Sciencemadness Discussion Board

sublimation scale up

pen1234567 - 27-12-2011 at 09:45

I am using a 3 liter cold finger sublimation apparatus to purify a metalorganic solid that is air-sensitive and water-sensitive. I use a turbomolecular pump to achieve good vacuum. The heating mantle is heated up to approx. 100 deg C (for sublimation) and the sublimator head is cooled down to approx. -10 deg C (for deposition/crystallization of final product).

Currently, I do batch sublimations, charging approx. 500 g crude material per batch. I would like to carry out sublimations of the material more efficiently. Instead of adding more lab scale 3 liter units, I would like to scale up the current apparatus to handle 2-3 kg batches.

Any ideas or thoughts on this? The sublimation unit ideally must fit inside a glove box because the material is sensitive to air and the sublimation is carried out in a glove box. The other consideration is that the crystals that form after sublimation+deposition must be uniformly distributed on the cold finger/collection apparatus.

Thanks all

hissingnoise - 27-12-2011 at 13:21

Can the compound be sublimed under an inert gas rather than reduced pressure?
And what *is* this fragile entity, pray tell?


pen1234567 - 28-12-2011 at 08:12

Quote: Originally posted by hissingnoise  
Can the compound be sublimed under an inert gas rather than reduced pressure?

The sublimation is done in a glovebox, which maintains a nitrogen atmosphere; generally [O2] in the glovebox is always less than 1.0 ppm. The sublimation is done under vacuum at moderate temperatures (opposed to standard pressure and high temps) because the material is unstable at high temperatures.
Quote: Originally posted by hissingnoise  
And what *is* this fragile entity, pray tell?

Good ol' PDMAT :cool:

hissingnoise - 28-12-2011 at 09:36

At near <big>ε</big> 66 per gm I can quite understand you finding the prospect of scaling up the process being, er, tantalising :D !