-
Happy Birthday ICMag! Been 20 years since Gypsy Nirvana created the forum! We are celebrating with a 4/20 Giveaway and by launching a new Patreon tier called "420club". You can read more here.
-
Important notice: ICMag's T.O.U. has been updated. Please review it here. For your convenience, it is also available in the main forum menu, under 'Quick Links"!
When is molecular sieve "full"
- Thread starter BigJohnny
- Start date
Usually by weight.
The more you handle mol sieve, the more dust you have to deal with. I would leave the BHO residue alone, unless its excessive, and then I would replace the beads.
Anything covering the surface that doesn't evaporate easily is subject to carbonization. Degradation of the zeolite and binder depends on operator manufacturer and what's gone by. Tossing a casserole of water wet sieves in the oven at 425 for instance is not the same as gradually heating a shallow layer of air dried sieves in a vacuum oven.
Douglas.Curtis
Autistic Diplomat in Training
**deleted** diplomacy fail...
clearheaded
Active member
Well typically u rinse them after each use. Forget what we did in the lab but wanna say an acid then di water. I am sure u can look up proticol online.
Going to jump in with some related questions if thats alright?
Would using a jacketed spool w/ mol sieve beads with sufficient heat and vacuum level applied, negate the need to transfer the beads to a vac oven and lessen handling/dust?
Also, I know its been discussed many times previously, but perhaps there is less or a change in consensus, BigJohnny, mentioned his 3A sized beads. Where do people stand on 3A vs 4A?
How much weight of beads are people running on medium to larger systems?
Some places seem to sell smaller sized spools which seem undersized but I dont know. Ive been upgrading my setup and planned on going overboard and using a 4"x36" jacketed spool and fillin'er up. Im planning on doing a lot of wet work so figure more beads the better.
Thanks.
Would using a jacketed spool w/ mol sieve beads with sufficient heat and vacuum level applied, negate the need to transfer the beads to a vac oven and lessen handling/dust?
Also, I know its been discussed many times previously, but perhaps there is less or a change in consensus, BigJohnny, mentioned his 3A sized beads. Where do people stand on 3A vs 4A?
How much weight of beads are people running on medium to larger systems?
Some places seem to sell smaller sized spools which seem undersized but I dont know. Ive been upgrading my setup and planned on going overboard and using a 4"x36" jacketed spool and fillin'er up. Im planning on doing a lot of wet work so figure more beads the better.
Thanks.
Hot gas in place is fine also. If the zeolite has been in contact with cannabinoids it goes without saying it should be washed with butane before heating. Acids and bases would be a last resort. I have reused my same old 3A sieves drying many gallons of solvents usually homebrew many times in the oven but I'm cautious about it. It's like epsom salt drying protocol - the difference between nice dry MgSO4 crystals and a big mess - but the effect is harder to see with sieves. Dust shouldn't be a problem if you wash it off before sealing the system? Maybe the problem isn't dust but containment with a pre and post filter perhaps of coarse silica gel? And another thing, wet zeolite may have more capacity to absorb more water, but the stream it's trying to dry will come out wetter.
mobin
Member
i have sieve traps with built in heaters for my diffusion pumps. old school shit for semiconductor work.
the way i was taught, run a pair of them together. bake one into the other changing order as needed.
you sieve material should have a bakeout temperature listed.
they have magical color changing sieve as well. you can see the blue/black -->grey white when full.
the way i was taught, run a pair of them together. bake one into the other changing order as needed.
you sieve material should have a bakeout temperature listed.
they have magical color changing sieve as well. you can see the blue/black -->grey white when full.
Last edited:
mobin
Member
Generally speaking 3A sieve is used for purifying methanol and ethanol. 4A is used for removing C02 and ammonia from natural gas streams as well as being a desiccant for refrigerants, medicines, and electrical components. 5A is used for sweetening natural gas and purifying hydrocarbon gas and liquid streams. 13X (which is really 10 Angstrom) is a multipurpose sieve, it can adsorb the all the particles that previous 3 sieves can adsorb, but it is usually used to sweeten natural gas streams and purify petrochemical liquids and gases. Ultimately the pore size of sieve can have a very specific use like 3A or it can have wide range of uses like 13X, it all depends on what you wish to accomplish.
For this example 3A sieve works best because the size of water molecule is approximately 2.8 angstrom and the size of an ethanol molecule is 3.8 angstrom. The 3A sieve adsorbs all of the water molecules because they are small enough to fit inside the pores. The ethanol molecules, which are too large to fit in the pores, are free to pass by thus separating water from ethanol. If this person were to use 4A, 5A, or 13X sieve it would not work because the pore sizes are large enough to adsorb both the ethanol and water molecules, and thus no separation would occur.
https://hengyeusa.com/community/molecular-sieve-pore-sizes
for drying of ethanol specifically they have a special 3A EDG grade, for getting anhydrous. they claim x>1%
https://www.deltaadsorbents.com/3a-edg-molecular-sieve-desiccant
Thanks for the good info.
I was browsing for sources and came across this one which had this statement:
https://www.impakcorporation.com/desiccants/bulk_desiccant/641A4MS55-13
I was browsing for sources and came across this one which had this statement:
https://www.impakcorporation.com/desiccants/bulk_desiccant/641A4MS55-13
which contradicts their other pages statement of:
mobin
Member
lost in translation maybe?
Molecules with an effective diameter <4 angstroms, incl. ethanol, H2S, CO2, SO2, C2H4, C2H6 and C3H6
notice no equal or less than sign. up to 4 angstroms but not 4. or am i high lol?
Last edited:
mobin
Member
i like using 13x for stank removal of shit tank fumes so my exhaust scent doesn't make people think i'm an asshole.
hear it works great on LPGs too. 3a/4a +13x = win for water/smells.
i like to keep them separate. while 13x will absorb water and other shit llike 3,4,5...i don't wanna waste it all on that if i'm chasing stank
hear it works great on LPGs too. 3a/4a +13x = win for water/smells.
i like to keep them separate. while 13x will absorb water and other shit llike 3,4,5...i don't wanna waste it all on that if i'm chasing stank
Last edited:
4A has a low capacity for propane and no butane. It will preferentially hold water more strongly than ethanol. You can use 4A to dry ethanol, but you will lose some to the sieves when they are in excess of drying need, and 3A drying will be drier. Zeolites are like carbon, silica, alumina (zeolite is aluminosilicate) in holding the more polar molecule, everything else being equal.
From the fifth edition of Purification of Laboratory Chemicals, Armarego and Chai,
Molecular sieves:
Molecular sieves are types of adsorbents composed of crystalline zeolites (sodium and calcium aluminosilicates). By heating them, water of hydration is removed, leaving holes of molecular dimensions in the crystal lattices. These holes are of uniform size and allow the passage into the crystals of small molecules, but not of large ones.
This sieving action explains their use as very efficient drying agents for gases and liquids. The pore size of these sieves can be modified (within limits) by varying the cations built into the lattices. The four types of molecular sieves currentlyavailable are:
Type 3A sieves. A crystalline potassium aluminosilicate with a pore size of about 3 Angstroms. This type of molecular sieves is suitable for drying liquids such as acetone, acetonitrile, methanol, ethanol and 2-propanol, and drying gases such as acetylene, carbon dioxide, ammonia, propylene and butadiene. The material is supplied as beads or pellets.
Type 4A sieves. A crystalline sodium aluminosilicate with a pore size of about 4 Angstroms, so that, besides water, ethane molecules (but not butane) can be adsorbed. This type of molecular sieves is suitable for drying chloroform, dichloromethane, diethyl ether, dimethylformamide, ethyl acetate, cyclohexane, benzene, toluene, xylene, pyridine and diisopropyl ether. It is also useful for low pressure air drying. The material is supplied as beads, pellets or powder.
Type 5A sieves. A crystalline calcium aluminosilicate with a pore size of about 5 Angstroms, these sieves adsorb larger molecules than type 4A. For example, as well as the substances listed above, propane, butane, hexane, butene, higher n-olefins, n-butyl alcohol and higher n-alcohols, and cyclopropane can be adsorbed, but not branched-chain C^ hydrocarbons, cyclic hydrocarbons such as benzene and cyclohexane, or secondary and tertiary alcohols, carbon tetrachloride or boron trifluoride. This is the type generally used for drying gases, though organic liquids such as THF and dioxane can be dried with this type of molecular sieves.
Type 13X sieves. A crystalline sodium aluminosilicate with a pore size of about 10 Angstroms which enables many branched-chain and cyclic compounds to be adsorbed, in addition to all the substances removed by type 5A sieves.
They are unsuitable for use with strong acids but are stable over the pH range 5-11.
Because of their selectivity, molecular sieves offer advantages over silica gel, alumina or activated charcoal, especially in their very high affinity for water, polar molecules and unsaturated organic compounds. Their relative efficiency is greatest when the impurity to be removed is present at low concentrations. Thus, at 25° and a relative humidity of 2%, type 5A molecular sieves adsorb 18% by weight of water, whereas for silica gel and alumina the figures are 3.5 and 2.5% respectively. Even at 100° and a relative humidity of 1.3% molecular sieves adsorb about 15% by weight of water.
The greater preference of molecular sieves for combining with water molecules explains why this material can be used for drying ethanol and why molecular sieves are probably the most universally useful and efficient drying agents. Percolation of ethanol with an initial water content of 0.5% through a 144 cm long column of type 4A molecular sieves reduced the water content to lOppm. Similar results have been obtained with pyridine.
The main applications of molecular sieves to purification comprise:
1. Drying of gases and liquids containing traces of water.
2. Drying of gases at elevated temperatures.
3. Selective removal of impurities (including water) from gas streams.
(For example, carbon dioxide from air or ethene; nitrogen oxides from nitrogen; methanol from diethyl ether. In general, carbon dioxide, carbon monoxide, ammonia, hydrogen sulfide, mercaptans, ethane, ethene, acetylene (ethyne), propane and propylene are readily removed at 25°. In mixtures of gases, the more polar ones are preferentially adsorbed).
The following applications include the removal of straight-chain from branched-chain or cyclic molecules. For example, type 5A sieves will adsorb n-butyl alcohol but not its branched-chain isomers. Similarly, it separates n- tetradecane from benzene, or n-heptane from methylcyclohexane.
The following liquids have been dried with molecular sieves: acetone, acetonitrile, acrylonitrile, allyl chloride, amyl acetate, benzene, butadiene, w-butane, butene, butyl acetate, n-butylamine, /i-butyl chloride, carbon tetrachloride, chloroethane, l-chloro-2-ethylhexane, cyclohexane, dichloromethane, dichloroethane, 1,2- dichloropropane, 1,1-dimethoxyethane, dimethyl ether, 2-ethylhexanol, 2-ethylhexylamine, n-heptane, n-hexane, isoprene, isopropyl alcohol, diisopropyl ether, methanol, methyl ethyl ketone, oxygen, n-pentane, phenol, propane, n-propyl alcohol, propylene, pyridine, styrene, tetrachloroethylene, toluene, trichloroethylene and xylene. In addition, the following gases have been dried: acetylene, air, argon, carbon dioxide, chlorine, ethene, helium, hydrogen, hydrogen chloride, hydrogen sulfide, nitrogen, oxygen and sulfur hexafluoride.
After use, molecular sieves can be regenerated by heating at between 300°-350° for several hours, preferably in a stream of dry inert gas such as nitrogen or preferably under vacumm, then cooling in a desiccator. Special precautions must be taken before regeneration of molecular sieves used in the drying of flammable solvents. However, care must be exercised in using molecular sieves for drying organic liquids. Appreciable amounts of impurities were formed when samples of acetone, 1,1,1-trichloroethane and methyl-f-butyl ether were dried in the liquid phase by contact with molecular sieves 4A (Connett Lab Pract 21 545 7972). Other, less reactive types of sieves may be more suitable but, in general, it seems desirable to make a preliminary test to establish that no unwanted reaction takes place. Useful comparative data for Type 4A and 5A sieves are in Table 19. (from pages 28-29)
n-Butane [106-97-8] M 58.1, m -135°, b -0.5°. Dried by passage over anhydrous Mg(ClO4)2 and molecular sieves type 4A. Air was removed by prolonged and frequent degassing at -107°. (from page 143)
I have a hard copy of the seventh edition, the fifth was the latest edition I could find at this time for free download. Try Library Genesis,
https://gen.lib.rus.ec/
Molecular sieves:
Molecular sieves are types of adsorbents composed of crystalline zeolites (sodium and calcium aluminosilicates). By heating them, water of hydration is removed, leaving holes of molecular dimensions in the crystal lattices. These holes are of uniform size and allow the passage into the crystals of small molecules, but not of large ones.
This sieving action explains their use as very efficient drying agents for gases and liquids. The pore size of these sieves can be modified (within limits) by varying the cations built into the lattices. The four types of molecular sieves currentlyavailable are:
Type 3A sieves. A crystalline potassium aluminosilicate with a pore size of about 3 Angstroms. This type of molecular sieves is suitable for drying liquids such as acetone, acetonitrile, methanol, ethanol and 2-propanol, and drying gases such as acetylene, carbon dioxide, ammonia, propylene and butadiene. The material is supplied as beads or pellets.
Type 4A sieves. A crystalline sodium aluminosilicate with a pore size of about 4 Angstroms, so that, besides water, ethane molecules (but not butane) can be adsorbed. This type of molecular sieves is suitable for drying chloroform, dichloromethane, diethyl ether, dimethylformamide, ethyl acetate, cyclohexane, benzene, toluene, xylene, pyridine and diisopropyl ether. It is also useful for low pressure air drying. The material is supplied as beads, pellets or powder.
Type 5A sieves. A crystalline calcium aluminosilicate with a pore size of about 5 Angstroms, these sieves adsorb larger molecules than type 4A. For example, as well as the substances listed above, propane, butane, hexane, butene, higher n-olefins, n-butyl alcohol and higher n-alcohols, and cyclopropane can be adsorbed, but not branched-chain C^ hydrocarbons, cyclic hydrocarbons such as benzene and cyclohexane, or secondary and tertiary alcohols, carbon tetrachloride or boron trifluoride. This is the type generally used for drying gases, though organic liquids such as THF and dioxane can be dried with this type of molecular sieves.
Type 13X sieves. A crystalline sodium aluminosilicate with a pore size of about 10 Angstroms which enables many branched-chain and cyclic compounds to be adsorbed, in addition to all the substances removed by type 5A sieves.
They are unsuitable for use with strong acids but are stable over the pH range 5-11.
Because of their selectivity, molecular sieves offer advantages over silica gel, alumina or activated charcoal, especially in their very high affinity for water, polar molecules and unsaturated organic compounds. Their relative efficiency is greatest when the impurity to be removed is present at low concentrations. Thus, at 25° and a relative humidity of 2%, type 5A molecular sieves adsorb 18% by weight of water, whereas for silica gel and alumina the figures are 3.5 and 2.5% respectively. Even at 100° and a relative humidity of 1.3% molecular sieves adsorb about 15% by weight of water.
The greater preference of molecular sieves for combining with water molecules explains why this material can be used for drying ethanol and why molecular sieves are probably the most universally useful and efficient drying agents. Percolation of ethanol with an initial water content of 0.5% through a 144 cm long column of type 4A molecular sieves reduced the water content to lOppm. Similar results have been obtained with pyridine.
The main applications of molecular sieves to purification comprise:
1. Drying of gases and liquids containing traces of water.
2. Drying of gases at elevated temperatures.
3. Selective removal of impurities (including water) from gas streams.
(For example, carbon dioxide from air or ethene; nitrogen oxides from nitrogen; methanol from diethyl ether. In general, carbon dioxide, carbon monoxide, ammonia, hydrogen sulfide, mercaptans, ethane, ethene, acetylene (ethyne), propane and propylene are readily removed at 25°. In mixtures of gases, the more polar ones are preferentially adsorbed).
The following applications include the removal of straight-chain from branched-chain or cyclic molecules. For example, type 5A sieves will adsorb n-butyl alcohol but not its branched-chain isomers. Similarly, it separates n- tetradecane from benzene, or n-heptane from methylcyclohexane.
The following liquids have been dried with molecular sieves: acetone, acetonitrile, acrylonitrile, allyl chloride, amyl acetate, benzene, butadiene, w-butane, butene, butyl acetate, n-butylamine, /i-butyl chloride, carbon tetrachloride, chloroethane, l-chloro-2-ethylhexane, cyclohexane, dichloromethane, dichloroethane, 1,2- dichloropropane, 1,1-dimethoxyethane, dimethyl ether, 2-ethylhexanol, 2-ethylhexylamine, n-heptane, n-hexane, isoprene, isopropyl alcohol, diisopropyl ether, methanol, methyl ethyl ketone, oxygen, n-pentane, phenol, propane, n-propyl alcohol, propylene, pyridine, styrene, tetrachloroethylene, toluene, trichloroethylene and xylene. In addition, the following gases have been dried: acetylene, air, argon, carbon dioxide, chlorine, ethene, helium, hydrogen, hydrogen chloride, hydrogen sulfide, nitrogen, oxygen and sulfur hexafluoride.
After use, molecular sieves can be regenerated by heating at between 300°-350° for several hours, preferably in a stream of dry inert gas such as nitrogen or preferably under vacumm, then cooling in a desiccator. Special precautions must be taken before regeneration of molecular sieves used in the drying of flammable solvents. However, care must be exercised in using molecular sieves for drying organic liquids. Appreciable amounts of impurities were formed when samples of acetone, 1,1,1-trichloroethane and methyl-f-butyl ether were dried in the liquid phase by contact with molecular sieves 4A (Connett Lab Pract 21 545 7972). Other, less reactive types of sieves may be more suitable but, in general, it seems desirable to make a preliminary test to establish that no unwanted reaction takes place. Useful comparative data for Type 4A and 5A sieves are in Table 19. (from pages 28-29)
n-Butane [106-97-8] M 58.1, m -135°, b -0.5°. Dried by passage over anhydrous Mg(ClO4)2 and molecular sieves type 4A. Air was removed by prolonged and frequent degassing at -107°. (from page 143)
I have a hard copy of the seventh edition, the fifth was the latest edition I could find at this time for free download. Try Library Genesis,
https://gen.lib.rus.ec/
Last edited:
