Author Topic: Acetic Anhydride from peracetic acid!?  (Read 18575 times)

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BillyBoy

  • Guest
Acetic Anhydride from peracetic acid!?
« on: December 17, 2002, 09:45:00 PM »
The following text was taken from book titled "Industrial Chemicals", wich is all about industrial processes for making chemicals for organic industry. I cant remember name of the author, but I have copied few pages from it and re-writen them:




ACETIC ANHYDRIDE  (CH3CO)2O


Reaction:


CH3CHO + O2 ----> CH3COOOH  (peracetic acid!)

CH3COOOH + CH3CHO ----> (CH3CO)2O + H2O

70-75% yield


Material Requrements:

Basis -1 ton acetic anhydride:

Acetaldehyde    2400 lbs          Diluent         3300 lbs
Catalyst           2 lbs          Air             variable


Process:


Air is bubbled trough liquid acetaldehyde in a reactor in the presence of 2% (based on the weight of acetaldehyde) catalyst, such as a mixture of copper and cobalt acetates or manganese acetate, wich prevents the formation of explosive amounts of peracetic acid. Approximately 1.4 parts of acetic acid per part of acetaldehyde is present as a diluent to promote acetic anhydride formation. Methyl or ethyl acetate, triacetin, or benzene may also be used as diluents, and the last is generally utilized in conjuction with acetic acid as a withdrawing agent in subsequent vacuum distilation to allow separation of the reaction mixture from water at lower temperatures.
   The reactor is maintained at a temperature of 50-60 °C, and the pressure is approx. 60 psi. The overhead from the crude vacuum coulumn is fractionated in a aldehyde column, yielding acetaldehyde for recycle as the overhead and water and diluent as bottoms. The diluent is returned to reactor after the water is separated.
   The dehydrated mixture of acetic anhydride and acetic acid from the bottom of the crude vacuum column is separated by distillation. Acetic acid is removed as overhead, and the acetic anhydride is withdrawn from a bottom plate. The catalyst is taken from the bottom to be re-used. The acetic anhydride may be further purified by vacuum distillation.
   Variations of this process involve type and amount of diluent, and several stages in reactor (with oxygen injection in each stage) under milder reaction conditions.
   Present trends are away from air and toward oxygen. In one continuous process using ethyl acetate as diluent and a catalyst concentration of 1% (cobalt acetate and copper acetate in a weight ratio 2:1), the reaction is carried out at 50°C and 45 psi. Oxygen is injected at various points along the path of liquid travel, with overall oxygen supply limited to 1-2% excess. Under these conditions, 95% conversations of acetaldehyde are obrained. Both acetic anhydride and acetic acid are produced in a 50:50 weight ratio.
   The same process carried out in the absence of diluent gives a higher oxidation rate but yields a lower acetic anhydride-acetic acid ratio(ca. 2:3)






Now the most interesting part of this process is when the peracetic acid reacts with acetaldehyde to form acetic anhydride + water

CH3COOOH + CH3CHO ===> (CH3CO)2O + H2O

We know that peracetic acid can be made with CH3COOH + H2O2 + H2SO4 so I propose next:

1. React CH3COOH + H2O2 + H2SO4 to get 15% solution of CH3COOOH in acetic acid (wich also acts as a diluent for next step)

2. React acetaldehyde with our 15% solution of CH3COOOH to get acetic anhydride (with a higher molar ratio of acetaldehyde to insure higher conversation of peracetic to anhydride)

Now, I know they operate this process @45-60 psi but IMO this is just to promote CH3CHO + O2
===> CH3COOH convertion.
I bet you 10$ if we react acetaldehyde with peracetic at atmospheric pressure we should get some aceic anhydride. Even if the yield would be some 30-50% it is still dirt cheap process, and MOST OF ALL totally OTC!

The only real problem I see here is that if we make peracetic acid via H2O2/CH3COOH we can only get something like 15% solution, can this be too diluted for step no.2?

P.S. how did all you beez miss this synthesis from all those books you read? As far as I could understand from this book, this process very largely used in industry, and it should be found most books about organic industry.

Rhodium

  • Guest
Very interesting! However, if ascetic anhydride ...
« Reply #1 on: December 17, 2002, 11:58:00 PM »
Very interesting! However, if ascetic anhydride and water is formed, why does this not equal two molecules of acetic acid?

Osmium

  • Guest
Acetaldehyde has a boiling point of 21°C.
« Reply #2 on: December 18, 2002, 01:55:00 AM »
Acetaldehyde has a boiling point of 21°C. How do you want to produce it? Chemical oxidation is too expensive.

I'm not fat just horizontally disproportionate.

PolytheneSam

  • Guest
dehydrogenation
« Reply #3 on: December 18, 2002, 02:08:00 AM »
Ye Olde Tube Furnace.

http://www.geocities.com/dritte123/PSPF.html


The hardest thing to explain is the obvious

BillyBoy

  • Guest
Acetaldehyde has a boiling point of 21°C.
« Reply #4 on: December 18, 2002, 11:13:00 AM »
Acetaldehyde has a boiling point of 21°C. How do you want to produce it?

Welll, maybe we could use an autoclave, or in the worst case a pressure cooker like those mushroom guys do. It`s not that expensive and lot of people have it just sitting at home.


Rhodium, what do you mean when you say two molecules of acetic acid???

This is the reaction mechanism:

CH3COOOH + CH3COH ==> (CH3CO)2O + H2O

Megatherium

  • Guest
He means: why isn't the acetic anhydride going to ...
« Reply #5 on: December 18, 2002, 12:20:00 PM »
He means: why isn't the acetic anhydride going to be hydrolyzed?  Acetic anhydride is used as a dehydrating agent: Ac-O-Ac + H20 --> 2 AcOH

BillyBoy

  • Guest
Maybe we can use some drying agent that uses ...
« Reply #6 on: December 18, 2002, 01:04:00 PM »
Maybe we can use some drying agent that uses chemisorption (CaO) rather than hydration (MgSO4, etc...)

I have seen in one patent about amines/imines(us 702 985), they use calcium oxide as a dehydrating agent wich works like this:

CaO + H2O ==> Ca(OH)2

This forms a calcium hydroxide, but I dont know if it reacts with a anhydride...

Megatherium

  • Guest
The Ca(OH) 2 base will most certainly react with ...
« Reply #7 on: December 18, 2002, 02:50:00 PM »
The Ca(OH)2 base will most certainly react with the acetic anhydride.  It 's probably a better idea to throw in a 4A molecular sieve for the water absorption.

BillyBoy

  • Guest
hmmm... well anyway, it seems that in the process ...
« Reply #8 on: December 18, 2002, 09:30:00 PM »
hmmm... well anyway, it seems that in the process described they do it without any drying/absorbing agents, but I cant really understand how they separate water becoause it is not described very well.

I have scanned the picture of this process, but it doesent tell me much, maybe Rhodium or somebody would like to take a look at it coz I can`t post it.

PolytheneSam

  • Guest
?
« Reply #9 on: December 19, 2002, 02:50:00 AM »
Maybe this would work for
EtOH --> CH3CHO

Patent US3884776


Note the use of the Cr redox couple.

Also see
 

Post 182782 (missing)

(PolytheneSam: "Re: potassium dichromate", Chemicals & Equipment)

Patent US3423300


Patent US3450623


Patent US3726914


Patent US3824160


Patent US5127999



http://www.geocities.com/dritte123/PSPF.html


The hardest thing to explain is the obvious

BillyBoy

  • Guest
What does that " ? " stand for?
« Reply #10 on: December 19, 2002, 09:52:00 AM »
What does that "?" stand for?

Aurelius

  • Guest
question
« Reply #11 on: December 19, 2002, 04:22:00 PM »
The question mark punctuation was just Polythene's way of saying that the following post is just a bunch of suggestions and ideas that may or may not work.  It's a matter of stating Sam's uncertainty.  Sam is just asking for opinions on some of what is posted.

Captain_Mission

  • Guest
acetaldehyde
« Reply #12 on: December 21, 2002, 12:50:00 AM »
acetaldehyde can be made from acetylene using HgSO4. It´s just a normal alkyne hydration forming an enol CH2=CH-OH, wich isomerises to CH3CHO.

BillyBoy

  • Guest
OK,I dont think the main problem here would be ...
« Reply #13 on: December 21, 2002, 11:28:00 PM »
OK,I dont think the main problem here would be obtaining acetaldehyde, but rather this forming of H2O that would decompose acetic anhydride, so i`m going to ask two questions:

1. does anybody know how fast acetic anhydride reacts with water? (i.e. will it react within a second, or slowly within a few minutes?)
What I mean by this is: maybe we can use some drying agent that will absorb water faster than it takes it to react with anhydride...

2. If we use drying agent that uses absorption of water, that means that water will still be present in a form of a cristal (example MgSO4 * XH2O), now the question here is: can anhydride still react with this water that is attached to our drying agent?

Rhodium

  • Guest
anhydride hydrolysis
« Reply #14 on: December 22, 2002, 01:29:00 AM »
The reaction of acetic anhydride with water at 25°C takes place over several minutes, not instantly - at higher temps the rate is higher.

Yes, water adsorbed to for example MgSO4 is still available for reaction with Ac2O, but the rate is slower than with free water in solution.

Mountain_Girl

  • Guest
AA from Acetaldehyde
« Reply #15 on: December 23, 2002, 08:57:00 AM »
Ullmann's Encyclopedia of Industrial Chemistry:
[Love this book!]

Oxidation of Acetaldehyde

Acetic anhydride can be obtained directly by liquid-phase oxidaton of acetaldehyde. The peracetic acid formed from oxygen and acetaldehyde reacts under suitable conditions with a second molecule of acetaldehyde to form acetic anhydride and water [64]:


Rapid removal of the reaction water and the use of suitable catalysts are essential in this process. Mixtures of acetic acid and acetic anhydride are always obtained; their ratio can be varied within wide limits by changing the reaction conditions. Generally, the highest possible anhydride yield is sought.
Because of the rapid hydrolysis of acetic anhydride above 60 °C, the process is operated preferably between 40 °C and 60 °C [65]. Suitable catalysts are combinations of metal salts [66]. Particularly important are mixtures of manganese acetate and copper acetate [67], of cobalt acetate and nickel acetate, and of cobalt and copper salts of higher fatty acids [68]. Manganese acetate should hinder the formation of explosive amounts of peracetic acid during the oxidation of acetaldehyde. For increasing the rate of oxidation, the use of pure oxygen at a pressure of several hundred kilopascals instead of air has been proposed [69].
The strongly exothermic reaction requires efficient cooling. For this purpose, the addition of low-boiling solvents has been found to be of assistance. Methyl and ethyl acetates are favored because they form azeotropic mixtures with water (but not with acetic acid or acetic anhydride) and hence allow a rapid, continuous separation of the water formed in the reaction. The ratio of acetic anhydride to acetic acid in the product depends on the ratio of ethyl acetate to acetaldehyde in the initial mixture (Table (1)).
In practice, a 1 : 2 mixture of acetaldehyde and ethyl acetate is oxidized with the addition of 0.05 to 0.1 % cobalt acetate and copper acetate at 40 °C; the ratio of Co:Cu is 1:2. The ratio of acetic anhydride to acetic acid obtained is 56:44, whereas on oxidizing in the absence of ethyl acetate this ratio is only 20:80 [16]. The optimization of other reaction conditions can also lead to an increase in the acetic anhydride-acetic acid ratio. For example, at 55 °C and atmospheric pressure, a ratio of 80:20 was achieved[70]. At a higher temperature (62 – 90 °C, 200 – 300 kPa, acetaldehyde concentration in the final mixture of up to 40 %) a ratio of 75:25 was obtained at high aldehyde conversion [71].
Other suitable low-boiling solvents are methylene chloride, diisopropyl ether, cyclohexanone, or ethylidene diacetate. Nonvolatile esters also can be used as diluents, provided they do not have to be removed from the reaction zone. These include alkyl benzoates and alkyl phthalates [72].
The acetaldehyde oxidation is illustrated in Figure (5) by the process of Usines de Melle [73]. The gas mixture containing oxygen and acetaldehyde is pumped into the reactor (a). The oxidation takes place in the liquid phase and in the presence of catalysts. The reactor effluent is sent through a water-cooled condenser (b) constructed as a separator; non-condensable gases are sent to the packed column (c). Fresh acetaldehyde is introduced at the top of this column. The condensates from both the cooler (b) and the column (c) are distilled to obtain the product. Acetaldehyde is recovered from the branch stream (d) of the non-condensable gas. The other part of the gas flow is supplemented with air and returned to the reactor.
Both towers and vessels are suitable as reactors if the heat of reaction can be dissipated. The    process of Distillers Co. [69] is shown in Figure (6) as an example. The off-gas contains combustible low-boiling products, such as acetaldehyde, and solvents, such as methyl acetate and ethyl acetate. These can be flared off.

[64]  Wacker-Chemie, DE 867 689, 1940 (A. Krug, J. Sixt).

Table 1:

Initial Ethyl Acetate/Acetaldehyde   20:80  30:70  60:40  70:30 
Acetaldehyde conv. %                   80      80     80     80
% Acetic Anhydride based on Acetaldehyde    13.5  57  64  68.5


Mountain Boy

BillyBoy

  • Guest
illustration needed
« Reply #16 on: December 23, 2002, 01:10:00 PM »
Now we are finally going somewhere!
Can you please PM me illustration of this process? Thnx  ;)

Osmium

  • Guest
Ketene lamp! Acetone pyrolysis! 1kg Ac2O per day!
« Reply #17 on: December 23, 2002, 01:30:00 PM »
[whisper]
Ketene lamp! Acetone pyrolysis! 1kg Ac2O per day! Unsupervised operation!
[/whisper]

I'm not fat just horizontally disproportionate.

BillyBoy

  • Guest
From Ketene
« Reply #18 on: December 23, 2002, 02:13:00 PM »
Yes, there is also a ketene synth in that book, it goes like this:




From Acetic Acid (Ketene)

Reaction


CH3COOH ==> CH2=C=O + H2O

CH3COOH + CH2=C=O ==> (CH3CO)2O

85-89% yield

Material Requrements:

Basis-1 ton Acetic Anhydride

Acetic Acid     2700 lbs
Catalyst        small

Process

 Vapors of GAA containing 0.2 to 0.3 % triethylphosphate (TEP) are passed into a tubular (chrome-iron alloy) reactor heated to 700 - 800 °C uder reduced pressure (200mm). As reaction gasses leave the converter , ammonia gas (1lb per 4.2 lb TEP) is injected into the stream to prevent reversion of the ketene in the product.
 The reactor exit vapors containing acetic anyhidride, acetic acid, ketene, and water are led to a series of condensers where weak aceic acid (30%) is condensed before it can react with ketene. The uncondensed ketene is absorbed in acetic acid to give acetic anyhidride (90% purity), wich is then fractioned to yield a specification product.




From Acetone

CH3COCH3 ==> CH2=C=O + CH4

Process

 Acetone vapors are passed through a void chrome-iron tube. The temperature of the tube is 650 - 670 °C, and contact time is about 0.25 - 5 sec. The unchanged acetone is condensed and recycled. The gaseous ketene is absorbed in GAA to give acetic anhydride.
 Yields based on acetone are about 80 to 95 %. Conversion per pass varies from 15 to 25 %.



 

Hmmm... this seems lot more complicated than procedure from peracetic acid.
I know that there are not many people who are willing to build a chemical reactor that operates @ 700°C vapor fase...

Unless... there are some easyer methodes of preparing ketene... or even OTC sources of ketene. Are there any?

hypo

  • Guest
erm....
« Reply #19 on: December 23, 2002, 02:32:00 PM »
> Unless... there are some easyer methodes of preparing ketene...
> or even OTC sources of ketene. Are there any?

have you tried to UTFSE!?!?

some people (cough) have been succesful, afaik others (acetyl)
had problems with their insulation.