Sciencemadness Discussion Board

molecular sieves

Magpie - 6-6-2006 at 10:06

I have spent considerable time trying to find a source of molecular sieves, ideally type 4A, size 8x12. It is easy to find a supplier if you want a 55 gallon drum, but difficult if you only want 500g.

Vitus_Verdegast, in a recent post says:
Quote:

Use 3A molecular sieves. They are cheap and easy.


Am I missing something obvious or is it only in the US that finding sieves is difficult?

[Edited on 6-6-2006 by Magpie]

solo - 6-6-2006 at 11:08

You might want to try Aldrich............solo

http://www.sigmaaldrich.com/Brands/Aldrich/Tech_Bulletins/AL...


69833
Fluka Molecular sieves, 3 Å
powder
Synonym
Molecular Sieve UOP Type 3Å
Molecular Formula
KnNa12-n[(AlO2)12(SiO2)12] · xH2O
CAS Number
308080-99-1
MDL number
MFCD00147627


Expand/Collapse All
Price and Availability
Product
Number Your Price
USD Available to Ship Quantity Actions
69833-250G 31.40 06/06/2006

details...

69833-1KG 92.40 06/06/2006

details...

Properties
form
powder
pore size
3 Å pore diameter
References
Fieser
Fieser 1,703 / Fieser 2,286 / Fieser 5,465 / Fieser 6,411
Safety
Hazard Codes
Xi
Risk Statements
36/37/38
Safety Statements
26-36
WGK Germany
3
F
3


..............source,

http://www.sigmaaldrich.com/catalog/search/ProductDetail/FLU...

Magpie - 6-6-2006 at 11:41

Yes Solo I know that the regular scientific supply houses carry just what I want and in the right size. I just presumed that (1) this would be very expensive, and (2) they wouldn't sell to individuals as this would be considered a chemical.

[Edited on 6-6-2006 by Magpie]

solo - 6-6-2006 at 11:47

I think that the price is cheap enough as for selling for individuals .....there the problem lies..........the situation sucks as it treats all buyers that are not institutions or labs as illegal projects and turn down our business...............solo

S.C. Wack - 6-6-2006 at 16:17

Would you be adverse to simply making the powder? Would love to know how they make the pellets or beads.

Eclectic - 6-6-2006 at 16:36

Google or Froogle for dessicant or air-drier. They are used in the air conditioning industry, in packaging, and for drying compressed air. Also a source for silica gel and activated alumina.

ordenblitz - 6-6-2006 at 16:37

I get them by the 500gm can from coleparmer.
http://www.coleparmer.com/catalog/Product_Index.asp?search=m...

I few years back Skylighter had gotten a seriously large volume of sieves in a surplus buy, and was selling them cheap for use as star cores. It is very possible that they still have some around.
http://www.skylighter.com/

Air-conditioning systems use an inline drier that contains sieves. You could contact a AC contractor and ask if you could get them to save you some used ones. Cut em open, cook the beads and their good as new. Alternatively, inline driers are cheap, buy em and hack them open.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=75318...

[Edited on 7-6-2006 by ordenblitz]

Magpie - 6-6-2006 at 18:27

Ordenblitz: I'm glad to hear that you can buy molecular sieves from a major scientific supply house. This surprises me. Do you have a special qualification, or could anyone buy from them?

I chased down the refrigerant cannister source fairly thoroughly. You have to be a little careful here. Some replaceable cores, like Sporlan, are ms mixed with alumina to remove acids. This in itself is probably OK for most uses but there is also a baked-in organic binder of unknown composition. I wouldn't want that getting into my ether purification scheme. I did find a supplier that uses a spring instead of a binder (Emerson). This would be OK. Without actually checking I assumed this would be an expensive route as you would have to cut open an engineered vessel good for several hundred psi.

I finally stumbled onto a supplier that had a drum of 4A, 4x8 for $1800. To my shock and delight they were willing to sell me a lb (454g) for $6. As I understand it the 4x8 size is designed for gas drying whereas the 8x12 size is for liquid drying.

S.C. Wack: I think the powder would be fine for drying liquids. How do you make it?

S.C. Wack - 7-6-2006 at 03:47

I wouldn't be at all surprised to find some compressor oil residue in used filter-driers.

The procedure in Inorg. Syn. for 4A molecular sieves:

"A. ZEOLITE A2
2NaAlO2 + 2(Na2SiO3·9H2O) -> Na2O·Al2O3·SiO2·4.5H2O + 4NaOH + 11.5H2O
Procedure
Sodium aluminate (13.5g, approximately 0.05 mol alumina and 0.07 mol Na2O; commercial sodium aluminate contains about 40% Al2O3, 33% Na2O and 27% H2O) and sodium hydroxide (25 g, 0.62 mol) are dissolved in 300 ml of water in a magnetically stirred 600 ml beaker and brought to a boil. The aluminate solution is added, with vigorous stirring, to a hot solution of sodium metasilicate, Na2SiO3.9H2O (14.2 g, 0.05 mol) in 200 ml water in a 1 l beaker, also equipped with a teflon coated magnetic stirrer. The entire mixture is heated with stirring at about 90C until the suspension will settle quickly when stirring is stopped (2-5 h). The suspension is then filtered hot and the solid washed repeatedly with water (four 100 ml portions) and dried in an oven at 110C to give about 7-8 g (80-90% yield based on SiO2) of Na2O.Al2O3.2SiO2.4.1H2O.

Anal. Calcd.: Na2O, 17.3; Al2O3, 28.5; SiO2, 33.5. Found: Na2O, 16.1; Al2O3, 28.8; SiO2, 34.2. The purity of the sample is determined by inspection of its X-ray diffraction pattern."

This is not what is described in the K-O article as the industrial process.

I've tried this using the solution from the calculated amount of NaOH and Al foil, and also the product obtained by evaporation of NaOH with excess Al; with the silicate being the calculated amount of the OTC pentahydrate. Haven't tested the product in any way, or tried cation exchange with CaCl2 or KCl (3A sieves have 9 out of 12 atoms of sodium replaced by potassium. 5A sieves have 4.5, Ca obviously being divalent). I'm not sure that this worked out right, as at no point was this a gel. The yield was also lower, despite some precaution from atmospheric CO2.

ordenblitz - 7-6-2006 at 17:46

Magpie,

I see nothing on Coleparmers site that states they wont sell to individuals.. at least not something as mundane as sieves. They are not the cheapest and I think their greed gets the better of any policy like that.
I am buying as a business but was never checked.. so make up a name and order away!

I like the price you found much better though.. care to share the supplier?

Magpie - 7-6-2006 at 18:21

I usually find out that the major scientific supply house won't sell to me far down in the ordering process. For one major I never found out officially they just wouldn't process my order even though they took my credit card number. I did look around and found the policy statement later in the fine print.

Molecular sieves (zeolite clay) do seem as innocuous as they come. But once a corporate bureacracy makes a blanket policy you are screwed. Molecular sieves would seem to be a good test case, however.

lordmagnus - 7-6-2006 at 20:40

Molecular sieves should be freely available from just about any supplier. I can't think of anything directly malicious you could do with them. They are used to remove water molecules from ethanol and various fuels. Try your local pet store (petsmart), besides high activity carbon, and granular ZEOLITE, "SEACHEM" markets a molecular sieve for removing organic contaminates, and discoloration in water. They say it's more effective than a DIATOM filter material, and it is a power similar to sugar in it's size, except it's round beads.

S.C. Wack - 8-6-2006 at 03:31

I'd sooner risk the mystery ebay product than pay C-P prices...for anything.

Mumbles - 8-6-2006 at 12:13

If anyone is interested, there is still a pyro supply shop selling molecular sieves. 50 cents a pound. Unfortunatly I do not know the pore diameter. My electron microscope is in the shop, sorry. Otherwise I'd check.:P If you also happen to be into the art of pyrotechnics and need some polystyrene shells, they are giving them away with orders of 50 casings or more. They are rather large prills. From the description they used to have, it sounded like they broke up into smaller segments with water. "1/8 tsp contains over 100 cores" or something to that effect.

http://www.discountpyro.com/index.htm

Magpie - 8-6-2006 at 13:08

Thanks mumbles for that site address. Although I am not a pyro I found they have interesting chemicals at good prices. I have asked them for specifications on their molecular sieves.

In reference to your combating boredom at the hardware store I offer that you can also study the plumbing section and visualize what processing equipment you might build! ;)

lordmagnus - 8-6-2006 at 16:55

I checked on the Seachem product, it's puregen, can't find much on it, some sort of polymer blend, it absorbs nitrite, nitrate, ammonia, and various discolorations from water. You regenerate it by soaking in a 1:2 bleach/water solution in a non metallic container for 24 hours, then rinse, and then soak for 2 hours in a mixture of water and dechlorinator, and check for a chloroine odor afterwards.

Mumbles - 9-6-2006 at 11:44

Quote:
Originally posted by Magpie
Thanks mumbles for that site address. Although I am not a pyro I found they have interesting chemicals at good prices. I have asked them for specifications on their molecular sieves.

In reference to your combating boredom at the hardware store I offer that you can also study the plumbing section and visualize what processing equipment you might build! ;)


Let us know about the specifications on the molecular sieves. I have a pound sitting in the basement. They are sold as star rolling cores, but they seem rather large for that purpose. If they do indeed break up with water, then the issue is a moot point. For those not familiar with the process of star rolling, think of it as a pearl. It starts as an irritant, sand/rock/dust/whatever, this is analougous to the core. Then layers of pearl material are put over it in many layers to make it less irritating to the oyster and pretty to us. The pearl layers would be composition rolled over the core to make it pretty for us.

I also happen to work primarily in the plumbing department, which is convenient. Toss in some power tools from hardware, and solvents from the paint section, and I may never want to leave. If I had my way, the water heaters, showers, bathtubs, giant grills(but not propane or charcoal;)), and the airconditioning units would be transfered somewhere else. I should try to negotiate a trade with the hardware. Might as well see if I can get some of the cute girls who work there too while I'm at it. :P

Vitus_Verdegast - 10-6-2006 at 09:22

Art supply stores is where it's at my friends.

It is used as a general or specialty dessicant, eg. for use in the art of art preservation.

Molecular sieves tend to be state of the art in the art of preventive conservation of art... :D


Ars gratia artis :cool:

Magpie - 12-6-2006 at 16:15

I put some of my recently acquired 4A, 4x8 molecular sieves to work today. I placed some in homemade isopropyl bromide, and some in homemade diethyl ether. I didn't think my IPB was wet but was pretty sure the ether was wet with water and ethanol. Both had been purified by simple distillation following the prescribed workups.

It was interesting to observe that there seemed to be no reaction in the IPB. But in the ether there appeared an immediate stream of fine bubbles from each ms bead. At first I thought that the ether might be boiling due to heat of adsorption of water/ethanol. Then I wondered if the bubbles weren't just air being pushed out of the sieves as the water/ethanol was entering. This stopped after a few minutes.

Does anyone know what was actually causing the bubbles?

[Edited on 13-6-2006 by Magpie]

Fleaker - 14-6-2006 at 10:17

Most likely air. I get that when I use them for drying methanol.

Magpie: "I finally stumbled onto a supplier that had a drum of 4A, 4x8 for $1800. To my shock and delight they were willing to sell me a lb (454g) for $6. As I understand it the 4x8 size is designed for gas drying whereas the 8x12 size is for liquid drying."

I might have missed it, but who did you say this supplier was? Either U2U or post it their name if you can :)

kazaa81 - 16-6-2006 at 15:08

I'm not sure about this, but won't diatomaceous earth be a good filter?
The size can vary, or can be just too large to filter what do you need...

I think diatomaceous earth doesn't react so easily, since SiO2 is attacked just by HF

Hope this helps

Magpie - 16-6-2006 at 17:05

Diatomaceous earth is a geat filter medium for particulate matter.

Molecular sieves are in a whole different league. They actually trap molecules based on their diameter in angstroms. E.g., type 3A traps molecules less than 3 angstroms in diameter (like water) while keeping out the larger bulk solvent molecules.

[Edited on 17-6-2006 by Magpie]

lordmagnus - 16-6-2006 at 17:12

Yeah,

3a and 4a are great for removing the last bit of water from ethyl alcohal. Or drying out other materials as well. The use them after they are done doing distillation on corn ethanol, to get it to near 100% Ethanol before they blend it with gasoline. They can also make ethanol out of cellulose waste as well, if they pretreat the cellulose with cellulase enzymes first so they will be able to ferment them.