Type 3A molecular sieves should be used to dry acetone, ethanol and methanol.

Molecular sieves are typically zeolite compounds that strongly adsorb water and have carefully controlled pore sizes. While both the solvent and the water will adsorb strongly to the molecular sieve surfaces, the large surface area within the pores is only accessible to the smaller water molecules, so they are effectively removed from the solvent. water (1.93A) will enter that 3A pore size while acetone (3.08A) will largely be excluded. Water will be able to occupy the large surface area inside the pores and thus be removed. If the solvent could also enter the pores, it would compete with water for the surface area and there would be little or no removal of the water from the bulk solvent. Type 4A molecular sieve is not suitable for drying ethanol, methanol, or acetone since the pore size does not exclude these solvents

Type 3A molecular sieves should be used to dry acetone, ethanol and methanol.

Molecular sieves are typically zeolite compounds that strongly adsorb water and have carefully controlled pore sizes. While both the solvent and the water will adsorb strongly to the molecular sieve surfaces, the large surface area within the pores is only accessible to the smaller water molecules, so they are effectively removed from the solvent. water (1.93A) will enter that 3A pore size while acetone (3.08A) will largely be excluded. Water will be able to occupy the large surface area inside the pores and thus be removed. If the solvent could also enter the pores, it would compete with water for the surface area and there would be little or no removal of the water from the bulk solvent. Type 4A molecular sieve is not suitable for drying ethanol, methanol, or acetone since the pore size does not exclude these solvents

Thanks Thiru, that was excellent answer with excellent explanation.

For really dry methanol you can distil it from magnesium turnings.

Hello,

in addition to Roland's answer, you can also add some iodine crystals to activate the Mg turnings; then reflux for 2-3h and destillation; store over molecular sieve 3A.

Regards.

Thanks, Roland and Simon.

Just to added on the part about using 3A molecular sieves, just remember to pre-dry the molecular sieves at 400 oC in a furnace prior to use. After drying, store the molecular sieves in a desiccator.

Use 3A MS

Thanks, everyone.

Probably excessive information but I enjoyed the article enough to think it's worth sharing. As removal of moisture/adsorbtion is a function of time and amount of molecular sieves(sites for adsorbtion), this seems important. Without performing a titration and using fresh molecular seives(or regenerated but not too old as they do have a life-time) this will give a range for about how dry the solvent may be.

According too:

Drying of Organic Solvents: Quantitative Evaluation of the Efficiency of Several Desiccants

D. Bradley G. Williams and Michelle Lawton

The Journal of Organic Chemistry 2010 75 (24), 8351-8354

http://pubs.acs.org/doi/abs/10.1021/jo101589h

Mg/I2 (0.5 g Mg/L) : 53.6 +/-(0.6)ppm(residual water content)

(methanol distilled from dessicant after Mg was consumed)

3 A molecular sieves (10% m/v)-

after 24 hours 40.6 +/- 0.6ppm(residual water content)

after 120 hours 18.2 +/- 0.9ppm(residual water content)

3A molecular sieves (20% m/v)-

after 24 hours 28.1+/-0.4 ppm(residual water content)

after 120 hours 10.5+/-0.9ppm(residual water content)

Thanks . I am going to start my reaction.

I suggest have a look in this paper: http://ccc.chem.pitt.edu/wipf/Web/Solvent_Drying.pdf

You may find this useful: Al-Asheh et al (2004) Chemical Engineering Research and Design, 82(A7): 855–864

http://ac.els-cdn.com/S0263876204725630/1-s2.0-S0263876204725630-main.pdf?_tid=5eac43d0-eb28-11e4-9304-00000aacb360&acdnat=1429952114_b16fba7e446b3f8c2833222ddb3b5ed8

Here's another article: Farhadpour and Bono (1996) 'Sorptive separation of ethanol-water mixtures with a bi-dispersed hydrophobic molecular sieve, silicalite: determination of the controlling mass transfer mechanism' Chemical Engineering and Processing 35 (1996) 141- 155  http://www.sciencedirect.com/science/article/pii/0255270195041389#

I tried drying methanol with 3A molecular sieves, but now it seems a little murky. Is this normal and can I use the MeOH as is for fixing my cells, or is there a way that I can get rid of this cloudiness?

I think he knows about molecular sieve 3A Zeolite , but i am sure he ask about "size" of the sieves it self, i would recommended of 1-3 mm .

how can I recycle molecular sieve?