Molecular sieve reactivation

[30578]

Hi everyone:
I just got this question that maybe it's been posted before, but I'm still not sure about it.
At our factory, we're trying to reactivate molecular sieve in order to determine % of water absorbed at our warehouse conditions.
We have tried pulling a vacumm of these molecular sieve cores (-8 inHg), in a 130°C oven during a 2-3 days, and then run dry nitogen through them... but didn't get good results. Cores didn't dry out, since they weighed more.
That's why we're interested in getting some more details regarding this test..

Thank you all

 

[Montemayor]

30578:

I can't tell how you mechanically have set up the reactivation of the mol sieve, but you should be able to determine the amount of water the adsorbent has adsorbed by weighing it before & after. However, you must do it under controlled, lab conditions. I can assure you that mol sieve will adsorb a lot of water - but it depends on how you are applying it. The best applications for employing mol sieve as a water moisture adsorbent is under a hefty amount of pressure and at ambient temperatures. I usually don't employ mol sieve adsorbent unless I have a gas stream at 500+ psig pressure and the product requirement is less than 1 or 2 ppm. The mol sieve is expensire and under more benign conditions activated alumina will suffice.

I usually require 600+ ^oF as the reactivating temperature for dry regen gas - especially when getting down to 1 or 2 ppm of moisture in the end product. All this is done without pulling a vacuum.

I seriously doubt your "cores" gained weight after being regenerated (reactivated) properly. Controlled lab conditions are essential and probably explain why your results are negative.

 

[30578]

Hi Montemayor:
(Just saw your handle, is there any chance you speak spanish? It would be better for me =))
You know, we just got into this new test suggested by someone, but not sure about the conditions.
He told us that when they dry the filters (molsieves cores) out, he place them in a 130°C oven and pull a vacuum for 2-3 days. Typically, he can achieve a 200millitorr vacuum on them during this period. After this time frame, he weight them. He will then run dry nitrogen through them, again in the 130°C oven, for 8-10 hours and have found this has been the best method for drying the filters.

But, according to such conditions, we didn't get such a good results...

 

[TD2K]

I don't think your 130C is hot enough to drive off the water. If memory serves we right, we had to heat our mol sieve up to about 450F/230C for their regeneration, 130C sounds way low.

We used to test mol sieve's absorption capacity using an oven as you are though I can't remember the temperature settings but your approach is correct. Mol seives should pick up about 20% water when new.

Have you talked to the vendor?