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Sauron
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If ketene reacted with those alloys they wouldn't be suitable for filament.
Just remember you can't scale a lamp up. To make lots of ketene you would need to go to a giant tube furnace at 750 C and feed it AcOH vapor not
acetone and also trimethylphosphate to trap water formed, it's a complex expensive industrial process requiring huge capital investment, and a LOT of
energy, the energy costs alone have made it obsolete since 40 years ago but some plants still operate because their initial costs were too high to
decommission them.
Does this sound like your 50 L a day solution? Most definitely not.
[Edited on 10-4-2007 by Sauron]
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jimmyboy
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Cheer up Sauron - it sounds like Chem is actually getting close.. maybe  -- I
am suprised Merck ships all that stuff to Hector -- maybe i should move to Mexico so I can do my experiments in peace..
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Sauron
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@chempower is very close but just took a sharp left in wrong direction. Nothing wrong with my level of cheer, I am merely a little cross at having to
say same things over and over, and feel like a teacher in a remedial class.
Anyway I have ordered some VA monomer so pretty soon I can try this for myself. I already have lots of routes to Ac2O, but a route that gives me Ac2O
and acetaldehyde at same time is still very attractive.
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Eclectic
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I wonder if net mercury catalized hydration of acetylene to acetaldehyde would occur in glacial acetic acid with the H2O provided by net dehydration
of AcOH to Ac2O (probably via vinyl acetate)?
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Sauron
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I previously found on the Internet a website on nichrome with various alloy compositions, trade names, and a wire gauge chart. I will see if I can
find it again.
http://www.mwswire.com/resist2.htm
This is a chart giving brand names for particular wire alloys from half a dozen makers. The one you want I believe is MWS-675 which is Nichrome from
one maker and Chromel C from another.
http://www.mwswire.com/resist3.htm
This what you need. B&S numbers vs wire diameter and resistence in ohms/linear foot @ 20 C
B&S # 24 is 0.0201 inch diameter or slightly more than half a mm.
Best of luck and remember I told you not to do this.
In order to make 1 liter a day with 1 lamp you must operate it 24 hours a day. You are going to run 5 lamps 24 hours a day?
About 3 times a day you will need to change filament on each lamp because the filament will cover itself with black carbon which will prevent contact
with vapor so reaction stops. So someone will be employed 24 hrs a day performing this opperation 15 times a day. What fun!
We call this kind of operation a Chinese fire drill. Self explanatory. No offense intended to our Chinese members.
[Edited on 11-4-2007 by Sauron]
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Sauron
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Please, I gave you a large file of articles detailing ketene lamp and ALL of them explain why and how carbon builds up on the wire and must be cleaned
off by scraping the wire over a sharp edge. The carbon will NOT dissolve in anything (it is CARBON, like graphite, what dissolves that?)
This difficulty is inherent in ketene process. It is the acetone that deposits carbon on hot wire not ketene.
STUDY those articles BEFORE wasting your time.
Resistance of MWS-650 per foot is 1.609 ohms nominally. For ohms per meter, multiply by 3.3.
HOWEVER, MWS 650 is Nichrome V or Chromel A rather than Nichrome/Chromel C as specified in two of the documents I sent you. That is MWS 675. Frankly I
do not think this matters so much, you can use either one, as long as you use the correct resistance which is different for the two.
You could also use platinum wire but that is probably more costly.
[Edited on 11-4-2007 by Sauron]
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chemicalpower
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i tried the cinyl acetate +acetic acid and hcl method. this time i used pyrex equipment, with a 15 plate fractional distillation column.
i got aldehyde i think at 40 45deg.
then i got a little more liquid till 80 degrees.
then i got upto 105 but then everything finished .
i gave aldehyde about four hours to evaporate and condence in a condenser and a cold trap.
the last product was acetic acid , judging from the smell of it. although it was far more pungent than acetic acid and i thought i had acetic
anhydride but alas it wasnt.
i think i should have kept the temperature at around 52 maybe this method also give acetyl chloride.
the other method in which i only use vinyl acetate and hcl (ans someone said i took a sharp left turn)i used 30cc hcl with 225cc vinyl acetate. and
got about 26cc acetyl chloride.then i used sodium acetate and got acetic anhydride. but as sauron said the quantity formed in this method is pretty
less and hence costly.
but the vinyl acetate method seems to be a failure i dont know why. i did give aldehyde condensation a good four hours. then increased the
temperature. and after the aldehyde is formed the colour of the mix changes to dark red brown. then at 80 degrees again i started getting clear
distilled liquid and it smelled like aldehyde and some plastic mix. then at 105 i got a light rec brown distillation liquid which smelled sharply of
acetic acid rather a little more pungent like anhydride but , it turns out to be acetic acid, i didnt check the density yet cause my scale was out of
order but it wouldnt settle in water.and would disperse like acetic acid.
can some correct me where i went wrong
maybe someone can help me and do the experiment himself also
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Sauron
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One of the pepers I gave you advises scraping off carbon by drawing the wire over a sharp edge. The carbon is brittle and flakes off. However what
always made me wonder is: the wire is wound into spiral coil, so drawing if over sharp edge will it return to coil on its own or must be rewound 3
times a day? I don't know. Also I won't know how easily this wire breaks.
Of course resistance will change a lot from 20 C to 700 C but, if you use calculated current for 20 C you will be fine.
Think carefully about how you will attach filant because you will have to unattach it and reattach it several times a day per lamp and so it needs to
be some sort of clamp or screw port attachment to be good electrical connection.
And you will need 10 lamp assemblies for 5 lamps because you will use the spare one while cleaning the main one right? You don't want to interrupt the
process.
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not_important
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| Quote: | Originally posted by hector2000
Mr sauron when the nichorome temp rise to 700 the resistance dont change?this is not important matter?
this is difficult to clean the wire from carbon?(time consume?)
[Edited on 11-4-2007 by hector2000] |
Yes, the resistance changes some but not a lot, there are tables that will give you the change at various temperatures. But the change isn't
important, you would be regulating the current to keep the filament at the proper temperature, and the cooling from the gas flow is a large variable
than the change in resistance.
Scraping carbon off of a wire grid isn't going to be the easiest task. Depending on the grid design it can be difficult to reach all of the grid, and
you need to be careful not to break the wire or supports.
It is possible to clean the filament by flushing the chamber with CO2 or N2, then flowing air over the hot filament to oxidise the carbon, then
flushing with CO/N2, and then back to acetone vapour. This assumes proper choice of filament material, most resistance heating wire is designed to
operate in an oxidising atmosphere. And therein lies a problem with the ketene lamp. Running those materials in a reducing atmosphere can actually
reduce their life, although the effect is not as much at the fairly low temperature of about 600 - 700 C. However some really do not take to cycling
between reducing and oxidising atmospheres, you need to check with the specific resistance wire you pick.
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chemicalpower
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thanks hector .
mr sauron can you read my post above and gve some advise. i know i am constanly annoying you by posting silly questions, but i need help here
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not_important
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The way that ketene production was scaled up was to go from the lamp to hot tubes, with or without packing. While only the acetic acid method, which
is slightly different as it runs a bit hotter and needs a catalyst, is still in use there have ketene production 'plants'.
You need good control over tube temperature, control of the flow rates and mixing as well as contact time, and quick cooling of the gases exiting the
hot tube. Plus you need to make very sure the apparatus does not leak, and that you absorb all the ketene in the exit gases. The ketene method is
only economic when acetone is very cheap, acetic anhydride or acetyl are inaccessible or you are after other products such as diketene, isopropenyl
acetate, or acetoacetic acid derivatives and don't or can't go the AcOEt condensation route.
If you want to do medium scale ketene production you should work with someone who has experience in chemical engineering, and who understands the
problems of working with ketene, to help design a tube ketene generator. The hot filament method will wear you out.
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Sauron
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The overhead of a ketene tube furnace at a scale of 5 to 50 L (Ac2) a day not to mention the cap.costs, seem to me to nix the idea. But @hector seems
very determined to try the lamp method and has resisted all my efforts to dissuade him, so I guess we will have to watch this slow-mo train wreck.
A 24 inch (60 cm) tube furnace as decribed in Org Syn actually had a throughput about 50% of a ketene lamp. Obviously, the tube reactor is scalable
and the lamp is not but, this will give you some idea of the scale of the tube which just to get to the equivalent of a lamp will need to be 1 to 1.5
meters, How to efficiently heat such a tube? An electric tube furnace of that size isn't cheap either to buy or to operate. Gas heating will be
inefficient. The temp range is I think above that of heating tapes unless Glas Col has some products I haven't seen. All in all it just seems like a
bad idea, and lacks any chance of economy of scale.
@chemicalpower, sorry to hear that you had no luck.
I think best way I can help you is to try to do this myself and when I get it working (hopefully) provide you with a detailed writeup and photos
posted here.
There are many possible methods and catalysts alluded to in the patent. Vapor phase, liquid phase, vacuum and pressure all are mentipned. Solid and
liquid catalysts singly or in combination. Based on the later article I cited the Hcl/HBr method seems likeliest but much testing may need to be done
before we can replicate the patent results -- trying to replicate the journal article results seems safer, but so far all I have is an abstract not
full text.
[Edited on 11-4-2007 by Sauron]
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Sauron
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Itmight. Or maybe not. You can try.
A similar idea I thought about was to try to react the carbon at 700 C with chlorine or bromine vapor
Again, not sure this will work.
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Sauron
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Perhaps. And perhaps so will oxygen in the air. In either case it has to get through the carbon first to do so doesn't it?
Also you can vary the electric current to reduce the temp to a point you determine by experiment will react the halogen with the carbon but not attack
the nichrome or so do only slowly.
Unless you have a better idea? Remember: I told you the lamps are a bad idea. Ketene is a bad idea.
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Sauron
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According to the attached article in Ber., vol 19, p.310-311 by Alfred Senier, acetyl chloride can be prepared by heating anhydrous sodium acetate
(three mol eq) and cyanuric chloride (one mol eq) in absence of solvent for 8 hours at 100 C.
For example 184 g CC and 246 g NaOAc anhydrous, mixed intimately and heated 8 hours at 100 C should yield about 234 g acetyl chloride.
So 4 mols CC (736 g) and 984 g anhyd NaOAc should produce about 1 Kg acetyl chloride.
According to the author this reaction also worked for sodium benzoate (anhydrous).
I would be interested to try the same reaction with one mol CC and 1.5 mol sodium oxalate to obtain 1.5 mol oxalyl chloride.
On a 1 Kg product basis as described above the reaction should run fine in a 5 L flask, which should have a thermometer and an efficient condenser set
for downward distillation. Acetyl chloride boils at 51 C so will flash off a 100 C melt.
A good hood is called for.
[Edited on 14-4-2007 by Sauron]
Attachment: SenierBer19p311y1886.pdf (103kB)
This file has been downloaded 883 times
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chemicalpower
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since i got some cyanuric chloride. i tried making acetyl chloride and hence acetic anhydride.
i mixed 510 grams of cyanuric chloride with 500cc of acetic acid.
i fractionalted the mixture to get the acetyl chloride. i collected a pale yellow liquid about 450cc but at the end when i switched the heat off the
mix in the reaction flask started heating up by itself and the temperature rose upto 130 by itself and then the evrything came out from every outlet.
could someone tell me what happened there.
secondly the smell from the apparatus during fractionating was pretty annoying and irritating i assume thats what abetyl chloride does.
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Sauron
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First of all, there are more than one method to make acetyl chloride from CC.
1. Old method 1. Refluc CC with a LARGE EXCESS of acetic acid. Now to understand what this means you must understand that CC has THREE active
chlorines not just one, so that means one mol of CC will chlorinate THREE mols of acetic acid.
So let's look at the MWs
CC 184 g/mol
AcOH 60 g/mol
So you mixed 2.75 mols CC with 8.5 mols AcOH.
But 2.77 mols CC is enough to chlorinate 8.25 mols AcOH
So you messed up. You needed a LOT more AcOH in there and you needed to reflux it for some time. You will need an efficient reflux condenser because
while the bp of AcOH is 117 the bp of AcCl is MUCH less so the AcCl will want to escape. Don't let it.
As the rxn progresses, cyanuric acid will precipitate out. You need to stir well or the precipitate will interfere with heating and cause bumping.Hwen
no more cyanuric acid precipitates out you are done. Stop stirring and let the ppt settle out and see if any jnew ppt forms. If not you are done.
The bp will drop throughout the procedure as you will be boiling more acetyl chloride and less acetic acid. Do not overheat. Use just enough heat to
maintain a low reflux and reduce the heat as the vapor temp in pot drops.
Figure this will take about 8 hours or so. Maybe longer.
When no more cyanuric acid drops out, then and only then do you replace reflux condenser with column and downward condenser and start distillation.
The acetyl chloride distills at about 51 C if I recall (look it up). When temp at top of column goes above 60, you starting to get AcOH coming over.
Stop.
YES acetyl chloride is VERY irritating and corrosive. This should all be done in a good fume hood. Acetic acid is bad but acetyl chloride is worse.
For 2.77 mols CC (510 g) I would recommend you use not less than 1500 ml AcOH.
After you strip off AcCl, let the AcOH cool and filter out the cyanuric acid. Then you can put the acetic acid back in the pot, add more till you have
1500 ml in there and add your CC and start over. The excess AcOH acts as solvent and heat exchanger and you saw what happend when you don't have
enough.
I have two more methods to tell you about but let's see if you can get this one right this time.
[Incidentally you collected about 2/3 the AcCl you should have, so I think you tried to rush things,.
The first two chlorine in CC react quickly, the third is much more sluggish so you must give it time.
When you switched off the heat the precipitated cyanuric acid solid fell down, the mantle was still hot, heat accumulated, and flask boiled over as
AcCl flashed off. You are lucky you did not have a nasty fire as AcCl is highly flammable like Ac2) and unlike AcOH.
Next time
Use 1500 ml to 2 L AcOH with 510 g CC
When you THINK reaction is done then strip AcCl but continue stirring and heating and continue till you have collected a 650 ml of AcCl and temp at
still head (top of column is not over 60 C. If it is then you are heating too fast.
This is an EASY preparation. If you started with 2 L AcOH at end you will have 0.65 L AcCl and 1.25 L AcOH left in pot, a bunch of cyanuric acid and
NO CC.
[Edited on 13-4-2007 by Sauron]
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chemicalpower
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thank you for the detailed reply.
i will try this out today as you described.
what are the two other methods maybe they suite me and my condition more
thanks once again for the help
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not_important
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| Quote: | Originally posted by hector2000
...
how can i make sodium methaphosphate ?
merck co.dont have sodium methaphosphate i think we must produce it ourself
thanks |
metaphosphate
http://www.indiamart.com/devdharchemicals/#products
http://www.thomasglobal.com/search/heading.asp?new=Y&hid...
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Sauron
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@chemicalpower
Here is protocol for acetyl chloride at room temperature from CC and AcOH in acetone with TEA (triethylamine)
TEA 2 mol is added to
acetic acid 2 mol 120 g
and CC 1 mol 184 g in
acetone 2 liters or minimum to obtain clear solution
Stir at RT 3 hours or until no more precipitate falls out.
The precipitate, 2-chloro-4,,6-dihydroxy-s-triazine, is filtered off and
washed with a little acetone, which is added to filtrate.
The filtrate contains acetyl chloride, TEA, and a little unreacted
AcOH. Strip off the acetone under reduced pressure through a column
at room temperature. Now fractionate the acetyl chloride off at normal
pressure on a water bath at 75 C.. A small forerun is acetone. The
acetyl chloride boils at 51 C at normal pressure.
The TEA and AcOH can be added to next run.
Yield 90-95% or about (140-148 ml)
So to do this on a scale to make about 1.5 liters you will need a 50 L flask. You will need mechanical or magnetic stirrer for 25 L, and large Buchner
funnel (fritted disk), vacuum distillation or rotavap, and fractional distillation (normal pressure) w/water bath.
As you can see the other two procedures are easier but, you are then making acetyl chloride in vapor phase and must condense it efficiently.
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Sauron
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I think you are asking for trouble.
You can't scale up the lamp. You can't increase flow rate of acetone or all you will do is distill acetone into acetic acid along with a little
ketene.
What you are doing is dangerous and ill advised.
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UnintentionalChaos
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Ketene may seem like the cheapest and most direct method, but you can't make it industrial scale. It just doesn't work. Ketene will probably kill you
if the construction on the device is not perfect and there are any leaks.
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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Sauron
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I've been telling @hector that for eight pages but he is stubborn.
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Sauron
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I have now provided in this thread three simple ways to make acetyl chloride from cyanuric chloride and either acetic acid or anhydrous sodium
acetate.
1. CC and acetic acid (no other solvent than excess acid)
2. CC and anhydrous sodium acetate mixture (dry distillation, 8 hours 100 C)
3. CC and acetic acid in acetone with triethylamine, room temperature, stirred 3 hours. No heating. The acetone is just solvent and can be recovered
and reused. The TEA is just acid scavenger and can be recovered and re-used. Yield 90%
ANOTHER process:
Acetic acid and excess (1.5 to 2 eq) benzoyl chloride, 92% yield. Reaction time 1 hr.
and ANOTHER Acetic acid and phthaloyl chloride (1:1 molar ratio) 89% yield, quick reaction time
Note that with benzoic acid, and possibly with phthalic anhydride, residue from the last two reactions, efficient recycling is possible and
reconversion to their chlorides with CC.
ANOTHER suggestion:
Keep buying acetyl chloride from Merck but, as soon as you unseal PE liner in drum, pump the acetyl chloride into suitable inert plastic or glass
carboys so it cannot react with the steel drum. Use an inert drum pump to do this.
Then you will have NO contamination and can cnue using sodium acetate/acetyl chloride process as you have been doing.
MEANWHILE I will work on the VA method.
If you wanted to make Ac2O on an industrial scale, which your own government will not let you do, you would use the methyl acetate (high pressure
catalytic) process or one of the other processes. NO ONE builds ketene process plants any more. They are TERRIBLY INEFFICIENT of energy because of
high price of oil since the 1970s (when the Shah started OPEC.) The only reason why the European and American companies have not retired these old
plants is because they cost too much to build and also now to replace.
[Edited on 14-4-2007 by Sauron]
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chemicalpower
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hector i didnt get anhydride , although once in many tries i did get a little yellow liquid which tested positive for anhydride.
but i couldnt replicate the procedure, but i think my fault was in my heating apparatus not the process. i think the method is correct
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