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Sauron
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@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
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Sauron
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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]
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Sauron
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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.
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Sauron
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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?
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not_important
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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).
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not_important
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| 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.
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Sauron
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@hector, I have no idea what process you are talking about, so you had better ask the advice of someone who does.
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not_important
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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.
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einstein(not)
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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)]
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not_important
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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.
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einstein(not)
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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.
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Sauron
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Relying on patents is a house of cards.
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chemicalpower
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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
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Sauron
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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.
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chemicalpower
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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
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Sauron
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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]
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Sauron
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tri ethyl amine
(Et)3N C6H15N
Do you need a CAS number?
You want the liquid amine not the solid hydrochloride
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Sauron
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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.
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Sauron
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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.
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Sauron
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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.
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Sauron
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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.
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Sauron
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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.
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Sauron
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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.
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not_important
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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]
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Sauron
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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.
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