Sciencemadness Discussion Board

keten lamp

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Sauron - 9-4-2007 at 13:20

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]

jimmyboy - 9-4-2007 at 19:44

Cheer up Sauron - it sounds like Chem is actually getting close.. maybe :D -- I am suprised Merck ships all that stuff to Hector -- maybe i should move to Mexico so I can do my experiments in peace..

Sauron - 9-4-2007 at 19:55

@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.

Eclectic - 10-4-2007 at 09:26

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)?

Sauron - 10-4-2007 at 11:21

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]

Sauron - 10-4-2007 at 12:08

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]

chemicalpower - 10-4-2007 at 13:41

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

Sauron - 10-4-2007 at 13:51

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.

not_important - 10-4-2007 at 14:00

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.

chemicalpower - 10-4-2007 at 14:03

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

not_important - 10-4-2007 at 14:14

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.

Sauron - 10-4-2007 at 20:48

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]

Sauron - 11-4-2007 at 09:28

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.

Sauron - 11-4-2007 at 11:02

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.

Sauron - 12-4-2007 at 06:18

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)
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chemicalpower - 12-4-2007 at 09:26

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.

Sauron - 12-4-2007 at 10:13

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]

chemicalpower - 12-4-2007 at 21:29

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

not_important - 12-4-2007 at 23:24

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...

Sauron - 13-4-2007 at 09:32

@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.

Sauron - 13-4-2007 at 10:27

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.

UnintentionalChaos - 13-4-2007 at 10:41

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.

Sauron - 13-4-2007 at 10:57

I've been telling @hector that for eight pages but he is stubborn.

Sauron - 13-4-2007 at 11:33

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]

chemicalpower - 14-4-2007 at 10:06

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

Sauron - 14-4-2007 at 10:13

@hector, if you can obtain quotes for the following in bulk (drum) and let me know your cost per Kg or cost per L (landed inside customs)

then I can finish comparing economics of 5 methods of making acetyl chloride for you

Three from TCT (CC)
One from Benzoyl chloride
One from Phthaloyl chloride (made from phthalic anhydride and benzotrichloride)

The chemicals are

Cyanuric chloride
Benzotrichloride
Phthalic anhydride
Benzoyl chloride

Sauron - 14-4-2007 at 10:39

Merck sells cyanuric chloride

Won't they import it for you if you buy a lot of it?

Making acetyl chloride that way is about 1/2 the cost of making it by either of the other two methods.

And after all these processes must be competitive with your $6/liter acetyl chloride that you are using now.

The other name for CC is trichloro-s-triazine but Merck sells it as cyanuric chloride. It is commonly used for making agricultural chemicals. It is a solid. Do you want the CAS number or Merck product number?


-------

I have eliminated one of the three TCT processes.

The 1886 Ber. article on dry distillation of anhydrous sodium acetate and cyanuric chloride (3:1) gives only 22%. It is conducted in a sealed metal pipe (today we would use an autoclave) at 100 C for 8 hours. Preparatively useless.

Same procedure with sodium benzoate gives 88%. Cold comfort since sodium benzoate and benzoyl chloride are close in price and available.

With sodium formate as would be expected no acid chloride is obtained (or at least no formyl chloride survives).

Benzamide is efficiently degrades to benzonitrile in same way.

[Edited on 15-4-2007 by Sauron]

Sauron - 14-4-2007 at 22:49

Can you get benzoyl chloride locally?

Or phthalic anhydride and benzotrichloride?

With those and AcOH you can make your own acetyl chloride.

If you can get them and can tell me your cost I can tell you how they compare to your $6/L cost for AcCl

If you can't get them it is immaterial.

CC is cheaper than benzoyl or phthaloyl chloride methods.

I have not yet studied cost of VA method as no need till we get it to work.

Sauron - 15-4-2007 at 02:14

Do you have $100 Million to build such a plant? It takes HUGE pressures, precious metal catalysts ($$$) and great investment, you can't scale it down.

Do you want to make 50 L a day or 50,000 L a day?

Please be realistic.

There are three or four main INDUSTRIAL processes for Ac2), NONE of them suitable for your purposes, resources, needs or capabilities.

Let's try to find for you a process that will work for you and that you can actually succeed with, okay?

not_important - 15-4-2007 at 03:39

Let me add this comment. Hector, you had previously rejected the process Sauron had found that required palladium; the methyl acetate method uses rhodium compounds. On the open market palladium is currently US$ 380 / oz, rhodium is US$6350 / oz - that is $6000 per ounce more expensive.

It also uses methyl iodide and ionic iodide salts - generally LiI and HI, methyl alcohol and a feed of high purity carbon monoxide plus hydrogen. The process runs at about 190 degrees C and 50 atmospheres pressure; the conversion rate is 50 to 70 percent per pass, so the plant has additional complexity in separating out the product and recycling unreacted materials.

It must include means to capture the rhodium that escapes into the product stream, which consists of 18-20% methyl iodide, 55-40% methyl acetate, 15-20% acetic acid, 15-20% acetic anhydride, and some tar that contains the rhodium. The volatiles are flashed off to be separated for recycling, the tar is dissolved in dichloromethane and extracted with aqueous HI, and then with concentrated aqueous ammonia and hydrazine, the second aqueous extract is concentrated and added to the first, and returned to the reactor. There is some loss of rhodium, part remains in the tar and part plates out on the equipment, so makeup rhodium must be added.

There are variants using less costly catalyst, but they require much higher pressure; the equipment is made from Hastelloy alloys, which are not cheap and can be bothersome to work with. These variants appears to need a larger minimum size plant than the rhodium based one. Actual working details are harder to come by as these variants are newer and under tight licensing (which does include assistance from the license holder in getting the plant operational).

not_important - 17-4-2007 at 02:53

Quote:
Originally posted by hector2000
Mr sauron i know there are another way for making anhydrid in industry like ketene method.in this method they heat acoh to 800 deg and then separate h20 from ac2o
may we use this method in smaller scale?like ketene method?
thanks

[Edited on 17-4-2007 by hector2000]


This is also a ketene method, and has been discussed in this thread. Quoting from a description of the process
Quote:
the optimum reaction temperature is in the range of 730°C to 750°C for maximum ketene yield. The reaction proceeds in the vapor phase in the presence of 0.2 to 0.3 percent triethyl phosphate. Equilibrium conversion is closely approached (85-90 percent on acetic acid). Ammonia is then injected to destroy the catalyst and to freeze the equilibrium. Selectivity to ketene is typically 90 to 95 mole percent. The gaseous ketene is removed from the heavier boiling acetic anhydride, acetic acid, and water in a system of graduated coolers. Ketene is then reacted with fresh and recycled acetic acid and converted to acetic anhydride.


As you can see, this is a little more complex than the acetone-ketene method, the equipment is more complex and control of temperatures and flow rates are critical. It has been run on a small scale for research purposes, but the economics on a small scale are not good.

Sauron - 17-4-2007 at 03:33

@hector, I have no idea what process you are talking about, so you had better ask the advice of someone who does.

not_important - 17-4-2007 at 07:31

Once again, just a patent on a process doesn't mean that the process is practical. If you can find references as to the process actually being used or having been used in industry, then you can assume it's fairly practical.

You should at least give the patent country and number, if not actually post the patent, if you want an answer to your question. There are dozens of patents regarding acetic anhydride production. One of the more recent ones, United States Patent 7199263, filled back in 2004 and assigned to Celanese International Corporation, is basically the method I posted earlier, using a phosphate catalyst.

I think that any high temperature route from acetic acid to acetic anhydride goes through ketene. Ketene might not be mentioned, especially in survey type articles, just the end products.

When you use a heated reactor you have more flexibility in materials than when the reactor must be a self-heating filament, which implies a certain degree of electrical resistance and strength. An externally heated reactor can use a surface coating of one material on a base layer of another, letting you select for ones less prone to carbon formation.

einstein(not) - 17-4-2007 at 14:23

I've seen a patent for making acetic acid, acetic anhydride or mixtures thereof (depending on ratio) by heating trichloroethene and water in sealed tube at around 100C. I'll post it if I can find it again.

Also might want to check out British patent #299342 Dehydration of acetic acid to acetic anhydride via phosphoric acid.

Edit: Found here's the link:http://v3.espacenet.com/textdoc?DB=EPODOC&IDX=US1856251&F=0

[Edited on 17-4-2007 by einstein(not)]

not_important - 17-4-2007 at 15:30

Actually the link is for a US patent, or is that for the one using trichloroethane?

If the British patent is the one I think it is, it is similar to the pyrosulfate method of making anhydrides. Whilr both may work, when I looked at them neither seemed to by useful for anything but small scale production of anhydrides; certainly industry seemed to feel the same as neither appears to have had much if any commercial use. The phosphate patent was linked with the Celanese Co. who would certainly used it if it scaled up and was economical.

einstein(not) - 17-4-2007 at 17:09

Hate to admit it but I was all ready to try this having bought brake cleaner at the local parts house only to find when I got home that the contents were tetrachloro not trichloro. I may still give it a try though.

Sauron - 17-4-2007 at 17:39

Relying on patents is a house of cards.

chemicalpower - 17-4-2007 at 22:00

i will be grateful if someone could write down here the process from CC and acetic acid.
as i understand the mix is refluxed slowly for 8 hours under a reflux condenser. then when a precipate starts to form it is put under a fractional distillation column connected to a condenser and then acetyl chloride is fractionated.
I have been trying this with 268grams CC and 1500ml acetic acid. but even after 8 hours no precipitate forms, and the colour of the mix in the reflux flask changes to light yellow. then when i put the fractioanting column on and try to fractionate . very very little liquid comes out at 55degrees however when i encrease the temp to about 75-80 degrees a pale yellow liquid starts distilling and the colour of the reflux flask liquid changes to milky white.
when i remove the liquids and keep them overnight the white precipitate settles down and the colour of the mix becomes transparent white, like water.
testing the pale yellow liquid from the condensation flask it is more towards acetic acid just the smell is stronger

Sauron - 17-4-2007 at 22:53

That is acetyl chloride. How much did you get, and what was the vapor temperature at the top of the column?

It should have been 51 C.

From that qty CC which is approx 1.5 mol you should have gotten 3 to 4.5 mols AcCl and that would be 240 to 360 g.

If you got less then you simply did not reflux the mix in pot long enough.

CC has 3 active chlorines, the first tewo react faster than the third.

The precipitate is cyanuric acid is you took the reaction to completion and if only partially then it is a mix of dichlorohydroxytriazine and chlorodihydroxytriazine. BTW way all the chlorines are off cyanuric acid mostly exists in its keto form isocyanuric acid.

chemicalpower - 18-4-2007 at 11:46

i got about330ml. if that is acetyl chloride why is it light yellow. it does fume a bit but not as much as i would expect from acetyl chloride. secondly when i mix it with sodium acetate which i heated to melting and then recrystallizing.it only forms strong smelling acetic acid, it mixes with water and unlike acetic anhydride doesnt form a drop in water or settle to the base. maye i should redistill the mix once more.
the temperature at the top of the fractionating column was mostly 50-55 degrees, however it would suddenly increase and even when i put the heat out, the temperature would rise to 80-90 degrees
how do i keep the temperature at the top of the column at 50-55 degrees.
secondly whats the process to mix acetyl chloride with sodium acetate and how do i get anhydride out of it

Sauron - 18-4-2007 at 17:00

You recrystallized your sodium acetate, BIG MISTAKE

As to your pale liquid product, redistill it and measure the boiling point at top of column and you will know what it is.

From reaction of CC and AcOH nothing can come (liquid) other than AcCl. So it is wither AcCl bp 51 or AcOH bp 117.

You succeeded.

Be happy.

You need to treat ANHYDROUS NaOAc with acetyl chloride, NOT RERCRYSTALLIZED.

So you either buy the anhydrous form or you take the normal form NaOAc.2H2O and you fuse it and then crush the solidified melt to powder. Forget recrystallizing.

--------

Preparing Ac2O from AcCl and NaOAc is simple

Mix equimolar amounts of the two (one solid one liquid) and stir. Mix SLOWLY, as this may be exothermic. Stir well.

No solvent required.

When done you will have one liquid (Ac2O and one solid (NaCl, common table salt.) Filter, press salt cake dry. Distill your Ac2O.

For proportions look up the MW of ANHYDROUS sodium acetate

And the MW of AcCl, also its density, that will let you calculate how many ml

And look up bp of Ac2O, never mind it is 140. So youcan easily seperate a liquid bp 140 from one bp 51 right?

How long to stir? The longer the better.

When the mixture no longer refluxes at 51 C you no longer have AcCl in there, you have only Ac2O. Got it?

-----------

There is an alternative to sodium acetate (anhydrous)/acetyl chloride.

However that is the most direct and simplest method and idiot ptoof as they get.

The alternative is acetyl achloride and acetic acid (glacial) in presence of a tertiary amine (classically pyridine) to trap HCl.

The tertiary amine precipitates as its solid hydrochloride, and may be recovered, liberated with base and reused.

HOWEVER you do not want to work with pyridine which is a powerful sterilent, you will never have children after that.

So substitute treithylamine for pyridine.

At end of reaction you will have Ac2O, a little unreacted AcCl, a little unreacted AcOH and a lot of TEA hydrochloride solid.

Filter off the TEA salt and distill the mixtire.

AcCl 51
AcOH 117
Ac2O 140

easy to seperate.

The advantage of this method is you do not have to worry about whether your sodium acetate is anhydrous.

@Hector, are you reading this? No more three day oven drying.

60 g AcOH
78 g AcCl
1 mol TEA = 101 g

Look up densities to see how many ml to use.

Produces

Ac2O 164 g yield by theory
TEA Hcl salt 137 g by theory

[Edited on 19-4-2007 by Sauron]

Sauron - 19-4-2007 at 05:44

tri ethyl amine

(Et)3N C6H15N

Do you need a CAS number?

You want the liquid amine not the solid hydrochloride

Sauron - 19-4-2007 at 06:16

Ratio 1 to 1 to 1 as I already said, on a MOLAR basis

Only one step

Ac2O forms, TEA snaps up the HCl

I think you will find the reaction makes it own heat.

Just add slowly and stir well.

Do not let it heat over 45 or you may lose some AcCl to air

In which case operate under reflux.

Did you redistill your AcCl yet?

What is the bp? vapor temp at top of column.

330 ml, you can probably squueze some more out of the batch if you boil it longer (boil first one again if not thrown away)

By theory you should have gotten 450 g from that much CC.

Now master the Ac2) step and you are on your way.

This stuff is easy.

I have to go sort out the VA process unless you are no longer interested in it.

Sauron - 19-4-2007 at 07:18

TEA hydrochloride is liberated with aqueous NaOH solution

This produces free TEA and NaCl solution.

Seperate by extraction. Yes you can reuse your TEA, but it is cheap enough that you may not want to bother.

Sauron - 19-4-2007 at 09:06

Cost will not increase if you reuse TEA

Run reaction on small scale and find out for yourself what conditions work best.

Heat or no heat? Stir how long?

Remember AcCl boils 51 C.

That is not very hot.

IF you reflux it at 51 C it will keep boiling till all AcCl has reacted and then it will not boil because Ac2O boils at 140 and you won't let pot get that hot.

IF you don't reflux, stir till no more TEA hydrochloride falls out of solution

If I were you I would mix the AcOH and TEA first then I would drip in AcCl dropwise from addn funnel and watch the temperature. Stirring well. Have a reflux condenser in place. If the reaction produces heat it may get hot enough to boil AcCl. If so you can monitor reaction, when all AcCl has been added, wait till no more heat is liberated then stir for another 1-2 hours. When at room temperature, filter off the TEA hydrochloride, and fractionate the product.

Sauron - 19-4-2007 at 11:42

No, you need a tertiary amine.

However you can use ammonia to recover the TEA from TEA-hydrochloride. Suspend the TEA-hydrochloride is a suitable solvent, bubble in ammonia gas, you will get TEA and NH4Cl. The ammonium chloride gets filtered off, and you have TEA in solvent, which you can easily distill apart. You want an inert solvent with a bp far from TEA.

Sauron - 19-4-2007 at 12:44

Why do you think TEA HCl will be difficult to filter? You get yourself a fritted disc tabletop Buchner funnel and you filter with suction.

And why are you talking about distilling at 300 C?

Highest boiling component is Ac2O at 140 C.

@hector, if you haven't fundamental skills at handling of materials in an elementary reaction like this, then there is little anyone can do to help you.

Sauron - 20-4-2007 at 00:40

You don't need a $2000 vacuum pump to do vacuum filtration, all you need is a cheap aspirator pump and cold running water. A decent water aspirator pulls down to 20-30 torr.

THAT is the sort of thing I mean by fundamental skills. You keep making excuses for why you can't do this or that, when there are OBVIOUS solutions that you ignore, or just don't know about.

You can also do the seperation of the TEA hydrochloride from the liquids as an inverse filtration. This is convenient when the liquid is air or moisture sensitive or nasty. Connect a tube with a fritted end to some inert tubing and hook that to a receiver vessel, large enough for the liquid. Connect receiver vessel to aspirator pump. With the TEA HCl settled to bottom, simply suck the liquid off carefully so as not to disturb the sediment. This way you can get 95% liquid off and you will only have to conventionally filter the 5% that is remaining.

not_important - 20-4-2007 at 01:27

Metal aspirator
http://www.spectrapor.com/labware/Aspirator.html?LiFrom=http...

plastic ones are also made, and offer the advantage of corrosion resistance.

vacuum filtration on a lab scale using an aspirator
http://orgchem.colorado.edu/hndbksupport/filt/filtration.htm...
http://eee.uci.edu/programs/gchem/RDGfiltration.pdf


Because you are working with water sensitive materials, besides the suck-back protection you would likely want either a cool trap or a water absorbing trap using molecular sieves, silica gel, or similar, between the filtration flask and the suck-back flask/jar.

The inverse filtration Sauron talks about was often done using a 'filter candle', a porous ceramic tube closed at one end and with a hose or pipe connection at the other. This form will leave more liquid behind, as most of the active filter area is in the side walls of the candle; however the candles are generally fairly rugged and can filter fairly fast because of the large filtering area they have.


Your current process would likely benefit from filtering off the solids before distilling. You also might be able to reduce or eliminate carbom formation by using a chaser.


[Edited on 20-4-2007 by not_important]

Sauron - 20-4-2007 at 01:51

Ac2O is insufficiently water sensitive to have to worry about too much. Cold trap is not necessary. A simple intervening empty wash bottle is adequate. A one way valve of the floating ball type prevents suckback.

Ac2O reacts only very slowly with cold water. Of course as it reacts is makes heat and the reaction speeds up.

chemicalpower - 22-4-2007 at 23:33

mrSauron If you think that J got Acetyl chloride then why is the colour light yellow How much time do you think is needed For the reflux reaction to complete I refluxed For 8 hours and then left the mix to cool overnight in morning a white precipitate had settled and the colour was Transparent I Fractionated the liquid and Collected a Liquid at 75 degrees. I mean to ask how much time is required for the fractionating as I Think I hurried because no or unoticABlE liquid came at 55 degrees further Should I refractionate the liquid once again

Sauron - 23-4-2007 at 00:10

It would not hurt to refractionate the product.

How are you measuring the temperature? And where?

Bath temperature, liquid temperature, vapor temperature in pot, vapor temperature at top of column?

Do the fractionation SLOWLY, allowing several hours at 100% reflux to equilibrate system. Then start collecting at a high reflux ratio, at least 10 drops returning to column for every drop taken off.

In this fashion you should see an accurate boiling point of acetyl chloride 51 C.

Don't worry about color. Light yellow is OK.

NO OTHER PRODUCT IS POSSIBLE THAN AcCl.

It isn't AcOH bp 117 and it certainly isn't Ac2O bp 140.

So most likely you are just doing the fractionation fast and you are getting AcCl and a little AcOH and bp is therefore a little high.

---------

As to making the AcCl: the literature source was vague, it was just a suggestion in the book "S-Triazines and Derivatives" by Smolin and Rapaport, amd it said that "long refluxing of cyanuric chloride in a large excess of glacial acetic acid is a good way to make cyanuric acid" The acetyl chloride is by product. The precipitate is cyanuric acid.

So, the 8 hours was my idea but it could be shorter or it could be longer, if I were you I would try 8 hours, 16 hours and 24 hours (using same amounts of CC and AcOH each time) REFLUX, that means BOILING all that time. Compares how much product you get at each reaction time. When you get 100% of the theoretical amount you can stop increasing the time. If you get close enough say 90-95% you can also stop increasing time if you want.

Remember you do not want AcCl to escape through condenser. So you keep reducing the heat as more and more AcCl forms so that all AcCl condenses in first half (bottom half) of condenser, you can see where this is happening.

chemicalpower - 23-4-2007 at 01:16

i am measuring the temperature at the top of the fractionating column i guess the vapour temp.i will do the reflux for 16hrs now

Sauron - 23-4-2007 at 01:54

Just remember to do the fractionation as slowly as you can stand to.

And don't let AcCl get out of the condenser during reflux.

As AcCl increases and AcOH decreases a little, bp will fall.

So heat input is slowly brought down to compensate

Sauron - 24-4-2007 at 01:50

Not yet. I have requested quote for VA, and I have purchased a pressure reactor in case the reaction requires that (it could just as easily require vacuum.) When I have any results I will post them here.

Meanwhile @chemicalpower is making very good progress with solventless chlorination of acetic acid to acetyl chloride with TCT as suggested in "S-Triazines and Derivatives" by Smolin & Rapaport. He is now working on optimizing reflux time vs yield.

chemicalpower - 24-4-2007 at 02:39

ok i have increaed the reflux time to 14hrs seems to be correct.but i just found outthe sodium acetate i have been using is trihydrate form not anhydrous.and anhydrous is not available here.what do i do about tht is there anyway to convert trihydrate to anhydrous sodium acetate.

Sauron - 24-4-2007 at 03:13

You heat the trihydrate in a drying oven (with the trihydrate in a large evaporation whish of shallow porcelein) at @125 C and the water is driven off. Break up the fused acetate into powder and immediately use it. Otherwise it simply readsorbs water from the air and reverts to trihydrate.

Frankly you need to do this even if you can buy "anhydrous" NaOAc because it is seldom anhydrous enough.

However, why worry about NaOAc? You can react AcCl with glacial AcOH in presence of a tertiary amine (like triethylamine) to obtain Ac2O.

And since you already have AcOH this is better.

not_important - 24-4-2007 at 03:27

Note that when fusing sodium acetate you do not want the temperature to rise too high or it will decompose. I think that 150 C is about the very hottest you should allow the aceate to reach.

Sauron - 24-4-2007 at 03:44

Yes, that's why I specified 125 C. A drying over usually has ventilation option, and temp control. I use a Memmert oven with both. You can track the extent of drying by weight loss. Tare the evaporating dish, and used a weighed amount of the trihydrate. You will lose three moles of water per mol of the trihydrate, that is a loss of 54 g per mol.

Sauron - 24-4-2007 at 06:55

I do not advise heating above 125 as you will inevitably get some decomposition.

It takes longer but is less wasteful.

You really need a dedicated drying oven designed for chemical applications.

UnintentionalChaos - 24-4-2007 at 23:55

Red phosphorus is a stabilized form of phosphorus. It is still pure, but unlike white phosphorus, it wont combust spontaneously in air, spreading clouds of P2O5 into every crevice of your workspace.

It will react just fine for what you need it to.

[Edited on 4-25-07 by UnintentionalChaos]

Sauron - 25-4-2007 at 04:37

Phosphorus will do nothing for you in this reaction.

PCl3 or PBr3 might but you do not get those from P and HCl or HBr

You get those from P and Cl2 or Br 2

Don't waste your time. When I have results I will let everyone know.

chemicalpowerII - 27-4-2007 at 09:43

dear mr sauron,
i refluxed the mix for 16 hours and the white precipitate settled down. then i filtered the precipitatae out and fractionated the liquid, once at 100degrees. then the second time at 55degrees. everything seems as expected. the fractionation column behaved nicely and the temp at the top was easy to keep at 55 degrees and about 450cc distilled over. now the sodium acetate is hard to make anhydrous and i when i heat it at 120degrees for half an hour and then mix with the liquid ( presumably acetyl chloride) it gives a clear liquid with similar smell to acetic acid rather a little more pungent and chlorine smelling.
but it fails all test , like it mixes in water on contact, is not combustable
tommorow i will try the TEA method.
isnt acetyl chloride conbustable.
to satisfy my curiosity i tried to refractionate the liquid for the third time, but as soon as the evaporation cloud reaches the top the temperature rises to 110 degrees , if it were acetyl chloride it should fractionally distill over at 55 degrees or so, whats going on here

by the way i changed my log in name because i lost my previous password and it wasnt sent to the email so i re registered

Sauron - 28-4-2007 at 00:33

I'd guess you did not dry the sodium acetate well enough, half an hour is nowhere near long enough.

There the water of hydration remaining in the sodium acetate simply converted your acetyl chloride - unquestionably that is what was distilling at 55 C - to AcOH and wasted it.

And that is why the sodium acetate must be thoroughly dried.

Good luck with the AcOH/AcCl/TEA method.

chemicalpowerII - 30-4-2007 at 04:57

ok i tried the TEA acetyllchloride method when i mixed the TEA acetic acid and acetyl chloride drop by drop the mix started heating up and i kept it under reflux.but i forgot to filter the teachloride out and started fractionating have fractionated a little liquid yet and have a dark brown liquid in the reaction flask dont know what will come out of it any ideas

Sauron - 30-4-2007 at 22:49

What was vapor temperature of product at top of column?

If 140 C then Ac2O

Dark brown liquid in pot is TEA, amines oxidize readily and turn dark which is why we distill them before use.

chemicalpowerII - 2-5-2007 at 04:56

i have again started the acetic acid cc process fot acetyl chloride. mr. sauron what is the pungent gas that escapes out even though the temperature at the top of the reflux condenser is 30degrees smells like hcl to me

Sauron - 20-5-2007 at 00:36

And I am still waiting for vinyl acetate to arrive. I think it may take substantial experimentation before find the right combination of variables described in that cursed patent (if any) that will work. Catalyst, pressure vs normal vs vacuum, etc.

You can disregard everything chemicalpower has said because he never obtained any TCT. What he thought was TCT (CC) was cyanuric acid. Not cyanuric chloride! And later all he could find was TCCA (trichloroisocyanuric acid) which is totally different and will not do same job. So all of his posts are worthless.

You at least have a cheap source of AcCl in bulk, and you have the capability to dry NaOAc in quantity. You just have to fix a few small details in the handling of the AcCl and in the fusing of the acetate salt. So you still have a good workable method at hand. Use it.

When I have anything to report about the VA method (good or bad) I will post it here.

chemicalpowerII - 26-5-2007 at 11:45

what will happen if he keep a mixture of acetic anhydride +acetic acid at 10degrees temp or below that. would the aceticacid glacial form crystals and can the anhydride be poured out.

Sauron - 12-6-2007 at 08:05

Phosphoris acid,

However you will have a very hard time seperating the acetyl chloride from the phosphorus compounds, the PCl3 is quite expensive, so are PCl5 and POCl3.

If you want to look at alternate chlorinating agents look at benzoyl chloride and phthaloyl chloride if available in your country.

But I think you already said you can't get them? Or was that the fellow in Pakistan? I don't remember.

No news yet on VA method, sorry.

garage chemist - 12-6-2007 at 11:17

Lets say one was building a 1000°C max. tube furnace with a 25mm quartz tube, would it be possible to generate useable quantities of ketene and react them to AA by heating the furnace to 750°C and slowly distilling acetone into one end of the pipe?
At the other end, the product gas would pass through a condenser with ice-water to condense unreacted acetone and then through a washing bottle with glacial acetic acid.

I am in the process of building an electric tube furnace, and when finished would like to try ketene/AA production just to see if it is possible. The furnace would predominantly be used for synthesis of carbon disulfide if that works and the technical difficulties (most importantly getting temperature-resistant gastight connections to the quartz tube) can be overcome.

Organikum - 12-6-2007 at 13:37

IIRC in the acetic anhydride thread is a post of mine, which names a patent which explains in detail the construction of an apparatus which produces ketene from acetone.
It consists mainly of a coppertube of 70cm length with 3mm inner diameter, which is in a zone of about 10cm to the end heated to 700°C to 800°C. Then the formed ketene is vented into acetic acid to be cooled rapidly and to form the AA.

The beauty of the patent is that it names exact temperatures, flow rates etc. something rarely found otherwise.
Another nice aspect is that such a 3mm tube is simply safe from explosion and flameback.

Temperature control in the hot zone is an issue - I suggest to lead the thin copper tube trough a big junk of metal and to heat this with a temperature sensor between tube and metal.

Rapid cooling of the formed ketene is essential or it will polymerize, an issue the ketene lamps all have.

/ORG

S.C. Wack - 12-6-2007 at 15:20

JACS 47, 1427 (1925):
Summary
An improved apparatus for the preparation of ketene from acetone is
described. The temperature, the rate of flow of acetone, and the percentage
decomposition of acetone all influence the yield of ketene.
For practical purposes, the following conditions seem best for ketene
production: temperature, 695-705°; rate of flow of acetone, 5 cc. per
minute, and the decomposition of acetone, between 25 and 40% of that
introduced. These conditions give consistent yields of ketene which range
between 35 and 45%.
The glass combustion tube becomes stratified after it has served in a number
of runs. No ketene results when the glass tube is replaced by an iron
pipe. Carbonization occurs instead, at temperatures which would allow
ketene production.

JACS 56, 1760 (1934):
...Below 600° the yield of ketene shows a
measurable diminution but above 600° the effect
of changing the temperature is not much greater
than our experimental error; we have verified
this up to temperatures of about 900°. We also
find that the temperature of the decomposition,
provided it is above 600°, is only at best a second
order effect compared with the effect of the extent
of the decomposition of the acetone...
Summary
In order to obtain good yields of ketene from
acetone it seems to be essential to decompose only
a small fraction of the acetone. Factors such as
the temperature of decomposition (provided it is
not much below 600°), time in the furnace and the
presence of inert gases do not appear to have any
very appreciable effect on the yield of ketene
except in so far as they affect the fraction of
acetone decomposed...

[Edited on 12-6-2007 by S.C. Wack]

Sauron - 13-6-2007 at 07:30

The literature of ketene generation is extensive and subject of a CR article which I posted early on in this thread.

If you examine and cross-compare the reliable checked methods the tube furnaces do not compare well to ketene lamps, the former producing about a quarter of a mol an hour compared to half a mol for the ketene lamp. The tube furnaces generally required rather long heated zones. My tube furnace is 2" x 12" while the one described in Org.Syn is more like 20" long which certainly speaks to the vapor residence time in the furnace.

The lamps' achilles heel is carbonization of filament requiring cleaning so spare filament assemblies are called for, increasing apparatus cost.

All in all I do not think this is a fruitful line of inquiry at least not for Ac2O prep for which better methods are at hand.

S.C. Wack - 13-6-2007 at 14:34

If one has a working tube furnace, I don't see how it cannot be fruitful. It can gather dust or be put into service. The electric furnace core in the first quote that I posted (by the same author as in the OS page) was 3 X 80 cm btw. No mention of glass tube diameter, and no mention of apparatus in the second quote - other than the tubes were quartz and did and didn't contain broken quartz or pyrex. Just giving the helpful hint of the ketene getting carried away by excess acetone vapor.

[Edited on 13-6-2007 by S.C. Wack]

garage chemist - 13-6-2007 at 15:05

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.

Sauron - 13-6-2007 at 22:38

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.

Sauron - 15-6-2007 at 03:29

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.

Sauron - 15-6-2007 at 17:47

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.

garage chemist - 15-6-2007 at 19:28

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.

Sauron - 15-6-2007 at 19:41

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.

not_important - 16-6-2007 at 08:30

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.

Sauron - 16-6-2007 at 23:03

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!)

Organikum - 17-6-2007 at 02:09

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.

Eclectic - 17-6-2007 at 06:45

Sauron - 18-6-2007 at 00:15

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.

Sauron - 19-6-2007 at 03:31

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.

garage chemist - 19-6-2007 at 07:30

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.

Eclectic - 19-6-2007 at 07:56

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.

Sauron - 19-6-2007 at 19:46

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.

Eclectic - 21-6-2007 at 07:57

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.

Sauron - 23-6-2007 at 05:08

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.

Sauron - 23-6-2007 at 14:20

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.

Sauron - 25-6-2007 at 04:16

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 1377 times

Eclectic - 26-6-2007 at 10:40

There is no error in the file. The error is yours.

not_important - 26-6-2007 at 14:43

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?

Sauron - 26-6-2007 at 19:08

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]

Eclectic - 27-6-2007 at 13:32

Hector, you are like a 3 year old playing the "WHY?" game.

Sauron - 29-6-2007 at 23:51

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]

chemicalpowerII - 30-8-2007 at 11:26

mr sauron any update on the vinyl acetate method.
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