alumina turns yellow...
dekens
solvent. (At T=120C) I have tried "aluminum oxide 90" (Merck) and tested
types "acid, basic and neutral type" Al2O3 in a column. I find the
neutral oxide to work best. However I don't know how to dry the oxide
properly. In drying stove (125C/5 mbar) it will turn yellow after >1
hour. My solution: adding 100% (w/w) of dry toluene and drying the moist
(not wet) mix in the stove for 30 minutes. (toluene entrains water). The
alumina dries quickly and it stays white. Can anyone tell me what causes
the yellow color?? I'd like a better solution. (Working without the
solvent.) Hope someone can help! Thank you. Folkert Dekens
Uncle Al
Toluene vapor in air is explosive. The yellow color is due to
progressive contamination from your oven. What does "dry" mean?
Percent water, ppm? How much are you drying, grams? tonnes? What is
the relative volatility of the acid and the solvent - distill them
apart (under reduced pressure if temp is a problem).
Why don't you dump out the acid as its sodium salt by running the
solution through a column of anhydrous sodium carbonate?
--
Uncle Al
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dekens
no bother. I appreciate the effort you put in all this (the NG and
questions I put forward in the past). All to willing to pay something
back. I can not be too specific. But the lactic acid should be
completely removed from the (lactone) solvent -the sodium salt is also
not welcome. The lactone should be very pure. Thanks for your wit and
interest, your relevant remarks. Folkert Dekens. (Cleaning the oven may
help, will try that. The [LA] must be reduced from ca. 1% down to less
than .01%. Toluene-vapour will not explode in a vacuumstove-? (My
guess..) I work for small company (R&D) I would like to continue my job.
Can't be too specific.
Uncle Al
Try a strong base *macroreticular* ion exchange resin (Amberlyst,
others - Aldrich or Sigma catalog) plus a dehydrating stage, possbily
mixed. That way you can recover the trapped lactate and don't have to
worry about solvent swell too much (but swell it will).
Toluene in vacuo is OK.
Paul J Franklin
> Hello everyone, I want to adsorb organic acid from a relatively apolar
> solvent. (At T=120C) I have tried "aluminum oxide 90" (Merck) and tested
> types "acid, basic and neutral type" Al2O3 in a column. I find the
> neutral oxide to work best. However I don't know how to dry the oxide
> properly. In drying stove (125C/5 mbar) it will turn yellow after >1
> hour. My solution: adding 100% (w/w) of dry toluene and drying the moist
> (not wet) mix in the stove for 30 minutes. (toluene entrains water). The
> alumina dries quickly and it stays white. Can anyone tell me what causes
> the yellow color?? I'd like a better solution. (Working without the
> solvent.) Hope someone can help! Thank you. Folkert Dekens
>
>
Putting toluene in an oven will result in an explosion due to the vapor
contact withthe heating elements.
Paul J.