jack-sparrow
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Distillation column packing
Hi, I am looking for experimental data for distillation column packing like glass helices, raschid rings, metal packing such as Pro-pak, etc... I am
looking for comparative data about the HETP (height of theoretical plates), surface area, etc.
I roamed the web and I did not find a lot on glass helices.
Thank you
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gsd
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Handbook of Laboratory Distillation
by Erich Krell
Elsevier - 1963
Laboratory Fractional Distillation
by Thomas P. Carney
Macmillan - 1949
These two books contain the data you need.
There is one more excellent book on laboratory distillation:
Laboratory Distillation Practice
by Coulson & Herington
George Newnes - 1958
I do have these books in my collection, unfortunately I don't have a scanner as of now.
GSD
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jack-sparrow
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Thank you I will check them out.
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Magpie
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I have used several types of column packing: "stainless steel" scrub pad, glass beads, and broken glass. My experiences with the "stainless steel"
scrub pad have been pretty good except when trying to distill acetic acid from water where the pad was severely attacked. The one time I tried to use
beads I had a lot of column flooding (also acetic acid/water). So now I use broken glass if I think the stainless scrub pad material may be
chemically attacked.
I like the broken glass for its inertness but have the feeling that small glass rashig rings (5mm x 5mm) would be better as they would pack evenly,
provide a lot of surface area, and provide a regular, fairly open pattern.
I am wondering what the experiences and opinions of the forum members are in regard to column packing materials?
[Edited on 22-2-2007 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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pantone159
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According to Williamson, Macroscale and Microscale Organic Experiments, 2nd 2d, p 83-84:
We find one of the best packings is a copper sponge (Chore Boy). It is easy to put into the column, does not come out of the column as beads do, has
a large surface area, good heat-transfer characteristics, and low holdup.
Haven't tried it myself.
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S.C. Wack
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I use a SS wool as well, though not from a scrubber; and lag with old cotton shirts or kitchen towels, unless the heating tape is really needed. We
used nothing but this same SS wool at the local community college. Works well.
studur is not alone in wanting to see that data.
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Sauron
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Glass beads suck as distillation packing. Raschig rings have a lot more surface area per unit volume. Berl saddles (porcelein) are also good. All of
these can be had in various sizes which should be seleted according to the ID of column. SS is just not inert enough, copper and brass are far too
reactive. Anyway with scrubbing pad style improvized packing you can never be sure of uniformity.
For applications where metal packing is compatible, knitted and compressed metal packing of proper diameters and high uniformity can be had from
Glitsch Specialty Products in Houston.
The really tricky bits aren't getting the packing right, it's column design, matching of pot size, heating source and boil up rate to column and the
all important reflux ratio. Those books will help. A computer program would help even more. Oh, I forgot to mention lagging and equilibration.
The best columns aren't the Hempel (packed) ones but the perforated plate sort, these allow lot higher boilup rates without flooding, this higher
throughput. They can be purchased in a great variety of diameters, lengths, numbers of plates and joint sizes, and with or without silvering and
bellows.
Of course the real deal is a spinning band still with PC control and 200 theoretical plates.
Or MUCH faster, prep HPLC, thousands of TPs and you can seperate 20 g samples in 30-60 min. All it takes is $$$
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Magpie
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My Hempel column is 19/22 scale with what looks like about a 15mm ID. Therefore I'm thinking that I should be using a small glass Raschig ring like
the 5mm x 5mm. But I can't find a source that is reasonably priced. In fact the only source I'v been able to find is Ace Glass and they want
$110/lb, selling only in 1 lb (454g) lots. 
The single most important condition for a successful synthesis is good mixing - Nicodem
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Sauron
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You might check out Aldrich but they are a bear to do business with.
www.partyman.se which specialize in bootleg liquor supplies may have inexpensive Raschig rings but last time I checked with them, they had only
sizes that IMO were suitable for 1 to2 inch ID Hempels.
I have several Hempels, one that I bought on LabX is 90 cm, silvered and w/bellows, vac jacketed, 29/42 at top and 50/50 ball at bottom. Fortunately I
have a 5L RB with the same socket and bought a clamp from Kontes. The ID is about 28mm. A good deal for $75, as this is a $1500 column.
The others I had made locally, all 1 meter long and 10 to 25 mm ID with 24/40 and 29/42 joints. Unjacketed.
One thing I have considered is cutting PTFE tubing into Raschig rings, this can be done with good precision if you make a simple fixture with a stop
to control length. A paper cutter ought to do the job. PTFE tubing is pretty rigid but it isn't hard to sheer, it is very inert and would be good for
distillations up to wht, about 250 C. Easier than making glass Raschigs for sure.
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leu
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Pall rings made from polypropylene have been used as an industrial distillation column packing when applicable for many decades, polyethylene tubing
could be used to make packing rings in many cases at a much lower cost  This
article from Analytical Chemistry 20 315-6 (1954) describes a packing made from nichrome wire coils that can provide many
theoretical plates at a reasonable cost, wire can be wound into coils using similar equipment to that depicted 
Attachment: mitchell-ogorman.zip (66kB)
This file has been downloaded 613 times
Chemistry is our Covalent Bond
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Sauron
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The packing has to be inert to the distillate at the temperatures involved and so there's no avoiding the consideration of possible reactivity or
catalytic effets when packing with Cu or even SS unless you are distilling something that will leave them alone and vice versa. The same goes for
plastic tubing.
Glass beads have very poor surface area to volume. They are good only for very low boilup rates and low RR's. That makes for very slow distillations
indeed. And not very good seperations.
The packing really ought to be highly regular and easily packed with consistency, without voids or gaps.
Tantalum wire coiled inside a Hempel column is an old method, Tantalum being very inert. Too bad they don't make scrub pads out of it. If Alfa or
anyone sold tantalum in a flexible sponge form like that it would have all the advantages of the scrub pad type packings but be inert enough to
distill almost anything: mineral acids, inorganic halides, carboxylic acids/anhydrides/halides etc.
Metex formerly of Edison NJ is now part of Glitch Specialties in Texas and they make cylindrical column packing from lab sizes to process sizes in
various wire mesh knits (not weaves) compressed in dies to precise dimensions. They service the petrochemical industry's needs. I know they do SS and
various Cu alloys and can probably do more exotic materials.
[Edited on 17-3-2007 by Sauron]
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Fleaker
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Just a random thought, but what about kaowool? It's a mullite blanket that's temperature resistant to 1200C. It's also inert and would have a lot more
surface area than anything else I can think of at the moment. I think a problem with it would be that it is too dense/not 'porous' enough and would
hold up flow through. Thoughts anyone?
You can see it here: http://www.anvilfire.com/sales/k_index.htm
It is fragile stuff, very easily ripped into pieces and ''fluffed up". I have a 130cm column with Raschig rings, and resistance temperature control,
but the column is so narrow there's no way in hell I could get the kaowool in there. I suppose I could use my short 50cm Hempel...
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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12AX7
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That doesn't make sense to me, wouldn't it fill up with condensation instead of remain with lots of wet surface area and open gaseous spaces?
Works fine as a filter though, a wad in the cut-off neck of a soda bottle does it.
Hey Fleaker... I wasted some kaowool the other day. I was making a few grams sodium chromate in the induction heater and it appears the sodium
chlorate oxidizer boiled over. :-x Green mush all over it...
Tim
[Edited on 3-18-2007 by 12AX7]
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chemrox
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Podbialnak column
Sauron almost described the Podbialnak column in which the column has nichrome or tantalum wire on the inside surface.. the wire being regulated as a
heater. More plates than anything other than spinning bands according to my old professor .. I'd be happy to scan the pages from his book on this
subject with details on construction of the column. You guys aren't talking about distillation heads. A partial takeoff head can give refulx control
you can't otherwise get. I'd almost rather have a vigraux column with a partial takeoff than a Podbialnak without. I can't afford spinning bands and
probably won't be able to anytime soon, alas. I would also like to hear any comparisons between a column packed with raschig rings and a vigeraux.
I'm getting a column that has little glass bubbles inside that should provide a lot of plates if it doesn't flood too badly. I'm also surfing for a
decent distillation head.
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Pyridinium
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| Quote: | Originally posted by chemrox
I would also like to hear any comparisons between a column packed with raschig rings and a vigeraux. I'm getting a column that has little glass
bubbles inside that should provide a lot of plates if it doesn't flood too badly. I'm also surfing for a decent distillation head.
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I have a J. Chem. Ed. article from 1932 where they compare Vigreaux (sp?), plain Hempel type, 2 types of packed columns, the Young pear column, and
the Snyder 3-ball column. They did EtOH/water and then benzene/toluene.
They ranked the Snyder as best overall, followed by a Hempel packed with glass tube sections (sort of Raschig rings, I guess), then the Vig., then the
other types. Obviousy YMMV depending on solvent composition.
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chemrox
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Snyder column
I'm really glad to hear this. I ordered a three ball Snyder column when I saw it in catlaog. I promptly forgot its name. So, again, thanks!
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