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garage chemist
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I am currently building a simple, crudely made tube furnace for up to 1000°C, 50cm long, with 40cm heated length. The quartz tube will be of 25mm
inner diameter and 1m long (the excess length serving as condensation zone for unreacted sulfur in CS2 preparation).
Ketene will be a second, less important use for it.
As I don't know at this moment if the tube furnace will even work, there is nothing I can do other than do experiments myself once it works. I will
report if and how well it works for ketene once I have tried it.
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Sauron
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I have nothing against tube furnaces per se, I own one myself.
BTW Vycor will handle the temps needed for ketene generation (but maybe not your other, primary applications), and me thermally and mechanically
stronger than quartz as well as, I think, less costly.
The most productive ketene preps using a tube furnace were with diketene as substrate while the others just seemed highly inefficient.
There are chemical preps of ketene rather than thermal, and these involve treating bromoacetyl bromide with Zn dust if I recall.
The reagent is a wee bit hard to come by and shipping is a nightmare as it must be refrigerated in transport and can't go by air, only sea. In a lot
of places it is restricted due to its use in making the tear gas phenacyl bromide (a-bromoacetophenone). So you'd need to build it.
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Sauron
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Why ask me? It isn't "my" anything and I do not recommend it. Ketene is a deadly corrosive carcinogen. My advide is, was, and will continue to be to
stay away from it.
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Sauron
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But, hector, it is very very clear that you do not have the skills or resources of "industry" (heavy chemical industry) nor the finances required
(many millions of dollars) and the scale of Ac2O you have stated that you requir (30-50 L a day) would certainly demand an ENORMOUS tube furnace.
Forget ketene lamp, THEY DO NOT SCALE UP. Tube furnace methods do scale up BUT NOT BY YOU. You do not know how, you can't afford it, and if you get
anywhere near producing that much ketene (enough to make 30-50 L acetic anhydride a day) you will most likely not only kill yourself but all your
workers and very possibly promulgate an industrial accident that we will read about in the newspapers. Do you want to be on CNN posthumously?
I don't think making cellulose acetate is worth dying for, do you?
You haven't sone your sums, hector, and you haven't thought this through.
Sorry we have not offered you any viable alternative yet to your present acetyl chloride process, but believe me: ketene is not an answer for you.
Garage chemist is talking about building a tube furnace that, unless I am mistaken, might produce 1/4 to at most 1 mol ketene per hour. So 1 mol Ac2O
per hour at best. IF he ran it round the clock, that might fetch 2.5 L a day. YOU need 20 X that scale. You think you can do that? I do not think so.
I think GC can make a couple mols ketene once in a while and get away with it, he has a fume hood and he is a clever resourceful experienced chemist.
I do NOT think you can make 20 mols ketene an hour, and if you try I think you will die and take many others with you.
I am not angry but I am exasperated and tired of re[eating myself.
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garage chemist
chemical wizard
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Haha, 2,5L a day, that would require quite a large setup apart from the tube furnace, and most importantly, you'd need a lot of glacial acetic acid!
I buy GAA in one liter amounts at a time, as 99% analytical grade, and dont have access to canisters of technical grade GAA.
I was planning to run, say, 100ml acetone at a time through the furnace, of which maybe 40% will be cracked, and bubble the uncondensable gases
through maybe 100ml GAA.
Then fractionally distill the GAA/AA/acetone mix that results in the washing bottle.
Upscaling would require some more sophisticated absorption equipment than a washing bottle, like a scrubber through which GAA is circulated constantly
by a pump.
Also, I'd need some larger distillation flasks, I only have 500ml ones.
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Sauron
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Take note, hector. 100 ml GAA is 1.5 mols and the conversion efficiency is not very good. So GC is talking about making maybe at best 100 ml Ac2O in a
run. You would need to upscale by 500 X and frankly, you really ought to be putting your time and energy to a more productive use.
What GC is proposing is amateur chemistry on an advanced level. What you are talking about is cottage industry scale, and what the ketene process is
done on is fullbore heacy chemical industrial scale.
Go hire a couple of chemical process engineers and get them to do a feasibility study for you. I doubt you can afford the study, but if you can you
will then have a clar picture of what you are proposing to invest. HINT: don't bother.
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not_important
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I'm seconding what's been said above:
A ketene lamp is useful for small scale purposes, especially when access to acetic anhydride or acetyl chloride is difficult. Ketene is also useful as
a route to acetoacetic esters without going through the more traditional condensation routes.
But the ketene lamp does not scale up well at all. It is also fragile if made from glass, and the filament is both fragile and needs frequent
cleaning. BTW - the best way to clean the filament is either careful brushing or controlled oxidation, resistance wires such as nichrome and kanthal
are meant to be heated in oxidising environments, reduction is hard on them as is halogens or halides.
Hot tube methods do scale up, but require expertise in the engineering methods. The notes you attached are for laboratory scale production, not on the
scale you want. You need to calibrate and tune the process in terms of flow rates, temperatures, and dwell times needed for your particular system.
The conversion rates are not high, you need to recycle your feedstock which in the case of acetic acid means having a decent fractionating column to
separate acetic acid from acetic anhydride. Using acetic acid as feed also usually means using a catalyst, typically an added phosphate ester.
And as stated many times, you're dealing with a pretty toxic substance. If great care is not taken in building the equipment, you have a disaster
waiting to happen. I've built a hot tube system, but I had the help of someone who worked with the construction techniques professionally and who
could make sure that the design and implementation was safe.
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Sauron
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This entire thread has been hector turning a deaf ear to anything not consonant with his own ideas of what to do.
And I hate to say so but hector is a fellow who seems incapable to taking acetyl chloride (lab grade Merck) out of a drum without contaminating it
with iron. (The yellow and reed color changes being likely Fe salts.)
Nor can he apparently deal with the fusing of sodium acetate.
If he solved those two problems he would already have a working solution at hanhd.
He is blessed with inexpensive acetyl chloride, $6 a liter, I wish I could get it from Merck for that. (Here we can't buy it al all without special
permit from the MOD, rots of ruck!)
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Organikum
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The production of ketene as outlined in the patent I am referring to is good-yielding and easily upscaled as it is no problem to run several
coppertubes throught a heating unit.
The real challenge is as outlined by GC the rapid cooling and the design of the receiving vessel.
Ketene is toxic but that is no problem as every well designed ketene lamp or tube setup simply burns off the exhaust gases (nozzle or other flameback
arrestor are understood).
We have already an acetic anhydride thread where all this was already dicussed without so much selfrighteous noise.
Everybody who buys chemicals from MERCK for industrial production of basic compounds as acetic anhydride is insane.
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Eclectic
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Sauron
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I suppose Organikum thinks $6 a L for Merck lab grade acetyl chloride is too expensive?? That is landed and taxed already in hector's country, in a
200 L steel drum with a HDPE liner.
Perhaps that is "selfrighteous noise" ??
Because the price from Acros for one liter of same is $60-something as I recall. I have not seen bulk pricing, as I can't import this chemical
anyway, there's no point. I am going by what hector says he is paying in Irtan for Merck. If he's insane, as Organikum impugns, then he is IMO crazy
like a fox.
Which, hector, is a Good Thing, in case you don't know the idiom. It means you are clever.
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Sauron
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Hector, "crazy like a fox" is a compliment. NOT an insult.
It means you are clever, NOT stupid.
Some one else called you insane for buying from Merck, NOT me.
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garage chemist
chemical wizard
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6$ a liter is way, WAY cheaper than what I would pay for acetic anhydride here! For that kind of price, I would definately make acetic anhydride that
way myself.
Hector has found a (for him) cheap and easy method to make acetic anhydride himself, and I think it doesnt matter that it is not an industrially sound
one.
Now that I think of it, isnt acetyl chloride manufactured industrially by cleaving acetic anhydride with HCl gas? If yes, acetyl chloride could be
regarded as an unregulated (in hectors land) "import form" of acetic anhydride which can be reverted back into its original form easily by the user
himself.
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Eclectic
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I still think Hector hasn't looked very hard for a cheap source of cellulose acetate powder. Of COURSE it's going to be too expensive to make glue
from if you order research grade material, but it's available as a VERY inexpensive industrial commodity for use as a plastic compression molding
powder.
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Sauron
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Do you really want to poke and prod at Hector's "legend"? Because if you collapse it in the process (and it is already pretty shaky) then we will all
be obliged, much against our will I might add, to draw some other inference about a demand for Ac2O in that part of the world.
As for myself, as long as someone goes to the trouble to construct a halfway plausible story (true or otherwise) about their legit intentions I am
happy to try to help. I have spent a lot of time trying to help Hector, though so far it hasn't panned out very much -- the patent dredged up by
S.C.Wack has so far eluded replication by anyone.
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Eclectic
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Can you import from China? Google "cellulose-acetate resin"
Can you recycle cheap plastic items?
It's a bit disturbing that you have been given MORE than enough info on how to build a ketene generator, and you STILL want someone to talk you
through all the details.
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Sauron
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Can you purchase carbon tetrachloride in Iran or import it?
If so, see article in Recent Journal Articles of Interest on making acetic anhydride (or anyother acyl anhydride) from CCl4 and iron or copper
chloride catalyst at ordinary temperature and pressure.
Reminds me of the reaction S.C.Wack dug up in a patent of trichloroethylene, but that was at higher temperature and pressure, and used water and
catalyst.
But I bet you can't get CCl4 any more than you could 1,1,1-trichloroethane (trichloroethylene) as they have both been mostly banned internationally.
So the method is pretty useless.
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Sauron
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That's what this Russian article says.
CCl4, sodium acetate (I'm sure, anhydrous) and catalytic amt iron or copper chloride. Room temperature, and 18-20 C. Supposedly it is a general
method, meaning it works for any carboxylic acid. A number of examples are given, and yields are 48-97%
Acetic anhydride is not one of the examples, but, if it is indeed a general method then you ought to have no problem.
The article is one of the last posts in RECENT JOURNAL ARTICLES OF INTEREST thread. Go find it and study it.
Ignore the stuff about amides.
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Sauron
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It is NOT a patent. It is a journal article.
Attached for your attention
[Edited on 25-6-2007 by Sauron]
Attachment: ccl4.pdf (335kB)
This file has been downloaded 1246 times
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Eclectic
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There is no error in the file. The error is yours.
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not_important
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| Quote: | Originally posted by hector2000
Mr sauron if is possible please yourself explain this patent.
| Quote: |
It is NOT a patent. It is a journal article.
|
(i think the site host has problem)
| Quote: |
What happens when you try to download it? |
i still has one question:AcoNa+Ccl4->Ac2o+? |
The answer is in the paper which several dozen people have successfully downloaded. If you just click on the link it should open the doc in
your browser, it requires nothing newer than Acrobat 4.X.
It is difficult to help you when you will not answer questions and do not seem to read what others say.
What did you do to try to open/download the file, and
What error(s) do you get?
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Sauron
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The Russian article, which is really a brief communication from 1977, contains no examples of making Ac2O and only one example of making any anhydride
at all. By scaling up that example and altering it for sodium acetate we arrive at the following:
334 g NaOAc (which I am sure needs to be freshly fused anhydrous)
700 ml CCl4
290 g CuCl (copper (I) chloride, cuprous chloride
190 g Cu (I am sure, powder, pref. electrolytic)
1500 ml acetonitrile as solvent
These suggest a 5 L flask
Heat and stir at 80 C 2 hrs
Filter off the solids and distill the filtrate through an efficient column.
The examples given yielded 48-97%.
The mechanism is supposed to be formation of CCl3 radical, which oxidizes to phosgene in situ, which gives the expected anhydride from the alkili
carboxylate.
It's worth a try. I can't test this rxn as CCl4 is forbidden here and if I go to the trouble of preparing CCl4 I won't waste it on making Ac2O!
So good luck with this one, Hector.
---------------
The same paper has a prep of diethylacetamide, so if we just neglect to include the diethylamine we ought to obtain the anyhydride or at least acetyl
chloride
57 ml (60 g) glacial acetic acid
350 ml CCl4
50 mg CuCl2 (cupric chloride, copper (II)chloride)
Reflux 4 hrs. Filter, distill through a good column. Note that no solvent is used other than excess carbon tet.
This procedure if it works is easier than the first one.
Give it a try.
Obviously is any of the thirty someodd members who managed to download the paper, want to contribute their own interpretations or modifications as
applied to acetic anhydride or propionic anhydride or any other anhydride of general interest to this community, feel free to do so.
The only modification that suggests itself to me is aeration or oxygenation, with dry air or O2, as the conversion of the CCl3 radical to phosgene
depends on that.
UV might assist in radical formation.
[Edited on 27-6-2007 by Sauron]
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Eclectic
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Hector, you are like a 3 year old playing the "WHY?" game.
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Sauron
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I FINALLY got a quote on 2.5 L vinyl acetate monomer, lab grade from Acros and it is cheap enough (my landed cost is about $60 US).
So I am ordering this along with nitromethane, benzotrichloride and benzoyl chloride, and so as of mid August or so, will be able to move forward with
several projects
Acyl chlorides anhydrides via benzoyl chloride
Same via phthaloyl chloride (from the benzotrichloride and phthalic anhydride)
The nitromethane is for stock. That stuff is getting pricey. The lab grade is $100/2.5 L ex Acros and landed here is $200. That's about $70/L for 95%,
the 99% is much higher.
and finally can try the vinyl acetate route.
[Edited on 2-7-2007 by Sauron]
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chemicalpowerII
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mr sauron any update on the vinyl acetate method.
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