regular Member
  • ***
  • Posts: 51
  • Mole Snacks: +3/-0
  • Gender: Male
Re: Equipment question: Metered addition to a reaction flask under vacuum
« Reply #1 on: September 29, 2022, 10:47:17 AM »
Since this topic is initiating so much conversation, I wanted to add this possible solution, a metered valve:
https://us.vwr.com/store/item/NA5132641/masterflex-metal-metering-valves-avantor

Since it is under vacuum, something like this should work. I just don't know how consistent it meters. I suppose it can't be worse than attempting to meter a tiny flow on an addition funnel, and possibly a lot better if it is sized close to my desired rate.

Offline wildfyr

  • Global Moderator
  • Sr. Member
  • ***
  • Posts: 1733
  • Mole Snacks: +194/-10
Re: Equipment question: Metered addition to a reaction flask under vacuum
« Reply #2 on: September 30, 2022, 07:14:23 PM »
I like the peristaltic pump better. It will "pinch" off with each rotation, so extra liquid won't be sucked through by the vacuum. With a metering valve, that is all based on STP and gravity. Its just a hole.

Offline rolnor

  • Chemist
  • Sr. Member
  • *
  • Posts: 1986
  • Mole Snacks: +135/-10
Re: Equipment question: Metered addition to a reaction flask under vacuum
« Reply #3 on: October 04, 2022, 03:01:41 AM »
I question if you can do the reaction via another route that dont needs the slow addition, this is complicated. A peristalitic pump has a tube, and this tube can collapse under vacuum.

Sponsored Links